Synthesis and Structural Characterization of High Spin M/Cu (M = Mn, Fe) Heterobimetallic and Fe/Cu2 Trimetallic Phosphinoamides

The heterobimetallic complexes [Mn­(iPrNPPh2)3Cu­(iPrNHPPh2)] (1) and [Fe­(iPrNPPh2)3Cu­(iPrNHPPh2)] (2) have been synthesized by the one pot reaction of LiNiPrPPh2, MCl2 (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(iPrNPPh2)3Cu2(iPrNPPh2)] (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.