Catalytic reduction of hydrazine to ammonia by a high-oxidation state molybdenum complex

[MoO2(acac)2] (acac = acetylacetonate) promotes the disproportionation of hydrazine in THF solutions. The active catalytic species, [MoVIO2]2+, are produced according to the reaction: [MoO2(C5H7O2)2] + 2N2H4 → [MoO2]2+ + 2C5H8N2 + 2OH− + 2H2O. The main product of the reduction of hydrazine is ammonia while 3,5-dimethylpyrazole (C5H8N2) was isolated as a side-product. A catalytic cycle was proposed and the probable reaction intermediate is a hydrazido-complex, [MoIVdouble bond; length as m-dashNNH2(OH2)2]2+. The intermediate species, [MoVIO2NH3]2+ reacts with hydroxide ion leading to the complex cis-[MoVIO2(OH)2(NH3)], which was isolated and characterized.