Reaction of azide ion with compounds of molybdenum (III) and (V) and the observation of proton hyperfine splitting of molybdenum E.S.R. signals in a model system

Abstract

Reaction of the azide ion with the molybdenum(III) complex, [Mo 2O 2Cl 2(H 2O) 6], (I), and mercaptoethanol complexes of molybdenum(V), [Mo 2O 4(SCH 2CH 2OH) 2], (II), and molybdenum(III), [Mo 2OCl(SCH 2CH 2OH) 3].2H 2O, (III), are described. Azide is reduced to dinitrogen and ammonia by the molybdenum(III) complexes via an intermediate which contains coordinated N 3 − and HN 3 species. The rate and extent of the reduction of azide are increased by mercaptoethanol. With the molybdenum(V) complex (II) reduction of azide occurs only in the presence of excess of mercaptoethanol, which reduces the molybdenum(V) complex to a molybdenum(III) complex which then reduces azide. E.s.r. signals of the various molybdenum species are described. Proton hyperfine splitting of the signals is observed during reduction of azide, showing that the reaction involves protonation of nitrogen bound to molybdenum. The relevance of the work to model studies of nitrogenase is discussed.