Ligand effects on the δ → δ* band energies and intensities in a series of diimine complexes of dimolybdenum

Article abstract of DOI:10.1016/0277-5387(95)00535-8

The complexes Mo₂X₄(diimine)₂ (X = Cl, Br, I and diimine = 2,2′-bipyridine, 4,4′-dimethyl-2,2′-bipyridine, 2,2′-bipyrazine, 3,3′-bipyridazine, 2,2′-bipyrimidine, 1,10-phenanthroline and 4,7-diphenyl-1,10-phenanthroline) have been prepared by reaction of Mo₂ (OAc)₄ with (CH₃)₃SiX in the presence of excess diimine. The product complexes apparently contain non-bridged quadruple molybdenum-molybdenum bonds. Each molybdenum is coordinated to a bidentate diimine and two halogen atoms. Electronic absorption and electrochemical studies have shown that shifts in the energy of the δ → δ* band are affected by the mixing of this transition with a metal-to-ligand charge transfer transition, probably a δ → π* transition. It was also found that the compounds Mo₂X₄(diimine)₂ react slowly with oxygen to form Mo₂O₄Cl₄(diimine)₂ and then MoO₂Cl₂(diimine). The crystal and molecular structure of MoO₂Cl₂ (4,4′-dimethyl-2,2′bipyridine), determined by a three-dimensional X-ray diffraction study, is reported. Copyright