Reactions of [W_2(OCH_2~tBu)_8] (M=M) with diazobenzene and trimethylsilyldiazomethane. Preparation and structures of W_2(OCH_2~tBu)_8(NPH) and W_2(OCH_2~tBu)_8(N_2C(H)SiMe_3)

摘要

Hydrocarbon solutions of W_2(OCH_2~tBu)_8 (M=M) react with azobenzene at room temperature to give the phenylimido-bridged compound W_2(μ-NPh)(μ-OCH_2~tBu)_2(OCH_2~tBu)_6 which has a confacial biooctahedral geometry with a W-W single bond length of 2.5613(2) A and W - N = 1.987(3) A (ave). Similarity, W_2(OCH_2~tBu)_8 (M=M) and trimethylsilyldiazomethane react to give the 1:1 adduct W_1(μ-N_2C(H)SiMe_3)(μ-OCH_2~tBu)_2(OCH_2~tBu)_6 with has a W-W distance of 2.5626(2) A and W - N = 1.985(1) A (ave). The μ-N_2CHSiMe_3 ligand can be described as a hydrazonido(2-) ligand. The N-N distance is 1.366(4) A and the N-N-C angle is 120.1(3)°. The NNC plane of the bridging ligand is perpendicular to the W-W bond axis. The bonding in these molecules is discussed in the light of electronic structure calculations employing density functional theory. The present findings are contrasted with related reactions involving MM multiply bonded compounds and with low valent early transition metal complexes that are similarly known to activate N-N bonds.