Syntheses and characterization of phenyldiazenido and mixed phenyldiazenido-isocyanide complexes of rhenium.: Crystal structure of [ReBr2(NNPh)2(PPh3)2]

The complex [ReBr2(NNPh)(2)(PPh3)(2)]Br 1, prepared by bromination of [ReCl(NNPh)(2)(PPh3)(2)], was reduced, in thf or acetone, to the paramagnetic phenyldiazenido-complex [ReBr2(NNPh)(2)(PPh3)(2)] 2 and its acetone solvate 2-Me2CO (formed in the presence of HSC6H2Pr3i-2,4,6 or CNMe), and converted spontaneously (via a conceivable nucleophilic displacement at phenyldiazenide) into [ReBr3(NNPh)(PPh3)(2)] 3 from which 2 can also be derived. The molecular structure of 2 has been determined by X-ray diffraction analysis which indicates that one of the diazenide ligands is doubly bent and the other singly bent, each being trans to a bromide ligand and exerting a significant trans influence. Complexes 1-3 react with isocyanides to give the reduced mixed diazenido-isocyanide complexes [ReBr2(NNPh)(CNR)(PPh3)(2)] (R = Me 4 or C6H4Cl-4 5), [ReBr2(NNPh)(CNMe)(2)(PPh3)] 6 or [ReBr(NNPh)(CNMe)(2)(PPh3)(2)] 7.