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3,793,355 United States Patent Office Patented Feb. 19, 1974 1. 2 atoms present in complexes according to the present in 3,793,355 vention may be present as: COMPOUNDS OF RUTHENUM Geoffrey Wilkinson, London, England, assignor to John son, Matthey & Co. Limited, London, England No Drawing. Filed Aug. 8, 1972, Ser. No. 278,804 Claims priority, application Great Britain, Aug. 11, 1971, 37,705/71 In C, CO7f 15/00 and with six monovalent anions may therefore form a U.S. C. 260-429 R 7 Claims monovalent cationic species, a neutral species or a mono O Valent anionic species respectively. Preferred embodiments of the present invention are, ABSTRACT OF THE DISCLOSURE therefore: This invention relates to a composition of matter hav ing the general formula (RusO(OCOCH3)6(HO)alt 5 RusC(OCOCH3)6(HO) M1M2M3XAnLLPL3 RusO(OCOCH)6(HO)- where M1, M2 and M3 are the same or different transition metals selected from the second or third series of the Periodic Table; X is , sulphur, nitrogen, phosphorus or boron; An is anionic element or group and L., L or Li 20 are neutral or anionic ligands. In each of the above, or triphenylphosphine might be replaced by other ligands, e.g. pyridine or methyl This invention relates to compounds of the second and pyridine. ". third transition series of metals, that is Y-Cd and La 25 Compositions according to the present invention may Hg. More particularly the invention relates to compounds also be in the form of salts derived from the above of those second and third transition series metals which described cations and anions. are members of the group, that is, the members Compositions according to the present invention may of the second and third transition series in Group VIII of be used in electrodeposition especially of ruthenium, for the Periodic Table. The invention is particularly concerned 30 homogeneous catalysis, in aqueous or other fluid media. with oxotriruthenium complexes and con The compositions may also be used in the impregnation pounds which may be obtained therefrom. of Substrates for the production of heterogeneous catalysts According to one aspect of the present invention, a and using the methods described in Pat. No. 1,116,943. new composition of matter comprises a complex com The compositions are useful for the catalysts of acidbase pound, cation or anion of the general formula: 35 reactions and for the catalysis of reduction, oxidation, hydrogenation, hydroformylation, carbonylation, iso merization reactions. Where M1, M2 and M3 are the same or different and one By the interaction of commercial hydrated ruthenium or more are transition metals of the second and third 40 trichloride with acetic , mixtures, the series, and preferably platinum group metals; where M', complex Ru(COMe)4C may be obtained; other car M2 and M3 are the same, their formal oxidation states boxylates may be prepared similarly. X-ray crystallog need not be the same, for example, M may have a formal raphy confirms a suggested tetra bridge binuclear oxidation state of --3 whereas M2 and M (atoms of the structure and shows that Ru(COMe)4]+ units are same metal) may have formal oxidation states of +2, 45 linked into chains by Ru-Cl-Rubridges. The complex has other combinations are also possible); X is oxygen, Sul equivalent ruthenium atoms in the mean oxidation state phur, nitrogen, phosphorus or boron, preferably oxygen of -2.5 or, as originally formulated, II, III. (X may not be N when M1, M2 and M8 are all Ir); An The above reaction gives not only [Ru(COMe)]Cl, is anionic element or group such as carboxylate, diethyl but a green solution and it was thought that the latter dithio-carbamate (SCNEta) or Sulphate (a preferred 50 might contain the corresponding neutral dimer. Using carboxylate is acetate), L., L or L, if present may be somewhat different, conditions, namely the interaction of the same or different, and neutral or anionic ligand species ruthenium chloride, and acetate in such as HO, pyridine (py), OH, triphenylphosphine , a green impure material was isolated. This was (PPh3) CO, etc. shown to form adducts with pyridine and triphenylphos One preferred embodiment of the present invention is 55 phine, which were formulated as adducts of the dimer by a complex compound, cation or anion of the general analogy with the well-known adducts of the dimeric tetra formula: bridged of Cril, Cui and Rh. RuO(OCOR) LI In further studies of these materials we have now found that the green acetate is not Ru3(COMe)4 bu an oxo which is an embodiment of the General Formula 60 centered ruthenium (III) basic acetate complex. Molecu lar weight determinations also indicated that the PPh ad MM2M3XAng duct was a trimer and the oxo-centered structure of the latter was proved by X-ray crystallographic study. Hence and in which An is carboxylate of General Formula this complex is Ru3O(COMe)6(PPh3)3, with identical OCOR (e.g. acetate) and L is H2O, py or PPh3. 65 ruthenium atoms in a mean oxidation state of -2%- or The group OCOR represents a generalized carboxylate less correctly using the stock nomenclature with Rur, in which R is an aryl or alkyl or substituted aryl Rult, RuTII. or alkyl group. A preferred carboxylate is acetate, in All of the previously known oxo-centered species have which R=CH. the metal atom in the --3 state; the ruthenium acetate The three ruthenium atoms may be in a formally --2 70 system provides the first example of an oxo acetate of a or --3 oxidation state and we believe are at the corners of second or third row element in the Periodic Table (long a triangle with oxygen at its center. The three ruthenium form) and also of reversible redox reactions.

