Symmetry Force Fields for Neutral and Ionic Transition Metal Carbonyl Complexes from Density Functional Theory

Symmetry force fields for neutral and ionic transition metal carbonyl complexes have been derived on the basis of gradient-corrected density functional calculations using effective core potential wave functions in conjunction with polarized triple-ζ basis sets. For the neutral carbonyls [M(CO)6] (M = Cr, Mo, W), Fe(CO)5, and Ni(CO)4, the calculated data are compared to experimentally derived force fields. For three different series of transition metal carbonyl ions, trends in the force fields are discussed in terms of bonding models and electrostatic effects, emphasizing the variation of the calculated results with the total charge of the carbonyl complex. The limitations of the empirical Cotton−Kraihanzel approach are analyzed