Mechanistic studies on hydrazido(2–)-complexes. Cleavage of the nitrogen–nitrogen bond in the reaction of [Mo{NN(CH2)4CH2}(Ph2PCH2CH2PPh2)2] with acid

Abstract

The kinetics of the reaction between [Mo{N[graphic omitted]H₂}(dppe)₂](dppe = Ph₂PCH₂CH₂PPh₂) and [NHEt₃]BPh₄ to yield [graphic omitted]H₂ and [MoN(NCR)(dppe)₂]BPh₄(RCN is the solvent; R = Me, Et, or Ph) has been studied. In general the mechanism of the reactions involves two parallel pathways. Initial rapid protonation of the hydrazido(2–)-ligand and attack of a solvent molecule at the metal yields the spectrophotometrically detected hydrazidium species, trans-[Mo{N[graphic omitted]H₂}(NCR)(dppe)₂]⁺. This species can either undergo slow nitrogen–nitrogen cleavage or react via an acid-catalysed pathway involving trans-[Mo{NH[graphic omitted]H₂}(NCR)(dppe)₂]²⁺ to yield the products. The factors influencing whether protonation of hydrazido(2–)-ligands results in amine formation (N–N bond cleavage) or hydrazine formation (N–N bond cleavage) are discussed.