Chemical nitrogen fixation by using molybdenum and tungsten complexes*

Dinitrogen complex cis-[W(N2)2(PMe2Ph)4] reacts with an excess of acidic dihydrogen complexes such as trans-[RuCl(η-H2)(dppe)2]BF4 (dppe = 1, 2-bis(diphenylphosphino)ethane) at 55 °C under 1 atm of H2 to form ammonia in moderate yield. The reaction is presumed to proceed through nucleophilic attack of the remote nitrogen of the coordinated dinitrogen on the dihydrogen ligand. The coordinated dinitrogen is also protonated by treatment with hydrosulfido-bridged dinuclear complexes such as [Cp*Ir(μ−SH)3IrCp*]Cl (Cp* = η-C5Me5) to afford ammonia. On the other hand, the synthetic cycle for the formation of pyrrole and N-aminopyrrole from dinitrogen and 2,5-dimethoxytetrahydrofuran has been established starting from dinitrogen complexes of the type trans-[M(N2)2(dppe)2] (M = Mo, W).