SYNTHESIS, STRUCTURE, AND REACTIVITY OF A NOVEL HAFNIUM CARBORANYL HYDRIDE COMPLEX

The reaction. of Cp(2)(C2B9H11)(2)Hf(2)Me(2) (1b; Cp* = C(5)Me(5)) wi th H-2 yields the novel hafnium carboranyl hydride complex (5)-C2B9H11 )Hf(mu-eta(5):eta(1)-C2B9H10)Hf(Cp)(H) (4), in which the two metal ce nters are linked by a C-metalated mu-eta(5):eta(1)-C2B9H10 ligand and Hf-H-Hf and B-H-Hf bridges. Complex 4 catalyzes the hydrogenation, of internal alkynes to cis-alkenes. It is proposed that the active specie s in this reaction is the mononuclear hydride Cp(C2B9H11)Hf(H) (5), w hich is formed by hydrogenolysis of 4 and undergoes rapid alkyne or al kene insertion and Hf-C hydrogenolysis steps.