Direct synthesis of doubly deprotonated, dearomatised lutidine PNP Cr and Zr pincer complexes based on isolated K and Li ligand transfer reagents.

Abstract

Double deprotonation of 2,6-bis-(di-tert-butylphosphinomethyl)-pyridine ((tBu)PN(tBu)P), with KCH2C6H5 afforded K2((tBu)P*Na(tBu)P*), Na = anionic amido N, (tBu)P* = di-tert-butyl vinylic P donor. The analogous [Li2((tBu)P*Na(tBu)P*)]2 (1) was reacted with [CrCl2(THF)2] and [ZrCl4(THT)2] to give the helical [Cr{Cr((tBu)P*Na(tBu)P*)Cl}2] (2) and [Zr((tBu)P*Na(tBu)P*)Cl2] (3), respectively. DFT calculations support dearomatisation of P*NaP* and its high donor ability.