Infrared and Raman spectra of (η6-C6H6−nXn)Cr(CO)3 complexes where X = Me (n = 0–6) or OMe (n = 0–2). A study of metal—ligand interactions

Abstract

A systematic study is reported of the infrared and Raman spectra of methyl and methoxy substituted benzene chromium tricarbonyl complexes (η6-C6H6−nXn)Cr(CO)3 where X = Me (n = 0–6) or OMe (n = 0–2). Bands have been assigned and intensities calculated for a number of vibrational modes. Trends in the wavenumbers and band intensities of the arenemetal, metalcarbonyl and carbonyl bonds are examined to gain an insight into metal—ligand interactions and intramolecular electron rearrangements with progressive substitution on the arene. The results are discussed with regard σ-, π- and δ-contributions to arenemetal bonding and of σ- and π-components in metal-carbonyl and carbonyl bonding. The intensities are related to the polarities and polarizabilities of individual bonds within the molecules, and variations in these bond electronic properties with arene substitution are examined.