An Atypically Bent Isocyanide at Iron in a Tetrapodal Penta-Carbene Framework

Abstract

Reduction of the previously reported Iron (III) complex PhCC4MeFeCl with sodium naphthalide forms the square pyramidal complex PhCC4MeFe (1), cleanly in moderate yield with short reaction times. The related diamagnetic complex PhCC4MeFe(CNtBu) (2) was prepared by addition of an equivalent of tert-butylisocyanide to a solution of 1. XRD of 2 reveals a rare bent form of the isocyanide moiety with a C−N−C bond angle of 142.67(18)° consistent with sp2 hybridization at the N-atom while IR spectroscopy reveals an atypically broadened isocyanide stretch at νCNR=1981 cm−1; taken together these metrics are demonstrative of the excellent donor ability of the dianionic penta-carbene framework and point to a degree of metal-to-ligand π-backbonding rarely seen at isocyanide complexes of iron.