Synthesis, Structural Characterization, and Volatility Evaluation of Zirconium and Hafnium Arnidate Complexes

Abstract

Attached

Treatment of tetrakis(dimethylamido)zirconium or tetrakis(dimethylamido)hafnium with four equivalents of N-rerr-butylacetamide. N-isopropylisobutyramide. N-isopropylacetamide. N-methylacetamide. or N-terr-butylformamide in refluxing toluene. followed by sublimation of the crude products at 105 -125 °CI0.05 Torr. afforded tetrakis(N-rerr-butylacetamido )zirconium (81 %). tetrakis(Nisopropylisobutyramido )zirconium (87%). tetrakis(N-isopropylacetamido )zirconium (51 %), tetrakis(Nterr-butylacetamido )hafnium (83%), tetrakis( N-isopropyliso-butyramido )hafnium (79%), tetralds(Nisopropylacetamido)hafnium (67%), tetrakis(N-methylacetamido)zirconium (5%), and tetrakis(N-rertbutylformamido)zirconium (1%) as colorless crystalline solids. The structural assignments for the new complexes were based upon spectral and analytical data and by X-ray crystal structure determinations for tetr akisl N-rerr -butylaceta m ido )zircon iurn. tetrakis( N-isopropylacetamido)z ircon iurn, tetrakis( N-isopropylacetamido)hafnium. tetralds(N-methylacetamido)zirconium, and tetrakis(N-rert-butylformamido) zirconium. These complexes are monomeric in the solid state, with eight-coordinate metal centers surrounded by four K 2-N,O-amidate ligands. Six of the eight new complexes undergo sublimation on a preparative scale from 130 to 140 °C at 0.05 Torr, with 84.5-95.8% sublimed recoveries and 0.68-3.06% nonvolatile residues. Tetrakis(N-methylacetamido jzirconium and tetrakis(N-terr-butylformamido )zirconium decompose extensively upon attempted sublimation. Solid state decomposition temperatures for the zirconium complexes range between 218 and 335 "C and 290-360 O( for the hafnium complexes. Tetrakis(N-isopropylisobutyramido)zirconium, tetrakis(N-tert-butylacetamido)hafnium, and tetrakis(Nisopropylacetamido)hafnium exhibit the highest solid state decomposition temperatures in the series, possess good volatility, and have useful properties for chemical vapor deposition and atomic layer deposition precursors.