Hydrolysis and reductive hydrolysis of nitridomolybdenum(VI) complexes: a model reaction in the purported catalytic cycles of dinitrogen fixation

Abstract

The hydrolysis of the MoN group in nitridomolybdenum(VI) complexes was studied using Raman spectroscopy by tracing the ν(MoN) band at 1027 cm −1 for [MoNCl 3(bpy)], 1045 cm −1 for [MoNCl 2(PPh 3) 2], 1042 cm −1 for [MoNCl 3(OPPh 3) 2] and at 1056 cm −1 for [Et 4N][MoNCl 4] in the solid state. The coordination of phosphine and phosphine oxide ligands to MoN species facilitates reductive hydrolysis to give ammonia in 11–13% yield under mild conditions. The MoN group of [Et 4N][MoNCl 4] is also reactive, but only a trace of ammonia was formed under the mild conditions. [MoNCl 3(bpy)] is photolabile and inert to the hydrolysis. The Raman study of the MoN vibration and the determination of ammonia indicate an increased formation of ammonia by basic hydrolysis, but suggest the formation of an undefined nitride species with acidic or reductive hydrolysis.