The dual role of cis-[RuCl2(dmso)4] in the synthesis of new water-soluble Ru(II)-phosphane complexes and in the catalysis of redox isomerization of allylic alcohols in aqueous-organic biphasic systems

The dual role of cis-[RuCl2(dmso)4] in the synthesis of new water-soluble Ru(II)-phosphane complexes and in the catalysis of redox isomerization of allylic alcohols in aqueous-organic biphasic systems Antal Udvardy, Attila Csaba Bényei, Ágnes Kathó* Department of Physical Chemistry, University of Debrecen, Debrecen, P.O.B. 7, H-4010, Hungary. * Corresponding author. Á. Kathó: phone: +36-52-512900; fax: +36-52-512915; E-mail: [email protected] Abstract New air-stable, water-soluble Ru(II)-phosphane complexes were synthesized in high purity by the reaction of cis-[RuCl2(dmso)4] with 2 equivalents of 1,3,5-triaza-7-phosphaadamantane (pta) and its N-methyl and N-benzyl derivatives (pta-Me and pta-Bn, respectively). All new complexes were characterized by elementary analysis and spectroscopic methods (NMR, ESI MS) and the molecular structures of cis-cis-trans-[RuCl2(dmso)2(pta)2], cis-cis-trans- [RuCl2(dmso)2(pta-H)2]Cl2 (obtained in acidic solutions) and that of cis-cis-trans- [RuCl2(dmso)2(pta-Me)2](CF3SO3)2 were determined by single crystal X-ray diffraction. Under mild conditions, cis-[RuCl2(dmso)4] actively catalyzed the transformation of allylic alcohols into the corresponding ketones with 100 % selectivity while in the same reaction the new Ru(II)-pta complexes showed moderate activity and selectivity. Highlights  cis-[RuCl2(dmso)4] (1) was used as a water-soluble Ru(II) source for synthesis  New water-soluble Ru(II)-complexes were obtained from 1 and phosphatriazaadamantanes (L).  Single crystal X-ray structures evidenced cis-cis-trans-[RuCl2(dmso)2L2] geometries.  1 and the new complexes actively catalyzed the isomerization of allylic alcohols. Keywords: water soluble phosphanes, ruthenium, allylic alcohols, isomerization, biphasic catalysis 1. Introduction Water is widely considered useful for elimination of hazardous organic solvents in organic synthesis and catalysis. An additional green feature of applying water-soluble catalysts is that the use of aqueous-organic biphasic systems allows recycling of the catalyst under mild conditions by easy phase separation.[1-4] The chemistry of Ru(II) catalysts containing water-soluble phosphanes as ligands has received considerable attention in recent years.[4] In many cases, Ru(II)-complexes of tertiary phosphanes applied in homogeneous catalysis are synthesized from RuCl3.aq as starting material. However, ligand exchange reactions of water-soluble Ru(II)-complexes containing sufficiently labile ligands allow more precise control of the composition and structure of the products.[5] For example, [Ru(H2O)6](tos)2 (tos = p-toluene-sulfonate) can be efficiently used for this purpose. However, this compound is tedious to synthesize, highly sensitive to oxygen and is stable only in acidic solutions.[6,7] The ruthenium(II) dimethylsulfoxide complexes, cisand trans-[RuCl2(dmso)4] are conveniently prepared and easy-to-handle compounds.[8,9] Earlier cis-[RuCl2(dmso)4], 1 was used as precursor for the synthesis of Ru(II)-complexes with aryl, sulfonated aryl, and cyclohexyl phosphanes, both in aqueous and in non-aqueous media.[8, 10-14] In addition, several ligands with Nand O-donor atoms were studied in substitution reactions of both isomers of [RuCl2(dmso)4].[15] This was –in part– motivated by the expected biological effects of the products.[16-19] While 1 itself also shows antitumor and remarkable antimetastatic activity, certain of its substituted derivatives are even more effective.