POLYCRYSTALLINE CO-59 NMR-STUDIES OF METAL-LIGAND INTERACTION IN AXIALLY-SYMMETRICAL DIAMAGNETIC CO(III) COMPLEXES - CORRELATION OF DELTA(CO-59) WITH NQCC DELTA-E(AV)

The polycrystalline Co-59 NMR spectra (1/2 <-- --> -1/2 transition) of the diamagnetic cobalt(III) complexes Na3[Co(NO2)6] and trans-[Co(en) 2(NO2)2]NO3 Were measured at 7.1 and 9.5 T. It is demonstrated that fo r axially symmetric diamagnetic cobalt(III) complexes the Co-59 chemic al shielding anisotropy (CSA) is semiquantitatively correlated (r = 0. 998) with the product of the nuclear quadrupole coupling constant (NQC C) and the inverse of the weighted average of the first d-d electronic transition energies (DELTAE(av)) through the similarity of the d-orbi tals population imbalance in the expressions for the CSA and the NQCC. The application of the correlation in the determination of the orbita l reduction factor ratio for D4h complexes containing nitrogen ligatin g atoms is presented.