Platinum assisted cyclization of S-methyl 3-acyl-2-methyldithiocarbazates under mild conditions. Crystal structure of [Pt-2(mu-SMe)(terpy)(2)][ClO4](3)

The reaction of the newly synthesized aqua complex [Pt(terpy)(OH2)][BF4](2) with S-methyl 3-acyl-2-methyldithiocarbazates under a variety of experimen tal conditions has been studied. Using a 2:1 metal to ligand ratio in metha nol, a platinum assisted cyclization was observed. The reaction products we re Delta(2)-1,3,4-oxadiazoline-5-thione derivatives and the binuclear trica tionic complex [Pt-2(mu-SMe)(terpy)(2)](3+) whose molecular structure has b een determined by X-ray crystallography. This platinum assisted transformat ion is proposed as a new synthetic route to Delta(2)-1,3,4-oxadiazoline-5-t hiones under mild conditions. In the presence of an excess of a non-co-ordi nating acid (HClO4, CH3SO3H or CF3SO3H) the cyclization is completely quenc hed and complexes with co-ordinated S-methyl 3-acyl-2-methyldithiocarbazate s have been isolated. A general mechanism which accounts for the observed t ransformations is proposed on the basis of H-1 NMR and UV/Vis evidence.