[20] 1,3,5-Triaza-7-phosphadamantane (1,3,5-Triaza-7-phosphatricyclo[3.3.1.1]decane, pta) is a small, aliphatic tertiary phosphane with a cage structure, well soluble in water. Ru(II)-pta complexes such as [RuCl2(pta)4] have already been applied in biphasic catalysis[21] and the field is well reviewed.[5, 22,23] In contrast to other tertiary aminoalkylphosphanes where alkylation takes place on phosphorus, pta is alkylated smoothly on one of its nitrogen atoms.[24] The charge and steric bulk of such ligands are changed by quaternarization and this is reflected also in their water-solubility.[25] Coordination properties of alkyl-pta derivatives and catalytic applications of their complexes received less attention than those of pta. Rare examples include the use of (pta-Bn)Cl (Scheme 1) in Rh-catalyzed hydroformylation of higher olefins[26,27] and that of [(η-arene)RuCl2(pta-Bn)]Cl in hydration of nitriles.[28] [CpRuCl(pta-Me)2](OSO2CF3)2 and [CpRu(pta-Me)2(H2O)](OSO2CF3)3 were found effective catalysts of the redox isomerization of allylic alcohols. [29 ] In addition, pta has been successfully used for synthesis of anticancer Ru(II)-arene complexes[30]. It is interesting, therefore, that reactions of pta and its derivatives with cisor trans-[RuCl2(dmso)4] hitherto have not been studied. Scheme 1. Water-soluble phosphanes used in this study Herein we report the use of 1 for the synthesis and characterization of several new watersoluble Ru(II)-complexes containing the ligands shown in Scheme 1, and an exploratory study of their catalytic activity in the hydrogenation and isomerisation of allylic alcohols. Strikingly, 1 itself was only scarcely used[31,32] as catalyst in such reactions so its study was also accomplished. 2. Results and Discussion 2.1. Reactions of cis-[RuCl2(dmso)4] with water-soluble phosphanes According to the literature,[10] boiling of a toluene suspension of 1 and three equivalents of the water-soluble phosphane, mtppms, for 2 h resulted in formation of the mononuclear [RuCl2(dmso)(mtppms)3]. However, we found this reaction rather slow and incomplete and 31P NMR indicated the formation of more than one product. No significant improvement/optimization could be reached by varying the ligands (mtppms or mtppts), ligand to metal ratio (1 to 3), solvents (toluene, methanol or water), reaction time or reaction temperature. In contrast to the aromatic phosphanes, pta reacted cleanly with 1 in chloroform. The reaction was followed by uv-vis spectrophotometry (Figure 1.). The isosbestic point at λ = 346 nm refers to the formation of a single product (2). Formation of 2 became complete in two hour and there were no further spectral changes. Figure 1. Changes in uv-vis spectra measured in the solution of cis-[RuCl2(dmso)4] (1) and 2 pta as a function of time. Conditions: c(1) = 0.001 M; T = 25 °C; t = 0, 15, 30, 45, 60, 90 and 120 min. Only one singlet at δ = -60.7 ppm (in CDCl3) appeared in the 31P NMR spectrum. Based on integrated 1H signal intensities of free and coordinated dmso as well as those of coordinated pta we concluded that the product was [RuCl2(dmso)2(pta)2] (2). The singlet 31P signal refers to the phosphanes being in trans position each to the other (Scheme 2). This observation is in agreement with that substitution of chloride in this solvent is not favoured. The molecular structure of 2 in solid state was confirmed by single crystal x-ray diffraction (see later). Scheme 2. Synthesis of Ru(II)-complexes containing triazaphosphaadamantanes At room temperature, coordination of a further phosphane ligand to 2 is slow and at a 4:1 [pta]:[1] ratio only [RuCl2(dmso)2(pta)2] (2) was formed in the first 90 min of the reaction. During the same reaction time but at reflux temperature, an approximately 3:2 mixture of 2 and the known trans-[RuCl2(pta)4], 5 was obtained (Scheme 2);[21,33] upon further boiling the latter compound precipitated from the solution. Based on these observations [RuCl2(dmso)2(pta)2] could be synthesized in pure form when [RuCl2(dmso)4] and pta were let to react in a 1:2 ratio in chloroform for two hours at room temperature (yield 82 %). In aqueous solution 2 is characterized by a singlet resonance at δ = -57.9 ppm in the 31P NMR spectrum (Table 1). Table 1. 31P-NMR data of water soluble Ru(II)–phosphane complexes in D2O 31P-NMR (ppm) [RuCl2(dmso)2(pta)2] (2) -57.9* [RuCl2(dmso)2(pta-Me)2](CF3SO3)2 (3) -38.9 [RuCl2(dmso)2(pta-Bn)2]Cl2 (4) -36.4 trans-[RuCl2(pta)4] (5) -51.6 trans-[Ru(H2O)2(pta)4]2+ (6) -52.9 * in CDCl3: δ = -60.7 ppm Since both pta and 1 are soluble in water, their reaction was studied in aqueous medium, as well. At room temperature, only the characteristic singlet resonance of 2 (δ = - 57.9 ppm in D2O) was observed in the 31P NMR spectra independent of the [pta]:[1] ratio being 1 or 2. In contrast, at [pta]:[1]=3, albeit in the first 30 min of the reaction exclusively 2 was detected, later a new singlet (δ = -52.9 ppm) grew in gradually. Formation of this new species at room temperature is slow even at higher ligand excess ([pta]:[1]=4).The singlet 31P NMR resonance of this new compound is slightly different from that of trans-[RuCl2(pta)4] (δ = -51.6 ppm in D2O),[21,33] however, it shows a similar presence of magnetically equivalent phosphane ligands. We reasoned, that during the reaction of 1 with pta in water, aquation could lead to the formation of trans-[Ru(H2O)2(pta)4]2+ (6). This is corroborated by the finding that when [RuCl2(dmso)2(pta)2] (2) was reacted first with AgNO3 followed by the addition of 2 equivalents of pta, after a reaction time of 2 h at room temperature only the singlet at δ = -52.9 ppm was observed. The same signal was observed when 1 was dehalogenated in reaction with AgNO3, followed by addition of 4 equivalents of pta. Furthermore, addition of KCl (5 Clˉ/Ru) to these solutions resulted in the appearance of the 31P NMR signal of trans-[RuCl2(pta)4] (5) on the expense of the one at -52.9 ppm. Note, that in the reaction of pta and [Ru(H2O)6]2+ only cis-[Ru(H2O)2(pta)4]2+ could be detected.[7] The cis-[Ru(H2O)2(pta)4]2+ compound was also obtained by addition of AgOTf to the product mixture of cis-[RuCl2(pta)4] and [RuCl(H2O)(pta)4]+ formed by visible light irradiation of 5 in water.[34] It is also worth mentioning, that in contrast to the reaction of [Ru(H2O)6]2+ and pta, formation of monoor tris-phosphane complexes was not observed. In acidic solutions both free and coordinated pta can be protonated on one of the nitrogen atoms. Figure 2 shows the shift of the 31P NMR signal of [RuCl2(dmso)2(pta)2] as a function of the acidity of its aqueous (D2O) solutions. Figure 2. Experimental (squares) and calculated (solid line) 31P NMR chemical shift of [RuCl2(dmso)2(pta)2] vs pD. Henderson-Hasselbach analysis of the data gave pKa = 3.40 (applying the pH = pD – 0.44 scaling[35]) and the 31P NMR shifts calculated with this value are also shown on Figure 2. Literature values of the pKa of pta vary in the range of 5.63-6.0,[7, 36-38] so the protonation of coordinated pta in 2 takes place under more acidic conditions relative to the free ligand. Single crystals of 2a were obtained from hydrochloric acid solutions of 2. X-ray diffraction analysis of the molecular structure