Bimetallic complexes based on carboxylate and xanthate ligands: synthesis and electrochemical investigations.

The homobimetallic ruthenium(II) and osmium(II) complexes [{RuR(CO)(PPh(3))(2)}(2)(S(2)COCH(2)C(6)H(4)CH(2)OCS(2))] (R = CH=CHBu(t), CH=CHC(6)H(4)Me-4, C(C[triple bond]CPh)=CHPh, CH=CHCPh(2)OH) and [{Os(CH=CHC(6)H(4)Me-4)(CO)(PPh(3))(2)}(2)(S(2)COCH(2)C(6)H(4)CH(2)OCS(2))] form readily from the reactions of [MRCl(CO)(BTD)(PPh(3))(2)] (M = Ru or Os; BTD = 2,1,3-benzothiadiazole) with the dixanthate KS(2)COCH(2)C(6)H(4)CH(2)OCS(2)K. Addition of KS(2)COCH(2)C(6)H(4)CH(2)OCS(2)K to two equivalents of cis-[RuCl(2)(dppm)(2)] leads to the formation of {(dppm)(2)Ru}(2)(S(2)COCH(2)C(6)H(4)CH(2)OCS(2)). The benzoate complexes [RuR{O(2)CC(6)H(4)(CH(2)OH)-4}(CO)(PPh(3))(2)] (R = CH=CHBu(t), CH=CHC(6)H(4)Me-4, C(C[triple bond]CPh)=CHPh) are obtained by treatment of [RuRCl(CO)(BTD)(PPh(3))(2)] with 4-(hydroxymethyl)benzoic acid in the presence of base. Reaction of [RuHCl(CO)(PPh(3))(3)] or [RuRCl(CO)(BTD)(PPh(3))(2)] with 4-(hydroxymethyl)benzoic acid in the absence of base leads to formation of the chloride analogue [RuCl{O(2)CC(6)H(4)(CH(2)OH)-4}(CO)(PPh(3))(2)]. The unsymmetrical complex [{Ru(CH=CHC(6)H(4)Me-4)(CO)(PPh(3))(2)}(2)(O(2)CC(6)H(4)CH(2)OCS(2))] forms from the sequential treatment of [Ru(CH=CHC(6)H(4)Me-4){O(2)CC(6)H(4)(CH(2)OH)-4}(CO)(PPh(3))(2)] with base, CS(2) and [Ru(CH=CHC(6)H(4)Me-4)Cl(CO)(BTD)(PPh(3))(2)]. The new mixed-donor xanthate-carboxylate ligand, KO(2)CC(6)H(4)CH(2)OCS(2)K is formed by treatment of 4-(hydroxymethyl)benzoic acid with excess KOH and two equivalents of carbon disulfide. This ligand reacts with two equivalents of [Ru(CH=CHC(6)H(4)Me-4)Cl(BTD)(CO)(PPh(3))(2)] or cis-[RuCl(2)(dppm)(2)] to yield {(dppm)(2)Ru}(2)(O(2)CC(6)H(4)CH(2)OCS(2)) or [{Ru(CH=CHC(6)H(4)Me-4)(CO)(PPh(3))(2)}(2)(O(2)CC(6)H(4)CH(2)OCS(2))], respectively. Electrochemical experiments are also reported in which communication between the metal centres is investigated.