Infrared spectra of aluminium carbonyl complexes in solid argon
Abstract
Infrared spectra of aluminium carbonyl complexes generated in argon matrices by co-condensation of aluminium atoms and carbon monoxide have been observed and analysed. AlCO, aluminium monocarbonyl, was isolated and clearly identified. It is characterized by a carbonyl force constant (Fco≈ 14 mdyn Å–1) markedly smaller than in Al(CO)2(15.5 mdyn Å–1), thus contradicting earlier studies concluding that an AlCO complex should be unbound or, at most, a weak van der Waals complex.
The new features in the low-frequency region for the previously characterized Al(CO)2 species are analysed based on a harmonic force field. The experimental results are consistent with the prediction of an aluminium dicarbonyl structure of C2v symmetry with bent Al—CO groups. The existence of isocarbonyl structures could not be confirmed, but the bimetallic species Al2CO and Al2(CO)4 were identified.