of 2a (see Supplementary Information: Figure S1) showed that both phosphane ligands had one protonated nitrogen each. The most intensive peak in the ESI mass spectrum of 2 at m/z = 643.030 belongs to the monoprotonated molecule, conceivably [RuCl2(dmso)2(pta)(ptaH)]+ (Figure S2), furthermore, loss of dmso and chloride are also indicated by the signals at m/z = 565.070 ([RuCl2(dmso)(pta)(ptaH)]+) and at m/z = 607.048 ([RuCl(dmso)2(pta)2]+). The reaction of 1 and (pta-Bn)Cl in aqueous solution at room temperature at a [ptaBn]:[ 1]=2 ratio yielded 3 with [RuCl2(dmso)2(pta-Bn)2]2+ as the sole product. The uv-visible spectrum of the reaction mixture underwent changes similar to those shown above for the case of 1 with two equivalents of pta, and the spectral parameters of 3 are also similar to those of 2. The reaction was complete in 1.5 h, and no sign of any other species was detected in the NMR spectra even at higher temperature (up to T = 70 °C). 3 is stable to air and its best solvent is water. Due to its charge solubility of 3 in water is approximately 1.5 times higher than that of the neutral 2 (see Experimental). The most intensive ESI MS peak at m/z = 576.100 belongs to [RuCl2(dmso)2(pta-Bn)]+ (Figure S2). The mono-dmso complex ion, [RuCl2(dmso)(pta-Bn)]+ (m/z = 500.003) and chloride-associated ions such as {[RuCl2(dmso)2(pta-Bn)2]Cl}+ (m/z = 860.100) and {[RuCl2(dmso)(ptaBn)2]Cl}+ (m/z = 782.100), could also be identified. [RuCl2(dmso)2(pta-Me)2](CF3SO3)2 (4) was prepared in the reaction of 1 with (ptaMe)CF3SO3. This ligand and 1 ([pta-Me]:[1]=2) were reacted in water (or methanol) at room temperature for 2 h yielding exclusively [RuCl2(dmso)2(pta-Me)2]2+ what was isolated as triflate salt. 4 is stable to air and its solubility is approximately the double of that of the neutral 2, and is somewhat higher than that of 3The most intensive ESI-MS peak at m/z = 499.947 belongs to [RuCl2(dmso)2(pta-Me)]+ (Figure S2). The mono-dmso complex ion, [RuCl2(dmso)(pta-Me)]+ (m/z = 421.947) and triflate-associated ions such as {[RuCl2(dmso)2(pta-Me)2](CF3SO3)}+ (m/z = 821.013) and {[RuCl2(dmso)(ptaMe)2](CF3SO3)}+ (m/z = 743.005), and {[RuCl2(pta-Me)2](CF3SO3)}+ (m/z = 665.039) could also be identified. 2.2. Molecular structures of cis-cis-trans-[RuCl2(dmso)2(pta)2] (2), cis-cis-trans- [RuCl2(dmso)2(ptaH)2]Cl2 (2a) and cis-cis-trans-[RuCl2(dmso)2(pta-Me)2](CF3SO3)2 (4) in solid state Results of X-ray structure determinations are summarized in Table 2. Search of the Cambridge Structural Database (Ver. 5.33, Update May, 2012)[39] revealed that all RuCl2P2S2 complexes in the database contain exclusively bidentate ligands with P-S, P-P or S-S donor pairs. In fact, 2, 2a and 4 are the first crystallographically characterized complexes with RuCl2P2S2 coordination containing monodentate ligands. The two phosphorus atoms are in trans-position, however, the P-Ru-P angles significantly deviate from 180° being 161° in 2, 168° in 2a and 165° in 4. In the vast number of RuP2 complexes (over 4500 hits in CSD) the P-Ru-P angles rarely deviate from 180° or 90°: in the crystals obtained from [Ru(H2O)6]2+ with pta or its derivatives[7] (trans-[Ru(H2O)4(pta)2]2+, trans-[Ru(H2O)4(ptaMe)2]4+, trans-[Ru(H2O)4(pta-H)2]4+) as well as in trans-[RuI4(pta-Me)2]40 and trans- [RuCl4(pta-H)2]41 this angle is 180° as ruthenium atom is in the inversion centre of the lattice. Concerning the reaction mechanism, one of the possible pathways is the isomerization of allylic alcohols to saturated ketones followed by hydrogenation of the latter to saturated alcohols. However, in independent reactions no hydrogenations of the respective ketones occurred (either with H2 or with formate), therefore with the catalysts described above we consider isomerization and hydrogenation of allylic alcohols as parallel reactions. 