EFFECTS OF CO-S TORSION ANGLE VARIATION IN A COBALT(II)-THIOLATE COMPLEX - X-RAY CRYSTAL-STRUCTURE ANALYSIS, SINGLE-CRYSTAL EPR MEASUREMENTS AND LIGAND-FIELD CALCULATIONS

X-ray structural determination and single-crystal EPR measurements were performed for (Me(4)N)(2)[Co(SPh)(4)]. The compound crystallizes in the tetragonal space group P4(1)2(1)2 with a=10.220(6), c=32,316(16) alpha and Z=4. It was found that the Co(SPh)(4)(2-) anion has an approximate S-4 geometry: the four S'-Co-S-C torsion angles are nearly the same (the mean value is 57.2 degrees), where the S'-Co-S angle is bisected by the approximate S-4 axis, and the Co-S-Ph units are almost planar. Analysis of the single-crystal EPR results provides effective g values of g'(x)=2.34, g'y=5.68 and g'z=1.64, The g'(z) axis is most likely parallel to the approximate S-4 axis, and such a g'(z) axis direction was found to be consistent with the single-crystal EPR results. The g' values correspond to E/D = 0.30 and g(\)=2.09, g(perpendicular to)=2.12 in the S=3/2 spin Hamiltonian description. These spin Hamiltonian parameters are contrasted with those of the D-2d conformation anion in (Ph(4)P)(2)[Co(SPh)(4)], which demonstrates the striking effects of the variation of the Co-S torsion angles. Ligand-field calculations based on the angular overlap model were made with the aim of understanding the effects of torsion angle variation. it is shown that the striking torsion angle dependence can be understood in terms of the torsion angle dependent nature of the directions of Co-S pi and off-axis sigma interactions. The calculations semi-quantitatively reproduce the contrasted magnetic properties of the two compounds.