RUTHENIUM TRIGOLD AND DIGOLD HYDRIDE CLUSTERS

The synthesis and characterization of ruthenium-gold clusters, of composition [(triars)RuH3{Au(L)}3][PF6]2(triars = CH3C(CH2AsPh2)3; L = PPh3, PEt3 P-i-Pr3) and [(triphos)RuH3{Au(L)}3] [PF6]2 (triphos = CH3C(CH2PPh2)3; L = PPh3, P-i-Pr3, AsPh3, As-i-Pr3), type C, is reported. They were obtained by reacting the gold cations {Au(L)}+ (3 equiv) with either [RuH4(triars)] or [RuH(BH4)(triphos)] (I equiv). The X-ray crystal structure of [(triphos)RuH3{Au(PPh3)}3] [PF6]2 shows the presence of a RuAu3 tetrahedron with the ruthenium atom capped by triphos, while each gold atom is coordinated to one PPh3. The hydride ligands, which could be located, occupy bridging positions above each of the Ru-Au2 faces but are displaced toward one RuAu edge. Crystal data: space group R3c, a = 20.150(3) angstrom, c = 45.229(9) angstrom, Z = 6, V = 15904(9) angstrom3, rho(calcd) = 1.501 g cm-3, and R = 0.051. The addition of the gold cations {Au(L)}+ (2 equiv) to either [RuH4(triars)] or [RuH(BH4)(triphos)] (I equiv), in the presence of a base, gave the trinuclear species [(triars)RuH3{Au(L)}2][PF6] (L = PPh3, P-o-Tol3, P-i-Pr3, AsPh3) and [(triphos)RuH3{Au(L)}2][PF6] (L = PPh3, P-o-Tol3, P-i-Pr3, AsPh3), respectively, type B. These complexes are highly fluxional in solution and have been assigned static structures based on a RuHAu2 tetrahedron, the ruthenium atom being capped by the tripod ligand and each gold being coordinated to a ligand L, while the other two H-atoms are assumed to bridge the Ru-Au edges. Some highly fluxional binuclear compounds of composition [(triars)RuH3{Au(L)}] (L = PPh3, P-o-Tol3) and [(triphos)RuH3{Au(P-o-Tol3)}], type A, could also be characterized in solution.