Investigation of N-Heterocyclic Carbene-Supported Group 12 Triflates as Pre-catalysts for Hydrosilylation/Borylation

摘要

N-Heterocyclic carbene (NHC) complexes of Cd and Hg triflates (OTf) were prepared and their attempted conversion into rare cadmium and mercury hydrides was explored. In contrast to zinc, which forms stable [ZnH](+) complexes with NHCs, the heavier Cd and Hg congeners could not be formed; the increased instability of Cd-H and Hg-H units was rationalized with the aid of computations. It was also discovered that the dimeric adduct [IPr center dot Cd(mu-OTf)(2)](2) (IPr=[(HCNDipp)(2)C:]; Dipp= 2,6-iPr(2)C(6)H(3)) is an active precatalyst for the hydrosilylation and hydroborylation of hindered aldehydes and ketones. The related zinc congener was inactive as a catalyst highlighting a distinct advantage of using heavy Group 12 metals to promote catalytic hydrosilylation/borylation.