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–NC_NHC (–N = substituted 2-picoline, R = Cy, t-Bu; C_NHC = N-heterocyclic carbene) (L^R) with KN(SiMe₃)₂ in ether gave [KL^Cy_–H(ether)]₂ featuring a dearomatised picoline backbone. Assisted by 18-crown-6, K⁺ dissociation afforded the Z- and E-isomers of [L^R_–H]⁻. Transmetallation of L^R_–H from KL^R_–H led to [CrCl(L^t-Bu_–H)].