Geometrically Constrained Cationic Low‐Coordinate Tetrylenes: Highly Lewis Acidic σ‐Donor Ligands in Catalytic Systems
Philip M. Keil, Terrance J. Hadlington
Abstract
Abstract A novel non‐innocent ligand class, namely cationic single‐centre ambiphiles, is reported in the phosphine‐functionalised cationic tetrylene Ni 0 complexes, [ PhR DippENi(PPh 3 ) 3 ] + ( 4 a/b (Ge) and 5 (Sn); PhR Dipp={[Ph 2 PCH 2 SiR 2 ](Dipp)N} − ; R=Ph, i Pr; Dipp=2,6‐ i Pr 2 C 6 H 3 ). 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 E II centres which readily bind nucleophiles, reversibly in the case of NH 3 . Further, the Ge II centre in 4 a/b readily abstracts the fluoride ion from [SbF 6 ] − to form the fluoro‐germylene complex PhR DippGe(F)Ni(PPh 3 ) 3 9 , despite this Ge II centre simultaneously being a σ ‐donating ligand towards Ni 0 . 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.