Catalytic exploration of NHC-Ag(I)HMDS complexes for the hydroboration and hydrosilylation of carbonyl compounds.

Abstract

The synthesis and full characterisation of two silver(I) amido complexes, stabilised by ancillary N-heterocyclic carbene (NHC) ligands is presented. The light stable complexes [Ag(IDipp)HMDS] 3 and [Ag(IAd)HMDS] 4 were explored as suitable pre-catalysts in the hydroboration and hydrosilylation of a range of carbonyl substrates, with complex 3 out-performing 4 and our previous phosphine-stabilised lead catalyst [Ag(PCy3)HMDS] 5. This study highlights that changing the stabilising Lewis donor in the silver(I)amide system has an influence on catalytic efficiency. Finally, to shed light on the catalytic differences of pre-catalysts 3-5, we used a suite of programs to examine the influence of steric bulk on the Lewis donor ligand including percent buried volume (%VBur), Solid-G and AtomAccess which revealed the most sterically protected Ag(I) metal centre correlated to the most effective pre-catalyst 3.