Synthesis of Bridged and Unbridged Group (lV) Metallocene Complexes as Catalyst Precursors for Ethylene Polymerization

Synthesis of Bridged and Unbridged Group (lV) Metallocene Complexes as Catalyst Precursors for Ethylene Polymerization Dissertation zur Erlangung des akademischen Grades eines Doktors der Naturwissenschaften (Dr. rer. nat.) der Fakultät fϋr Biologie, Chemie und Geowissenschaften der Universität Bayreuth Vorgelegt von Mohamed Elnaiem Mohamed Abdelbagi aus Khartoum, Sudan Bayreuth, Germany 2011 This thesis fulfils the requirements of the doctoral degree of the Faculty of Biology, Chemistry and Geological Sciences at the University of Bayreuth. Thesis submitted: 11.10.2011 Date of Scientific Colloquium: November 22, 2011 Examination Committee: Prof. Dr. Helmut G. Alt (1. Referee) Prof. Dr. Jürgen Senker (2. Referee) Prof. Dr. Rainer Schobert (Vorsitzender) Prof. Dr. Peter Strohriegl The following work was performed during the period from April 2008 to March 2011 under the supervision of Prof. Dr. Helmut G. Alt at the Lehrstuhl fϋr Anorganische Chemie ll and at the Lehrstuhl fϋr Makromolekulare Chemie I der Universität Bayreuth. My sincere acknowledgement to my supervisor Herrn Professor Dr. Helmut G. Alt for his guidance, encouragement and enthusiastic support during the course of this research work. I am grateful to the DAAD for the financial support Acknowledgement I am very grateful to Dr. Christian Görl for his guidance and help in research work and thesis writing. Thanks are also due to his valuable suggestions and the wonderful leisure time activities we shared. My thanks are also due to Dr. Matthias Dötterl for translating the summary. I am grateful to Dr. Khalil Ahmed for his assistance in GC/MS and NMR measurements during the first stages of my research. I would like to express my deep thanks and gratitude to my labmates in the “Alt group”: Dr. Christine Denner, Dr. Haif Alshammari, Dr. Hamdi Elagab, Dr. Julian Lang, Dr. Andrea Rimkus, Dr. Tanja Englmann and Frank Lϋdel for their help, support and valuable suggestions. I would like to express my gratitude to all members in AC ll and MC I at the University of Bayreuth for providing a friendly and cooperative atmosphere. To all my friends in Bayreuth, I wish to express my sincere thanks for genuine relations and wonderful time I spent with them. Finally I would like to extend my deepest thanks and gratitude to my family members in Sudan for their constant encouragement and moral support throughout the period of my study. To My Parents & My Children Ahmed & Rahaf With my Love Abbreviations___________________________________________________________ Abbreviations [1,2-3] Reference number αalphaÅ Angstrom βbetan-Bu n-Butyl °C Degree Celsius cat. catalyst CDCl3 deuterated chloroform CD2Cl2 deuterated methylene chloride C6D6 deuterated benzene Cen Centroid Cp Cyclopentadienyl Cq quaternary carbon δ chemical shift in ppm d doublet in NMR spectroscopy dd doublet of doublet in NMR spectroscopy Et ethyl Flu Fluorenyl g gram GC gas chromatography h hour Hz Hertz Ind Indenyl i-Pr isopropyl kg kilogram M metal M+ Molecular ion MAO methylaluminoxane Me methyl Abbreviations___________________________________________________________ mg milligram min minute ml milliliter mol mol mmol millimol m/e mass/elemental electric charge Mn number average molar mass Mw weight average molar mass MS mass spectrometry NMR Nuclear Magnetic Resonance n.d. not determined PE polyethylene Ph phenyl PP polypropylene ppm parts per million q quartet in NMR spectroscopy r.t. room temperature s singlet in NMR spectroscopy THF tetrahydrofuran TMA trimethylaluminum t triplet in NMR spectroscopy X halide Contents______________________________________________________________ Contents 1 Introduction 1 1.1 General 1 1.2 Research goal 7 2 General Part 8 2.1 Unbridged 1and 2-substituted bis(silylindenyl) zirconium (IV) and hafnium (IV) complexes 8 2.1.1 General remarks 8 2.1.2 Preparation of the 1-substituted silylindenyl compounds 5-8 9 2.1.3 Preparation of the 2-substituted silylindenyl compounds 9-12 11 2.1.4 Characterization of compounds 1-12 12 2.1.5 Synthesis of the transition metal complexes 20 2.1.6 Characterization of the complexes 22 2.1.7 Ethylene polymerization experiments 32 2.1.7.1 General aspects and mechanism 32 2.1.7.2 Ethylene polymerization activities of complexes 13-18 34 2.1.7.3 Ethylene polymerization activities of complexes 19-24 35 2.1.7.4 Comparison between the polymerization activities of 1and 2substituted zirconocenes 37 2.1.7.5 Polymer analysis 38 2.2 1,2-Bis(dimethylsilyl)phenylidene-bridged zirconocene and hafnocene dichloride complexes 40 2.2.1 General remarks 40 2.2.2 Synthesis of the ligand precursor 41 2.2.3 Characterization of compound 27 42 2.2.4 Synthesis and characterization of compounds 29 and 30 44 2.2.5 Synthesis and characterization of the 1,3-bis(dimethylsilyl) phenylidene bridged bis(indenyl) compound 33 46 2.2.6 Synthesis of 1,2-phenylidene-bis(inden-1-yldimethylsilyl) complexes of zirconium (34) and hafnium (35) 49 Contents______________________________________________________________ 2.2.7 Characterization of the complexes 34 and 35 49 2.2.8 Crystal structures of complexes 34 and 35 54 2.2.9 Reactions of compounds 29, 30 and 33 with zirconium tetrachloride 59 2.2.10 Ethylene polymerization experiments with complexes 34 and 35 60 2.3 2,2’-Bis(methylene)biphenylidene-bridged 1-indenyl complexes of group (IV) metals 63 2.3.1 General remarks 63 2.3.2 Preparation of the ligand precursors 38 and 39 63 2.3.3 Characterization of compounds 38 and 39 65 2.3.4 Synthesis of the titanium, zirconium and hafnium complexes 40-42 68 2.3.5 Characterization of the complexes 40-44 69 2.3.6 Crystal structure of complex 41 73 2.3.7 Ethylene polymerization studies of complexes 40-44 76 2.4 9-Substituted silylfluorenyl complexes of zirconium and hafnium 80 2.4.1 General remarks 80 2.4.2 Synthesis of the potential ligand 45 80 2.4.3 Characterization of compound 45 80 2.4.4 Synthesis of complexes 46 and 47 83 2.4.5 Characterization of complexes 46 and 47 84 2.4.6 Ethylene polymerization experiments with complexes 45 and 46 86 3. Experimental Part 87 3.1 General 87 3.2 NMR spectroscopy 87 3.3 GC/MS 87 3.4 Mass spectrometry 88 Introduction and research goals ____________________________________________ 6 The publication of Waymouth’s complex has opened up a path for extensive ongoing studies directed to explore the relationships between catalyst activity, polymer properties and substituent effects at the 1and 2-positions of the indenyl rings of unbridged metallocene complexes.[40-44] 2-Substituted bis(indenyl) metallocene catalysts have met particular interest in the production of linear low density polyethylene (LLDPE) due to their high comonomer incorporation rate in the copolymerization of ethylene with α-olefins (particularly 1hexene).[45-48] On the other hand, the activities of 1-substituted metallocene catalysts in the polymerization of olefins are significantly higher than the 2-substituted analogues bearing the same ligands. Electron donating groups, when connected directly to indenyl or cyclopentadienyl ligands, are known to have a favourable effect on the catalyst activity in ethylene polymerization reactions by stabilizing the metal coordination site, while the presence of electron withdrawing groups leads to the opposite effect providing less active catalysts. Introduction and research goals ____________________________________________ 7 1.2 Research goals As indicated in chapter 1.1, the ligand structure plays a key role in terms of the activity and selectivity of a catalyst. Minor changes in the ligand structure or the bridging moiety can lead to dramatic effects on the productivity and selectivity of a catalyst. Keeping this in focus, our primary interest is to synthesize new bridged metallocene complexes and unbridged metallocene complexes with functionalized silyl substituents at the 1and 2positions of the indenyl ring. The proposed potential ligands include: - 1,2-bis(dimethylsilyl)phenylidene bridged bis(indenyl) compounds. - 2,2’-dimethyl-1-1’-biphenylidene bridged bis (indenyl) compounds. - 2-silyl substituted indenyl compounds. - 1-silyl substituted indenyl compounds. - 9-silyl substituted fluorenyl compounds. Group (IV) metal complexes derived from the above mentioned potential ligands should be synthesized and their catalytic activity in ethylene polymerization, in combination with methylaluminoxane (MAO) as a cocatalyst, should be tested. We were also interested in the extent to which the steric and electronic properties of these substituents affect the subsequent catalyst performance and the control over polymer properties through ”structure-property relationships”. General part ___________________________________________________________ 8 2. General Part 2.1 Unbridged 1and 2-substituted bis(silylindenyl) zirconium (IV) and hafnium (IV) complexes 2.1.1 General remarks Metallocene complexes received substantial attention in industry and research due to their capability of being highly active catalyst precursors for ethylene homopolymerization, copolymerization and stereospecific polymerization of higher αolefins. Unlike traditional Ziegler and Natta[8-10] catalysts, the facile ligand modification with various substituents has led to the preparation of a large number of metallocene complexes to improve the activity of the catalysts and the properties of the produced polyolefins. The size, nature and position of the substituents attached to the cyclopentadienyl, indenyl, or fluorenyl moieties play a key role on the catalytic activity as well as on the molecular weight and molecular weight distribution of the produced polymer.[49-56] Since Waymouth et al.[35,57] have reported the successful application of unbridged bis(η5-2-phenylindenyl) zirconium dichloride, activated with MAO, in the production of elastomeric polypropylene (ePP), a wide range of unbridged bis(2-indenyl) metallocene complexes bearing siloxy, amino, aryl, alkyl and alkenyl substituents at the 2-position of the indenyl moiety have been synthesized and investigated as catalyst precursors for the polymerization of olefins.[58-67] The symmetric metallocene complexes derived from substituted indenes exist in two conformations: racand meso-diastereomers. The ratio rac/meso depends on the bulkiness of the substituent.[68] Silyl groups have been extensively used as bridging groups in ansa-metallocene complexes.[25] However, little has been reported on the catalytic behavior of unbridged indenyl complexes containing silyl substituents attached directly to the ligand. The synthesis of racand meso-bis(1-dimethylsilylindenyl)-zirconium dichloride was briefly described in a review[69], while the syntheses of 1and 2-substituted bis[(trialkylsilyl)indenyl]-zirconium dichlorides were only recently reported in the literature.[70-73] General part ___________________________________________________________ 9 In this study, novel complexes of the type [1-(4-XC6H4SiMe2)-η5-Ind]2MCl2 and [2-(4XC6H4SiMe2)-η5-Ind]2MCl2 (where X = Me, MeO, F; M = Zr and Hf) are reported. The characteristic features of these ligands are the bulky silyl groups functionalized with an electron donating group (Me), a hetero atom with a lone pair of electrons (MeO) or an electron withdrawing group (F). The substituents were chosen to cover a wide range of electronic properties and located at the 4-position of the aryl moiety. The behavior of these complexes towards ethylene polymerization, after activation with MAO, is investigated. 