Monomeric and Dimeric Amidinate Complexes of Magnesium

• Published in: Inorganic chemistry 2001-12, Vol.40 (25), p.6349-6355
• Main Authors: Sadique, Azwana R, Heeg, Mary Jane, Winter, Charles H
• Format: Article
• Language: English
• ISSN: 0020-1669; 1520-510X
• DOI: 10.1021/ic0106928

Treatment of anhydrous magnesium bromide with 2 equiv of (1,3-di-tert-butylacetamidinato)lithium, (1,3-di-tert-butylbenzamidinato)lithium, (1,3-diisopropylacetamidinato)lithium, or (1-tert-butyl-3-ethylacetamidinato)lithium (prepared in situ from the corresponding carbodiimide and alkyllithium) in diethyl ether at ambient temperature afforded bis(N,N‘-di-tert-butylacetamidinato)magnesium (81%), bis(N,N‘-di-tert-butylbenzamidinato)magnesium (82%), bis[bis(N,N‘-diisopropylacetamidinato)magnesium] (70%), or bis[bis(1-tert-butyl-3-ethylacetamidinato)magnesium] (93%), respectively, as colorless crystalline solids. These complexes were characterized by spectral and analytical data and by single-crystal X-ray crystallography for bis(N,N‘-di-tert-butylbenzamidinato)magnesium, bis[bis(N,N‘-diisopropylacetamidinato)magnesium], and bis[bis(1-tert-butyl-3-ethylacetamidinato)magnesium]. In the solid-state structure, bis[bis(1-tert-butyl-3-ethylacetamidinato)magnesium] was found to contain μ,η2:η1-amidinato ligands. Bis[bis(N,N‘-diisopropylacetamidinato)magnesium] exists in a monomer−dimer equilibrium in toluene-d 8 between −20 and +60 °C. A van't Hoff analysis of this equilibrium afforded ΔH° = −14.7 ± 0.2 kcal/mol, ΔS° = −44.9 ± 0.2 cal/(mol·K), and ΔG°(298 K) = −1.32 ± 0.2 kcal/mol. The potential application of the new compounds in the chemical vapor deposition of magnesium-doped group 13 compound semiconductor films is discussed.