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

Abstract

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.