Synthesis and structure of sulfur and selenium capped dihydride triruthenium clusters [Ru3(CO)7(μ-H)2(μ-dppm)(μ3-E)] (E = S, Se)

Reaction of [Ru3(CO)10(μ-dppm)] (1) with H2S at 66 °C affords high yields of the sulfur-capped dihydride [Ru3(CO)7(μ-H)2(μ-dppm)(μ3-S)] (2), formed by oxidative-addition of both hydrogen–sulfur bonds. Hydrogenation of [Ru3(CO)7(μ-dppm)(μ3-CO)(μ3-S)] (3) at 110 °C also gives 2 in similar yields, while hydrogenation of [Ru3(CO)7(μ-dppm)(μ3-CO)(μ3-Se)] (4) affords [Ru3(CO)7(μ-H)2(μ-dppm)(μ3-Se)] (5) in 85% yield. The molecular structures of 2 and 5 reveal that the diphosphine and one hydride simultaneously bridge the same ruthenium–ruthenium edge with the second hydride spanning one of the non-bridged edges. Both 2 and 5 are fluxional at room temperature being attributed to hydride migration between the non-bridged edges. Addition of HBF4 to 2 affords the cationic trihydride [Ru3(CO)7(μ-H)3(μ-dppm)(μ3-S)][BF4] (6) in which the hydrides are non-fluxional due to the blocking of the free ruthenium–ruthenium edge.