2.1.2 Preparation of the 1-substituted silylindenyl compounds 5-8 The reactions of the arylchlorodimethylsilanes 1-4 with stoichiometric amounts of indenyllithium, freshly prepared via deprotonation of indene with n-butyllithium (n-BuLi), afforded the 1-silyl substituted indenyl compounds 5-8 (Scheme 5). The arylchlorodimethylsilanes 1-4 as intermediates were prepared according to published methods[74,75] through reactions of 4-substituted bromobenzene derivatives with magnesium and a two fold excess of dichlorodimethylsilane in THF (Scheme 5). In these reactions, a large excess of dichlorodimethylsilane was used to avoid the problems arising from substitution reactions of both chlorine atoms at the Si atom leading to the formation of bisaryldimethylsilyl compounds as heavier byproducts as detected by GC/MS analysis in some reactions. Therefore, cleaner reactions and better yields were only achieved when using a large excess of dichlorodimethylsilane. Scheme 5: Preparation of silane precursors 1-4 and potential ligands 5-8. General part ___________________________________________________________ 10 Table 1: Overview of the silyl compounds 1-8 Compound R Structure 1 Methyl Si Cl 2 Methoxy MeO Si Cl 3 Fluoro FSi Cl 4 Trifluoro F 3 CSi Cl 5 Methyl Si 6 Methoxy MeO Si 7 Fluoro FSi 8 Trifluoro F 3 CSi General part ___________________________________________________________ 11 2.1.3 Preparation of the 2-substituted silylindenyl compounds 9-12 The 2-silyl substituted indenyl compounds 9-12 were readily prepared via a synthetic route that comprises the reaction of the Grignard reagent of 2-bromoindene and the corresponding aryldimethylchlorosilanes 1-4. Therefore, 2-bromoindene, prepared according to the literature[76] by the reaction of indene with N-bromosuccinimide (NBS) followed by dehydration (Scheme 6), was reacted with magnesium powder in THF to yield the corresponding deep red Grignard reagent. Subsequent addition of a THF solution of an equivalent amount of the aryldimethylchlorosilanes 1-4 afforded the 2substituted silylindenyl compounds 9-12 in 65-80% yields (Scheme 7). NBS H 2 O / DMSO / 0°C Br p-TosOH toluene -H 2 O Br OH Scheme 6: Preparation of 2-bromoindene. RSi Cl RSi 1-4 9-12 +BrMg THF / reflux -MgBrCl No. R 9 Me 10 OMe 11 F 12 CF3 Scheme 7: Preparation of the ligand precursors 9-12. General part ___________________________________________________________ 12 2.1.4 Characterization of compounds 1-12 Silyl substituted indenes 5-12 and their parent chlorosilanes 1-4 were characterized by 1H and 13C NMR spectroscopy, the complete data are given in Table 2. The 1H and 13C NMR spectra of compounds 7 and 9 are discussed as examples. The 1H NMR spectrum of compound 7 (Scheme 8) shows two doublets at δ = 7.28 (d, 3J = 8.3 Hz, 2H) and δ = 7.24 (d, 3J = 7.2 Hz, 2H) ppm which can be assigned to the aromatic protons H11 and H10. The indene six-membered ring protons H7, H6, H5 and H4 display signals at δ = 7.09 (t, 1H), 7.03 (d, 3J = 7.4 Hz, 1H), 6.98 (d, 3J = 7.3 Hz, 1H) and 6.90 (t, 1H) ppm. The two doublets at δ = 6.75 ppm (3J = 5.2 Hz, 1H) and 6.42 ppm (3J = 5.2 Hz, 1H) are assigned to the protons H3 and H2 of indene, while the signal corresponding to the proton at the 1-position of indene (H1) appears at δ = 3.54 ppm (s, 1H). The six protons of the methyl groups (H8 and H9) produce the two singlets at δ = 0.03 and 0.00 ppm (6H, Si(CH3)2). Scheme 8: 1H NMR spectrum of compound 7. General part ___________________________________________________________ 13 The 13C NMR spectrum of compound 7 (Scheme 9) shows a doublet signal at δ = 163.9 ppm identifying the quaternary carbon atom C15 bearing the fluorine atom; the splitting of the signal is due to the 1J coupling with the fluorine atom [1J(19F-13C = 249 Hz)] which was observed also for C12, C13, and C14. The other quaternary carbon atoms in the molecule (C8, C9 and C12 (d)) display signals at δ = 144.6, 144.2 and 132.7(d) ppm. The signals arising at δ = 135.7, 135.2, 129.4, 125.0, 123.6, 122.8, 121.1, 114.9 ppm are assigned for the CH-type carbon atoms (C14 (d), C2, C3, C4, C5, C6, C7, and C13 (d)). The signal at δ = 45.7 ppm corresponds to the carbon atom at the 1-position of the indenyl moiety (C1) while the silyl methyl groups (C10 and C11) display the high field shifted signals at δ = -4.2 and -4.8 ppm. Scheme 9: 13C NMR spectrum of compound 7. General part____________________________________________________________ 14 The 1H NMR spectrum of compound 9 (Scheme 10) shows two signals at δ = 7.36 (br, 2H) and 7.32 (br, 2H) ppm corresponding to the aryl aromatic protons H9 and H10 while the proton attached at the 3-position of indene (H2) gives a multiplet at δ = 7.29 ppm. The four aromatic protons of indene (H3, H4, H5, and H6) display a multiplet at δ = 7.12-7.07 (m, 4H) ppm while the protons at the 1-position of indene (H1) give rise to the singlet at δ = 3.36 (s, 2H) ppm. At δ = 2.26 ppm, the methyl group protons (H11) appear (s, 3H) while the two equivalent methyl groups attached to the silicon atom (H7, H8) display a singlet at δ = 0.40 ppm. A set of signals appearing beside the main signals (H1-H11) is assigned to the 1-substituted isomer which exists in approximately 10-15%. Scheme 10: 1H NMR spectrum of compound 9. General part____________________________________________________________ 15 The 13C NMR spectrum of compound 9 (Scheme 11) shows three signals shifted to down field at δ = 147.3, 146.9 and 145.4 ppm that correspond to the quaternary carbon atoms in the indenyl moiety (C8, C9, and C2) while the signals resulting from the phenyl ring, the quaternary carbon atoms (C11 and C14) appear at δ = 138.9 and 134.6 ppm. The signal at δ = 142.1 ppm is assigned to the carbon atom C3. The CH groups’ carbon atoms in the phenyl ring (C12 and C13) are characterized by the doubly intensive signals appearing at δ = 133.9 and 128.6 ppm. The four signals at δ = 126.2, 124.8, 123.6, and 120.9 ppm can be assigned to the aromatic CH carbon atoms in the indene six membered ring (C4, C5, C6, and C7). The signal at δ = 42.6 ppm corresponds to the indenyl CH2 group (C1). The signal at δ = 21.5 ppm is assigned to the tolyl carbon atom C15 while the signal at δ = -2.4 ppm represents the two identical methyl groups attached to the silicon atom (C10). Scheme 11: 13C NMR spectrum of compound 9. General part____________________________________________________________ 22 Si RSi R Si R M Cl Cl 2 1) 2 n-BuLi, Et 2 O, -78°C - rt -2 BuH 2) MCl 4 , Et 2 O, -78°C - rt -2LiCl 9-12 19-24 No. R M 19 Me Zr 20 Me Hf 21 OMe Zr 22 OMe Hf 23 F Zr 24 F Hf Scheme 15: Synthesis of the metallocene complexes 19-24. 2.1.6 Characterization of the complexes The complexes 13-24 were characterized with NMR spectroscopy, mass spectroscopy, and elemental analysis (see experimental part). The silyl substituted bis(indenyl) metallocene complexes were characterized with 1H and 13C NMR spectroscopy (Table 3). The NMR spectra of few complexes exhibited the existence of two or more isomers. The 1H and 13C NMR spectra of complexes 15 and 20 are discussed as examples. The 1H NMR spectrum of complex 15 (Scheme 16) shows two overlapping doublets at δ = 7.50 ppm [3J = 7.8 Hz, 4H] corresponding to the indene six-membered ring protons H3 and H6, while the signals of protons H4 and H5 appear at δ = 7.16-7.10 ppm (dd, 4H). The aromatic phenyl protons H9 and H10 exhibit two signals: a doublet at δ = 7.33 General part____________________________________________________________ 23 ppm (3J =7.9 Hz, 4H) corresponding to H9 and a doublet at δ = 6.83 ppm (3J =7.9 Hz, 4H) which could be assigned to H10. The protons at the 2-position of the indene ring (H1) gives rise to the doublet appearing at δ = 6.34 ppm (3J = 3.0 Hz, 2H) and the proton at the 3-position of the indene ring (H2) produces the doublet at δ = 6.00 ppm (3J = 3.0 Hz, 2H). The methoxy protons (C11) can be associated with the singlet that appears at δ = 3.72 ppm (6H), while the silyl methyl groups (H7 and H8) can be detected as two singlets appearing further upfield at δ = 0.60 and δ = 0.53 ppm (each with 6H intensity). Scheme 16: 1H NMR spectrum of complex 15. The 13C NMR spectrum of complex 15 (Scheme 17) exhibits sixteen resonance signals interpreted as followed: the signal far downfield at δ = 160.6 ppm is assigned to the quaternary carbon atom C15 bonded to the methoxy group. The doubly intensive signal appearing at δ = 135.6 ppm results from C14. The remaining quaternary carbon atoms C12, C8 and C9 afford the signals at δ = 134.5, 129.9 and 128.9 ppm. At δ = 127.0, 126.8, 126.3, 126.1, and 125.5 ppm, the CH-type carbon atoms C3, C4, C5, C6, and C7 appear, while the CH-type carbon atom C13 affords the signal at 113.7 ppm. The signal associated with the carbon atom at the 1-position of the indenyl moiety (C1) arises at δ = 113.8 ppm while the carbon atom at the 2-position of the indene ring (C2) is identified by the signal at δ = 105.3 ppm. The methoxy carbon atom (C16) is characterized by the General part____________________________________________________________ 24 signal at δ = 55.1 ppm, while the two methyl groups attached to the silicon atom (C10 and C11) appear at δ = -0.5 and -1.1 ppm. Scheme 17: 13C NMR spectrum of complex 15. The 1H NMR spectrum of complex 20 (Scheme 18) shows a multiplet signal at δ = 7.717.69 (4H) and a multiplet signal at δ = 7.20-7.18 (4H) ppm assigned to the protons H2 and H3 of the 6-membered indene ring. The aromatic protons H5 and H6 give rise to two doublets which appear at δ = 7.10 ppm (d, 3J = 7.2 Hz, 4H) and δ = 7.02 ppm (d, 3J = 7.2 Hz, 4H). The singlet at δ = 5.90 ppm (s, 4H) is characteristic for the proton H1 at the indenyl moiety. The tolyl CH3 protons (H7) produce the signal at δ = 2.25 ppm (s, 6H) while the six equivalent protons of the silyl methyl groups (H4) appear further upfield at δ = 0.41 ppm (s, 12H). General part____________________________________________________________ 25 Scheme 18: 1H NMR spectrum of complex 20. The 13C NMR spectrum of complex 20 (Scheme 19) shows three signals downfield at δ = 138.8, 138.1 and 135.4 ppm assigned to the quaternary carbon atoms C7, C10, and C5. The two signals at δ = 133.8 and 128.4 ppm are associated with the CH-type carbon atoms of the phenyl ring of the silyl group (C8 and C9) while the CH-type carbons of the indene six-membered ring (C3 and C4) display signals at δ = 125.8 and 125.3 ppm. The quaternary carbon atom C2 gives rise to the signal at δ = 128.6 ppm. The signal at δ = 109.3 ppm is characteristic for the CH group carbon atom C1 located at the 1-position of the indenyl moiety. The methyl group at the para position to the silicon atom (C11) produces the signal at δ = 21.3 ppm, while the signal at δ = -2.4 ppm arises from the methyl groups attached to the silicon atom (C6). Due to the high symmetry of the complex (as well as for the other 2-indenyl substituted complexes), the NMR spectra are easier to evaluate compared with the spectra of the 1-substituted bis(indenyl) complexes. General part____________________________________________________________ 26 Scheme 19: 13C NMR spectrum of complex 20. The mass spectrometrical characterization of 1and 2-substituted bis(silylindenyl) complexes using a direct inlet mass spectrometer (EI, 70 eV) was unsuccessful. Using this high energy (70 eV) ionization technique, the molecules proved to break into smaller fragments. For instance, complex 17 when analyzed by mass spectroscopy (70 eV) exhibited only peaks corresponding to the fragment from the loss of one ligand (m/z = 425). Accordingly, matrix-assisted laser desorption ionization (MALDI-TOF) was used as a milder ionization technique for mass spectra measurements. The MALDI-TOF mass spectra of complexes 17 and 19 are discussed as representative examples. In the mass spectrum of the zirconium complex 17 (Scheme 20), the molecular ion peak is not observed. The ion formed by the loss of one chlorine atom [M+-Cl] produces the peak at m/z = 659 with 36% intensity. Further loss of a second chlorine atom [M+-2Cl] gives the peak at m/z = 624 (intensity: 10%). The loss of one indenyl ligand from the complex molecule gives a peak at m/z = 429 with 16% intensity, while further loss of a chlorine atom results in the peak at m/z = 391 with 18% intensity. The base peak appears at m/z = 343. General part____________________________________________________________ 27 Scheme 20: Mass spectrum of complex 17 obtained from MALDI-TOF analysis. In the mass spectrum of complex 19 (Scheme 21) the molecular ion peak was again not observed. The peak at m/z = 653.1 with 4% intensity could be explained by the loss of one chlorine atom from the molecule, while the peak at m/z = 616.4 (6% intensity) is generated from the loss of two chlorine atoms. The loss of a ligand molecule gives rise to the peak at m/z = 425.3 (15% intensity), further loss of a chlorine atom generates the peak at m/z = 388.3 (25% intensity). The 4-tolyldimethylsilyl fragment gives the peak at m/z = 149.38 with 55% intensity. General part____________________________________________________________ 28 Scheme 21: Mass spectrum of complex 19. Table 3: 1H and 13C NMRa spectra of complexes 