STRUCTURE AND FLUXIONAL BEHAVIOR OF (ETA(4)-BUTADIENE)FE(CO)(2)L (L=CO, PH3, PME(3)) COMPLEXES - A DENSITY-FUNCTIONAL STUDY

The structure and fluxional behavior of (eta(4)-butadiene)Fe(CO)(2)L ( L = CO, PH3, PMe(3)) complexes have been studied using density functio nal methods. For (butadiene)Fe(CO)(3), the geometry obtained is in exc ellent agreement with the gas-phase experimental data. The calculation of the harmonic vibrational frequencies has permitted the reassignmen t of several frequencies observed in the IR and Raman spectra. The com puted Fe-butadiene binding energy is in all cases about 52 kcal mol(-1 ), in excellent agreement with the experimental data corresponding to the (butadiene)Fe(CO)(3) complex. The nature of the bonding has been a nalyzed in terms of steric and electronic interactions. The butadiene- Fe rotational barriers have been computed, and the origin of the barri er has been discussed.