Syntheses and structures of chalcogen-bridged binuclear group 5 and 6 metal complexes

Abstract

Syntheses and structural elucidations of a series of chalcogen stabilized binuclear complexes of group 5 and 6 transition metals have been described. Room temperature reaction of [Cp*CrCl]2 (Cp* = g5 - C5Me5) with Li[BH3(SePh)] afforded a Se inserted binuclear chromium complex, [(Cp*Cr)2(l-Se2SePh)2], 1. In an attempt to make the analogous complexes with heavier group 6 metals, reactions of [Cp*MCl4] (M = Mo and W) with Li[BH3(SePh)] were carried out that yielded Se inserted binuclear complexes [(Cp*M)2(l-Se)2(l-SePh)2], 2 and 3 (2: M = Mo and 3: M = W) along with known [(Cp*M)2B5H9], 4a– b (4a: M = Mo and 4b: M = W). Similarly, the reactions of [Cp*NbCl4] with Li[BH3(EPh)] (E = S or Se) followed by thermolysis led to the formation of binuclear chalcogen complexes [(Cp*Nb)2(l-E2)2], 5 and 6 (5: E = S and 6: E = Se) and known [(Cp*Nb)2(B2H6)2], 7. All these complexes have been characterized by 1 H and 13C NMR spectroscopy and mass spectrometry. The structural integrity of complexes 1, 3, 5 and 6 was established by the X-ray diffraction studies. The DFT studies further exemplify the bonding interactions present in these complexes, especially the multiple bond character between the metals in 1–3.