The vibrational spectra of bridging carbonyl groups in transition metal carbonyl clusters

The spherical harmonic model (SHM), previously used for the analysis of the terminal ν(CO) vibrations of transition metal carbonyl clusters, is applied to the corresponding bridging CO modes. The model is applicable, although the spectra show a greater sensitivity to the molecular geometry than is the case for their terminal counterparts. The reasons for this sensitivity are discussed. When both μ₂ and μ₃ CO groups are present in a molecule, a spectral distinction may not be apparent.