Cleavage of the relatively inert dinitrogen (N-2) molecule, with its extremely strong N=N triple bond, has represented a major challenge to the development of N-2 chemistry. This report describes the reductive cleavage of N-2 to two nitrido (N3-) ligands in its reaction with Mo(NRAr)(3), where R is C(CD3)(2)CH3 and Ar is 3,5-C6H3(CH3)(2), a synthetic three-coordinate molybdenum(III) complex of known structure. The formation of an intermediate complex was observed spectroscopically, and its conversion (with N=N bond cleavage) to the nitrido molybdenum(VI) product N-Mo(NRAr)(3) followed first-order kinetics at 30 degrees C. It is proposed that the cleavage reaction proceeds by way of an intermediate complex in which N-2 bridges two molybdenum centers.