Reactions between trans-bis[1,2-bis(diethylphosphino)ethane]bis-(dinitrogen)molybdenum and hydrogen chloride in tetrahydrofuran : a mechanistic study

Abstract

The reactions between trans-[Mo(N₂)₂(depe)₂][depe = 1,2-bis(diethylphosphino)ethane] and hydrogen chloride in tetrahydrofuran have been studied. The initial reaction involves rapid formation of the isolable [MoH(N₂)₂(depe)₂]⁺[k₁, =(2.7 ± 0.2)× 10³ dm³ mol^–1 s^–1]. Subsequent rate-limiting dinitrogen loss [k₂=(4.5 ± 0.4)× 10^–4 s^–1] results, at low concentrations of acid ([HCl] < ca. 0.3 mol dm^–3), in the predominant formation of [MoH₂Cl₂(depe)₂]. At higher concentrations of acid the major product is trans-[Mo(NNH₂)Cl(depe)₂]⁺. Discrimination between the two products occurs after the rate-limiting loss of dinitrogen. Detailed analysis shows that the two products are formed, at various concentrations of hydrogen chloride, according to the expression [Mo(NNH₂)Cl(depe)₂ ⁺]/[MoH₂Cl₂(depe)₂]= 8.0[HCl]².