Cycling between Molybdenum-Dinitrogen and -Nitride Complexes to Support Reaction Pathway for Catalytic Formation of Ammonia from Dinitrogen.

Interconversion between molybdenum(I)-dinitrogen and molybdenum(IV)-nitride complexes was investigated under ambient reaction conditions.   The kinetic study of the second-order reaction rate for the conversion of the molybdenum--dinitrogen complex into the molybdenum-nitride complex indicates that the formation of dinitrogen-bridged dimolybdenum complex is involved in the rate-determining step.   The result of DFT calculations of the interconversion between the molybdenum-dinitrogen and -nitride complexes indicates that the reaction of molybdenum-dinitrogen complex into molybdenum-nitride complex proceeds via direct cleavage of nitrogen-nitrogen triple bond of the bridging dinitrogen ligand in dinitrogen-bridged dimolybdenum complex and the reverse reaction of the molybdenum-nitride complex into the molybdenum-dinitrogen complex proceeds via the ligand exchange of ammonia with dinitrogen at the dinitrogen-bridged dimolybdenum complexes.   A modified reaction pathway has been newly proposed based on our findings of the experimental and theoretical results in the present manuscript.