Photoelectron spectroscopic study of the bonding in tetracarbonyl(ethylene)iron

Abstract

The iron 2p/sub 3/2/, carbon 1s, and oxygen 1s binding energies of gaseous tetracarbonyl (ethylene) iron (Fe(CO)/sub 4/C/sub 2/H/sub 4/) have been measured. Atomic charge calculations based on binding energy shifts indicate that the ethylene group of (Fe(CO)/sub 5/) is affected by three equatorial CO ligands; (3) the total back-bonding of the (d/sub xz/, d/sub yz/) orbitals of Fe(CO)/sub 4/C/sub 2/H/sub 4/ is less negatively charged. Interpretation of the published UPS spectrum of Fe(CO)/sub 4/C/sub 2/H/sub 4/ with the aid of core binding energy shifts leads to the following conclusions: (1) there is significant sigma interaction between the ethylene ligand and the Fe(CO)/sub 4/ group of Fe(CO)/sub 4/C/sub 2/H/sub 4/; (2) the energy of the (d/sub xy/, d/sub x/sup 2/-y/sup 2//) orbitals of Fe(CO)/sub 4/C/sub 2/H/sub 4/ is affected by the two equatorial CO ligands and the ethylene ligand to the same extent as the energy of the (d/sub xy/, d/sub yz/) orbitals of Fe(CO)/sub 4/C/sub 2/H/sub 4/ is less than that of Fe(CO)/sub 5/, as expected from the orthogonality of these orbitals and the ..pi.. orbital of coordinated C/sub 2/H/sub 4/ in Fe(CO)/sub 4/C/sub 2/H/sub 4/.