The electronic state of butadiene bonded to an iron tricarbonyl residue

A theoretical study of tricarbonylbutadieneiron by the all valence electron SCFMO method is presented.The charge distribution on the butadiene group in the complex appears to correspond to a mixture of excited electronic states of the free molecule and this is found to be consistent both with the experimental geometry of the molecule and its reactions. The charge distribution shows that the iron atom assumes a negative charge in the complex and that this arises from the carbonyl carbon atoms. The bonding pattern of the molecule involves mainly the electronic levels of butadiene, although the set are also somewhat perturbed When the Fe-diene distance is increased, the excited electronic states are retained in the organic moiety.We thank the S.R.C. and the Scottish Education Committee for Maintenance Grants (to I.C.R. and J.M.S.).