- 3,793,355 4 ; : (A) THE -OXOTRIRUTHENIUM (III) with glacial acetic acid. The latter was shown to be ...... . . . . anionic in and to be reconverted to the aquo (1) Synthesis of oxo carboxylates acetate by water. Hence we have CH3C O The acetate is prepared as described above in an im RusO (COMe) (EO)lt -v- a Rus O (COMe) (COMe)32 pure state; the use of an inert atmosphere is not neces sary, and a reflux time of one hour is sufficient. The Thus it appears that the main product of Mond's reaction crude product contains a considerable excess of sodium is the oxo acetate with unidentate acetate groups replacing acetate, from which it can be separated by a number of water molecules. The other minor green components prob techniques. A preliminary purification is readily achieved ably have both water and acetate coordinated, e.g. the by dialysis in water using a cellophane membrane (Visk 0 neutral RuO (COMe) 6(H2O ) 2CCOMe) l. ing tubing), and the pure acetate has been obtained by (2) Attempts to synthesize the trifluoroacetate chromatography, on Sephade (grade G10). It is best puri fied, however, by recrystallization from methanol-, The synthetic procedure fails for trifluoroacetate, from which it separates as a green powder. Analysis Sup probably due to the much greater strength of CFCOOH, ports the stoichiometry (RuO(COMe)6(H2O)3CO2Me. which possibly prevents the formation of species with The complex is paramagnetic with ueff=1.77 B.M. at 298 Ru-OH-Ru bridges and which, presumably, are inter K. in the solid state (Gouy method). This is consistent mediates in the formation of the Ru3O types. Using neu with an RuTO unit, in which marked spin-spin interac tral or almost neutral solutions gives green or yellow So tion would be expected, via the central oxygen atom. lutions whose electronic spectra are quite different from The complex as formulated would be a unipositive 20 those of the RuO species. cation, but in protonic , ionization of the aquo Other methods have also failed. On refluxing hydrated ligands may occur. High voltage paper electrophoresis ruthenium oxide with no reaction experiments show that in acidic buffers (pH 2) acetate occurs in two hours whereas acetic acid has almost com oxotriruthenium(III) migrates as a cation, and in alka pletely dissolved the oxide in this time. On prolonged re line-buffers (pH 9), as an anion, the rates of migration in 25 fluxing (several days) or in sealed tubes at 120-160, the two cases being equal. In unbuffered dilute potassium green solutions are obtained but the electronic spectra are chloride solution, cationic, neutral, and anionic species not those of RusO species. are observed. On titration of an of ace The interaction of a and its anhydride tato oxotriruthenium(III) acetate (pH=6.2) with solu on "RuCin.HO” which produces in addition to tions of and , a two 30 Ru (COR) 4l Cl proton protonation is observed with pK=4.35. This is in considerable amounts of the green oxo species, fails for the region expected for water coordinated to ruthenium trifluoroacetic acid and there is no apparent reaction, the (III), and is so assigned. This result, together with the trichloride remaining undissolved. electrophoretic behaviour requires that the cationic and 35 Finally, the exchange of acetate and trifluoroacetate anionic species be univalent. The third aquo ligand does also fails. There is no change for up to 48 hours on re not deprotonate in the pH range covered by the tritration fluxing the oxo acetate in trifluoroacetic acid (even pure curve (1-12 pH), but the electronic spectrum of the com acid) as judged by the proton spectrum (al plex undergoes a reversible change in more alkaline solu though the oxoacetate is paramagnetic a methyl resonance tions, which is probably due to the loss of this proton 40 can be observed at T 7.70-see Table 2 which shows the and hence we obtain: proton resonance spectra of ruthenium carboxylates. On -Eh + refluxing the oxo acetate with and it (Rua O (COMe) (H2O)2(OH)) . trifluoroacetic acid in ethanol (as in the synthesis of the oxo acetate) only partial exchange occurs. Conversion of Treatment of methanolic solutions of the acetate with 45 the product to the pyridine and triphenylphosphine com pyridine produces the blue complex, which may be pre plexes, which could be isolated, showed that only ca. 50% cipitated from solutions with a number of anions, for ex of the COMe groups were replaced by COCF3 groups ample ClO, BF, B.Ph., or PF. From chilled solu and this was confirmed also by H and Fn.M.r. (Hydro tions containing chloride , blue needle crystals are gen and fluorine nuclear magnetic resonance) spectra. No obtained...... 