N-Heterocyclic carbene–phosphino-picolines as precursors of anionic ‘pincer’ ligands with dearomatised pyridine backbones; transmetallation from potassium to chromium†‡
Abstract
Deprotonation of the α-picolinyl-CH2 in the hybrid ligands R2P–NCNHC (–N = substituted 2-picoline, R = Cy, t-Bu; CNHC = N-heterocyclic carbene) (LR) with KN(SiMe3)2 in ether gave [KLCy–H(ether)]2 featuring a dearomatised picoline backbone. Assisted by 18-crown-6, K+ dissociation afforded the Z- and E-isomers of [LR–H]−. Transmetallation of LR–H from KLR–H led to [CrCl(Lt-Bu–H)].