DIAMAGNETIC (PENTAMETHYLCYCLOPENTADIENYL)TUNGSTEN COMPLEXES CONTAINING UNSUBSTITUTED, MONOMETHYL, OR 1,1-DIMETHYL HYDRAZINE OR HYDRAZIDO LIGANDS

Hydrazine adducts are formed upon adding hydrazine, methylhydrazine, or 1,1-dimethylhydrazine to [Cp*WMe4]PF6. They are readily deprotonated to yield hydrazido(1-) complexes of the type Cp*WMe4[eta2-hydrazido(1-)], or they decompose by loss of methane to yield complexes of the type {Cp*WMe3[eta2-hydrazido(1-)]}+. {Cp*WMe3[eta2-hydrazido(1-)]}+ complexes are deprotonated at low temperature to give complexes of the type Cp*WMe3[eta2-hydrazido(2-)], which rearrange readily to complexes of the type Cp*WMe3[eta1-hydrazido(2-)] above approximately -20-degrees-C. Addition of acid to complexes of the type Cp*WMe3(eta1-NNRR') yields [Cp*WMe3(NNRR'H)]+ complexes first. Loss of a proton from N(beta) followed by addition of a proton to N(alpha) yields the thermodynamically preferred [Cp*WMe3(eta2-NHNRR')]+ complexes. [Cp*WMe3(eta2-NHNH2)]Cl decomposes much more readily than the triflate salt by losing methane to give trans-Cp*WMe2Cl(eta1-NNH2). Methylation of Cp*WMe3(eta1-NNMe2) yields [Cp*WMe3(NNMe3)]+; [Cp*WMe3(NNMe3)]+ also is obtained upon methylating Cp*WMe3(eta1-NNH2) in the presence of a base. Cp*WMe3(eta1-NNH2) reacts with [Cp*WMe3(eta2-NHNH2)]+ to yield [Cp*WMe3]2(mu-N2) and [N2H5]+, while Cp*WMe3(eta1-NNH2) decomposes to Cp*WMe3(mu-NNH)Cp*WMe2(mu-NN)Cp*WMe3. These findings are discussed in relation to the proposal that both nitrogen atoms of an N2Hx intermediate must bind to the metal in preparation for formation of a d2 eta2-N2H4 complex in which the N-N bond is cleaved to yield 1 equiv of ammonia.