title: Mixed amido/imido/guanidinato complexes of niobium: potential precursors for MOCVD of niobium nitride thin films.
abstract: Novel mixed amido/imido/guanidinato complexes of niobium are reported. The complexes were synthesized by insertion of two equivalents of di-isopropylcarbodiimide (i-Pr-cdi) or bis-cyclohexylcarbodiimide (Cy-cdi) respectively, into the niobium-amido bonds of [Nb(NR(2))(3)(N-t-Bu)] (, R = Me; , R = Et) starting out from [NbCl(3)(N-t-Bu)(py)(2)] and the respective LiNR(2) reagent (py = pyridine). Four representative examples of these mixed ligand amido/imido/guanidinato compounds were synthesized and were characterized by (1)H-NMR, (13)C-NMR, (15)N-NMR, CHN-analysis, mass spectrometry and infra-red spectroscopy. The molecular structures of [Nb(NR(2)){eta(2)-(i-Pr-N)(2)C(NR(2))}(2)(N-t-Bu)] (, R = Me; , R = Et) in the solid state were determined by single-crystal X-ray diffraction studies and are discussed together with the molecular structure of the starting compound [Nb(NMe(2))(3)(N-t-Bu)] (). The thermal properties of the new compounds depend on the substitution at the guanidinato ligand. Complexes of i-Pr-cdi are significantly more volatile than complexes of Cy-cdi as revealed by thermogravimetric analysis. Preliminary experiments using as a single-molecule source for metal-organic chemical vapour deposition (MOCVD) in the absence of ammonia indicate the formation of the stoichiometric, and surprisingly carbon-free, cubic niobium nitride phase.
authors.affiliation: Lehrstuhl für Anorganische Chemie II, Organometallics and Materials, Ruhr-Universtät Bochum Universitätsstr. 150, D-44780, Bochum, Germany.
authors.forename: Arne
authors.initials: A
authors.lastname: Baunemann
authors.forename: Daniela
authors.initials: D
authors.lastname: Bekermann
authors.forename: Tobias B
authors.initials: TB
authors.lastname: Thiede
authors.forename: Harish
authors.initials: H
authors.lastname: Parala
authors.forename: Manuela
authors.initials: M
authors.lastname: Winter
authors.forename: Christian
authors.initials: C
authors.lastname: Gemel
authors.forename: Roland A
authors.initials: RA
authors.lastname: Fischer