INFRARED AND RAMAN-SPECTRA OF (ETA-6-C6H6-NXN)CR(CO)3 COMPLEXES WHEREX=ME (N=0-6) OR OME (N=0-2) - A STUDY OF METAL-LIGAND INTERACTIONS

A systematic study is reported of the infrared and Raman spectra of me thyl and methoxy substituted benzene chromium tricarbonyl complexes (e ta6-C6H6-nXn)Cr(CO)3 where X = Me (n = 0-6) or OMe (n = 0-2). Bands ha ve been assigned and intensities calculated for a number of vibrationa l modes. Trends in the wavenumbers and band intensities of the arene-m etal, metal-carbonyl and carbonyl bonds are examined to gain an insigh t into metal-ligand interactions and intramolecular electron rearrange ments with progressive substitution on the arene. The results are disc ussed with regard to sigma-, pi- and delta-contributions to arene-meta l bonding and of sigma- and pi-components in metal-carbonyl and carbon yl bonding. The intensities are related to the polarities and polariza bilities of individual bonds within the molecules, and variations in t hese bond electronic properties with arene substitution are examined.