Ullmann-Type And Related Redox Reactions Of Nitrosyl Molybdenum Complexes Bearing A Large-Bite-Angle Diphosphine

The reactions of ArX (X = Cl and Br) with [Mo(NO)(PP)(NCMe)(3)][BAr4F] PP = 2,2-bis(diphenylphosphanyl)diphenyl ether (DPEphos), BAr4F = tetrakis[3,5-bis(trifluoromethyl)phenyl]borate at 120 degrees C resulted in the formation of biphenyl (through C-Ar-C-Ar reductive homocoupling) and the dinuclear halide salts [Mo-2(NO)(2)(PP)(2)(NCMe)(2)(-X)(2)][BAr4F](2) (X = Cl, 1; Br, 2). Complexes 1 and 2 potentially show cisoid (1c and 2c) and transoid (1t and 2t) regioisomerism with respect to the position of the NO ligand. The crystal-structure determinations of 1 and 2 revealed the presence of the transoid isomers 1t and 2t and M-I-M-I bonding in both cases. A proposed mechanism for the formation of 1t and 2t involves reductive C-Ar-C-Ar coupling to form biphenyl from two Ph-Mo-II centers. In addition, the complexes Mo(NO)(PP)(CO)(2)Cl (3) and [Mo(NO)(mer-(3)-P,P,O-DPEphos)Cl(PR3)] (R = Me, 4; Ph, 5) were obtained through the reductions of [Mo-2(NO)(2)(PP)(2)Cl-4(-Cl)(2)].