3. Conclusions The easily available cis-[RuCl2(dmso)4] is useful as a Ru(II)-source not only in organic solvents, but in water, as well. 1,3,5-Triaza-7-phosphaadamantane (pta) is soluble in both types of media and its reactions with cis-[RuCl2(dmso)4] resulted in the same product, cis-cistrans-[RuCl2(dmso)2(pta)2] (2) in both CHCl3 and water. N-alkyl derivatives of pta (L = {ptaBn}Cl; {pta-Me}CF3SO3) also easily replace two dmso ligands in trans positions of cis- [RuCl2(dmso)4] in aqueous solution to form air-stable, cis-cis-trans-[RuCl2(dmso)2(L)2] complexes (3, 4). Of the new compounds, 2, 2a and 4 are the first crystallographically characterized complexes with RuCl2P2S2 coordination containing monodentate ligands. The P-Ru-P angles in these trans-bisphosphane complexes significantly deviate from 180° (161° in 2, 168° in 2a and 165° in 4). It was shown here for the first time, that apart from its useful role in the synthesis of water-soluble Ru(II)-complexes, cis-[RuCl2(dmso)4] is an excellent catalyst for aqueousorganic biphasic isomerization of allylic alcohols. The reactions proceeded with 100 % to the respective ketones using Na-formate as a H-source. Under the same conditions the activities of 2, 3 and 4 are 45-65 % of that of cis-[RuCl2(dmso)4], and the reactions are also less selective leading to the formation of small amounts of octan-3-ol, too. 4. Experimental Section 4.1. General Remarks Allylic alcohols (Aldrich) and other reagents and solvents were commercially available and used as received. The water-soluble phosphane ligands, mtppms,[50] mtppts (mtppts = P(C6H43-SO3Na)3),[51] pta,[52] (pta-Bn)Cl (1-benzyl-1-azonia-3,5-diaza-7-phosphaadamantyl chloride),[36] and cis-[RuCl2(dmso)4] (1),[8] were prepared according to the literature. (ptaMe)CF3SO3[25] was kindly supplied by Prof. A. Romerosa (U. Almería, Spain). 1 is a light sensitive compound,[9,53] therefore its reactions were studied with the careful exclusion of light. All reactions and manipulations were carried out under argon atmosphere. Reaction mixtures were analyzed by gas chromatography (HP5890 Series II; Chrompack WCOT Fused Silica 30m*32mm CP WAX52CB; FID; carrier gas: argon). The products were identified by comparison to known compounds. 1H, 31P and 13C NMR spectra were recorded on a Bruker Avance 360 MHz spectrometer and referenced to 3-(trimethylsilyl)propanesulfonic acid Nasalt (DSS). ESI mass data were collected on a BRUKER BioTOF II ESI-TOF spectrometer. Solubilities were determined by incremental addition of the compounds to water. Complete dissolution was checked by laser light scattering. 4.2. Synthesis and characterization of Ru(II) complexes 4.2.1. Preparation of cis-cis-trans-[RuCl2(dmso)2(pta)2], (2) In the dark, a mixture of 1 (400 mg 0.82 mmol) and pta (259 mg, 1.64 mmol ) in chloroform (5 mL) was stirred for 2 h at room temperature. Then most of the solvent was removed under vacuum and the residue was triturated with diethyl ether to provide a pale yellow solid. This was washed with acetone and with diethyl ether and dried under Ar to result in a strongly hygroscopic solid. Yield 527 mg (82 %). X-ray quality crystals were grown by slow diffusion of diethyl ether into a chloroform solution of 2 at -15 °C . Anal. calc. for RuC16Cl2H36N6O2P2S2 (2.0.5 CHCl3) (M=642.30) C 28.22, H 5.23, N 11.97, S 9.13 %; found C 28.67, H 5.40, N 12.17, S 9.98 %. S25 °C=34 mg/mL water. λmax(H2O)/nm 338 (ε/dm3mol-1cm-1 449) 1H NMR: (360 MHz, CDCl3, 25 °C) δ = 3.35 (s, 12 H, S-dmso, CH3), 4.43 (s, 12 H, PCH2N), 4.52 (s, 12 H, NCH2N) ppm; 1H NMR: (360 MHz; D2O, 25 °C) δ = 3.31 (s, 12 H, S-dmso, CH3), 4.26 (s, 12 H, PCH2N), 4.43 (s, 12 H, NCH2N) ppm; 13C NMR (90 MHz, CDCl3, 25 °C) δ = 51.18 (s, S-dmso, CH3), 51.39 (t, JPC= 7 Hz PCH2N), 73.07 (s, NCH2N ), ppm; 31P{1H} NMR (145 MHz, 25 °C) in CDCl3 δ = -60.7 (s), in D2O δ = -57.9 (s) ppm. MS (ESI+): m/z observed 643.030, calcd. 