Mechanism of the reaction between trans-[W(NNH2)(p-MeC6H4SO3)(Ph2PCH2CH2PPh2)2]+ and NEt3: the influence of the metal on the rates of proton transfer of hydrazido(2–)-ligands

Abstract

The reaction between an excess of NEt₃ and trans-[W(NNH₂)(p-MeC₆H₄SO₃)(dppe)₂]⁺[dppe = 1,2-bis(diphenylphosphino)ethane] in tetrahydrofuran, under an atmosphere of dinitrogen, ultimately to yield trans-[W(N₂)₂(dppe)₂], has been studied. The mechanism of the reaction involves rate-limiting deprotonation of the hydrazido(2–)-residue to generate trans-[W(NNH)(p-MeC₆H₄SO₃)(dppe)₂]. The subsequent pathway involves the dissociation of p-MeC₆H₄SO₃ and deprotonation of the diazenido-residue to generate [W(N₂)(dppe)₂]. Rapid attack of dinitrogen, present in solution, yields the product. The influence of the metal (Mo or W) on the rates of proton transfer in this reaction is discussed.