The modes between 250 and 400 cm -1 include normal modes that couple metal-metal and metalligand motions. While not all of these modes are confirmed to be Raman active, those that shift upon isotope substitution are consistent with the observed experimental bands, albeit systematically shifted to lower values. The PES calculations along the ν(Cr 2 ) normal mode and observation of improved Cr-Cr bond distances with the inclusion of the IPEA shift support the hypothesis by Da Re et al. that there is a distorted Cr-Cr potential in these Cr(II) 2 complexes similar to that inferred for Cr(0) 2 contributing to the vibrational behavior of the Cr-Cr complexes. Finally, the ν(Cr 2 ) mode is anharmonic and including cubic and quartic corrections shifts the vibrational mode to lower values by 10 to 20 cm -1 . Nevertheless, questions remain in describing this complicated low frequency region, in particular the nature of peaks assigned to an excited state transitions observed in the spectra, assumed to arise from the so-called δ → δ * transition. These results emphasize that the interpretation of vibrational spectra for complexes with strong metal-metal and metal-ligand interactions is challenging requiring insights from both experiment and theory. CASPT2 vibrational analysis is anticipated to be a valuable tool in furthering understanding of multiconfigurational bonds in larger complexes with metal-metal bonds.