50 further exchange occurred on refluxing the product with Analysis of salts indicates the stoichiometry fresh trifluoroacetic mixture, Ru3O(COMe) spyal, (B) REDUCTION OF u-OXOTRIRUTHENIUM (X=CIO, Cl). Paper electrophoresis experiments CARBOXYLATES show this complex to be cationic, migrating at the same 55 rate, as the aquo complex itself; pH-titrations show no (1) Reduction by hydrogen protonation or deprotonation in the range 1-12 pH, con The acetate Ru3O(COMe)6(HO) (COMe), in firming that the behaviour described above is due to dis water or methanol, is readily reduced by hydrogen at 2 sociation of the aquo ligands. atm. pressure at 25 using platinum oxide catalyst, first to The perchlorate of the pyridine complex is also 60 a light green and then to a yellow solution. In methanol paramagnetic, with piett-2.46 B.M. (at 298). The solu the first stage takes ca. 1 hr. and the second, ca. 3 hr. The bility in organic solvents increases on substitution of the yollew methanol solution slowly gives a yellow precipitate. aquo ligands by pyridine, and, of course, with increasing In water the first stage takes ca. 4 hr. and the solution chain length of the carboxylate group in both cases. throws down a light green complex which is very insoluble : The electronic absorption spectra given in Table 1 65 serve as guide for characterization of the species. in water, so that reduction of the latter to the yellow com The Mond reaction: Hydrated ruthenium oxide dis plex, which is also insoluble, takes about 24 hr. solves in refluxing acetic acid quite rapidly. The electronic The light green and yellow complexes are hence readily spectrum of the product varies with the mode of prepara isolated due to their different in water and tion of the oxide, probably with the water content. methanol. Analysis of the yellow complex made in water Chromatography of the green products (after removal of 70 indicates the composition Ru3(COMe)6(H2O), where acetic acid) in methanol on alumina gave several bands as from methanol it is Ru3(COMe)6(MeOH)3]; the but the main product had the same electronic spectrum as presence of methanol or water is readily shown by ap the product obtained on treating propriate differences in the infra-red spectra (aquo species, 3500, 3480 s. (s.-strong), cm.1 (br. =broad); meth (RuO(COMe)6(H2O)3(COMe) 75 anolate, 3400 w. (w =weak), br., 996 (sharp Me rock) 3,793,355 5 6 cm.). Evidence for the lack of the central oxygen atom three, 5-coordinate ruthenium(II) atoms. This would ac is given below. The yellow species in solution react in count for the extreme sensitivity to oxygen-and the re stantly with oxygen to give the light green complex, which formation of the oxo-centered light green III,III,II species is in turn more slowly oxidized to the starting green OXo on oxidation. acetate on standing. This redox cycle has been repeated Positive proof for the re-insertion of a single oxygen three times without evidence of decomposition. The yel atom into the yellow complex is as follows. The butyrate low and green solids are also air-sensitive but may be Ru3(CO2CH) spys, which is very soluble in methanol, stored in sealed ampoules under nitrogen. was prepared and treated with a stoichiometric amount The green complex, which analyses as of pyridine-N-oxide under rigorously oxygen-free condi O tions (where the yellow species was unaffected for several RuO(COMe)6(H2O) hours at least). Re-Oxidation to the light green complex is diamagnetic, but the yellow complex is Weakly para occurred within a few minutes and g.l.c. (gas-liquid magnetic with pier ca. 0.4 BM per Ru at 298 K. chromotography) analysis confirmed the presence of The blue pyridine complex (RuO(COMe)6pyal pyridine. To eliminate any possibility of the formation of is similarly reduced but more rapidly. The yellow end pyridine by dissociation or decomposition of the yellow product in solution is again rapidly oxidised by air first to 5 pyridine complex, the experiment was repeated using a light green intermediate and then very slowly (several pyridine-N-oxide to oxidize the 3-methyl pyridine butyr hours) to the blue starting material. The triphenylphos ate, G.l.c. analysis showed that the expected amount of phine complex (RuO(COMe)6(PPh3)3] is not reduced pyridine was formed: in methanol. The aquo or pyridine complexes with other carboxylic undergo similar redox processes as shown 20 in the reaction of oxotriruthenium complexes given in F.G. 1. On exposure to the air the green solutions were re Electrochemical studies discussed later show that the oxidized to the blue Ru3O(COR) spy -- complexes. first stage is a one-electron and the second stage a fur Hence the complete reduction-oxidation sequence is: ther two-electron reduction. The reversibility shows that 25 the trimer structure is always retained. Infra-red and n.Mr. (nuclear magnetic resonance) spectra of the light green and yellow complexes show no evidence for Ru-H bonds and only a single methyl resonance is observed. 