Quantum-chemical and spectroscopic studies of structures of 1 : 2 complexes of carbonyl compounds with aluminum halides

Quantum-chemical calculations of model systems, namely, benzaldehyde and its 1 : 1 and 1 : 2 complexes with AlCl₃, were carried out by the MNDO method. In the 1 : 2 complex, a bridging Al-Cl-Al bond occurs. Apparently, this complex is stabilized through the Coulomb interaction between the positively charged C atom of the carbonyl group and the AlCl₃ fragment, which carries an excessive negative charge and which is not involved in donor-acceptor bonding with the carbonyl O atom. The IR spectra of the 1 : 1 and 1 : 2 complexes of benzophenone with AlBr₃ were recorded, and the differences in the low-frequency regions of these spectra, which are indicative of the presence of the Br₂Al-Br-AlBr₃ fragment in the 1 : 2 complex, are discussed.This article is dedicated to Academician M. G. Voronkov on the occasion of his 75th birthday.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2866–2871, December, 1996.