643.031 for [RuCl2(dmso)2(pta)(pta-H)]+. Crystals of cis-cis-trans-[RuCl2(dmso)2(ptaH)2]Cl2, (2a) were obtained by dissolving 10 mg of 2 in 1 mL of 0.1 M HCl and then it was layered with 1 mL of ethanol. Anal. calc. for RuC16Cl4H38N6O2P2S2 (2a.3H2O) C 24.97, H 5.76, N 10.92, S 8.33 %; found C 24.91, H 5.53, N 10.82, S 8.33 %. 4.2.2. Preparation of cis-cis-trans-[RuCl2(dmso)2(pta-Bn)2]Cl2, (3) 1 (200 mg 0.41 mmol) dissolved in 3 mL of water was added to an aqueous solution (2 mL) of (pta-Bn)Cl (234 mg, 0.82 mmol). The mixture was stirred for 2 h at room temperature in the dark. Then the solvent was removed under vacuum and the residue was redissolved in a small amount of methanol. Diethyl ether was added to the solution whereupon a yellow solid precipitated. This was washed with acetone and with diethyl ether and dried under Ar. Yield 246 mg, 66 %. Anal. calc. for RuC30Cl4H50N6O2P2S2 (3.2H2O) (M=895.71) C 38.67, H 5.84, N 9.02 %; found C 38.25, H 6.17, N 8.79 %. λmax(H2O)/nm 341 (ε/dm3 mol-1 cm-1 691) . 1H NMR: (360 MHz, D2O, 25 °C) δ =3.29-4.27 (m, 8 H, NCH2P), 3.64 (s, 12 H, S-dmso, CH3), 4.19 (m, 4 H, N+CH2Ph), 4.31 (m, 4 H, N+CH2P), 4.51-4.61 (m, 4 H, NCH2N), 4.925.09 (m, 8 H, N+CH2N), 7.57-7.46 (m, 10 H, Ph) ppm; 13C NMR (90 MHz, D2O, 25 °C), δ = 47.25 (t, JPC=8 Hz, NCH2P), 50.16 (s, S-dmso, CH3), 51.99 (d, JPC=8 Hz, N+CH2P), 66.37 (s, NCH2N), 69.80 (s, N+CH2Ph), 78.71 (s, N+CH2N), 124.22 (s, Ph), 129.46 (s, Ph), 131.18 (s, Ph), 132.83 (s, Ph) ppm; 31P{1H} NMR (145 MHz, D2O, 25 °C) δ = -36.4 (s) ppm. MS (ESI+): m/z observed 860.100, calcd. 860.265 for {[RuCl2(dmso)2(pta-Bn)2]Cl}+. S25 °C= 50 mg/mL water. 4.2.3. Preparation of cis-cis-trans-[RuCl2(dmso)2(pta-Me)2](CF3SO3)2, (4) In the dark, 1 (100 mg 0.21 mmol) and (pta-Me)(CF3SO3) (132.7 mg, 0.41 mmol) was dissolved in 5 mL of water. The solution was stirred for 4 h at room temperature and then the solvent was removed under vacuum. The residue was dissolved in a small amount of methanol and 4 was precipitated with diethyl ether to yield a pale yellow solid. This was washed with acetone and with diethyl ether and dried under Ar. Yield 134 mg, 67 %. X-ray quality crystals were obtained by slow diffusion of methanol into aqueous solution of 4. Anal. calc. for RuC20Cl2F6H42N6O8P2S2 (4.2H2O) (M=906.62)) C 23.86, H 4.60, N 8.34, S 12.74 %; found C 23.99, H 4.53, N 8.18, S 13.00 %. λmax(H2O)/nm 344 (ε/dm3mol-1cm-1 480). 1H NMR: (360 MHz, D2O, 25 °C), δ = 2.84 (s, 6 H, N+-CH3), 3.38 (s, 12 H, S-dmso, CH3), 4.32 (s, 8 H, NCH2P), 4.44-4.38 (4 H, m, N+CH2P), 4.52 (m, 4 H, NCH2N), 4.91-5.10 (m, 8 H, N+CH2N) ppm; 1H NMR: (360 MHz, MeOD, 25 °C), δ = 4.31 (s, 6 H, N+-CH3), 4.81 (s, 12 H, S-dmso, CH3), 5.83 (m, 8 H, NCH2P), 5.90 (m, 4 H, N+CH2P), 5.95 (m, 4 H, NCH2N),6.61-6.69 (m, 8 H, N+CH2N) ppm; 13C NMR (90 MHz, D2O, 25 °C) δ = 46.97 (t, JPC= 7 Hz, NCH2P), 49.43 (s, N+-CH3), 50.14 (s, S-dmso, CH3), 55.38 (t, N+CH2P), 68.79 (s, NCH2N), 79.99 (s, N+CH2N), 121.34 (m, CF3SO3-) ppm; 31P{1H} NMR (145 MHz, 25 °C) in D2O δ = -39.61 (s), in MeOD δ = -37.67 (s) ppm; 19F{1H} NMR (283 MHz, D2O, 25 °C) δ = -79.10 (s, CF3SO3-) ppm. MS (ESI+): m/z observed 821.013, calcd. 821.022 for {[RuCl2(dmso)2(pta-me)2](CF3SO3)}+. S25 °C=63 mg/mL water. 