Synthesis and structural characterization of high spin M/Cu (M = Mn, Fe) heterobimetallic and Fe/Cu 2 trimetallic phosphinoamides

Abstract

The heterobimetallic complexes [Mn( iPrNPPh 2) 3Cu( iPrNHPPh 2)] (1) and [Fe( iPrNPPh 2) 3Cu( iPrNHPPh 2)] (2) have been synthesized by the one pot reaction of LiN iPrPPh 2, MCl 2 (M = Mn, Fe), and CuI in high yield. Addition of excess CuI into 2 or directly to the reaction mixture led to the formation of a heterotrimetallic [Fe( iPrNPPh 2) 3Cu 2( iPrNPPh 2)] (3) in good yield. Complexes 1-3 have been characterized by means of elemental analysis, paramagnetic 1H NMR, UV-vis spectroscopy, cyclic voltammetry, and single crystal X-ray analysis. In all three complexes, Mn or Fe are in the +2 oxidation state and have a high spin electron configuration, as evidenced by solution Evans' method. In addition, the oxidation state of Fe in complex 3 is confirmed by zero-field 57Fe Mössbauer spectroscopy. X-ray crystallography reveals that the three coordinate Mn/Fe centers in the zwitterionic complexes 1-3 adopt an unusual trigonal planar geometry. © 2012 American Chemical Society.