BACK DONATION IN DICHLORO-BIS(PYRIDINE) COBALT(II) COMPLEXES

The electronic structures of dichloro-bis(2-chloropyridine)-cobalt(II) and dichloro-bis(2-methylpyridine)-cobalt(II) were calculated at the SINDO1 on INDO semiempirical levels. By comparing the valence electron densities at the ring atoms, the back donation was described quantita tively. The effects of substituent electron releasing and withdrawing groups are discussed. The calculated charge on the central cobalt atom and the valence index of the Co-N bond were in accordance with measur ed dissociation energies. Comparison of the electron densities on the coordinated and free ligands was found to be useful for describing the back donation.