MECHANISM OF THE REDUCTION OF MOLECULAR NITROGEN TO HYDRAZINE BY NIOBIUM(III) HYDROXIDE

The effect of the concentration of water on the rate of reduction of m olecular nitrogen to hydrazine by niobium(III) hydroxide in alkaline H 2O-MeOH and D2O-MeOD mixtures was studied. In both cases, the reaction rate is maximum when [H2O] = 4 mol L-1, and the inverse isotopic effe ct (k(D)/k(H) > 1) is observed when [H2O] < 20 mol L-1. Similar regula rity was observed for the reaction of hydrogen elimination. It was fou nd that HD is formed in the H2O-MeOH system in the presence of D-2. Th e conclusion was made that the rate-determining stage in hydrazine for mation is the transfer of a hydride ion to the dinitrogen molecule coo rdinated to the binuclear Nb-III center. A kinetic scheme satisfactori ly explaining the effect of the concentration of water ([H2O] = 1.5-49 .0 mol L-1) on the reaction rate constant was proposed.