Organometallic Complexes Supported on a Metal-Oxide Cluster.pH-Dependent Interconversion between the Monomeric and Dimeric Species of the Polyoxoanion-Supported [(arene)Ru]2+ Complex

摘要

Keggin polyoxometalate(POM)-supported two(arene)Ru~(2+)complexes,i.e.,the monomeric species(type-m)[{(arene)Ru(H2O)}PW_(11)O_(39)]~(5-)and the dimeric species(type-d)[({(arene)Ru}PW_(11)O_(39))2(mu-WO2)]~(8-),were prepared as water-soluble Et2NH2+ salts by pH-controlled reactions in aqueous solutions of the in situ-generated,mono-lacunary Keggin POM [PW_(11)O_(39)]~(7-)with the organometallic precursor [{RuCl2(arene)}2].The effects of the arene(benzene(1),toluene(2),p-cymene(3),and hexamethylbenzene(4))on the proportion of the type-m to type-d complex produced were examined.pH-Varied ~(31)PNMR spectroscopy showed that there was a pH-dependent interconversion between type-m and type-d complexes,i.e.,the ratio of the dimeric species increased as pH of the solution was lowered.Under the reaction conditions,the dimeric species d1,d3,and d4 as water-soluble(Et2NH2)+ salts were successfully isolated as the major products.It was concluded that(1)steric repulsion between the two(arene)Ru2+ fragments in the dimeric species was not significant,(2)the proportion was strongly dependent on the pH of the solution rather than the bulkiness of the arene,and(3)the use of the in situ-generated [PW11O39]~(7-),but not the isolated lacunary species,such as K7[PW_(11)O_(39)]·nH2O,had an effect on the reaction.