Syntheses,Structures And Properties Of Ruthenium-Containing Polyoxometalates

The chemistry of ruthenium-containing polyoxometalates?RCPs?has attracted continuously growing attention,owing to their excellent catalytic activity toward photo/electro-catalysis water oxidation and organic substrates oxidation reaction,which has been developed rapidly in recent years.In this paper,we have successfully synthesized seven different types of RCPs by reacting RuCl₃·nH₂O with phosphor-tungstate/molybdate precursors or simple tungstate?molybdate?salts,of which structures were fully characterized by IR,UV-vis,TGA,XPS and other instrumental methods.Moreover,we focused on the catalytic or electronic porperties and solution behaviors of some selected compounds.Four pure inorganic ruthenium-containing polyoxoanions:1.Novel 14-isopolymolybdate-based RCPs:Cs₃Na₆H[H₄Mo₁₄Ru₂O₅₂]·24H₂O?1?,?CN₃H₆?₆Na₄[H₄Mo₁₄Ru₂O₅₂]·15H₂O?2?.Compounds 1 and 2 contain the same structure of the polyoxoanions.Compound 1 is the first representative of pure inorganic RCP constructed by isopolymolybdate,which consisted of three ladder-like {Mo₁₄} unit incorprorating a di-ruthenium cluster.Remarkably,1 shows good catalytic activity toward the reaction of 1-phenylethanol oxidating into acetophenone.Parallel tests indicated that the optimized conditions of 0.15 mol%catalyst loading with 8 equiv.of aqueous tert-butyl hydroperoxide?TBHP?in acetonitrile for 3 hours at 85 ? allowed for 100%conversion and selectivity of the starting material to product.The catalyst was at least recycled 10 times with only a bit of decline in yield.2.SeO₃^2--bridged,ruthenium-substituted monolacunary metatungstate trimers:Rb₁₀Na₃H[SeO₃(H₃RuW₁₁O₃₈)₃]·35H₂O?3?,Cs₁₀Na)3H[SeO)3?H?3RuW₁₁O₃₈)₃]·28H₂O?4?.It is the first time to obtain the pure inorganic RCPs based on isopolytungstates.3 and 4 contained a similar trimeric polyoxoanion[SeO₃(H₃RuW₁₁O₃₈))3]^14-,which was constructed from three mono-ruthenium substituted{RuW₁₁} units bridged by a three-coordinated SeO₃^2-ion.The ESI-MS study confirmed the existence of the trimeric polyoxoanion in aqueous solution.Six organic-inorganic hybrid ruthenium-containing polyoxometalates:3.A crossing-type polyoxoanion[P₄W₈O₄₀]^12--based supported-type RCP:Na₆[P₄W₈O₄₀?Ru?dmso?₃?₄)]?OH?Cl·19H₂O?5?.The polyoxoanion of 5 is consisted of two equal[P₂W₄O₂₀]^6-subunits staggered in a perpendicular fashion,resulting a crossing-type polyoxoanion[P₄M₈O₄₀]^12- with four {Ru?dmso?₃}²⁺ groups supported on its surface by two Ru-O-W bonds and one Ru-O-P bond.Furthermore,the polyoxoanion of 5 can lead to a three-dimensional network by the connection of Na+ and Cl-ions.The existence of the novel polyoxoanion[P₄W₈O₄₀?Ru?dmso?₃?₄)]^4- in aqueous solution was confirmed by the ESI-MS spectrometry.4.A supported-type RCP based on Silverton-type polyoxoanion[NaMo₁₂O₄₂]^11-:Na₄[(NaMo₁₂O₄₂)?Ru?dmso?₃?₄]?OH?·2H₂O?6?.The polyoxoanion of 6 can be described as a Silverton-type polyoxoanion[NaMo₁₂O₄₂]^11- modified by four[Ru?dmso?₃]²⁺ groups on its surface,which can further give a three-dimensional network bridged by Na+ ions.5.A supported-type RCP based on cyclic-type polyoxoanion[H₆W₉O₃₃]^6-:NaH[H₆W₉O₃₃]?Ru?dmso?₃?₂]·4.5H₂O?7?.The polyoxoanion of 7 is composed of a cyclic[H₆W₉₃₃]]^6- stabilized by two[Ru?dmso?₃]²⁺ groups,and which are,in turn,linked by Na+ showing a chain-like structure.6.A substituted-type RCPs based on monolacunary Dawson-type polyoxoanion[P₂W₁₇O₆₁]^10-:Cs₃NaH₅[P₂W₁₇O₆₁Ru?dmso?3?H₂O?]Cl·3.5H₂O?8?.This novel polyoxoanion consists of a monolacunary[P₂W₁₇O₇₁]10-Dawson unit substituted by a {Ru?dmso?)3?H₂O?} fragment via two Ru-O-W bonds.7.Aion-type RCPs constructed by polyoxoanions and Ru complexes:NaH₅[(P₂M₁₈O₆₂)][?Ru?dmso?₄Cl₂?₄]·nH₂O?M = W?9?,n=12;M = Mo?10?,n = 10?.Compounds 9 and 10 are isomorphic structures and both consist of a saturated Dawson-type[P₂M₁₈O₆₄]^10- unit and four dissociative {Ru?dmso?₄Cl₂} complexes.