Theoretical study of the vibrational spectra of the transition metal carbonyls M(CO)6 M=Cr, Mo, W, M(CO)5 M=Fe, Ru, Os, and M(CO)4 M=Ni, Pd, Pt

The harmonic force fields of the title compounds have been calculated at the level of Hartree–Fock (HF) theory, Mo/ller–Plesset second-order perturbation theory (MP2), and gradient-corrected density functional theory (DFT) using all-electron and effective core potential wave functions in conjunction with polarized double- and triple-zeta basis sets. The DFT results are in very good agreement with the available experimental data, whereas the HF results are inadequate and the MP2 results are satisfactory only for the 5d and (partly) the 4d transition metal complexes, but not for the 3d transition metal complexes. The calculated DFT frequencies are accurate enough to suggest reassignments in the vibrational spectrum of Fe(CO)5. In the case of Ru(CO)5, Os(CO)5, Pd(CO)4, and Pt(CO)4 where experimental data are scarce, the DFT predictions may guide future experimental work.