30 (2) Electrochemical reductions Solution electrophoresis on the light green aquo and pyri The polarogram of RusO(COMe)6(H2O)-- in water dine complexes in aqueous acidic (to suppress ionisation using potassium chloride as electrolyte was prepared. of coordinated water) or methanolic media show that A cathodic wave occurs as E/2= -0.13 v. (versus both species are neutral. Considering also the electro S.C.E.) (standard calomel electrode) and the catalysed chemical reversibility of the first stage reduction, this then 35 reduction of hydrogen ions commences at ca. -0.9 v. is evidently The height of the cathodic wave is linearly proportional RuO(COR) Late to the concentration of the acetate, and to the square = RuO(COR) L (L=H2O, py) root of the height of the mercury reservoir (corrected for back pressure). The cyclic volt-ammogram of the The light green complexes are hence the counterparts of 40 cathodic wave was obtained in aqueous sodium fluoro the diamagnetic trimer RusO(COMe)6(PPh3)3 and have borate solution, in which the anodic wave of mercury the ruthenium atoms in a mean oxidation state 2%. occurs at a more positive potential, permitting a suitable If the oxi-centers structure were preserved on the fur voltage range to be scanned. The voltammogram and the ther 2-electron reduction to the yellow species, the latter E/4-E/4 separation observed in the polarogram, both would, inescapably, have to be a dianion. Although the 45 indicate a reversible one-electron reduction. Using the yellow form of the acetate is anionic in neutral and alka Heyrovsky-Ilkovick equation an n-value of 1.08 was line aqueous solution, we have shown by solution elec obtained. This value was confirmed by coulometric re trophoresis, that this is a result of dissociation of coordi duction at the dropping mercury electrode and an n-value nated water. The species is neutral in acidic media and in of 0.81 obtained. This low value lies outside the experi neutral methanol but becomes anionic only in alkaline 50 mental error, and is attributed to a slow chemical reduc methanol solution. Further, the yellow pyridine complex tion by the mercury pool accumulating from the electrode, is neutral irrespective of the or acidity confirming as confirmed separately. that the behavior of the aquo species is due to ionization The reversibility of the couple is further confirmed by of coordinated water. The yellow pyridine complex was the polarogram of the partially electrochemically reduced readily isolated from reduction of strong solutions of 55 Solutions, which shows a composite reduction-oxidation RuO(COMe)spys Cl in methanol; the precipitate can wave. Confirmation of the identity of the electrochemical be recrystallized from petroleum-benzene. Molecular ly reduced solutions, which shows a composite reduction weight determinations on different samples gave a mean oxidation wave. Confirmation of the identity of the elec value of 860 with a maximum deviation of 8% from the trochemically reduced species with those obtained by value of 894 calculated for Ru3(COMe)6pys. Repeti 60 chemical reduction is provided by the exact similarity of tion of analyses and molecular weights using the 3 the polarograms of species undergoing reduction by either methylpyridine analogue were in agreement with this method; controlled potential electrolysis at the dropping stoichiometry. mercury electrode produces the light green intermediate. Hence, to maintain neutrality, the yellow complex can The Second stage of the reduction, producing the yellow (a) gain two protons (b) lose two acetate ligands or 65 Species cannot be investigated electrochemically for oxo (c) lose the central oxygen atom. Electrophoresis rules triruthenium(III) acetate, because of the catalytic reduc out (a) I.R. (infra-red) and N.M.R. spectra on the of the solvent. The pyridine complex, which is soluble in propionate (preferred to the acetate because of its higher a wider range of solvents than the aquo form, was there ) are consistent only with the formulation fore studied. The polarograms in methanol, acetone, 70 Sulpholane, dimethylsulphoxide and showed a cathodic wave in all cases similar to that of the as is analytical and molecular weight data which shows aquo-form, and occurring at ca. -0.1 to -0.2 v. In the trimer structure to be retained. Hence we conclude methanol, the second reduction is again obscured by re that the two-electron reduction requires removal of the duction of the solvent, but this wave may be observed central oxygen atom to give a trimer containing formally 75 in aprotic solvents; the best results being obtained in 3,793,355 7 8 acetone, using sodium perchlorate as supporting elec The above behavior suggests that Martin's complex trolyte. may be polymeric containing mainly ruthenium(III), The first cathodic wave occurred at E/2= -0.20 v. which is reduced via mixed oxidation state complexes. If (vs. S.C.E.) and a second cathodic wave as seen at this is so, the pyridine