Polar Tensors, Effective Charges, And Vibrational Intensities Of The M(co)6 (m = Cr, Mo, W) And Ni(co)4 Complexes

Semiempirical quantum mechanical calculations (CNDO and extended Hückel) on the Cr(CO)6 and Ni(CO)4 complexes have been performed with the aim of resolving the sign ambiguities in the ∂p/∂Qi's. Sets of polar tensor values corresponding to the preferred signs of these derivatives are presented for both complexes. A test of the usefulness of these polar tensor values, obtained from intensities measured in solution, for the prediction of the infrared intensities of Mo(CO)6 and W(CO)6, also measured in solution, are reported. Although strict transference of the Cr(CO)6 atomic polar tensors leads to accurate estimates of the intensities for the heavier metal group VIB complexes, the atomic polar tensors of Ni(CO)4 are less satisfactory in representing the magnitudes of the electronic changes for the molecular vibrations of Mo(CO)6 and W(CO)6. © 1980 American Chemical Society.842635933597 European Physical Society (EPS