Charge selfhyphen;consistent semiempirical calculations including all valence sigma orbitals of the ligands are reported for ferrocene, aminoferrocene, chloroferrocene, and nickelocene. The computations follow the Wolfsbergmdash;Helmholz scheme, and use Slater atomic orbitals which mimic the overlaps, including distance dependence, of the SCF atomic orbitals. An attempt is made to assign electronic excitation energies in a manner consistent with computation and experiment. The only assignment which may be considered reasonably secure is that of the very intense absorption at 51 200 cmminus;1which is taken to be the allowed component of thee1glarr;e1uorbital excitation (fcalc/fobs=0.549/0.691). The ionizing orbital in ferrocene was found to bea1g(minus;9.78 eV) and in nickelocene wase1g(minus;6.874 eV). The formal charge on the metal was found to be positive in all cases. A discussion of metalmdash;ligand bonding is included.
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