adduct probably arises via bridge E1/2=-1.36 v. Reduction of the solvent begins at ca. splitting but on the available evidence, no satisfactory -1.85 v. Cyclic voltammetry shows that the Wave at formulation can be given. -0.20 v. is reversible, but that the second wave at -1.36 v. is irreversible. Use of the Heyrovsky-Ilkovick equation TRIS(AQUO)HEXA-u-ACETATO-u-OXOTRIRU gives an n-value of 0.96. Controlled potential electrolysis THENIUM (III, III, III)ACETATE at -0.4 v. (versus aqueous S.C.E.) produces the light 10 The green complex may be prepared according to the green intermediate, and at -1.5 v., the yellow form is original method. After 4 hr. reflux, the dark green re obtained. Coulometric reduction on mercury electrodes action mixture was cooled at (-40) for 2 hr., and is not possible owing to reaction of the complex with the precipitate of and was mercury, but reduction at -0.4 v. (versus aqueous S.C.E.) removed. The filtrate was evaporated on a rotary evapo on platinum electrodes, gave n-values of 0.91 and 0.99, 5 rator, dissolved in methanol, filtered, and again evapo confirming that the first cathodic wave is again a one rated. The resulting solid was dried (12 hr.) in vacuo electron process. From the ratio of the heights of the two over sodium hydroxide pellets, to give the crude acetate waves, the second wave arises from a two-electron in almost quantitative yield based on ruthenium content process. but containing about 15% of sodium acetate. This prod The polarograms of aquo and pyridine oxotrirutheni 20 uct may be used directly for preparative purposes. The um(III) propionate and n-butyrate, are analogous to those pure acetate was obtained by two recrystallizations from of the acetate. The potentials of the various reductions methanol-acetone, the complex separating as a green are summarized in Table 3. powder on cooling to -40°. The thermodynamic reversibility of the first reduction wave of those complexes may be expected, as the electrode 25 TRIS (PYRIDINE)HEXA-u-ACETATO-a-OXOTRI- . reaction involves only a simple one-electron transfer. The RUTHENIUM (III) PERCHLORATE loss of the central oxygen atom on reduction to the second stage clearly accounts for the lack of thermody To crude oxotriruthenium(III) acetate (0.5 g.) in namic reversibility for this process. methanol (5 ml.) was added pyridine (2 ml.). The solu The triphenylphosphine complexes of acetate, propio 30 tion was heated for 5 min. on steam, the color chang nate, and n-butyrate, which are in the same oxidation ing from dark green to dark blue. After cooling to room state (2/3) as the first reduced species of the corre temperature, sodium perchlorate monohydrate (0.125 g.) sponding aquo and pyridine adducts, also undergo a two in methanol (2 ml.) was added, the blue precipitated electro reduction at potentials of ca. -1.1 v. (various complex collected, washed with methanol, and dried in S.C.E.). However, these reductions are not simple and 35 vacuo over silica gel. 0.32 g. (55%, based on Ru content evidently lead to break up of the trimeric cluster. The of crude acetate). Addition of lithium chloride in meth difference of more than one volt in the two reduction anol produces the chloride salt in similar yield. potentials of the acetate accounts for the ready forma TRIS (TRIPHENYLPHOSPHINE)HEXA-u-ACETA stion potentials of the acetate accounts for the ready TO-u-OXOTRIRUTHENIUM (II, III, III) formation of the complex RuO(COR)6(PPh3)3, since 40 the first reduction is well within the reducing power of Triphenylphosphine (1.1 g.) in warm methanol (25 the phosphine although the reduction is slow and takes ml.) was added under nitrogen to crude oxotriruthenium several hours. It is noteworthy that in contrast to the slow (III) acetate (0.5 g.) in methanol (5 mi.) and the mix reduction of RuO (COR)6(H2O) -- by PPh3, the in ture was stirred overnight. After removal of the meth teraction of PPh3 with the light green species 45 anol, the residue was dissolved in benzene, and the solu tion was filtered. Ethanol (ca. 5 vols.) was added to RuO(COR)6(HO) the filtrate, which was then stored at 7 to yield light green crystals of the complex which were collected, in methanol is rapid (a few minutes) since it merely in washed with ethanol and then ether, and dried in vacuo volves ligand replacement. 