13-24. No. Structure 1 H NMR 13 C NMR 13 Zr Cl Cl Si Si 7.52-7.46 m (4H) 7.30-7.28 m (4H) 7.13-7.06 m (8H) 6.3 br (2H, C3-Ind) 6.0 br (2H, C2-Ind) 2.3 s (6H, Ar-CH3) 0.58 s (6H, Si-CH3) 0.53 s (6H, Si-CH3) 139.3, 134.5, 134.4 (Cq) 134.2 (2C, Ar-CH) 130.0 (Cq) 128.8, 127.0, 126.8, 126.4, 126.1 (CH), 125.5 (2C, Ar-CH) 113.5 (Cq, C1-Ind) 105.3 (CH, C2-Ind) 21.5 (Ar-CH3) -0.6, -1.3 (Si(CH3)2) General part____________________________________________________________ 29 14 Hf Cl Cl Si Si 7.49-7.43 m (4H) 7.31-7.29 m (4H) 7.13-7.08 m (8H) 6.3 d (3J =2.8 Hz, 2H, C3-Ind) 5.8 d (3J =2.8 Hz, 2H, C2-Ind) 2.3 s (6H, Ar-CH3) 0.6 s (6H, Si-CH3) 0.5 s (6H, Si-CH3) 139.3, 134.5 (Cq) 134.2 (2C, Ar-CH) 133.5, 130.1 (Cq) 128.8, 126.9, 126.4, 126.3, 125.9 (CH), 125.5 (2C, Ar-CH) 110.1 (Cq, C1-Ind) 102.8 (CH, C2-Ind) 21.5 (Ar-CH3) -0.4, -1.2 (Si(CH3)2) 15 Zr Cl Cl Si Si O O 7.50 d (3J =7.8 Hz, 4H) 7.33 d (3J =7.9 Hz, 4H, Ar-H) 7.16-7.10 dd (4H) 6.83 d (3J =7.9 Hz, 4H, Ar-H) 6.33 d (3J =3.0 Hz, 2H, C3-Ind) 6.00 d (3J =3.0 Hz, 2H, C2-Ind) 3.72 s (6H, O-CH3) 0.60 s (6H,Si-CH3) 0.53 s (6H,Si-CH3) 160.6 (Cq) 135.6 (2C, CH) 134.5, 129.9, 128.9 (Cq) 127.0, 126.8, 126.3, 126.1, 125.5 (CH) 113.8 (Cq, C1-Ind) 113.7 (2C, CH) 105.3 (CH, C2-Ind) 55.1 (O-CH3) -0.5, -1.1 (Si(CH3)2) 16 Hf Cl Cl Si Si O O 7.56-7.47 m (4H) 7.35 m (4H, Ar-H) 7.21 m (4H) 6.91 m (4H, Ar-H) 6.38 br (2H, C3-Ind) 6.05 br (2H, C2-Ind) 3.74 s (6H, O-CH3) 0.61 s (6H, Si-CH3) 0.53 s (6H, Si-CH3) 160.9 (Cq) 135.8 (2C, CH) 134.6, 129.7, 129.0 (Cq) 127.2, 126.9, 126.6, 126.3, 125.9 (CH) 111.2 (Cq, C1-Ind) 113.9 (2C, CH) 102.7 (CH, C2-Ind) 55.1 (O-CH3) -0.5, -1.0 (Si(CH3)2) General part____________________________________________________________ 30 17b Zr C l C l Si Si F F 7.46 br (4H, Ar-H) 7.30 br (4H, Ar-H) 7.10 m (2H) 6.89 m (2H) 6.34 m (2H) 6.20 m (2H) 6.03 m (2H, C3-Ind) 5.63 m (2H, C2-Ind) 0.53 s (6H, Si-CH3) 0.49 s (6H, Si-CH3) 163.9 d (Cq, 1JC-F = 247 Hz) 136.0 d (2JC-F = 7.3, CH-Ar, 2C) 133.6 d (Cq, 4JC-F = 3.8 Hz, C-F) 130.0, 128.5 (Cq) 127.6, 127.0, 126.3, 125.8, 125.3 (CH) 114.9 d (3JC-F = 19.8 Hz, CH-Ar, 2C) 113.8 (Cq, C1-Ind) 106.1 (CH, C2-Ind) -0.5, -0.9 (Si(CH3)2) 18 Hf C l C l Si Si F F 7.50 dd (4H) 7.32 t (4H) 7.13 d (4H) 6.95 t (4H) 6.25 d (3J = 3.2 Hz, 2H, C3-Ind) 5.94 d (3J =2.8 Hz, 2H, C2-Ind) 0.58 s (6H, Si-CH3) 0.57 s (6H, Si-CH3) 163.8 d (Cq, 1JC-F = 248 Hz, C-F) 136.0 d (2JC-F=7.3, Ar-CH, 2C) 133.9 d (Cq, 4JC-F= 3.8 Hz, C-F) 133.4, 128.6 (Cq) 127.2, 126.9, 126.4, 126.0, 125.3 (CH) 115.0 d (3JC-F = 19.5 Hz, Ar-CH, 2C) 110.7 (Cq, C1-Ind) 102.8 (CH, C2-Ind) 0.6, -1.1 (Si(CH3)2) 19 Si Si Zr C l C l 7.65-7.63 m (4H) 7.11-7.09 m (4H) 7.04-6.95 dd (8H, Ar-H) 5.96 s (4H, C1-Ind) 2.19 s (6H, Ar-CH3) 0.35 s (12H, SiCH3) 138.7, 138.4, 135.2 (Cq) 133.7 (CH) 129.3 (Cq) 128.4, 125.7, 125.4, 112.3 (CH) 21.3 (Ar-CH3) -2.5 (CH3, Si(CH3)2) 20 Si Si Hf C l C l 7.71-7.69 m (4H) 7.20-7.18 m (4H) 7.10 d (3J =7.2 Hz, 4H, Ar-H) 7.02 d (3J =7.2 Hz, 4H, Ar-H) 5.90 s (4H, C1-Ind) 2.25 s (6H, Ar-CH3) 0.41 s (12H, SiCH3) 138.8, 138.1, 135.4 (Cq) 133.8 (CH) 128.6 (Cq) 128.4, 125.8, 125.3, 109.3 (CH) 21.3 (Ar-CH3) -2.4 (Si(CH3)2) General part____________________________________________________________ 31 21 Si Si Zr Cl Cl O O 7.34-7.27 m (8H) 7.00-6.92 m (8H) 6.11 s (4H, C1-Ind) 3.84 s (6H, O-CH3) 0.10 s (12H, SiCH3) 159.7, 144.9, 144.0 (Cq) 129.4 (CH) 129.2 (Cq) 126.3, 126.0, 120.6, 113.9 (CH) 55.1 (O-CH3) 2.1 (Si(CH3)2) 22 Si Si Hf Cl Cl O O 7.40-7.32 m (8H) 7.09-7.01 m (8H) 6.16 s (4H, C1-Ind) 3.84 s (6H, O-CH3) 0.11 s (12H, SiCH3) 160.0, 145.0, 144.1 (Cq) 129.7 (CH) 129.1 (Cq) 126.4, 126.0, 120.8, 114.3 (CH) 55.2 (O-CH3) 2.1 (Si(CH3)2) 23b Si Si Zr Cl Cl F F 7.42 m (4H, Ar-H) 7.29-7.13 m (8H) 7.07 m (4H, Ar-H) 6.20 s (4H, C1-Ind) 0.08 s (12H, SiCH3) 164.1 d (1JC-F = 253 Hz, Cq) 144.7 d (4JC-F = 3.6 Hz, Cq) 143.4 (Cq) 135.7 d (2JC-F = 7.9 Hz, Ar-CH) 132.8 (Cq) 129.4, 125.0 (CH) 115.0 d (3JC-F = 19.5 Hz, Ar-CH) 105.3 (CH, C1-Ind) -4.0 (Si(CH3)2) 24b Si Si Hf Cl Cl F F 7.43 m (4H, Ar-H) 7.28-7.16 m (8H) 7.05 m (4H, Ar-H) 5.90 s (4H, C1-Ind) 0.45 s (12H, SiCH3) 163.5 d (1JC-F = 254 Hz, Cq) 138.2 d (4JC-F = 3.6 Hz, Cq) 136.0 d (2JC-F = 6.9 Hz, Ar-CH) 133.5, 128.6 (Cq) 126.0, 125.7 (CH) 115.0 d (3JC-F = 19.5 Hz, CH) 109.1 (CH, C1-Ind) -2.3 (Si(CH3)2) a δ (ppm) rel. CHCl3 (7.24 ppm, 1H NMR) and rel. CDCl3 (77.0 ppm, 13C NMR) at 298 K. b Two isomers. General part____________________________________________________________ 38 This pattern indicates that 1-substituted indenyl complexes are much more active in ethylene polymerization than their 2-substituted counterparts. This behavior may be explained in the way that the same silyl substituent in position 2 can exert more steric hindrance around the metal center compared to the 1-substituted analogues. 2.1.7.5 Polymer analysis The produced polyethylene samples were analyzed by differential scanning calorimetry (DSC) and viscosimetry. The results of the polymer analyses are summarized in Table 6. Table 6: DSC and viscosimetry molecular weight analysis of polyethylenes produced with complexes 13-24 Complex ∆Hm [J/g] Tm [°C] Crystallinity [α] Mη [g/mol] 13 162.3 135.4 0.56 292000 14 151.2 136.2 0.52 355000 15 141.9 135.5 0.49 n.d. 16 142.0 136.2 0.49 n.d. 17 152.7 136.9 0.53 270000 18 141.7 135.9 0.49 535000 19 169.2 135.4 0.58 265000 20 144.9 135.2 0.50 445000 21 158.5 137.5 0.55 350000 22 138.9 135.0 0.48 n.d. 23 151.1 135.4 0.52 385000 24 130.8 137.3 0.45 n.d. From DSC analyses of the polyethylene samples no significant differences in the melting points were observed. However, molecular weight measurements showed that the molecular weights of polymers produced with hafnium complexes are significantly higher than those of the polymers produced with the analogous zirconium complexes. General part____________________________________________________________ 39 This could be attributed to the thermodynamically more stable bond between hafnium and the polymer chain.[79] The crystallinity values were obtained from the following equation: α = ΔHm/ΔHm,0 with ΔHm,0 = 290 J/g extrapolated for 100% crystalline polyethylene.[81] While the molecular weights of the hafnium catalyzed polyethylene samples were higher compared with the zirconium catalyzed polymers, the opposite trend could be observed for the crystallinity values. General part____________________________________________________________ 40 2.2 1,2-Bis(dimethylsilyl)phenylidene-bridged zirconocene and hafnocene dichloride complexes 2.2.1 General remarks A wide range of bridged bis(indenyl) metallocene complexes has been synthesized and tested as catalyst precursors for olefin polymerization. These complexes include different bridging-type moieties. However, the most commonly used bridges are the dimethylsilylene, ethylene, isopropylidene, and methylene units.[26,28,82-86] The structure of the bridging unit in ansa metallocene complexes has a strong influence on the catalyst activity and the molecular weight of the generated polymers.[87] The activity can be improved by enlarging the reaction space around the metal center, mainly by increasing the metal-centroid distance and the dihedral angle between the two indenyl based π-ligands. In contrast to silylene and alkylidene bridged metallocene complexes, few examples of ansa-metallocene complexes are known containing bulky aromatic groups as bridges. For instance, o-xylideneand naphthylidene-bridged catalysts have recently been synthesized and evaluated as catalysts for ethylene and propylene polymerization after activation with MAO. [88,89] Herein, a synthesis of new ansa-complexes of zirconium and hafnium is described, which possess two indenyl ligands that are linked through a 1,2bis(dimethylsilyl)phenylidene bridge (Scheme 25), together with a study of their catalytic behavior in the homogeneous polymerization of ethylene. SiSi M Cl Cl M= Z r ,Hf Scheme 25: General structural formula of the metallocene complexes 34 and 35. General part____________________________________________________________ 41 2.2.2 Synthesis of the ligand precursor 1,2-Bis(inden-1-yldimethylsilyl)benzene 27 was prepared via a three steps method that comprises a Grignard coupling of 1,2-dibromobenzene with chlorodimethylsilane to give 1,2-bis(dimethylsilyl)benzene (25), followed by chlorination with carbon tetrachloride in the presence of a catalytic amount of palladium dichloride to obtain 1,2bis(chlorodimethylsilyl)benzene (26).[90] The desired compound was readily prepared by the reaction of compound 26 with two equivalents of indenyllithium (prepared separately via reaction of indene and n-butyllithium in ether) (Scheme 26). This reaction was necessarily conducted in ether at room temperature. If another solvent such as THF is used, the undesired monoindenyl spiro compound is formed as a side product. This proceeds by the deprotonation at the C1-position in the already silyl-bonded indene followed by an intramolecular reaction with the chlorine atom of the same molecule leading to the formation of the cyclic mono substituted indenyl derivative with a sp3hybridized carbon atom. Compound 27 was initially obtained with trace amounts of the monoindenyl-substituted derivative as side product. Thus, the purity was improved via prolonged evacuation at elevated temperature. 1) Mg 2) ClSiH(CH 3 ) 2 PdCl 2 / CCl 4 25 26 Si Si Si Si Cl Cl SiH HSi Br Br -2MgBrCl - CHCl 3 27 Li2 - 2LiCl Si Si less than 5% (GC/MS) + Scheme 26: Three-step synthesis of compound 27. General part____________________________________________________________ 42 2.2.3 Characterization of compound 27 Compound 27 was characterized by 1H NMR, 13C NMR and GC/MS (Table 7). The 1H NMR spectrum of compound 27 (Scheme 27) shows multiplet signals at δ = 7.76-7.73 (m, 2H), 7.50-7.46 (m, 2H), 7.29-7.26 (m, 4H) and 7.14-7.09 ppm (m, 4H) for the aromatic protons of both the bridge and the indenyl moiety (H10, H11, H4, H5, H6 and H7). The two signals appearing at δ = 6.96 (d, 3J(H,H) =5.2 Hz, 2H) and 6.57 ppm (dd, 2H) can be attributed to the protons at the 3and 2-positions of the indenyl moiety (H3 and H2). The protons at the 1-positions of the indenyl moieties (H1) produce the signal at δ = 4.00 ppm (s, 2H) while the signal for the silyl protons (H8 and H9) appears at δ = 0.20 ppm (s, 12H). Scheme 27: 1H NMR spectrum of compound 27. General part____________________________________________________________ 43 The 13C NMR spectrum of compound 27 (Scheme 28) shows three resonance signals at δ = 145.0, 144.4 and 144.0 ppm attributed to the quaternary carbon atoms C8, C9, and C12. The two signals at δ =136.2 and 135.7 ppm correspond to C2 and C3 of the indene five membered ring, while the CH–type carbon atoms in the indenyl moiety (C4, C5, C6 and C7) give signals at δ =129.7, 125, 123.6, and 123.0 ppm. The two signals at δ =128.3 and 121.0 ppm can be assigned to the carbon atoms of the phenyl ring (C13 and C14). The carbon atom at the 1-position of the indenyl ligand (C1) shows a signal at δ = 45.8 ppm while the silyl methyl groups (C10 and C11) show signals at δ = -1.3 and - 1.9 ppm. Scheme 28: 13C NMR spectrum of compound 27. General part____________________________________________________________ 44 The mass spectrum of compound 27 (Scheme 29) shows the molecular ion peak at m/z = 422 with 88% intensity. The ion formed by the loss of one indenyl unit [M+-indenyl] generates the peak at m/z = 306 (intensity 45%) while the loss of two indenyl units from the molecule gives rise to the base peak at m/z = 191. Scheme 29: Mass spectrum of compound 27. 2.2.4 Synthesis and characterization of compounds 29 and 30 Compounds 29 and 30 were synthesized by the reactions of one equivalent of 1,2bis(chlorodimethylsilyl)benzene (26) with two equivalents of 2-methylindenyllithium and fluorenyllithium, respectively (Scheme 31). Both reactions were conducted in ether at room temperature. Fluorenyllithium was prepared by the reaction of fluorene and nbutyllithium in diethylether, while 2-methylindene (28) was prepared by the reaction of 2indanone with methyl magnesium bromide in diethyl ether followed by a water elimination reaction of the resulting carbinol intermediate with para-toluenesulfonic acid in toluene (Scheme 30).[91] General part____________________________________________________________ 45 1) C H 3 MgB r 2) H 2 O/ H + 28 O OH p-TosOH toluene H 2 O _ -MgBr(OH) Scheme 30: Preparation of 2-methylindene. 