Volatile 1,1-dimethyl-2-(trimethylsilyl)hydrazido(1-) complexes of niobium, tantalum, molybdenum, and tungsten have been synthesized and fully characterized for use as precursors in their chemical vapor deposition to metal nitrides. Different reaction patterns were observed in the hydrazinolysis of imido complexes of those four metals with (trimethylsilyl)dimethylhydrazine HN(SiMe3)NMe2 (H-TDMH). [Ta((NBu)-Bu-t)Cl3Py2] gave [Ta(TDMH)(2)Cl-3] (1) with loss of the imido functionality, and [M((NBu)-Bu-t)(2)Cl2Py2] gave [M((NBu)-Bu-t)(2)(TDMH)Cl] (M = W, 8a; Mo, 8b). Reactions of both types of metal imido complexes with magnesium hydrazides produced [M((NBu)-Bu-t)(TDMH)(2)X] (M = Ta, X = Cl, 2a; X = Br, 3a; M = Nb, X = Cl, 2b; X = Br, 3b) and [M((NBu)-Bu-t)(2)(TDMH)X] (M = W, X = Cl, 8a; X = Br, 9a; M = Mo, X = Cl, 8b; X = Br, 9b). Halogen substitution reactions at 2 and 3 by -NMe2, -(NHBu)-Bu-t, and CH2Ph groups as well as imido ligand replacement reactions have been investigated. The results of crystal structure determinations of 1, 4a, 5a, 6a, 7b, and 9b are presented.