SPECTROSCOPIC PROPERTIES AND LIGAND-FIELD PARAMETERS OF BIS(HYDROTRIS(1-PYRAZOLYL)BORATO) TRIVALENT METAL-COMPLEXES - ANOMALOUS COVALENCY IN THE METAL-PYRAZOLYL NITROGEN BOND AND ENERGY-LEVEL SPLITTINGS DUE TOANISOTROPIC PI-BONDING

On the basis of W-Vis absorption, magnetic circular dichroism, lumines cence, and multinuclear NMR spectra of bis(hydrotris(1-pyrazolyl)borat o) chromium(III) and cobalt(III) complexes, the ligand held parameters were discussed in comparison with those of the corresponding hexaam(m )ine complexes. The trigonal splitting of the quartet excited T-4(2g) and T-4(1g) states and the large separation of the lower frequency dou blet states ((2)E(g) and T-2(1g)) were elucidated in terms of the angu lar overlap model.