It is shown here that a good insight into thegpar;shift ofd7ions in elongatedD4hsymmetry requires one to go beyond the crystal field approach and consider the levels arising from a molecular orbital picture. Within this scheme is demonstrated the appearance of a second order contribution to thegpar;shift which depends on the spinhyphen;orbit coefficient and the covalency of equatorial ligands. This new contribution can reasonably account for the positivegpar;shift observed for Pd3+and Rh2+doped silver halides. Furthermore, the smallness of the spinhyphen;orbit coefficient of equatorial ligands in cases such as lsqb;Rh(CN)4Cl2rsqb;3minus;or lsqb;Fe (CN)4Cl2rsqb;5minus;is consistent with the slightly negativegpar;shift observed for these systems.
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