The chemistry of niobium and tantalum dithiocarbamato-complexes. Part 6. The kinetics and mechanism of the hydrazine-forming reactions between [{Ta(S2CNEt2)3}2(µ-N2)] and HBr: cleavage of the binuclear unit

The kinetics of the reaction between [{Ta(S2CNEt2)3}2(µ-N2)] and an excess of HBr in MeCN, to yield hydrazine and [TaBr2(S2CNEt2)3], have been studied. The reaction involves the rapid formation of the intermediate [(Et2NCS2)3Ta(µ-NHNH2)TaBr(S2CNEt2)3]2+, which subsequently undergoes rate-limiting tantalum–nitrogen bond cleavage to give [TaBr(S2CNEt2)3]+ and [Ta(NHNH2)(S2CNEt2)3]+. The former complex rapidly picks up Br–, and the latter is further protonated to yield hydrazine and the second mole equivalent of the dibromo-product ultimately.