50 over silica gel. 0.45% g. (55% based on Ru content of (C) THE NATURE OF MARTIN'S ACETATE Crude acetate). It is now clear that Martin's acetate cannot have the OXOTRIRUTHENIUM (III) PROPIONATE AND ITS oxo-centered structure. This complex is difficult to study PYRIDINE AND TRIPHENYLPHOSPHINE DE as it is insoluble in most solvents. It is slightly soluble RVATIVES in water, but the solutions decompose rather quickly 55 and even the solid decomposes on standing. Analysis sup Sodium hydroxide (0.59 g.) was dissolved by warm ports a ratio Ru:COMe=1:2 but analysis of the pyridine ing in a mixture of ethanol (25 ml.), was propionic acid adduct, isolated as C10 or BF salts supports an ap (26 ml.). To the resulting solution was added (at room proximate stoichiometry Rug(COMe)pyax} temperature), ruthenium trichloride trihydrate (1 g.), 60 and the mixture was refluxed under nitrogen for 4 hr. The solution was cooled at -40 for 2 hr., filtered, and evaporated on a rotary evaporator. The residue was dried BF). Determination of the oxidation state of the in vacuo over sodium hydroxide overnight. The resulting ruthenium atoms in Martin's complex by the original crude aquo oxotrirutheinum(III) propionate was dis method confirms the formulation as ruthenium (III), 65 solved in methanol (15 ml.) and the solution was filtered but the accuracy of the method is too low to exclude and divided in three parts. the possibility of non-integral oxidation states. The Martin complex is weakly paramagnetic, showing a moment of (a) TRIS AOUO-HEXA-u-ACETATO-us-OXOTRI ca. 0.6-0.7 B.M. per ruthenium atom (Gouy method). RUTHENIUM (III) PROPIONATE The pyridine adduct (perchlorate salt) is diamagnetic. Martin's complex is reduced in water by hydrogen at two To the methanolic solution (5 ml.) was added a large atmospheres on platinum to a dark green, and then to a excess of diethyl ether, and the solution was stored at yellow species, the latter stage being accompanied by -40. After one week, dark green, almost black crystals the formation of much ruthenium metal. The reduction of the complex had formed. These were collected, washed is not reversible on exposure to air. 75 with ether, and dried in vacuo over silica gel. 0.06 g. 3,793,355 9 10 (b) TRIS (PYRIDINE)HEXA-u-PROPIONATEug (b) TRIS(AQUO)HEXA-u-ACETATO OXOTRIRUTHENIUM (III) PERCHLORATE TRIRUTHENIUM(II) To the methanolic solution (5 ml.) was added pyridine Crude oxotriruthenium(III) acetate (0.5 g.) in water (2 ml.) and the solution was stirred for 1 hr. Sodium 5 (5 ml.) was stirred under hydrogen (2 atm.) in presence perchlorate monohydrate (0.1 g) in methanol (1 ml.) of Adams' catalyst (35 mg.) for 2 days. The yellow pre was added and the solution was left for 1 hr. at -40. cipitate which formed was collected, washed, dried and The blue crystalline complex was collected, washed with stored as for the light green reduced complex. The dry diethyl ether, and dried in vacuo over silica gel, 0.22 g. solid is oxidized fairly quickly in air. The complex is in (c) TRIS(TRIPHENYLPHOSPHINE)HEXA-u-PRO O Soluble in most solvents. PIONATE-us-OXOTRIRUTHENIUM(II, III, III) (c) TRIS(METHANOL) HEXA-u-ACETATO To the methanolic solution (5 ml.) was added tri TRIRUTHENIUM(II) phenylphosphine (0.5 g.) and the solution was stirred overnight under nitrogen. The resulting solution was 5 This complex was prepared as for the aquo form, using cooled at -40° for 4 hr., and filtered. The precipitate methanol as solvent and for washing. was washed with ether, then dissolved in benzene and again filtered. Ethanol (ca. 5 vols.) was added to the (d) TRIS(PYRIDINE)HEXA-u-ACETATO filtrate, which was left at -40 overnight. The light green TRIRUTHENIUM(II) crystals were collected, washed with ethanol and dried 20 in vacuo over silica gel, 0.2 g. The complex (RuO(COMe)Pyl Cl was reduced in methanol as described above for the aquo form. The yell OXOTRIRUTHENIUM (III) N-BUTYRATE AND ITS low precipitate which formed was recrystallized (under PYRIDINE AND TREPHENYLPHOSPHINE DE deoxygenated nitrogen) from benzene-petroleum (60 RVATIVES 25 80). The resulting complex was washed with petroleum and dried in vacuum. It is soluble in and in The n-butyrate was prepared as for the propionate. The benzene. crude product, after drying, was dissolved in methanol The yellow 3-methylpyridine complex as before. Tris(aquo)-hexa-u-n-butyrato-us-oxotrirutheni um(III) n-butyrate could not be isolated in solid form, 30 but the crystalline derivatives were readily obtained. Ru3(COMe)6(MeCHN) TRIS(PYRIDINE)HEXA-u-N-BUTYRATO-u-OXO was prepared and recrystallized (twice) by the above TRIRUTHENIUM (III) PERCHLORATE methods. 35 Mond's reaction This complex was prepared as for the propionate, ex cept that ethanol was used as solvent. After the reaction Hydrated ruthenium oxide was prepared by addition of mixture had been stirred for 1 hr. sodium perchlorate strong aqueous solutions of sodium hydroxide to monohydrate (0.2 g.) was dissolved in the solution. Pe ruthenium trichloride trihydrate in 4 N hydrochloric acid. troleum (60-80) was added, and the solution was stored 40 The resulting black precipitate was washed until alkali at -40°. After ca. 3 hr., the blue crystals of the complex free with water. which formed were collected, washed with petroleum and On refluxing the resulting wet oxide with glacial acetic dried in vacuo over silica gel, 0.2ig. acid for 2 hrs., most of the oxide dissolved to give a green solution. After removal of acid and immediate chroma TRIS(TRIPHENYLPHOSPHINE)HEXA-u-N-BU 45 tography on alumina, using methanol, the electronic spec TYRATO--OXOTRIRUTHENIUM (II,III,III) trum of the main band indicated that it was This complex was prepared and purified as for the propionate analogue, 0.11g. RuO (OCMe) gl 2-. 