Ligand field interpretation of high-spin trigonal-bipyramidal cobalt(II) complexes

Single-crystal polarized spectra have been recorded for a high-spin trigonal-bipyramidal CoNS3Br chromophore. These spectra as well as those of the chromophores CoNP3Br and CoNN3Br have been interpreted on the basis of ligand field and angular overlap parameters. These parameters, which have been estimated either from metal-ligand orbital overlaps or from the experimental transitions. are quite meaningful for the interpretation of the coordination bond. In particular, it appears that the metal to ligand T bonding is significant for both sulfur and phosphorus donor atoms. A comparison between the point charge model where the radial integral ratio 12/14 is held constant within a given chromophore and the angular overlap model is presented.