26 Si Si Cl Cl 2 - 2LiCl _ Li + Si Si 30 2 - 2LiCl 29 Si Si _ Li + Scheme 31: Preparation of compounds 29 and 30. Compounds 29 and 30 were characterized by 1H NMR and 13C NMR spectroscopy (Table 7). General part____________________________________________________________ 46 2.2.5 Synthesis and characterization of the 1,3-bis(dimethylsilyl)phenylidene bridged bis(indenyl) compound 33 The reaction of 1,3-dibromobenzene with magnesium powder in the presence of two equivalents of diethoxydimethylsilane in refluxing THF afforded 1,3bis(ethoxydimethylsilyl)benzene 31. Ethoxy – chlorine exchange at compound 31 was achieved via reaction with excess acetyl chloride in the presence of a catalytic amount of pyridine to yield compound 32.[90] A subsequent reaction of one equivalent of compound 32 with two equivalents of indenyllithium in diethylether at room temperature, afforded the desired bis(indenyl) compound 33 in 70% overall yield (Scheme 32). BrBr Si Cl Si Cl Si O Si O 2 - 2LiCl SiSi 1) Mg 2) SiMe 2 (OEt) 2 - 2 MgBr(OEt) THF/ reflux, 3 h CH 3 COCl / Pyridine reflux, 24 h 31 32 33 _ Li + Scheme 32: Preparation of compound 33. Compound 33 was fully characterized by means of 1H NMR, 13C NMR and GC/MS. The full spectral data are given in Table7. General part____________________________________________________________ 47 Table 7: 1H, 13C NMR and GC/MS data for compounds 25-33 No. 1 H NMR 13 C NMR MS [m/z] (%) 25a 7.64-7.60 m (2H) 7.44-7.38 m (2H) 4.78-4.72 m (2H) 0.43 s (6H, Si-CH3) 0.41 s (6H, Si-CH3) 144.3 (Cq) 134.3, 128.4 (CH) -2.6 (Si(CH3)2) 194 [M+] (10) 179 M+-Me (46) 134 (100) 26a 7.90-7.88 m (2H) 7.47-7.45 m (2H) 0.80 s (12H, Si(CH3)2) 141.7 (Cq) 135.5, 129.3 (CH) 5.2 (Si(CH3)2) 247.0 M+-Me (100) 211 M+-HCl (38) 119 (23) 27b 7.76-7.73 m (2H) 7.50-7.46 m (4H) 7.29-7.26 m (2H) 7.14-7.09 m (4H) 6.96 d (3J =5.2 Hz, 2H, C3-Ind) 6.57 dd (2H, C2-Ind) 4.00 s (2H, C1-Ind) 0.22 s (6H, Si-CH3) 0.20 s (6H, Si-CH3) 145.0, 144.4, 144.0 (Cq) 136.2 (CH, C2-Ind) 135.7 (CH, C3-Ind) 129.7, 128.3, 125.0, 123.6 123.0, 121.0 (CH) 45.8 (CH, C1-Ind) -1.3, -1.9 (Si(CH3)2) 422 M+ (88) 306 M+-Ind (45) 135 (85) 191 M+-2Ind (100) 28a 7.43-7.40 d (1H) 7.31-7.24 m (2H) 7.17-7.12 m (1H) 6.54 s (1H) 3.34 s (2H) 2.21 s (3H) 145.9, 145.8, 143.3 (Cq) 127.1, 126.1, 123.4, 123.2, 119.6 (CH) 42.6 (CH2) 16.7 (CH3) 130 M+ (100) 115 M+ -Me (92) 29a 7.75-7.71 m (2H) 7.46-7.43 m (2H) 7.33 d (2H) 7.20-7.16 m (2H) 7.00-6.89 m (4H) 6.59 s (2H, C3-Ind) 3.83 s (2H, C1-Ind) 1.97 s (J =4.0 Hz, 6H, CH3) 0.26 s (6H, Si-CH3) 0.21 s (6H, Si-CH3) 145.1, 144.8, 144.7, 144.2 (Cq) 136.5, 128.1, 126.3, 125.0, 123.1, 122.4, 119.6, 48.5 (CH) 17.6 (CH3) -1.2 (Si(CH3)2) 450 M+ (1) 321 (70) 191 (100) 30b 7.72-7.69 m (4H, Ar-H) 7.24-7.05 m (16H) 4.22 s (2H, C9-Flu) 0.00 s (12H, Si(CH3)2) 145.6, 144.3, 141.3 (Cq) 137.2, 128.4, 126.3, 125.9, 124.7, 120.3, 42.4 (CH) -1.5 (Si(CH3)2) n.d. General part____________________________________________________________ 54 2.2.8 Crystal structures of complexes 34 and 35 Single crystals suitable for the X-ray diffraction analyses of complexes 34 and 35 were obtained by slow solvent evaporation from concentrated solutions of pentane/toluene mixtures in an approximately 9:1 ratio. The molecular structures of the complexes have been established by single crystal X-ray diffraction analyses. The ORTEP diagrams of 34 and 35 are displayed in Schemes 37 and 38. Table 9 summarizes the crystal data and structural refinement of complex 34, while the crystal data and structural refinement of 35 is given in Table 10. Selected bond lengths and angles for complexes 34 and 35 are presented in Tables 11 and 12. Scheme 37: ORTEP diagram of complex 34, ellipsoids are drawn in 30% probability level. Hydrogen atoms are omitted for clarity. General part____________________________________________________________ 55 Scheme 38: ORTEP diagram of complex 35, along with atom numbering scheme, ellipsoids are drawn in 30% probability level. Hydrogen atoms are drawn as spheres with fixed small radius. Hydrogen atom names are omitted for clarity. The solid state crystal structure analysis shows that the metallocene dichloride complexes 34 and 35 are isostructural and adopt a pseudotetrahedral coordination geometry around the metal atom formed by two chlorine atoms and two η5-coordinated indenyl ligands. As both complexes have closely equivalent bond lengths and angles, the following description of complex 34 is also valid for 35. One of the important features is that the indenyl ligand planes in the molecule are twisted from being perfectly C2-symmetric thus leading to a distorted rac orientation. In 34, the angle Cl(1)- Zr-Cl(2) is 96.81° which is comparable to that of the unbridged zirconocene complex Ind2ZrCl2 (94.71°)[92] and the Me2Si bridged metallocene complex Me2Si(Ind)2ZrCl2 (98.76°).[93] The angle that comprises the zirconium atom and the two five membered ring planes, Cen-Zr-Cen, is 130.45° which is larger than that of Ind2ZrCl2 (128.3°) and the bridged Me2Si(Ind)2ZrCl2 (127.8°). The Zr-C bond distances are different; the General part____________________________________________________________ 56 quaternary carbon atoms between the fiveand six-membered rings, C(2), C(7), C(23), and C(28), are apparently further away from the zirconium atom compared to the three remaining carbon atoms. These two common carbon atoms are covalently bonded to three other carbon atoms, which reduces their bonding ability to zirconium.[94] The value of the dihedral angle between the two planes of the five ring centroids is 51.37° which is smaller than that of Me2Si(Ind)2ZrCl2 with a difference of Δ = 10.57°. For metallocene complexes prepared for catalytic functions, the greater dihedral angle allows better access of the monomer molecules to the cationic metal center. Therefore, catalysts with wider dihedral angles should show comparatively higher activities. The distance between the zirconium and the Cen1 plane is 2.2513 Å being slightly longer than the ZrCen2 distance (2.2114 Å), the distance between the two centroids is 4.05 Å and the zirconium atom is located 0.935 Å out of this Cen1-Cen2 vector. Table 9: Crystal data and structure refinement for 34. Empirical formula C28 H28 Cl2 Si2 Zr Formula weight 582.80 Temperature 293(2) K Wavelength 0.71073 Å Space group P-1; Triclinic a (Å) 9.1925(18) b (Å) 10.110(2) c (Å) 15.726(3) α(°) 91.63(3) β(°) 100.26(3) γ(°) 111.24(3) Volume 1333.6(5) Å3 Z 2 Density (calculated) 1.451 Mg/m3 Absorption coefficient 2.65 to 26.01°. F(000) 596 Crystal size 0.28 x 0.18 x 0.16 mm3 Theta range for data collection 0.718 mm-1 General part____________________________________________________________ 57 Index ranges -10<=h<=9, 9<=k<=12, -19<=1<=19 Reflections collected 6271 Independent reflections 4372 [R(int) = 0.0396] Completeness to theta = 26.01° 83.0 % Absorption correction None Refinement method Full-matrix leastsquares on F2 Data / restraints / parameters 4372 / 0 / 298 Goodness-of-fit on F2 0.938 Largest diff. peak and hole R1 = 0.0398, wR2 = 0.0956 R indices (all data) 0.534 and -0.314 e.Å-3 Final R indices [I>2sigma(I)] R1 = 0.0547, wR2 = 0.1022 Table 10: Crystal data for the hafnium complex 35. Formula C28H28Cl2Si2Hf Space group P-1, Triclinic Z 2 a (Å) 10.0503(18) b (Å) 9.1624(16) c (Å) 15.643(3) α(°) 91.567(19) β(°) 100.285(18) γ(°) 111.167(8) Volume (Å3) 1315.0(4) F(000) 660 Temperature (K) 293 Wave length (Å) 0.71069 Crystal dimensions (mm3) 0.3 × 0.2 × 0.2 Rint 0.056 General part____________________________________________________________ 58 [Sin( θ )/ λ ]max (Å-1) 0.8709 Density (g cm-3) 1.6918 Absorption coefficient (mm-1) 4.276 Observed Criteria I > 3σ(I) No. of observed/all reflections 8001/ 11018 wRF(obs/all) 0.0395/0.0663 RF(obs/all) 0.0422/0.0446 Δ ρ max/ Δ ρ min (eÅ-3) 1.61/1.79 GoF(obs/all) 1.01/-0.87 Table 11: Selected Bond lengths and angles of 34. Selected bond lengths [Å] Si(1)-C(1) 1.867(4) Zr-Cl(1) 2.4230(14) Si(2)-C(20) 1.872(4) Zr-Cl(2) 2.4398(11) Cen1-Zr 2.2513 Zr-C(1) 2.499(3) Cen2-Zr 2.2114 Zr-C(2) 2.634(3) Cen1-Cen2 4.0520 Zr-C(7) 2.654(3 Selected bonds angles[°] Zr-C(8) 2.506(4) Cl(1)-Zr-Cl(2) 96.81(5) Zr-C(9) 2.490(3) C(1)-Si(1)-C(12) 111.68(18) Zr-C(20) 2.491(3) C(20)-Si(2)-C(17) 114.49(16) Zr-C(21) 2.465(3) C(2)-C(1)-Si(1) 126.2(3) Zr-C(22) 2.479(3) C(28)-C(20)-Si(2) 129.1(3) Zr-C(23) 2.565(4) Dihedral angle 51.368 Zr-C(28) 2.617(4) Cen1-Zr-Cen2 130.453 General part____________________________________________________________ 59 Table 12: Selected Bond lengths and angles of 35. Selected bond lengths [Å] Si(1)-C(1) 1.868(4) Hf-Cl(1) 2.4095(14) Si(2)-C(10) 1.855(4) Hf-Cl(2) 2.3921(14) Cen1-Hf 2.194(4) Hf-C(1) 2.469(4) Cen2-Hf 2.231(5) Hf-C(2) 2.449(4) Cen1-Cen2 4.024(8) Hf-C(3) 2.464(4) Selected bonds angles[°] Hf-C(4) 2.549(4) Cl(1)-Hf-Cl(2) 95.91(4) Hf-C(9) 2.596(4) C(1)-Si(1)-C(23) 113.77(15) Hf-C(10) 2.473(4) C(10)-Si(2)-C(24) 111.32(19) Hf-C(11) 2.452(4) C(9)-C(1)-Si(1) 129.7(3) Hf-C(12) 2.485(4) C(18)-C(10)-Si(2) 125.8(3) Hf-C(13) 2.644(4) Dihedral angle 51.478(150) Hf-C(18) 2.625(4) Cen1-Hf-Cen2 130.813(10) 2.2.9 Reactions of compounds 29, 30 and 33 with zirconium tetrachloride Many futile attempts were made to prepare the zirconium complexes derived from compounds 29, 30 and 33. The titled compounds were reacted with ZrCl4 by a similar method used in Scheme 29. The attempts to characterize the obtained powders with NMR spectroscopy were unsuccessful due to their insolubility in common organic solvents. In the mass spectra, the molecular ion peak or any of the cracking patterns relevant to the targeted complexes were not detected. Instead, a peak for the dilithium salt appeared [m/z = 435 corresponding to the compound 33 dilithium salt]. The use of different solvents such as toluene or diethyl ether, besides THF, and prolonged heating failed to drive these reactions towards completion. General part____________________________________________________________ 60 2.2.10 Ethylene polymerization experiments with complexes 34 and 35 Complexes 34 and 35 are ansa bis(1-indenyl) metallocene dichloride complexes, the two indenyl ligands are tethered via a 1,2-bis(dimethylsilyl) phenylene bridge. (Scheme 39). SiSi M Cl Cl 34 (M = Zr) 35 (M = Hf) Scheme 39: Structural formula of complexes 34 and 35. The catalytic activities of complexes 34 and 35 in the homogeneous polymerization of ethylene along with the results of the polymer analyses are summarized in Table 13. Methylaluminoxane (MAO) was used as a cocatalyst (M:Al = 1:2000), the experiments were conducted at a polymerization temperature of 60°C, 10 bar ethylene pressure, and in 250 ml of pentane for one hour. The produced polyethylene samples were analyzed by DSC and viscosimetry. Table 13: Ethylene polymerization activities and analyses of the polymers produced with complexes 34/MAO and 35/MAO. Complex No. M Activitya DSC Mη [g/mol] ∆Hm [J/g] Tm [°C] [α] 34 Zr 7610 124.5 135.5 0.43 366000 35 Hf 3590 124.6 135.5 0.43 375000 a (kg PE/mol cat. h) General part____________________________________________________________ 61 Both MAO-activated zirconium and hafnium catalysts were active in ethylene polymerization. The zirconium catalyst 34/MAO gave a higher activity compared to the hafnium complex derived from the same ligand while the hafnium catalyst 35/MAO produced polyethylene with apparently higher molecular weight. This result is consistent with the fact reported previously that zirconocene catalysts provide higher activities while the hafnocene analogues produce polyolefins with greater molecular weights.[95] The difference in the polymerization behavior between Zrand Hf-based catalysts could be attributed to thermodynamically stronger σ-bonds between hafnium and the polymer chain (Hf-C), hindering not only the chain propagation but also the release of the chain, giving rise to less activities and higher molecular weight polyethylenes.[79] In line with this assumption, a recent study of hafnocene catalysts demonstrated that the activation energies for chain propagation and termination are significantly higher compared with zirconium catalysts.