Reactions of W2(H)(OR)7, W2(OR)6(py)2 and W4(OCH2cC4H7) 12 compounds (R = Pri, CH2But, cC5H9) with azobenzene, 1,2-diphenylhydrazine and 1,1-dimethylhydrazine

Article abstract of DOI:10.1016/S0277-5387(96)00490-1

The reaction of W₂(H)(OR)₇, W₂(OR)₆(py)₂ and W₄(OCH₂^cC₄H₇) ₁₂, compounds (R = Prⁱ, CH₂Bu^t, ^cC₅H₉) in hydrocarbon solvents with azobenzene, 1,2-diphenylhydrazine and 1,1-dimethylhydrazine have been studied. The tetranuclear cluster proved to be inert while W₂(H)(OR)₇ was the most kinetically labile. In all cases where a reaction was observed the dinuclear center was ultimately oxidized with the formation of imido (NR^2-) or hydrazido (NNR^2-₂) ligands being formed. These were isolated as compounds of W(6+) supported by four OR ligands. These products require alkoxide group scrambling and no compound from which OR groups were lost was detected. Studies of the reactions between W₂(H)(OR)₇ compounds and hydrazines by low-temperature NMR spectroscopy indicate the initial formation of 1 : 1 adducts followed by elimination of H₂ and ROH as the hydrazine is activated. The following compounds were isolated and crystallographically characterized by single crystal studies: [W(OPrⁱ)₄NPh]₂, [W₃(μ₃-H)(OPrⁱ)₉(NPh)(Py)], [W(OPrⁱ)₄(NPh)(py)] and [W(OPrⁱ)₄(NNMe₂)(py)]. The trinuclear tungsten compound is noteworthy in being a rare, if not the only, example of a 12-electron triangular metal cluster capped by a hydrido ligand. In the other structures the W(6+) center is in a distorted octahedral coordination and the imido or hydrazido(2-) ligand is terminal with significant contribution from the resonance form having a W - N triple bond.