Synthesis, Spectra and Crystal Structure of Two Copper( I ) Complexes of Acetonethiosemicarbazone

The reaction of copper(I) chloride with acetonethiosemicarbazone (tscac) in a copper to tscac molar ratio of 1:2 forms the cationic complex [Cu(tscac)2]Cl (1). When the ratio of the copper to tscac was reduced to 1:1, a dimeric complex [Cu2Cl2(tscac)2]2 (2) was obtained. In complex 2, two CuCl2 species act as bridging groups between two Cu(tscac)2 moieties forming an eight‐membered ring, whereas in complex 1, there is no CuCl2 moiety in the structure. In both complexes the copper(I) center is coordinated in a distorted tetrahedral geometry to two tscac groups through the sulfur and the imine nitrogen atom. In dimeric complex 2, the sulfur atom in each tscac ligand coordinates weakly to copper(I) in the CuCl2 moiety giving the distorted tetrahedral geometry. For the free ligand, the νc=s vibration at 789 cm−1 appears at lower energy than in complexes 1 and 2 (754 and 744 cm−1 respectively) indicating coordination at the sulfur atom. The complexes synthesized by either electrochemical or chemical methods are identical. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)