Reactivity of a coordinatively unsaturated diruthenium hydride: reversible insertion of alkynes

The chemistry of the coordinatively unsaturated hydridodiruthenium complex cation [Ru2(mu-H)(mu-CO)(CO)3(mu-dppm)2]+, 1, is described. Complex 1 adds CO to give [Ru2(mu-H)(mu-CO)(CO)4(mu-dppm)2]+, reacts with hydrogen to give [Ru2(mu-H)2(CO)4(mu-dppm)2] and H+ and, in the presence of Et3N, is an efficient catalyst for decomposition of formic acid to CO2 and H2. Complex 1 reacts easily with acetylene to give [Ru2(mu-CHCH2)(CO)4 (mu-dppm)2]+, with PhCCH to give the coordinatively unsaturated alkenyl complex [Ru2{C(Ph)CH2}(mu-CO)2(CO)2(mu-dppm)2]+ which then rearranges to the isomeric, coordinatively saturated complex [Ru2(E-mu-CHCHPh)(CO)4(mu-dppm)2]+, and reacts reversibly with PhCCPh to give [Ru2{Z-C(Ph) CHPh}(mu-CO)2(CO)2(mu-dppm)2]+.