New octahedral Ta(V) hydrazido-substituted compounds for atomic layer deposition: Syntheses, X-ray diffraction structures of TaCl(NMe2)3[N(TMS)NMe2] and Ta(NMe2)4[N(TMS)NMe2], and fluxional behavior of the amido and hydrazido ligands in solution

The synthesis and structural characterization of new tantalum(V) compounds containing a single hydrazido(I) ligand are reported. Hydrazinolysis of TaCl(NMe2)4 using trimethylsilyl(dimethyl)hydrazine affords the compound TaCl(NMe2)3[N(TMS)NMe2] in essentially quantitative yield. Metathetical replacement of the chloride ligand in TaCl(NMe2)3[N(TMS)NMe2] by LiNMe2 gives the all-nitrogen coordinated compound Ta(NMe2)4[N(TMS)NMe2]. VT 1H NMR studies support the existence of low-energy pathways involving rotation about the Ta–N bonds of the ancillary amido and hydrazido ligands in both hydrazido-substituted compounds. X-ray crystallographic analyses confirm the octahedral disposition about the tantalum metal in TaCl(NMe2)3[N(TMS)NMe2] and Ta(NMe2)4[N(TMS)NMe2] and the presence of an η2-hydrazido(I) ligand. Preliminary data using Ta(NMe2)4[N(TMS)NMe2] as an ALD precursor for the preparation of tantalum nitride and tantalum oxide thin films are presented.