ZnH2 as a Precursor to Catalytically Active Ru-ZnH Heterometallic Complexes

Abstract

Reaction of [Ru(IPr)2(CO)H][BArF4] (1; IPr = 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene; BArF4 = B{3,5(CF3)2C6H3}4) with an excess of ZnH2 in THF gives the structurally characterized neutral Ru(ZnH) complex [Ru(IPr)2(CO)(ZnH)H3] (6) and Ru(ZnH)2 salt [Ru(IPr)2(CO)(ZnH)2H3][BArF4] (5). Crystallographic and computational analyses show the presence of both bridging Ru-H-Zn hydrides and terminal Ru-hydrides in the two products. Calculations also identify a low-energy H/ZnH exchange pathway that rationalizes the experimentally observed (EXSY) fluxionality of the hydrides in 5. At room temperature, this compound undergoes stoichiometric exchange with ZnMe2 to give [Ru(IPr)2(CO)(ZnMe)2H3][BArF4] (7), and also proves to be catalytically active for the hydrogenation of 1-hexene and 5-hexene-2-one.