N-heterocyclic carbenes with N-ferrocenyl-N′-methyl-substitution:: synthesis, reactivity, structure and electrochemistry

Benzimidazolium salts with one N-ferrocenyl substituent and with one N-methyl substituent are prepared by a synthetic sequence involving coupling of the metallocenyl group to a non-cyclic orthophenylene-diamine precursor. ring closure, and oxidation. From these carbene progenitors a range of carbene derivatives are synthesized, including thiourea, azine, and metal complexes with W(0), Pd(II) and Hg(II). Spectroscopic, structural and electrochemical properties in this series of compounds are compared with those of recently published analogous but methylene-spacered benzimidazoline-2-ylidene derivatives, indicating significant electronic communication between the carbene moiety and the N-ferrocenyl substituent. (C) 1999 Elsevier Science S.A. All rights reserved.