50 When the wet oxide was washed with methanol and REDUCTION OF OXOTRIRUTHENIUM (III) ether, and dried in vacuo before refluxing with acetic acid, ACETATE chromatography of the resulting green solutions produced Reductions were carried out in glass pressure bottles diffuse bands, showing absorption maxima in the region (Fisher and Porter 8 oz. Compatibility Bottles) at two 620-700 nm. No species similar to RuO(OCMe)2 atmospheres pressure, using Adams' catalyst (PtO2). 55 were obtained. Water or methanol was used as solvent. Where used, commercial "White Spot” nitrogen was purified by passage OXIDATIONS OF THE YELLOW COMPLEXES through chromium(II) solutions. WITH PYRIDNE-N-OXIDE 60 All operations (except reductions) were carried out (a) TRIS(AQUO)-HEXA-u-ACETATO-u-OXOTRIRU under argon, which was purified by passage through two THENIUM(II,III,III) Dreschel baths of chromium(II) solution, two of concen Crude oxotriruthenium(III) acetate (1.5 g.) in water trated Sulphuric acid, and two of methanol. Hydrogen (10 ml.) was stirred under hydrogen (2 atmospheres) (at one atmosphere) was passed through one Dreschel in presence of catalyst (ca. 3-5 mg.) The dark green solu 65 bottle of chromium(II) and one of methanol. tion became light green. The precipitate, formed after ca. Pyridine-N-oxide (British Drug Houses) was purified 4 hr., was transferred under nitrogen to a centrifuge tube, as follows. The solid (5 g.) was placed in a cold-finger centrifuged, and the supernatant liquid discarded. The type sublimation apparatus, which was connected to a product was then stirred with deoxygenated water, cen vacuum line. With continuous pumping, the lower por trifuged, and the supernatant liquid was again discarded. tion of the apparatus was heated in an oil-bath to 160. The product was dried on a vacuum line, to yield the When the melt ceased to boil, the apparatus was removed complex as a light green powder. The dry solid was stored from the vacuum line and allowed to cool. The condens in sealed ampoules under nitrogen. It is slowly re-oxidized ing surface of the cold-finger was cleaned, and the ap to the starting material by air. The complex is insoluble paratus was then returned to the vacuum line. Dry Ice in most solvents. 75 acetone mixture was placed in the cold finger, and the 3,793,355 11. 12 apparatus was again heated in an oil-bath, with continuous pumping to ca. 160°. Pure pyridine-N-oxide collected on TABLE 1. the condensing surface as a white crystalline deposit. Electronic absorption spectra of ruthenium carboxylates. When sufficient had collected, the apparatus was allowed Complex Spectrum Mnm, v) to cool, and air was then admitted. The pure product is RusO(OCR)6(H2O): A , Acetate------686(1,100);629(1,000); 391sh (ca. 1,250). quite hygroscopic, and was stored in a desiccator, over Acetate (Mond) b------ca. 720sh; 64; ca. 530sh;366. . silica-gel. Tris(3 - methylpyridine) hexa-u-n-butyrato-us Agta, (from acetic ca. 720sh; 610; ca. 530sh; 366. oxotriruthenium(III) perchlorate (0.3 g) in methanol Propionate------3C o 672(880); 617(810); 370sh (ca. 1,180). (4 ml.) was placed in a 25 ml. conical flask containing n-Butyrate- 674; 168; 375sh. ... ', Benzoate------... 686; 633; 386sh. PEO (ca. 10 mg.) The flask was swept with argon and O 2-ethylhexanoate-- - 676; 613; 388sh. n-Octoate------672; 619; 385sh. then hydrogen was passed until the complex was reduced (RusO(OCR) opylt: A to the yellow species (24 hrs.). Argon was passed Acetate---- 686(4,280); ca. 620sh; ca. 500sh; 312 (8,450). through a solution of pyridine-N-oxide (0.025 g.) in Propionate- ... 686 (5,280); ca. 620sh; ca. 500sh; 309 (12,900). n-Butyrate- ... 686(4,690); ca. 620sh; ca. 500sh; 304(10,900). methanol (2 ml.) contained in a 10 ml. "Quickfit” flask. IRu3O (OCR)6( After 1 hr., the exit tube from the flask containing Acetate.--- ... 974(6,280); ca.790sh; ca. 410sh; 347(1,900). pyridine-N-oxide was inserted into the flask containing the Propionate- --- 974(6,630); ca.790sh; ca. 410sh; 343(12,000). ruthenium solution. The hydrogen inlet tube was then re n-Butyrate------974(5,060); ca.790sh; ca. 410sh; 338(12,200). Ru3O(OCMe)Ru3(O2CMe)6(H2O)3 (H2O)3)4-...-- a.---- 847(1,620);850(2,100); 36,838:391 (1,250). moved from the latter flask. Argon was thus passed first Ru3O(O2CMe) spy3).------890(7,290); 382(9,000). through the pyridine-N-oxide solution and then through Ru3(OCMe)6pyl------893(8,630); 382(9,680). the ruthenium solution. No oxidation of the latter solu 20 A In methanol. tion had occurred after 30 min., indicating that no oxygen b Made in glacial acetic acid, measured in methanol. was present in the system. The exit tube from the 10 ml. O In chloroform. flask was then inserted into the pyridine-N-oxide solution, NOTE.-ca.=approximately; sh=shoulder. which was forced over into the ruthenium solution. The latter solution was greenish yellow within 1 min, and 25 TABLE 2 green in ca. 5 min. After 1 hr., gl.c. analysis of the re Proton resonance spectra of ruthenium carboxylates-(it values at 100 action mixture showed the presence of pyridine, the mHz. relative to benzene as external reference) amount of pyridine being within 10% of that expected. Complex py or PPh3 Carboxylate On exposure to air, the green solution was oxidized back Ru3O(O2CMe)6(H2O)3l ------7.70s. to the blue starting material which was recovered. G.l.c. 30 Ru3O(O2CMe) opyl b------3.57, 4.09 broad.