Interaction of benzo-1,3-thiazoline-2-thione and related ligands with copper(II) salts and the single-crystal X-ray structure of µ-[1,2-bis-(diphenylphosphino)ethane]-bis{(benzo-1,3-thiazole-2-thiolato-S)[1,2-bis(diphenylphosphinoethane]copper(I)}

Abstract

A reinvestigation of the reaction of benzo-1,3-thiazoline-2-thione (HL¹) with copper salts has shown, in contradiction to earlier reports, that only two compounds are formed, viz. [Cu(L¹)] from aqueous ethanol and [Cu(HL¹)₂Cl] from absolute ethanol. The incorrect formulations arise from contamination of the copper(I) complexes with bis(benzo-1,3-thiazol-2-yl) disulphide (L¹–L¹). These findings are supported by the reaction of other heterocyclic thioamides and diphenyldithiophosphinic acid with copper(II) salts. The complex [Cu(L¹)] reacts with the chelating phosphines 1,2-bis(diphenylphosphino)methane (dppm) and 1,2-bis(diphenylphosphino)ethane (dppe), to give [Cu(L¹)(dppm)] and [Cu₂(L¹)₂(dppe)₃]. The crystal and molecular structure of [Cu₂(L¹)₂(dppe)₃] has been determined by X-ray diffraction techniques. The crystals of the complex are triclinic, space group P, with a= 17.334(3), b= 17.348(2), c= 20.110(2)Å, α= 82.54(1), β= 120.73(1), γ= 123.86(1)°, and Z= 2. After full-matrix least-squares refinement the final R value was 0.096 for 3 317 reflections. The complex consists of a centrosymmetric dppe-bridged dimer. Each copper atom has a distorted tetrahedral geometry with one phosphorus from the bridging dppe, two phosphorus atoms from a chelating dppe, and the exocyclic sulphur atom from the anionic L¹ ligand making up the co-ordination sphere.