Localized molecular orbitals many electron correlation effects

Chemical Properties. Simple molecular-orbital theory predicts that many organometallic molecules should show electronic effects similar to conjugated systems, since the electronic structure is generally expressed in terms of molecular orbitals which involve both ring and metal orbitals. The ESR spectra (Sec. III.C) provide physical evidence for this formulation however correlation between chemical reactivities and theoretical quantities, such as charge densities and localization energies, which has been of use in aromatic systems (60) has not been attempted. Indeed, very few detailed kinetic studies of organometallic compounds have been reported with which to compare theory. We consider the different classes of compounds in turn. 

This theorem is recognized as an approximation as, apart from the inaccuracies inherent in the S.C.F. method (such as neglect of electron correlation and relativistic effects), it assumes that the molecular orbitals are the same for the molecule and the molecular ion. Many ASCF calculations have shown (see for example 14 16)) that if an electron is removed from a metal localized orbital, considerable charge migration towards the metal occurs this is termed relaxation. These relaxation effects give ionization energies smaller values than those expected on the basis of Koopmans theorem. For ionization from ligand based orbitals, relaxation effects are smaller and more constant. 

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