[96] The catalytic activity of 34/MAO in the homogeneous polymerization of ethylene is, as expected, lower, than the activities observed for the unbridged bis-indenyl metallocene complex[77] and that of the single atom bridged metallocene complexes such as -CH2- [97,98], -Me2C-[97,99], and -Me2Si-[29,85] bridged species. Similar results are observed when comparing the activity of 34/MAO with the widely known ethylidene bridged catalyst precursor,[100,101] rac-[Et(Ind)2)]ZrCl2 ("Brintzinger catalyst"). However, in terms of molecular weight, catalyst 34/MAO produces the polyethylene with the highest molecular weight compared with the above mentioned catalysts (except the Me2Sibridged one). The comparatively lower activity of 34/MAO can be rationalized by the existence of the 4 atoms-bridge, 1,2-bis(dimethylsilyl)phenylene, incorporating 2 C and 2 Si atoms. This rigid and long bridge resulted in a smaller dihedral angle and thus the zirconium center becomes more shielded. From the crystal structure data of complex 34/MAO (Scheme 37, Table 9), the value of the dihedral angle was determined to 51.4°, whereas the dihedral angle reported for CH2-, Me2C-, Me2Si-, and C2H4-bridged metallocene complexes are 72.4°, 70.9°, 61.6° and 62.1°. A greater value of the dihedral angle between the ligand planes enhances the activity in olefin polymerization by increasing the reaction space of the metal center.[87] General part____________________________________________________________ 62 Catalyst 34 exhibited a far better catalytic performance in terms of both activity and molecular weight compared with the known metallocene catalysts comprising 4-atombridges such as o-xylidene-bridged[88] and (-Me2Si-CH2-CH2-Me2Si-)-bridged[102] catalysts. This distinction could be explained by the favourable replacement of the two methylene groups with two dimethylsilyl groups in 34. Changing the metal centre in this catalyst system seems to have no influence on the melting points and crystallinity values of the polyethylenes. General part____________________________________________________________ 63 2.3 2,2’-Bis(methylene)biphenylidene-bridged 1-indenyl complexes of group (IV) metals 2.3.1 General remarks The activity and stereoselectivity of a metallocene-based catalyst in olefin polymerization can be significantly influenced by slight structural variations in the bridging unit (structure property relationship).[25] In this study, the synthesis of new ansa-titanocene, zirconocene, and hafnocene dichloride complexes is reported. The titled complexes comprise two indenyl or 3-methylindenyl ligands tethered, at the 1position, via a 2,2’-bis(methylene)-1,1’-biphenylidene bridge. Moreover, the catalytic behavior of the prepared ansa-metallocene catalysts in the homopolymerization of ethylene was investigated after activation with MAO. 2.3.2 Preparation of the ligand precursors 38 and 39 Diphenic acid was converted to the corresponding 2,2-bis(hydroxymethyl) biphenyl 36 according to a reported method.[103] Reduction of diphenic acid with lithium aluminium hydride in THF and purification by crystallization from a chilled methanol solution gave 36 in good yield. Treatment of the diol compound 36 with phosphorus tribromide in methylene chloride afforded 2,2'-bis(bromomethyl) biphenyl 37.[104] Compounds 38 and 39 were then obtained via reactions of 2,2'-bis(bromomethyl) biphenyl 37 with two equivalents of indenyllithium or 2-methylindenyllithium. Both reactions were carried out in THF at -78°C Thus the indenyl moieties were coupled through the 3-position (Scheme 40). General part____________________________________________________________ 70 display four signals at δ = 7.50 (d, 2H), 7.35-7.31 (m, 6H) 7.27-7.24 (t, 2H) and 7.227.17 (m, 6H) ppm. The protons located at the 2-positions of the indenyl rings (H2) generate the doublet at δ = 6.08 (d, 3J = 3.3 Hz, 2H) ppm while the protons at the 1positions of the indenyl rings (H1) produce the doublet at δ = 5.11 (d, 3J = 3.3 Hz, 2H) ppm. The protons of the methylene group (H7, H8) give the two signals at δ = 4.23 (d, J = 15.9 Hz, 2H) and 4.00 (d, J =16.2 Hz, 2H) ppm. Scheme 45: 1H NMR spectrum of complex 41. General part____________________________________________________________ 71 The 13C NMR spectrum of complex 41 (Scheme 46) shows two resonances at δ = 141.4 and 136.2 ppm attributed to the quaternary carbon atoms in the biphenyl bridging unit (C11 and C16). The two signals appearing at δ = 131.1 and 130.7 ppm are assigned to C5 and C6 of the indenyl rings. The remaining quaternary carbon atoms C8, C9 and C3 are identified with the signals appearing at δ = 127.9, 126.0, and 118.4 ppm. The signal at δ = 127.8 ppm can be assigned to the CH carbon atom C7 while the carbon atom C4 corresponds to the chemical shift at δ = 122.8 ppm. The aromatic CH-type carbon atoms in the biphenyl moiety (C12, C13, C14, and C15) are associated with the signals at δ =126.6, 126.2, 125.9, and 124.9 ppm. The signal at δ = 122.1 ppm is assigned to the carbon atom at the 2-positions of the indenyl groups (C2) while the signal at δ = 104.7 ppm is characteristic for the carbon atom at the 1-position of the indenyl moieties (C1). The benzylic CH2 carbon atoms (C10) appear at δ = 30.8 ppm. Scheme 46: 13C NMR spectrum of complex 41. General part____________________________________________________________ 72 The mass spectrum of complex 42 is also discussed as an example. In the mass spectrum of complex 42 (Scheme 47), the molecular ion peak appears at m/z = 658 with 14% intensity. The ion with m/z = 530 and 14% intensity can be explained by the loss of one methylene-indenyl fragment from the molecule, while the peak appearing at m/z = 410 with 78% relative intensity arises from the free bis(indenyl) ligand. Further loss of one indenyl fragment from the ligand gives rise to the peak at m/z = 293 with 47% intensity relative to the base peak. The base peak at m/z = 117 is generated by indanyl fragments. Scheme 47: Mass spectrum of complex 42. Table 15: 1H, 13C NMR and MS data for complexes 40-44. No. 1 H-NMR 13 C-NMR MS [m/z] (%) 40a) 7.64-7.61 m (2H) 7.40-7.36 m (2H) 7.26-7.19 m (8H) 7.18-7.12 m (4H) 5.99 br (2H) 5.12 br (2H) 4.30 d (J =15.4 Hz, 2H) 4.14 d (J =15.4 Hz, 2H) 142.4, 141.3, 132.8 (Cq) 131.5, 131.0, 129.6 (CH) 129.4 (Cq) 128.8, 128.4, 128.3, 127.1, 125.8, 123.3 (CH) 120.9 (Cq) 108.1 (CH) 32.6 (CH2) 526 M+ (12) 491 M+-Cl (52) 455 M+-Cl-HCl (15) 409 ligand-H (100) 293 (90) 41b) 7.50 d (3J =8.6 Hz, 2H) 7.35-7.31 m (6H) 7.27-7.24 t (2H) 141.4, 136.2 (Cq) 131.1,130.7 (CH) 127.9 (C q ) 570 M+ (45) 410 ligand (100) 293 (67) General part____________________________________________________________ 73 7.22-7.17 m (6H) 6.08 d (3J =3.3 Hz, 2H, C2-Ind) 5.11 d (3J =3.3 Hz, 2H, C1-Ind) 4.23 d (J =15.9 Hz, 2H) 4.00 d (J =16.2 Hz, 2H) 127.8, 126.6, 126.5, 126.2 (CH) 126.0 (Cq) 125.9, 122.8, 122.1 (CH) 118.4 (Cq) 104.7 (CH) 30.8 (CH2) 117 (96) 42a) 7.52-7.49 m (2H) 7.40-7.38 m (2H) 7.28-7.21 m (8H) 7.17-7.12 m (4H) 6.10 d (3J =3.4 Hz, 2H) 5.02 br (2H) 4.29 d (J =16 Hz, 2H) 4.15 d (J =16 Hz, 2H) 142.1, 137.0 (Cq) 131.7, 131.2, 128.3, 127.0, 126.9, 126.5, 126.3 (CH) 126.2 (Cq) 123.3, 122.2 (CH) 118.6, 116.5 (Cq) 101.8 (CH) 31.1 (CH2) 658 M+ (14) 529 (14) 410 ligand (78) 293 (47) 117 (100) 43a)c) 7.85-6.76 m (16H, Ar-H) 6.35 s (2H) 4.54 d (J =15.8 Hz, 2H, CH2) 4.03 d (J =15.8 Hz, 2H, CH2) 2.21 br (6H, CH3) 141.5, 138.3, 136.7 (Cq) 133.0, 131.1, 129.5 (CH) 129.1 (Cq) 127.7, 126.1, 125.8, 124.3, 123.0, 119.8 (CH) 117.0, 114.5 (Cq) 34.3 (CH2) 21.8 (CH3) 599 M+ (5) 527 M+-2Cl (13) 437 M+-ZrCl2-H (22) 307 (33) 131 (100) 44a)c) 7.95-7.08 m (8H, Ar-H) 6.85 s (1H) 4.58 d (J =16.3 Hz, 1H, CH2) 4.07 d,(J =16.3 Hz, 1H, CH2) 2.32 br (3H, CH3) 144.0, 140.1, 137.7 (Cq) 134.8, 132.1, 130.1 (CH) 129.0 (Cq) 128.8, 126.9, 126.4, 124.9, 123.5, 121.0 (CH) 117.3, 115.9 (Cq) 34.7 (CH2) 22.0 (CH3) n.d. a) δ (ppm) rel. CD2Cl2 (5.30 ppm, 1H NMR and 54.0 ppm, 13C NMR) at 298 K. b) δ (ppm) rel. CDCl3 (7.24 ppm, 1H NMR and 77.0 ppm, 13C NMR) at 298 K. c) Two isomers, data given for the most intensive signals. 2.3.6 Crystal structure of complex 41 The solid state molecular structure of the zirconocene complex 41 was determined by single crystal X-rays diffraction analysis. Crystals suitable for X-ray measurements were grown from a concentrated solution of a pentane/toluene mixture. The ORTEP view of the molecular structure of complex 41 is displayed in Scheme 48. The crystallographic General part____________________________________________________________ 74 data and structural refinement are presented in Table 16 while the selected bond lengths and angles are collected in Table 17. The arrangement of the two fivemembered ring centroids and the two chlorine atoms around the zirconium can be described as a pseudo tetrahedral geometry. The two indenyl ligands are aligned in a staggered conformation leading to an asymmetric rac orientation. In consistence with this, the values of the angles Cl1-Zr-Cl2 and Cen-Zr-Cen are 97.23° and 128.73°. These values correspond to those of previously characterized bridged metallocene complexes.[87] The bond lengths of the zirconium atom with the carbon atoms vary between 2.46-2.61 and 2.43-2.65 Å. for the two five-membered rings. The two phenyl rings of the biphenyl bridge are aligned in different planes with a dihedral angle of 79.8°. The value of the dihedral angle between the two planes of the five rings centroids is 53.72° which is smaller compared to the value known for Me2Si(Ind)2ZrCl2 (61.9°).[93] Scheme 48: The ORTEP diagram of the complex 41, ellipsoids are drawn in a 30% probability level. Hydrogen atoms are omitted for clarity. General part____________________________________________________________ 75 Table 16: Crystal data for complex 41. Formula C32H24Cl2Zr1 Space group I 41/a, Tetragonal Z 16 a (Å) 26.045(2) b (Å) 26.045(2) c (Å) 14.9997(10) α(°) 90 β(°) 90 γ(°) 90 Volume (Å3) 10175.1(13) F(000) 4640.0 Temperature (K) 293 Wave length (Å) 0.71069 Crystal dimensions (mm3) 0.30 × 0.28 × 0.20 Rint 0.125 [Sin( θ )/ λ ]max (Å-1) 0.600 Density (g cm-3) 1.4896 Absorption coefficient (mm-1) 0.662 Observed Criteria I > 3σ(I) No. of observed/all reflections 2054/4589 wRF(obs/all) 0.0435/0.0544 RF(obs/all) 0.0522/0.1801 Δ ρ max/ Δ ρ min (eÅ-3) 1.22/-1.46 GoF(obs/all) 1.59/2.00 General part____________________________________________________________ 76 Table 17: Selected bond lengths and angles Selected bond lengths[Å] C(23)-C(24) 1.5075(1) Zr-Cl(1) 2.4245(1) Zr-Cen1 2.2230(5) Zr-Cl(2) 2.4279(1) Zr-Cen2 2.2486(5) Zr-C(1) 2.6147(2) Cen1-Cen2 4.0317(2) Zr-C(6) 2.5122(1) Selected bonds angles[°] Zr-C(7) 2.4627(1) Cl(1)-Zr-Cl(2) 97.233(2) Zr-C(8) 2.4989(1) C(1)-C(9)-C(10) 124.566(4) Zr-C(9) 2.5434(1) C(9)-C(10)-C(11) 115.183(4) Zr-C(24) 2.5775(2) C(23)-C(24)-C(25) 123.387(4) Zr-C(25) 2.6504(1) C(22)-C(23)-C(24) 113.375(4) Zr-C(30) 2.6049(2) Cen1-Zr-Cen2 128.734(3) Zr-C(31) 2.4291(1) Cen (1) ^ Cen(2) 53.723(4) Zr-C(32) 2.4723(1) Ph(1) ^ Ph(2) 79.829(5) C(9)-C(10) 1.5092(1) 2.3.7 Ethylene polymerization studies of complexes 40-44 Complexes 40-44 are ansa-metallocene dichloride complexes of group IV metals (Ti, Zr, and Hf). The two indenyl ligands are tethered through the 3-positions via a 2,2’- bis(methylene)-1,1’-biphenylidene bridge. The general structure formula of the complexes is illustrated in Scheme 49. M C l C l R R Scheme 49: Structural formula of complexes 40-44. General part____________________________________________________________ 77 The catalytic activities of complexes 40-44 in the homogeneous polymerization of ethylene were investigated after activation with methylaluminoxane (M:Al = 1:2000). The experiments were conducted at a polymerization temperature of 60°C, 10 bar ethylene pressure, and in 250 ml of pentane for one hour. The produced polyethylene samples were analyzed by DSC and viscosimetry. The results are illustrated in Table 18. Table 18: Activities and polymer analysis results of catalysts 40-44 Complex No. Activity [kg PE/mol cat. h] DSC ∆Hm [J/g] Tm [°C] [α] Mη [g/mol] Ti C l C l 40 Inactive - - Zr C l C l 41 12460 148.1 135.0 0.51 355000 Hf C l C l 42 3810 144.9 135.2 0.5 310000 General part____________________________________________________________ 78 Zr C l C l 43 3010 145.1 135.4 0.5 485000 Hf C l C l 44 1020 n.d. n.d. In the series of complexes 40-44, the zirconium catalyst 41/MAO was the most active catalyst [12460 kg PE/mol cat. h] whereas the hafnium catalyst 42/MAO bearing the same ligand showed lower activity [3810 kg PE/mol cat. h]. The titanium complex 40 was inactive in ethylene polymerization under the prescribed conditions. This inactivity can be attributed to the instability of Ti(IV) complexes and their tendency to reduction to give inactive Ti(III) species at conventional polymerization temperatures.