CHROMIUM(III) COMPLEXES OF D(-)TARTARIC AND L(-) MANDELIC-ACIDS

The binary complexes of anhydrous chromium(III) chloride with D(-) tartaric acid L(-) mandelic acids have been characterized by elemental analyses, magnetic susceptibility, vibrational, electronic and circular dichroism spectra. The magnetic susceptibility data are close to the spin only value for a d3 chromium(III) ion. Three (Cr-Cl) vibrational modes in the region 420-290 cm-1 are observed for the formed complexes indicating C2 local symmetry of ligand atoms around the chromium(III) rather than C3, which would allow two modes. In the visible spectra, two peaks in the 21052-22222 and 15384-16129 cm-1 range are observed and are assigned to the 4A2g --> 4T1g(F) and 4A2g --> 4T2g transitions. The parameters (Dq, B, beta35) place the ligands in the higher end of the spectrochemical series and provide reassurance that the hydroxy acid oxygen complexes to chromium(III) ion. The Cotton effects observed in the spin-forbidden band are assigned to the 2E(2E(g)), 2A2 (2T1g) and 2E(2T1g), while that in the spin-allowed band area results of the splitting of the 4A2g(4T2g) to 4A1(4T2g) and 4E(4T2g) transitions. The tartaric acid chelates are likely to be fac in terms of ligand carboxylate and/or hydroxy groups since stronger and better defined Cotton effects are observed while mandelic acid chelates are weak suggesting formation of the mer structure.