Adduct formation of some tris (N, N dialkyl-di thiocarbamato) Cr(III) complexes with iodine

Spectrophotometric studies of dichloromethane solutions containing iodine and some Cr(S2CNR2)3 complexes (where R2NCS-2 are: OC4H8NCS-2 = modtc; (C2H5)2NCS-2 = Et2dtc; (C6H5CH2)2NCS-2 = Bz2dtc) have shown the formation of 1:1 adducts whose spectral features were studied and which suggested that charge-transfer interaction involving iodine and a sulphur atom of a coordinated dithiocarbamato ligand occurred. A new BASIC non-linear least-squares program which performs an optimization of the absorbance data taken at several wavelengths was devised to evaluate reliable formation constants. The thermodynamic parameters have been calculated and compared with those obtained in the same conditions as above by a reinvestigation of the known 1:1 complex formation of iodine with the corresponding tetraalkylthiuram-disulphides, where the donor site is also the sulphur atom of the thiocarbonyl group. The -ΔH° values related to the Cr(dtc)3 · I2 complexes are about 2 kcal lower than those of thiuram disulphides, showing a lowering of the donor strength of the thiocarbonyl sulphur as a consequence of the coordination to the metal. © 1984.