The infrared intensities of the carbonyl stretching modes of a series of compounds, X3M—Mn(Co) 5 ( X = Cl, Br and I; M = Si, Ge and Sn)

Abstract

The i.r. intensities of the carbonyl stretching vibrations of a series of compounds, X 3 M—Mn(CO) 5( X = Cl, Br and I; M = Si, Ge and Sn) with C 4ν, local symmetry around the manganese atom have been measured. The intensities of the A 1 mode of the four planar carbonyl groups increase as the halogen atom changes from Cl to I and/or the IVb metal atom changes from Si to Sn, and these increases correlate with the decrease of the metal-metal stretching force constants. This relationship between the i.r. intensities and the metal-metal stretching force constants can be interpreted in terms of the interaction of the IVb metal-manganese σ-orbitals with the π ∗ (radial) orbitals of the four planar carbonyl groups.