Ground Term Splitting of High-Spin Co(2+) as a Probe of Coordination Structure. 1. Dependence of the Splitting on Coordination Geometry

Article abstract of DOI:10.1021/ja00304a035

The sign and magnitude of the splitting between the two lowest Kramers doublets (Δ) of high-spin Co(2+) in a variety of structurally defined, small molecule coordination complexes is determined.The range of values of Δ is found to be <13 cm^-1 in tetracoordinate sites, ca. 20-50 cm^-1 in pentacoordinate sites of trigonal-bipyramidal or square-pyramidal geometry, and <*>50 cm^-1 in hexacoordinate sites.It is shown on the basis of group theoretical arguments and estimates of the zero-field splitting derived by second-order perturbation theory that the observed range of values of Δ correlates well with that predicted by theory.On this basis, it is suggested that the splitting between the two lowest Kramers doublets of high-spin Co(2+) may provide a diagnostic signature of coordination geometry.