4.3. 31P-NMR pH titrations A pH-dependent series of 31P-NMR spectra were recorded on a Bruker 360 MHz instrument at 25 °C and 0.2 mol/dm3 KNO3 ionic strength. D2O was used as a solvent. The pH measurements in the pH range 1.1-7.0 for [RuCl2(dmso)2(pta)2], 2 were performed in 0.5 cm3 vessels at a complex concentration of 0.01 mol/dm3. Small amounts of cc. NaOD and DNO3 solutions were used to adjust the pH measured using a Radelkis OK117 pH meter and a combined electrode. 4.4. X-ray crystallographic studies X-ray data collection was performed using a Bruker-Nonius MACH3 diffractometer equipped with a point detector using graphite-monochromated Mo-Kα radiation, λ = 0.71073 Å. The structures were solved by the SIR-92 program[54] and refined by full-matrix least-squares method on F2, with all non-hydrogen atoms refined with anisotropic thermal parameters except in the solvent region in 2 since chloroform in two orientations occupies a channel in the lattice (Figure S1.a). Refinement was performed using the SHELXL-97 package;[55] publication material was prepared with the WINGX suite.[56] Hydrogen atoms were located geometrically and refined in the rigid mode or found at the difference Fourier map. Solvent water molecules in 2a and 4 (Figure S1.b and S1.c) have partial occupancy and can have various orientations forming different hydrogen bond networks with acceptors resulting shift and errors even in the last stage of the refinement. 4.5. General Procedure for Catalytic Isomerization of Allylic Alcohols Under an inert atmosphere, the catalyst precursor (0.01 mmol) and Na-formate (0.5 mmol) were dissolved in 3 mL of deoxygenated water. The solution was then heated to the indicated temperature and then allylic alcohol (0.5 mmol, in 1 mL of toluene) was introduced. The system was rapidly stirred for one hour and then was cooled to room temperature. The separated organic phase was filtered through a short silica gel column and was subjected to gas chromatography. Supplementary material CCDC 859702859704 contain the supplementary crystallographic data for the ruthenium complexes 2, 2a and 4. These data can be obtained free of charge from Cambridge Crystallographic Data Centre via http://www.ccdc.cam.ac.uk/data-request/cif. Supplementary data related to this article can be found in the online version, at doi…. Acknowledgments The authors are indebted to Prof. Antonio Romerosa (U. Almería, Spain) for the generous supply of (pta-Me)CF3SO3 and for the useful advices on the synthesis of 4, as well as for support of the stay of A. Udvardy in his laboratory. Helpful discussions with Prof. Ferenc Joó, Dr. Katalin Ősz and Mr. Imre Szatmári are gratefully acknowledged. Thanks are due to Dr. Attila Kiss-Szikszay for the elementary analyses and to Dr. Lajos Nagy for the ESI-MS measurements. This research was supported by the EU and co-financed by the European Social Fund through the Social Renewal Operational Programme under the projects TÁMOP-4.2.1/B09/1/KONV-2010-0007 and TÁMOP-4.2.2-08/1-2008-0012 (CHEMIKUT). Financial support of TEVA Hungary Ltd. and that of the National Research Fund of Hungary (OTKA K 101372) is also appreciated. A. Udvardy is grateful for the predoctoral employment grant TÁMOP-4.2.2/B-10/1/KONV-2010-0024. References [1] F. Joó in Water in Organic Synthesis (in the series of Science of Synthesis), Ed. S. Kobayashi, Georg Thieme Verlag KG, Stuttgart. New York, 2012, pp. 95-119 [2] F Joó, Á Kathó in Handbook of Green Chemistry: Reactions in Water (ed.: Chao-Jun Li) Weinheim: Wiley-VCH, 2010, pp. 389-408 [3] F. Joó, Á. 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