Theoretical studies on vibrational spectra of some mixed carbonyl-halide complexes of Osmium(II)

The vibrational spectra of Os(CO)62+ and some of its mixed carbonyl-halide complexes, cis-Os(CO)2X42−, fac-Os(CO)3X3− and Os(CO)5X+ (X = F, Cl, Br and I), have been systematically investigated by ab initio RHF and density functional B3LYP methods with LanL2DZ and SDD basis sets. The calculated vibrational frequencies of complexes Os(CO)62+, cis-Os(CO)2X42− and fac-Os(CO)3X3− are evaluated via comparison with the experimental values. In infrared frequency region, the C-O stretching vibrational frequencies calculated at B3LYP level with two basis sets are in good agreement with the observed values with deviations less than 5%. In the far-infrared region, the B3LYP/SDD method achieved the best results with deviations less than 9% for Os-X stretching and less than 8% for Os-C stretching vibrational frequencies. The vibrational frequencies for Os(CO)5X+ that have not been experimentally reported were predicted.