NHC–copper(I) bifluoride complexes: “Auto-activating” catalysts

(NHC)copper(I) hydrides catalyse the hydrosilylation of ketones. (NHC)copper(I) (bi)fluoro species were shown to be active catalysts that do not require an activating agent. In this contribution, the self-activating mechanism of a (NHC)copper(I) (bi)fluoro pre-catalyst has been elucidated by a combined theoretical and experimental study. Experimental NMR studies show the fluorosilane by-product to intervene in the activation mechanism. Thus, bifluoride copper(I) complexes are auto-activating catalysts. Several hypotheses on the activation mechanism have been investigated, and experimental and theoretical results, point towards the formation of a tight ion pair between a difluorosilicate and a cationic copper(I) complex. Results furthermore yield insight into the mechanism of the Cu(I) hydride formation.