Catalytic activity of cyclobutadiene rhodium complexes in hydrosilylation and other transformations of alkynes

Abstract

The catalytic activity of cyclobutadiene rhodium complexes was investigated in various transformations of alkynes. Complexes [Rh(C₄Et₄)Hal]_n (at 1 mol% loading) were found to promote hydrosilylation of 1-octyne selectively giving 1-Z-, 1-E-, or 2-Et₃Si-1-octene depending on the nature of the halide ligand and the presence of additional ligand PPh₃. Complex [Rh(C₄Et₄)(p-xylene)]⁺ (1 mol%) also efficiently catalyzed the polymerization of phenylacetylene. At the same time, we found that various cyclobutadiene rhodium complexes do not catalyze the Diels–Alder reaction, alkyne hydration, and 1,4-addition of boronic acids to cyclohexanone. New complexes [Rh(C₄Et₄)(PPh₃)₂]BF₄ and [Rh(C₄Et₄)(C₁₀H₈)]PF₆ were also synthesized and their structures were established by X-ray diffraction.