[105] On going from 41/MAO to the 3-methyl substituted zirconium catalyst 43/MAO, a marked decrease in activity is observed (from 12460 to 3010 kg PE/mol cat. h). A similar decrease in activity has been observed when using the 3-alkyl substituted Me2Sibridged catalysts [Me2Si(3-R-Ind)2]ZrCl2[85]. In this regard, the drop in activity can be attributed to the increase of steric congestion around the metal center caused by the two methyl groups at the indenyl ligands. Across the series, changing the metal and introduction of methyl groups proved to have no influence on the thermal properties and the crystallinities of the produced polymers. By comparing the catalytic performance of 41/MAO with the previously reported relevant ansa-catalysts, there is a good correlation between the catalytic activity of the ansacatalysts and their dihedral angles. The dihedral angle of complex 41 is 53.7° (Table 17) which is smaller than that of the CH2-bridged (72.4°) and the Me2C-bridged metallocene General part____________________________________________________________ 79 complexes (70.9°). However, catalyst 41/MAO exhibited higher catalytic activity (12460 kg PE/mol cat. h) than the CH2-bridged catalyst (6900 kg PE/mol cat. h)[97] and the Me2C-bridged catalyst (10000 kg PE/mol cat. h)[97]. This could be originated to the thermal instability of the single carbon atom bridged metallocene complex. Moreover, catalyst 41/MAO produces a polyethylene with higher molecular weight compared with the above mentioned single carbon atom bridged metallocene complexes. Additionally, catalyst 41/MAO showed a better catalytic performance in terms of both activity and molecular weight of the produced polymers compared with the o-xylylene-[88] and the 1,2-bis(dimethylsilyl)ethylene-bridged[102] metallocene catalysts. The catalytic activity performed by 41/MAO is significantly lower than the activity reported for the unbridged catalyst (29300 kg PE/mol cat. h)[77], the Me2Si-bridged catalyst (19870 kg PE/mol cat. h)[85], and the ethylidene-bridged catalyst[101] (16500 kg PE/mol cat. h) due to the remarkable difference in the dihedral angle values and thus the accessibility of the metal center. General part ___________________________________________________________ 86 Table 19: 1H and 13C NMRa spectra of complexes 46 and 47. No. 1H NMR 13C NMR 46 7.78 d (3J = 8.2 Hz, 4H, Ar-H) 7.33 d (3J = 8.2 Hz, 4H, Ar-H) 7.20-7.17 t (4H) 7.00-6.94 m (8H) 6.87 d (3J = 7.3 Hz, 4H) 2.15 s (6H, Ar-CH3) 0.70 s (12H, Si(CH3)2) 138.3, 137.4, 136.3 (Cq) 134.0, 128.3 127.5, 126.2, 124.0, 123.3 (CH) 120.4, 102.0 (Cq) 21.3, (CH3) 0.5 (Si(CH3)2) 47 7.81 d (3J = 9.1 Hz, 4H, Ar-H) 7.39 d (3J = 9.1 Hz, 4H, Ar-H) 7.21-7.12 t (4H) 7.05-6.89 m (8H) 6.85 d (3J = 7.3 Hz, 4H) 2.15 s (6H, Ar-CH3) 0.70 s (12H, Si(CH3)2) 139.7, 137.9, 136.1 (Cq) 134.6, 128.4 127.7, 126.5, 124.2, 123.1 (CH) 120.9, 103.1 (Cq) 21.4, 0.5 (CH3) 0.5 (Si(CH3)2) a δ (ppm) rel. CDCl3 (7.24 ppm, 1H NMR and 77.0 ppm, 13C NMR) at 298 K. 2.4.6 Ethylene polymerization experiments with complexes 45 and 46 Complexes 46 and 47 were tested for ethylene polymerization after activation with methylaluminoxane (MAO) with a M:Al ratio of 1:2000. The experiments were conducted at 60°C and 10 bar ethylene pressure in 250 ml of pentane. These complexes were found to be inactive in polymerization reactions. The same result was reported by Alt et al.[107] using unbridged 9-substituted phenyl fluorenyl complexes for the polymerization of ethylene and propene. The inertness of the fluorenyl complexes 46 and 47 could be attributed to the thermal instability resulting from ring-slippage reactions changing the hapticity of the fluorenyl rings from η5→ η3→ η1[106] The bulkiness of the substituents may also be a reason for the inactivity of 46 and 47. Experimental part________________________________________________________ 87 3. Experimental Part 3.1 General All reactions were carried out under an inert gas atmosphere of pure oxygen-free argon using standard Schlenk techniques. n-Pentane, n-hexane, diethyl ether, toluene, and tetrahydrofuran were purified by distillation over Na/K alloy. Diethyl ether was additionally distilled over lithium aluminum hydride. Toluene was additionally distilled over phosphorus pentoxide. Methylene chloride and carbon tetrachloride were dried over phosphorus pentoxide. Deuterated organic solvents (CDCl3, CD2Cl2, and C6D6) for NMR spectroscopy were purchased from Euriso-Top and stored over molecular sieves (3 Å). Argon (5.0) and ethylene (3.5) were purchased from Rieβner Company. Methylaluminoxane (10% in toluene) was purchased from Chemtura Europe Limited (Bergkamen). All other starting materials were commercially available and used without further purification. 3.2 NMR spectroscopy NMR spectra were recorded with Bruker ARX (250 MHz), Varian Inova (300 MHz) or Varian Inova (400 MHz) spectrometers. All spectra were recorded at 298 K. In the 1HNMR spectra, the chemical shift of the residual proton signal of the solvent was used as a reference (δ = 7.24 ppm for chloroform, δ = 5.32 ppm for methylene chloride, δ = 7.16 ppm for benzene). In the 13C-NMR spectra, the chemical shift of the solvent was used as a reference (δ = 77.0 ppm for chloroform-d1, δ = 54.0 ppm for methylene chloride-d2, δ = 128.0 ppm for benzene-d6). 3.3 GC/MS GC/MS spectra were recorded with a Thermo FOCUS gas chromatograph combined with a DSQ mass detector. A 30 m HP-5 fused silica column (internal diameter 0.32 mm, film 0.25 µm and flow 1 ml/min) was used and helium (4.6) was applied as carrier gas. The measurements were recorded using the following temperature program: Starting temperature: 50 °C, duration: 2 minutes; Heating rate: 20 °K/minute, duration: 12 minutes; Experimental part________________________________________________________ 88 Final temperature: 290 °C, duration: 27 minutes. 3.4 Mass spectrometry Mass spectra were recorded with a VARIAN MAT CH-7 instrument (direct inlet, EI, E = 70 EV) and a VARIAN MAT 8500 spectrometer at the Zentrale Analytik of the University of Bayreuth. Matrix Assisted Laser Desorption Ionization Time-of-Flight Mass Spectrometry (MALDI-TOF-MS) measurements were performed on a Bruker Daltonic Reflex TOF using graphite as the matrix. The laser intensity was set to 60-65 %. The sample solutions were prepared in toluene or methylene chloride at a concentration of 1 mg/ml. 3.5 Elemental analysis Elemental analyses were performed with a Vario EL ІІІ CHN instrument. Therefore, 4-6 mg of the complex were weighed into a standard tin pan. The tin pan was carefully closed and introduced into the auto sampler of the instrument. The values of C, H and N were calibrated using acetamide as a standard. 3.6 DSC analysis DSC analyses were performed on a Mettler Toledo DSC/SDTA 821e instrument. The polymer samples were prepared by enclosing 4-6 mg of the polymers in standard aluminum pans. The samples were introduced into the auto sampler of the instrument and the measurements were recorded using the following temperature program: First heating phase: from 50 °C to 160 °C (10 °C/minute); Cooling phase: 160 °C to 50 °C (10 °C/minute); Second heating phase: from 50 °C to 160 °C (10 °C/minute). Liquid nitrogen was used as a cooling medium. Melting enthalpies and melting points were taken from the second heating phase. The values were calibrated using indium as a standard (m.p. 429.78 K, Hm = 28.45 J/g). Experimental part________________________________________________________ 89 3.7 Viscosimetry analysis Viscosimetry analyses for the determination of the viscosity average molecular weights [Mη] of the polyethylene samples were performed on an Ubbelohde precision capillary viscometer in cis/trans-decalin at 135 ± 0.1 °C. For the preparation of the sample solutions, an amount of 50 mg of the polymer was dissolved in decalin (45 ml) by heating for 3 hours at 135 °C. Mη values were determined by comparing the obtained values with calibration curves available for different polymer concentrations. 3.8 Single crystal X-rays diffraction The crystal structure analysis of complex 34 was performed with a STOE-IPDS II diffractometer equipped with an Oxford Cryostream low-temperature unit. The crystal structure analysis of complexes 35 and 41 was performed with a MarIP MAR345DTB devise (Mo-Kα radiation, γ = 0.71073 Å). Crystal data: Complex 34: Yellow cubic crystals, crystal system is triclinic; space group is P-1; a = 9.1925 (18) Å, b = 10.110(2) Å, c = 15.726(3) Å; α = 91.36(3)°, β = 100.26(3)°, γ = 111.24(3)°; volume is 1333.6(5) Å3; d (calc) = 1.451 g/cm3; wavelength = 0.71073 Å; absorption coefficient = 0.718 mm-1 ; F(000) = 596; reflections collected 6271; independent reflections 4372 [R(int) = 0.0396]; Goodness-of-fit = 0.938; R indices (R1 = 0.0547, wR2 = 0.1022). Complex 35: Yellow cubic crystals, crystal system is triclinic; space group is P-1; a = 10.0503(18) Å, b = 9.1624 (16) Å, c = 15.643(3) Å; α = 91.567(19)°, β =100.285(18)°, γ = 111.167(8)°; volume is 1315.0(4) Å3; d = 1.6918 g/cm3; wavelength = 0.71069 Å; absorption coefficient = 4.276 mm-1 ; F(000) = 660; no. of all reflections 11018; no. of observed reflections 8001 [R(int) = 0.056]; GOF (obs/all) = 1.01/-0.87; R(F) = 0.0422 (wR(F) = 0.0395). Experimental part________________________________________________________ 90 Complex 41: Yellow cubic crystals, crystal system is tetragonal; space group is I 41/a; Z = 16; a = b = 26.045 (2) Å, c = 14.9997(10) Å,; α = β = γ = 90°; volume is 10175(13) Å3; d = 1.4896 g/cm3; wavelength = 0.71069 Å; absorption coefficient = 0.662 mm-1 ; F(000) = 4640; no. of all reflections 4589; no. of observed reflections 2054 [R(int) = 0.125]; GOF (obs/all) = 1.59/2.00; R(F) = 0.0522 (wR(F) = 0.0435). 3.9 Polymerization of ethylene Few milligrams of the complexes were dissolved or suspended in toluene (5-10 ml) and mixed with the appropriate amount of methylaluminoxane (MAO). The activated complexes were suspended in pentane (250 ml) in a 1l Schlenk flask and then transferred under argon to a 1l Büchi autoclave. The temperature of the thermostat was adjusted to the desired value and an ethylene pressure of 10 bar was applied for one hour. After releasing the pressure, the obtained polymer was filtered over a frit, washed with dilute hydrochloric acid, water, and finally with acetone and dried under vacuum. 3.10 Synthesis procedures 3.10.1 General synthesis of the arylchlorodimethylsilane compounds 1-4 A solution of a 4-substituted 1-bromobenzene (15.0 mmol) in THF (40 ml) was added dropwise at room temperature to a mixture of magnesium powder (20.0 mmol) and dichlorodimethylsilane (52.0 mmol) in THF (100 ml). After the addition was complete, the flask content was heated at reflux for approximately 4 hours and subsequently stirred at room temperature overnight. The solvent and the excess dichlorodimethylsilane were removed in vacuo (25 mbar). The residue was extracted three times with n-pentane (300 ml) and the excess magnesium and magnesium salts were filtered off. The combined pentane solutions were concentrated under vacuum and the residue was distilled under reduced pressure. The compounds 1-4 were obtained as colorless liquids in 60-75% yields. Experimental part________________________________________________________ 91 3.10.2 General synthesis of the 1-(aryldimethylsilyl)indenyl compounds 5-8 An amount of 10 mmol of n-butyllithium (1.6 M in hexanes) was added to 10 mmol of indene dissolved in 100 ml of diethyl ether at 0°C. The solution was stirred for 2 hours at room temperature. The solution was again cooled to 0 °C and then an equivalent amount of the appropriate arylchlorodimethylsilane (1-4) in diethyl ether was added slowly. The resulting solution was stirred overnight at room temperature. The solvent was removed in vacuo and the residue was extracted twice with pentane. The suspension was filtered and passed through silica gel. After removing the solvent, compounds 5-8 were obtained as yellow oily liquids in 70-80% yields. 