Geometrically Constrained Cationic Low-Coordinate Tetrylenes: Highly Lewis Acidic σ-Donor Ligands in Catalytic Systems.

Abstract

A novel non‐innocent ligand class, namely cationic single‐centre ambiphiles, is reported in the phosphine‐functionalised cationic tetrylene Ni0 complexes, [PhRDippENi(PPh3)3]+ (4 a/b (Ge) and 5 (Sn); PhRDipp={[Ph2PCH2SiR2](Dipp)N}−; R=Ph, iPr; Dipp=2,6‐iPr2C6H3). The inherent electronic nature of low‐coordinate tetryliumylidenes, combined with the geometrically constrained [N−E−Ni] bending angle enforced by the chelating phosphine arm in these complexes, leads to strongly electrophilic EII centres which readily bind nucleophiles, reversibly in the case of NH3. Further, the GeII centre in 4 a/b readily abstracts the fluoride ion from [SbF6]− to form the fluoro‐germylene complex PhRDippGe(F)Ni(PPh3)3 9, despite this GeII centre simultaneously being a σ‐donating ligand towards Ni0. Alongside the observed catalytic ability of 4 and 5 in the hydrosilylation of alkynes and alkenes, this forms an exciting introduction to a multi‐talented ligand class in cationic single‐centre ambiphiles.