A series of C3-symmetric heterobimetallic Cr–M (M = Fe, Co and Cu) complexes

Abstract

A series of tris(phosphinoamide) heterobimetallic Cr–M (M = Fe, Co and Cu) complexes has been investigated in an effort to probe and contribute to the understanding of the electronic structure and metal–metal bonding in heterobimetallic complexes of the first row transition metals. The chromium tris(phosphinoamide), [Cr(ⁱPrNPPh₂)₃] (1), is a useful isolable precursor and can be treated with MI₂ under reducing conditions to form [Cr(ⁱPrNPPh₂)₃M–I] (M = Fe (2), Co (3)). Both of these complexes can be reduced by one electron to generate [Cr(ⁱPrNPPh₂)₃M–PMe₃] (M = Fe (4), Co (5)). The Cr–Cu complex [Cr(ⁱPrNPPh₂)₃Cu–I] (6) has also been synthesized for comparison. The solid state structures of 2–6 have been determined crystallographically, revealing relatively short metal–metal interatomic distances. Mössbauer spectroscopy, cyclic voltammetry, and computational methods have been used to evaluate the electronic structure and metal–metal interactions in these unique bimetallic complexes in an effort to uncover the underlying factors that affect metal–metal bonding between elements of the first row transition series.