3.10.3 Synthesis of 2-bromoindene To a mixture of indene (200 mmol), distilled water (15 ml) and dimethyl sulfoxide (70 ml) was added portion wise an amount of 210 mmol of N-bromosuccinimide. The resulting orange solution was stirred for 10 hours at room temperature, hydrolyzed with chilled water (100 ml), and extracted with diethyl ether (3 x 100 ml). The combined extracts were dried with magnesium sulphate and concentrated to give crystals of 2bromoindan-1-ol upon standing overnight at -24 °C. The obtained 2-bromoindan-1-ol (120 mmol) was suspended in 100 ml of toluene and mixed with a catalytic amount of para-toluenesulfonic acid monohydrate. The mixture was heated at reflux for 12 hours, and water was removed by a Dean-Stark apparatus. The resulting dark brown suspension was filtered and the volatiles were removed under vacuum. The residue was passed through silica gel using pentane as eluent, then the solvent was evaporated, and the crude product was distilled in vacuo. 2-Bromoindene was finally obtained as yellow crystals in 55% yield. 3.10.4 General synthesis of the 2-(aryldimethylsilyl)indenyl compounds 9-12 Magnesium powder (18.0 mmol) and 15 ml of THF were placed in a 250 ml flask. A solution of 2-bromoindene (15.0 mmol) in 40 ml of THF was added over a period of 40 minutes using a pressure equalizing-addition funnel. After the addition was completed, the reaction mixture was heated at reflux for 4 hours. The unreacted magnesium was filtered off and the violet-red coloured Grignard solution was added dropwise to a stirred Experimental part________________________________________________________ 92 solution of the appropriate arylchlorodimethylsilane 1-4 (15.0 mmol) and 50 ml of THF at room temperature. The resulting mixture was stirred for another 12 hours. The solvent was removed under vacuum and the residue was extracted twice with n-pentane. The suspension was filtered and passed through silica gel. After removing the solvent, compounds 9-12 were obtained as red or yellow oily liquids in 65-80% yields. 3.10.5 General synthesis of the transition metal complexes 13-24 An amount of 2 mmol of the appropriate 1or 2-substituted indenyl compound was dissolved in 50 ml of diethyl ether. To this solution, n-butyllithium (2 mmol 1.6 M in hexanes) was added at -78 °C. This solution was allowed to warm to room temperature and stirred for further 3 hours. Subsequently, this mixture was transferred to a suspension of zirconium tetrachloride (1 mmol) or hafnium tetrachloride (1 mmol) in 20 ml of diethyl ether at -78 °C. The mixture was slowly allowed to come to room temperature and stirred for further 24 hours. Diethyl ether was removed and toluene (100 ml) was added. The toluene suspension was filtered, the volume of the filtrate was reduced, and the complexes were precipitated by addition of n-pentane. After filtration, the precipitate was washed several times with n-pentane and dried in vacuo to obtain the desired complexes as coloured powders in 60-70% yields. Table 20: Elemental analysis data of complexes 13-24. No. Cex p % Ctheor% Hex p % Htheor% 13 62.21 62.76 5.41 5.56 14 54.93 55.70 4.52 4.93 15 59.10 59.97 4.88 5.31 16 52.75 53.50 4.35 4.74 17 58.15 58.60 4.82 4.63 18 51.20 52.08 4.25 4.11 19 62.05 62.76 5.22 5.56 20 54.01 55.70 5.30 4.93 21 58.99 59.97 5.04 5.31 22 52.66 53.50 4.37 4.74 23 58.03 58.60 4.99 4.63 24 51.66 52.08 4.55 4.11 Experimental part________________________________________________________ 93 3.10.6 Preparation of 1,2-bis(chlorodimethylsilyl)benzene (26) A solution of 1,2-dibromobenzene (16.5 g, 70 mmol) in 70 ml of THF was added slowly to a stirred mixture of magnesium powder (3.7 g, 147 mmol) and chlorodimethylsilane (14.0 g, 147 mmol) in 15 ml of THF. The mixture was refluxed for 3 hours. After cooling, the solution was decanted from solid magnesium salts and the solvent was removed under vacuum. The residual oil was extracted and washed with a large amount of nhexane. After removal of the solvent, the residue was purified by distillation under reduced pressure to afford 1,2-bis(dimethylsilyl)benzene (25) in 60% yield. Compound 25 (20 mmol) was mixed with 40 ml of dry carbon tetrachloride and 0.2 g of palladium dichloride in a 100 ml two necked flask equipped with a reflux condenser. The mixture was refluxed for 3 hours and excess carbon tetrachloride and chloroform were removed by evacuation. The residual oil was distilled at 85 °C (1 mbar) to obtain compound 26 in 90% yield. 3.10.7 Preparation of 2-methylindene (28) A quantity of 48 mmol of methyl magnesium bromide (3M in ether) was added dropwise to a solution of 2-indanone (6.0 g, 48 mmol) in 100 ml of diethyl ether. Afterwards, the resulting mixture was stirred for 2 hours at room temperature and then hydrolyzed with 150 ml of diluted hydrochloric acid (1.0 M). The ether containing layer was separated and the aqueous layer was extracted four times with ether (each 100 ml). The organic extracts were combined, dried over sodium sulphate, and the solvent was removed with a rotary evaporator. The residue was mixed with 100 ml of toluene and a catalytic amount of para-toluenesulfonic acid monohydrate (PTSA). The suspension was refluxed for 3 hours in a Dean-Stark apparatus. The resulting dark brown suspension was filtered and the volatiles were removed under vacuum. The residue was passed through silica gel using pentane as eluent. The solvent was removed by distillation at atmospheric pressure to afford 2-methylindene as a light yellow oil in 40% yield. 3.10.8 General synthesis of the ligand precursors 27, 29, and 30 An amount of 16 mmol of indene, 2-methylindene, or fluorene was dissolved in 70 ml of diethyl ether and cooled to -5 °C. Subsequently, n-butyllithium (16 mmol) was added Experimental part________________________________________________________ 94 dropwise over 30 minutes followed by stirring at room temperature for 2 hours. To this mixture, another solution of 1,2-bis(chlorodimethylsilyl)benzene (8 mmol) in 50 ml of diethyl ether was added dropwise from a dropping funnel equipped with a pressure equalizer. After the addition was completed, the solution was stirred for one hour and filtered from the solid lithium chloride. The solution was evaporated and methylene chloride (200ml) was added. After filtration, the solvent was removed under high vacuum. Compounds 27 and 29 were obtained as heavy brownish waxy materials in 8090% yields, while compound 30 was obtained as a solid which was further purified by crystallization from methylene chloride at -24 °C. 3.10.9 Preparation of 1,3-bis(chlorodimethylsilyl)benzene (32) A mixture of 1,3-dibromobenzene (19.0 g, 80 mmol) and diethoxydimethylsilane (166 mmol) in THF (40 ml) was added over a period of 1 hour to magnesium powder (170 mmol) suspended in 20 ml of THF. After the mixture was heated to reflux for 3 hours and then cooled, the resulting magnesium salts were filtered off. The solvent was evaporated and the residue was distilled under reduced pressure to give pure 1,3bis(ethoxydimethylsilyl)benzene (31) in 70% yield. An amount of 50 mmol of compound 31 was placed in a 100 ml two-necked flask and mixed with 0.2 ml of pyridine and 30 ml of acetyl chloride. After the mixture was heated to reflux for 72 hours, excess acetyl chloride and the resulting ethyl acetate were evaporated, and the residue was distilled under reduced pressure to give the desired compound as a colourless liquid in 95% yield. 3.10.10 Preparation of 1,3-bis(inden-1-yldimethylsilyl)benzene (33) To a solution of indene (23 mmol) in diethyl ether (100 ml) at 0 °C, n-butyllithium (23 mmol) was added dropwise. The resulting solution was stirred for 2 hours at room temperature till gas evolution had ceased. A solution of 1,3bis(chlorodimethylsilyl)benzene (32) (11.5 mmol) in diethyl ether (40 ml) was added over 1 hour at room temperature. After the addition was completed, the mixture was stirred for further 4 hours and distilled water (100 ml) was added. The organic layer was separated and the aqueous layer was extracted with ether (2×100 ml). The organic Experimental part________________________________________________________ 95 portion was dried over sodium sulphate, and the volatiles were removed under high vacuum to obtain the desired compound as a brown coloured oil in 70% yield. 3.10.11 General synthesis of the transition metal complexes 34 and 35 A quantity of 2 mmol of 1,2-bis(1-indenyldimethylsilyl)benzene (27) was dissolved in 50 ml of THF and cooled to -78 °C. To this solution, n-butyllithium (4 mmol, 1.6 M in hexanes) was slowly syringed. This solution was allowed to warm to room temperature and stirred for further 3 hours till no more gas evolution was observed. The resulting solution was transferred via cannula to a solution of zirconium tetrachloride (2 mmol) or hafnium tetrachloride (2 mmol) in 20 ml of THF at -78 °C. After warming to room temperature, the mixture was subsequently stirred for 48 hours at 60-65 °C. The solvent was removed in vacuo and toluene (100) ml was added. The toluene suspension was filtered, the clear solution was concentrated to approximately 5 ml and the complexes were precipitated by the addition of n-pentane. After filtration, the precipitate was washed several times with n-pentane and dried in vacuo to obtain the desired complexes as yellow powders in 70-75% yields. Both complexes were crystallized from concentrated pentane/toluene mixtures to obtain yellow cubic crystals suitable for X-ray crystallography analysis. Table 21: Elemental analysis data of complexes 34 and 35. No. Cex p % Ctheor% Hex p % Htheor% 34 57.65 57.70 4.79 4.84 35 49.75 50.19 4.25 4.21 3.10.12 Preparation of 2,2’-bis(bromomethyl) biphenyl (37) A solution of diphenic acid (7.74 g, 32 mmol) in 40 ml of THF was added over 40 minutes to a suspension of lithium aluminum hydride (2.508 g, 66.0 mmol) and 50 ml THF at 0 C°. After the addition, the flask contents were heated under reflux over night. Then, the reaction was carefully hydrolyzed with water (75 ml) and a 15% sodium hydroxide solution (75 ml). Diethyl ether (100 ml) was added and the organic phase was separated, dried over sodium sulphate, and evaporated to dryness. The residue was Summary______________________________________________________________ 102 deprotonation of the ligand precursors using n-BuLi followed by reactions of the corresponding metal tetrachloride. M Cl Cl RR R = H, Me; M = Ti, Zr, Hf The series of the unsubstituted ansa-complexes (R = H) showed higher activities compared to the methyl substituted counterparts. The zirconium complex 42 showed the highest activity (12460 kg PE/mol cat. h) followed by the hafnium complex 43 (3820 kg PE/mol cat. h) while the titanium complex 40 was inactive which could be attributed to thermal instability and a tendency to decomposition. The introduction of methyl groups at the 1-position of the indenyl moieties leads to a remarkable decrease in the activity probably due to steric hindrance resulting from the two methyl groups. The obtained polyethylenes were analyzed by differential scanning calorimetry (DSC) and viscosimetry. A series of symmetric unbridged 9-substituted dimethyl(tolyl)silyl-fluorenyl complexes of zirconium and hafnium was synthesized, characterized and tested in catalytic ethylene polymerization reactions. These complexes were inactive in the MAO assisted polymerization of ethylene. This could be referred to their instability towards ringslippage reactions changing the hapticity (η5→ η3→ η1) of the fluorenyl rings. Zusammenfassung______________________________________________________ 103 5. Zusammenfassung Die Ziel der vorliegenden Arbeit waren die Synthese und Charakterisierung neuartiger verbrückter und unverbrückter Bis(indenyl)-Komplexe von Metallen der IV. Nebengruppe und die Untersuchung ihrer katalytischen Eigenschaften bei der homogenen Ethenpolymerisation. Zu diesem Zweck wurden verschiedene Ligandenvorstufen synthetisiert, wie z.B. Silylindenyl-Verbindungen mit Substituenten in 1und 2-Position, 1,2-Bis(inden-1-yldimethylsilyl)benzol, 2,2’-Bis(inden-1-ylmethyl)-1,1’- biphenyl und Fluorenylderivate mit Silylsubstituenten in 9-Position. Die entsprechenden Dichlorid-Komplexe der Gruppe-IV-Metalle wurden synthetisiert und als Katalysatorvorstufen für die Ethenpolymerisation eingesetzt. Der erste Teil dieser Arbeit beschreibt die Synthese symmetrischer, unverbrückter Zirkoniumund Hafniumkomplexe mit Silylindenyl-Liganden, die Substituenten in 1und 2-Position tragen, und die Untersuchung ihres Potentials für die Ethenpolymerisation. Silylindenyl-Verbindungen mit Substituenten in Position 1 resultierten aus der Reaktion der entsprechenden