---- 5.55s. Ru3O(O2CMe)6(PPh3)3 - 1.59, 1.98, broad.--- 7.97s. analysis on the pyridine-N-oxide, on both the initial Ru3(O2CEt) opyl b------2.12, -0.22, broad. 7.01 quartet; 8,60 ruthenium complex, and an air-oxidized solution of the triplet. yellow species, showed that pyridine was not arising from a D2O solution. these sources. The entire experiment was repeated, with b CDCl3 solution. identical results. 35 o Cold 6 solution. Electrophoresis and pH titrations NoTE.-s=singlet. High voltage paper electrophoresis was carried out at TABLE 3 2 or 4 kV. (50 or 100 v./cm). Solution electrophoresis Heat-wave potentials for reduction of ruthenium carboxylates (relative was as 120 v. (10 v./cm.). Formic acid-acetic acid buffer 40 to external aqueous S.C.E.) (standard calomel electrode) (25 and 75 ml, per litre respectively, pH 1.8) and sodium Complex First wave (v.) Second wave (v.) borate buffer (0.05 M, pH 9.2) were used for acidic and RusO(OCR)6(EI2O)3+: a. Acetate------0.19 alkaline experiments. On experiments with the reduced Propionate.-- -0.24 forms, solution electrophoresis was carried out under ni n-Butyrate.-- -0.24 45 Benzoate.------0.14 trogen, purified by chromium(II) solutions. 2-ethylhexanoate- -0.35 For pH titrations, solution of concentration 2x10 in-Octoate------0.30 Ru3O(OCR) 6pyat:b M were titrated with standardized 1 M sodium hydroxide Acetate------0.20 or hydrochloric acid solutions. A micropipette was used, Propionate.-- -0.24 the internal volume of which had been determined by cali 50 bration with mercury. Acetate.---- Titrations were performed at 25 under nitrogen, which Propionate was purified by passage through Dreschel bottles of chro n-Butyrate mium(II) (oxygen removal) and potassium hydroxide ( dioxide removal) solutions, and then through an 0.1M sodium perchlorate in methanol. - Water. 55 bIn 0.1M sodium perchlorate in acetone.

TABLE 4 Analytical Data for Ruthenium Carboxylato Complexes Found Required Complex C B N CIP Ru C E. N CIP Ru Ru3O(CO2Me)6(H2O)3CO2Me------22.2 3.4 ------39.4 21, 4 3.4 32.0 3.4 4.0 3.4------32.0 3.3 55.0 4.5 ------6.0 20.1 54.2 4.5 Ru3O(CO2Me)6(H2O)3).------19.4 3.2------4. 6 19.7 3.3 Ru3(COMe)6(H2O)3Ru3(CO2Me)6(MeOH)3-Comparative. -Comparative 19.9 3.4 ------20, 2 3,4 Ru3(COMe)6pysb-Comparative----- 24.3 3.5 ------... 24.0 3.. 6 Ru3(COMe)5(Mepy)30 -Comparative 35.7 3.8 4.5 ... 36.2 3.7 27.3 4.3 28.7 36.0 4.0 36. 57.2 5.3 57.7 39, 6 4,9 39.6 56.7 5.9 57.3 s M=1420 (benzene); M required 1.459. b M= (methanol), (i) 870,855 (ii) 825,875, Mrequired, 894. e Ms. (methanol) 975,910; M required, 939. 3,793,355 13 14 Figure 1. Reactions of Oxotriruthenium Complexes py Ruso (COR) (H2O)st --) (RuO (COR)pylt dark green blue Pr4.^ o +e +e PPh py (Ruso (COR) (PPh3)) (- RusO(CO2R) (H2O) --) (RuO (COR)py) light green fast light green lightgreen NNPPh. +2e. +2e II fastN py Ru(COR)(H2O) - Rus (COR)py yellow yellow What I claim is: in which R is selected from the group consisting of alkyl 1. A composition of matter comprising a cation of the and aryl radicals, L., L and L3 are selected from the formula: group consisting of water, pyridine, hydroxyl, triphenyl MM2M3XAnLLL 20 phosphine, carbonyl, methanol, methylpyridine, and car boxylate as defined and having Nat as cation. where M', M and Mare ruthenium atoms having a for 3. A composition according to claim 1 in which the mula oxidation state of --2 or --3, X is oxygen, An is a carboxylate is selected from the group consisting of ace carboxylate anion having the general formula: tate, propionate, butyrate, benzoate, 2-ethylhexanoate and (OCOR) 25 Octoate. in which R is selected from the group consisting of alkyl 4. A composition according to claim 2 in which the and aryl radicals, L., L and L are selected from the ruthenium atoms are present as ORuIII,II,III5+ group consisting of water, pyridine, hydroxyl, triphenyl 5. A composition according to claim 2 having the for phosphine, carbonyl, methanol, methylpyridine, and car mula Ru3O(OCOCH3)3(H2O)- 30 6. A composition according to claim 2 having the for boxylate as defined above and an anion selected from the mula RusO(OCOCH) (PPh)- group consisting of perchlorate, fluoroborate, tetraphenyl 7. A composition according to claim 2 having the for borate, fluorophosphate, chloride and carboxylate mula Ru3O(COMe) (HO) (OH)- (OCOR) wherein R is selected from the group consisting of alkyl 35 References Cited and aryl. Legzdins et al.: J. Chem. Soc. (A), 1970, pp. 3322 2. A composition of matter comprising an anion of the 3326. formula: MMPM3XAnLLLs 40 PATRICK. P. GARVIN, Primary Examiner A. P. DEMERS, Assistant Examiner where M', M and M are ruthenium atoms having a formal oxidation state of --2 or --3, X is oxygen, An is a U.S. Cl. X.R. carboxylate anion having the general formula: 252-431 C, 431 N, 431 P; 260-270 R; 423-417, 544, OCOR 45 592