Searching for highly active cobalt catalysts bearing Schiff base ligands for Markovnikov-selective hydrosilylation of alkynes with tertiary silanes

Abstract

The search for simple and easy-to-synthesize ligands for bench stable cobalt (pre)catalysts that would ensure high activity and selectivity in alkyne hydrosilylation reactions is an interesting current challenge. Herein, we report that a cobalt(II) complex bearing pyrimidine-imine-2H-imidazole ligand activated by LiHBEt3 exhibits not only high catalytic activity, but also unprecedented tolerance towards tertiary silanes in highly regioselective Markovnikov hydrosilylation of aliphatic and aromatic terminal alkynes to give α-vinylsilanes. In addition, a variety of 1-aryl-2-(trimethylsilyl)acetylenes have been hydrosilylated efficiently by diphenylsilane in the presence of [Co(L)Cl2]/LiHBEt3 catalytic system to yield (E)-1-aryl-1,2-bis(silyl)ethenes with high selectivity. Such selectivity is very rarely observed for cobalt-catalyzed hydrosilylation of silylacetylenes.