Monochlorsilane mit Indenyllithium. Silylindenyl-Ligandvorstufen mit Substituenten in Position 2 wurden durch die GrignardReaktion von Aryldimethylchlorsilanen mit 2-Brominden erhalten. Zusammenfassung______________________________________________________ 104 Um die entsprechenden Dichlorid-Komplexe zu erhalten wurden zunächst die substituierten Indenylverbindungen mit n-Butyllithium deprotoniert und anschließend mit Zirkoniumoder Hafniumtetrachlorid in Diethylether umgesetzt. RSi R Si R Si M Cl Cl 2 1) 2 n-BuLi, Et2O, -78°C - rt - 2 BuH 2) MCl4, Et2O, -78°C - rt - 2 LiCl R = Me, OMe, F M= Z r , Hf Si RSi R Si R M Cl Cl 2 1) 2 n-BuLi, Et 2 O, -78 °C-rt -2 BuH 2) MCl 4 , Et 2 O, -78 °C-rt -2 LiCl R = Me, OMe, F M= Z r , H f Die so hergestellten Komplexe wurden mit MAO als Cokatalysator für die Ethenpolymerisation eingesetzt, um den Einfluss des Substitutionsmusters auf die Aktivität zu untersuchen. Komplex 17 mit einem Fluoratom in para-Position der Silylphenyl-Gruppe zeigte dabei die höchste Aktivität (7740 kg PE/mol Kat. h) unter den Metallocenkomplexen 13-18 mit Substituenten in Position 1. Zusammenfassung______________________________________________________ 105 Im Gegensatz dazu wies Komplex 16 mit einer Methoxygruppe an derselben Position die geringste Aktivität (50 kg PE/mol Kat. h) auf. Ein ähnliches Verhalten war bei den Komplexen mit Substituenten in Position 2 (19-24) zu beobachten. Grundsätzlich waren jedoch die Komplexe mit Substituenten in Position 1 sehr viel aktiver als deren Analoga mit Substituenten in Position 2. Die erhaltenen Polymere wurden mit Hilfe von „differential scanning calorimetry“ (DSC) und Viskosimetrie-Messungen charakterisiert. Der zweite Teil der Arbeit beschäftigt sich mit der Synthese und Charakterisierung einer neuen Klasse von Zirkoniumund Hafniumkomplexen mit ansa-Bis(indenyl)-Liganden, in welchen die beiden Indenylreste durch eine 1,2-Bis(dimethylsilyl)benzol-Brücke in den Positionen 1 und 1’ verbunden sind. Die Ligandenvorstufen wurde in drei Schritten hergestellt. Nach der Grignard-Reaktion von Chlordimethylsilan mit 1,2-Dibrombenzol und der PdCl2-katalysierten Chlorierung wurde die Ligandenvorstufe durch die Umsetzung mit Indenyllithium erhalten. Si Si Br Br 1) Mg, 2 Me2SiHCl -2 MgBrCl 2) PdCl2, CCl4 -CHCl3 3) [Ind]-Li+ -2 LiCl Die entsprechenden Zirkoniumund Hafniumkomplexe resultierten aus der Deprotonierung der Bis(indenyl)-Verbindung mit n-BuLi gefolgt von einer Umsetzung mit dem entsprechenden Metalltetrachlorid in THF. Zusammenfassung______________________________________________________ 106 SiSi M Cl Cl Si Si 1) 2 n-BuLi / THF, -78 °C 2) MCl4 / THF, 60 °C, 72 h -2 LiCl -2 BuH M = Zr, Hf Die Festkörperstrukturen beider Komplexe wurden mit Hilfe von KristallStrukturanalysen aufgeklärt. Beide Komplexe erwiesen sich als sehr aktiv bei der Ethenpolymerisation. Der Zirkonium-Komplex 34 war dabei noch aktiver (7610 kg PE/mol Kat. h) als sein Hafnium-Analogon 35 (3590 kg PE/mol Kat. h). Weiterhin wurde ein zweiter Strukturtyp von ansa-Metallocenekomplexen synthetisiert und dessen Eigenschaften bei der homogenen Ethenpolymerisation untersucht. Das Ligandsystem besteht aus zwei Indenylgruppen, die über eine 2,2’-DimethylbiphenylBrücke an den Positionen 3 und 3’ verbunden sind. Die Reduktion von Diphensäure mit Lithiumaluminiumhydrid (LiAlH4) gefolgt von den Reaktionen mit Phosphortribromid und Indenyllithium lieferte die Ligandvorstufe. Um die entsprechenden Komplexe der Gruppe-IV-Metalle zu erhalten, wurden zunächst die substituierten Indenylverbindungen mit n-Butyllithium deprotoniert und anschließend mit den entsprechenden Metalltetrachloriden umgesetzt. M Cl Cl RR R = H, Me; M = Ti, Zr, Hf Zusammenfassung______________________________________________________ 107 Im Vergleich zu den methylsubstituierten Derivaten (R = Me) zeigten die unsubstituierten ansa-Komplexe (R = H) höhere Aktivitäten. Die höchste Aktivität wurde dabei vom Zirkoniumkomplex 42 erzielt (12460 kg PE/mol Kat. h) gefolgt vom Hafniumkomplex 43 (3816 kg PE/mol Kat. h). Der Titan-Komplex 40 hingegen war inaktiv, was durch dessen thermische Instabilität und Tendenz zur Zersetzung begründet werden könnte. Die Einführung von Methylsubstituenten in Position 1 der Indenylgruppen führt zu einem beachtlichen Rückgang der Aktivität. Der Grund dafür liegt wahrscheinlich in der sterischen Hinderung durch die beiden Methylgruppen. Die erhaltenen Polyethylene wurden mit Hilfe von „differential scanning calorimetry“ (DSC) und Viskosimetrie-Messungen charakterisiert. Weiterhin wurden eine Reihe symmetrisch unverbrückter (Tolyl)fluorenyl-Zirkoniumund Hafniumkomplexe synthetisiert, charakterisiert und für die Ethenpolymerisation untersucht. Diese Komplexe erwiesen sich dabei als inaktiv in Kombination mit MAO. Der Grund für deren Inaktivität ist sehr wahrscheinlich in “ring-slippage“-Reaktionen zu suchen, die mit wechselnden Haptizitäten (η5→ η3→ η1) der Fluorenylliganden einhergehen. Diese Reaktionen sind allgemein bekannt für unverbrückte Fluorenylkomplexe. References____________________________________________________________ 108 6.References [1] S. S. Ivanchev, Russ. Chem. Rev., 2007, 76 (7), 617. [2] S. Neufeldt, Chronik der Chemie 1800-1980, VCH, Weinheim, 1987. [3] I. Strube, Geschichte der Chemie, Verl. der Wissenschaften, Berlin, 1987. [4] R. B. Seymour, T. Cheng, History of Polyolefins, 1986, Riedel Pub. Co., New York. [5] J. P. Hogan, R. L. Banks, Belg. Pat. 530617, 1955; U. S. 2825721, 1958. [6] K. Ziegler, H. Gellert, H. Kühlhorn, H. Martin, K. Meyer, K. Nagel, H. Sauer, K. Zosel, Angew. Chem. 1952, 64, 323. [7] K. Ziegler, H. Kühlhorn, H. Breil, H. Martin, Angew. Chem. 1955, 67, 541. [8] G. Natta, Angew. Chem. 1956. [9] K. Ziegler, Angew. Chem. 1964, 76, 545. [10] G. Natta, Angew. Chem. 1964, 76, 553. [11] V. Warzelhan, D. Scherzer, Int. Symp. On Engineering Plastics, 2007, Aug. 19– 24, Urumqi, Chinese Academy of Sciences, Beijing, China. [12] W. Kaminsky, Rap. Rev. Rep. 1999, 10, 115. [13] D. S. Breslow, N. R. Newburg, J. Am. Chem. Soc. 1957, 79, 5072. [14] G. Natta, P. Pino, G. Mazzanti, V. Giannini, J. Am. Chem. Soc. 1957, 79, 2975. [15] H. Sinn, W. Kaminsky, H. J. Vollmer, Angew. Chem. 1980, 92, 396. [16] H. Sinn, W. Kaminsky, Adv. Organomet. Chem. 1980, 99, 18. [17] Y. Koide, S.G. Bott, A. R. Barron, Organometallics 1996, 15. 2213. [18] W. Kaminsky, Macromol Chem. Phys. 1996, 197, 3907. [19] H. Sinn, Makromol. Chem., Makromol. Symp. 1995, 97, 27. [20] M. R. Mason, J. M. Smith, S. G. Bott, A. R. Barron, J. Am. Chem. Soc. 1993, 115, 4971. [21] P. Cossee, J. Catal. 1964, 3, 80. [22] E. J. Arlman, J. Catal. 1964, 3, 89. [23] E. J. Arlman, P. Cossee, J. Catal. 1964, 3, 99. [24] J. Zhang et al., Coord. Chem. Rev. 2006, 250, 95. [25] H. G. Alt, A. Köppl, Chem. Rev. 2000, 100, 1205. References____________________________________________________________ 109 [26] F. R. W. P. Wild, L. Zsolnai, G. Huttner, H. H. Brintzinger, J. Organomet. Chem. 1982, 232, 233. [27] J. A. Ewen, J. Am. Chem. Soc. 1984, 106, 6355. [28] J. A. Ewen, R. L. Jones, A. Razavi, J. D. Ferrara, J. Am. Chem. Soc. 1988, 110, 6255. [29] W. A. Herrmann, J. Rohrmann, Angew. Chem., Int. Ed. Engl. 1989, 28, 1511. [30] C. J. Schaverien, R. Ernst, P. Schut, T. Dall’Occo, Organometallics 2001, 20, 3436. [31] C. J. Schaverien, R. Ernst, J. D. van Loon, T. Dall’Occo, Eur.Pat Appl. 1999, 941997. [32] R. L. Halterman, T. M. Ramsey, Organometallics 1993, 12, 2879. [33] H. G. Alt, W. Milius, S. J. Palackal, J. Organomet. Chem. 1994, 472, 113. [34] W. Kaminsky, Catalysis Today 2000, 62, 23. [35] G. W. Coates, R. M. Waymouth, Science 1995, 267, 217. [36] E. Hauptman, R. M. Waymouth, J. Am. Chem. Soc. 1995, 117, 11586. [37] R. Kravchenko, A. Masood, R. M. Waymouth, Organometallics 1997, 16, 3635. [38] J. L. M. Petoff, M. D. Bruce, R. M. Waymouth, A. Masood, T. K. Lal, R. W. Quan, S. J. Behrend, Organometallics 1997, 16, 5909. [39] M. D. Bruce, G. W. Coates, E. Hauptman, R. M. Waymouth, J. W. Ziller, J. Am. Chem. Soc. 1997, 119, 11174. [40] R. Schmidt, M. Deppner, H. G. Alt, Journal of Molecular Catalysis A: Chemical 2001, 172, 43. [41] R. Leino, P. Lehmus, A. Lehtonen, Eur. J. Inorg. Chem. 2004, 3201. [42] C. Schmidt, H. G. Alt, M. Bruce, Eur. Pat. Appl. 1997, EP 798306. A1 19971001 [43] N E. Grimmer, N. J. Coville, C. B. de Koning, J. Organomet. Chem. 2002, 642, 195. [44] A. Hannisdal, A. C. Möller, E. Rytter, R. Bolm, Macromol. Symp. 2004, 213, 79. [45] S. E. Reybuck, R. M. Waymouth, Macromolecules 2004, 37, 2342. [46] S. E. Reybuck, R. Meyer, R. M. Waymouth, Macromolecules 2002, 35, 637. [47] J. S. Yoon, D. H. Lee, E. S. Park, D. K. S. O Jung, J. Appl. Polym. Sci. 2000, 75, 928. References____________________________________________________________ 110 [48] J. A. Van Beek, J. G. de Vries, H. J. Arts, R. Persad, G. H. J. van Doremaele, U.S. Patent 5646322, 1997. [49] N. Piccolrovazzi, P. Pino, G. Consiglio, A. Sironi, M. Moret, Organometallics 1990, 9, 3098. [50] H. H. Brintzinger, D. Fischer, R. Mühlhaupt, B. Rieger, R. Waymouth, Angew. Chem. 1995, 107, 1255. [51] M. Bochmann, J. Chem. Soc., Dalton Trans. 1996, 255. [52] P. C. Möhring, N. J. Coville, J. Organomet. Chem. 1994, 479, 1. [53] A. C. Möller, R. Blom, R. H. Heyn, O. Swang, J. Kopfc, T. Seraidaris, Dalton Trans. 2006, 2098. [54] S. Lin, E. Hauptman, T. K. Lal, R. M. Waymouth, R. W. Quan, A. B. Ernst, J. Mol. Catal. A: Chem. 1998, 136, 23. [55] G. Jany, M. Gustafsson, T. Repo, E. Aitola, J. A. Dobado, M. Klinga, M. Leskelä, J. Organomet. Chem. 1998, 553, 173. [56] R. Leino, H. Luttikhedde, P. Lehmus, C. Wilen, R. Sjöholm, A. Lehtonen, J. V. Seppälä, J. H. Näsman, Macromolecules 1997, 30, 3477. [57] H. H. Brintzinger, D. Fischer, R. Mülhaupt, B. Rieger, R. M. Waymouth, Angew. Chem., Int. Ed. Engl. 1995, 34, 1143. [58] R. Leino, H. Luttikhedde, C. Wilén, R. Sillanpää, J. H. Näsman, Organometallics 1996, 15, 2450. [59] S. Knüppel, J.-L. Fauré, G. Erker, G. Kehr, M. Nissinen, R. Fröhlich, Organometallics 2000, 19, 1262. [60] H. Luttikhedde, R. Leino, M. J. Ahlgrén, T. A. Pakkanen, J. H. Näsman, J. Organomet. Chem. 1998, 557, 227. [61] H. Luttikhedde, R. Leino, C. Wilén, J. H. Näsman, M. J. Ahlgrén, T. A. Pakkanen, Organometallics 1996, 15, 3092. [62] T. Dreier, G. Erker, R. Fröhlich, B. Wibbeling, Organometallics 2000, 19, 4095. [63] T. Dreier, G. Unger, G. Erker, B. Wibbeling, R. Fröhlich, J. Organomet. Chem. 2001, 622, 143. [64] T. Dreier, K. Bergander, E. Wegelius, R. Fröhlich, G. Erker, Organometallics 2001, 20, 5067. References____________________________________________________________ 111 [65] H. Schumann, D. F. Karasiak, S. H. Mühle, W. Kaminsky, U. Weingarten, J. Organomet. Chem. 2001, 636, 31. [66] R. Schmidt, H. G. Alt, J. Organomet. Chem. 2001, 621, 304. [67] G. Y. Lee, M. Xue, M. S. Kang, O. C. Kwon, J.-S. Yoon, Y.-S. Lee, H. S. Kim, H. Lee,I.-M. Lee, J. Organomet. Chem. 1998, 558, 11. [68] S. C. Collins, Y. Hong, R. Ramachandran, N. J. Taylor, Organometallics 1991, 10, 2349. [69] T. Cuenca, P. Royo, Coord. Chem. Rev. 1999, 193–195, 447. [70] O. W. Lofthus, C. Slebodnick, P. A. Deck, Organometallics 1999, 18, 3702. [71] N. E. Grimmer, N. J. Coville, C. B. de Koning, J. M. Smith, L. M. Cook, J. Organomet. Chem. 2000, 616, 112. [72] N. E. Grimmer, N. J.Coville, C. B. de Koning, J. Organomet. Chem. 2002, 642, 195. [73] A. C. Möller, R. H. Heyn, R. Blom, O. Swang, C. H. Görbitz, J. Kopf, Dalton Trans. 2004, 1578. [74] C. Eaborn, K. L. Jones, P. D. Lickiss, J. Organomet. Chem. 1994, 466, 35. [75] C. Beyer, U. Böhme, C. Pietzsch, G. Röwer, J. Organomet. Chem. 2002, 654, 187. [76] W. A. Lindley, D. W. H. MacDowell, J. Org. Chem. 1982, 47, 705. [77] C. Schmid, Ph.D. Thesis, University of Bayreuth 1996. [78] E. Aitola, M. Surakka, T. Repo, M. Linnolahti, K. Lappalainen, Kaisa Kervinen, M. Klinga, T. Pakkanen, M. Leskelä, J. Organomet. Chem. 2005, 690, 773. [79] J. A. Simoes, J. L. Beauchamp, Chem. Rev. 1990, 90, 629. [80] I.M. Lee, W. Gauthier, J. M. Ball, B. Iyengar, S. Collins, Organometallics 1992, 11, 2115. [81] G. Luft, M. Dorn, Angew. Makromol. Chem. 1991, 188, 177. [82] F. Wild, M. Wasiucionek, G. Huttner, H. H. Brintizinger, J. Organomet. Chem 1985, 288, 63. [83] S. Miyake, Y. Okumura, S. Inazawa, Macromolecules 1995, 28, 3074. [84] L. Resconi, F. Piemontesi, I. Camurati, O. Sudmeijer, I. E. Ninfant’ev, P. V. Ivchenko, L. G. Kuz’mina, J. Am. Chem. Soc. 1998, 120, 2308.