Synthesis, structural characterization, and properties of chromium(III) complexes containing amidinato ligands and η2-pyrazolato, η2-1,2,4-triazolato, or η1-tetrazolato ligands

Treatment of anhydrous chromium(III) chloride with 2 or 3 equivalents of 1,3-di-tert-butylacetamidinatolithium or 1,3-diisopropylacetamidinatolithium in tetrahydrofuran at ambient temperature afforded Cr(tBuNC(CH3)NtBu)(2)(Cl)(THF) and Cr(iPrNC(CH3) NiPr)(3) in 78% and 65% yields, respectively. Treatment of Cr(tBuNC(CH3)NtBu)(2)(Cl)(THF) with the potassium salts derived from pyrazoles and 1,2,4-triazoles afforded Cr(tBuNC(CH3) NtBu)(2)( X), where X = 3,5-disubstituted pyrazolato or 3,5-disubstituted 1,2,4-triazolato ligands, in 65 - 70% yields. X-Ray crystal structure analyses of Cr(tBuNC(CH3) NtBu)(2)(Me(2)pz) (Me(2)pz = 3,5-dimethylpyrazolato) and Cr(tBuNC(CH3) NtBu)(2)(Me(2)trz) (Me(2)trz = 3,5-dimethyl-1,2,4-triazolato) revealed eta(2)-coordination of the Me2pz and Me2trz ligands. Treatment of Cr(tBuNC(CH3) NtBu)(2)( Cl)( THF) with trifluoromethyltetrazolatosodium (NaCF(3)tetz) in the presence of 4-tert-butylpyridine afforded Cr(tBuNC(CH3) NtBu)(2)(CF(3)tetz)(4-tBupy) in 30% yield. An X-ray crystal structure determination showed eta(1)-coordination of the tetrazolato ligand through the 2-nitrogen atom. The complexes Cr(iPrNC(CH3) NiPr)(3) and Cr(tBuNC(CH3) NtBu)(2)(X) are volatile and sublime with < 1% residue between 120 and 165 degrees C at 0.05 Torr. In addition, these complexes are thermally stable at > 300 degrees C under an inert atmosphere such as nitrogen or argon. Due to the good volatility and high thermal stability, these new compounds are promising precursors for the growth of chromium-containing thin films using atomic layer deposition.