The platinum(ii) complexes [PtCI(S,CNMe,) (EtS,CNEt,)] ( l ) , [PtCI(S,CNEt,) (MeS,CNMe,)] ( Z ) , and [PtCI(S,CNEt,) (MeS,CNEt,)] (3) have been prepared and characterized b y i.r. and 'H n.m.r. spectroscopy. The crystal and molecular structure of compound (3) has been solved by X-ray diffraction methods and refined b y least squares to a final R value of 0.037. The platinum atom is bonded, in the usual square-planar arrangement, to the sulphur atoms of the bidentate -S,CNEt, group, to the thiocarbonyl sulphur of the dithioester molecule, and to the chlorine atom. In solution the complexes release the weakly bonded dithioester molecule.Recently we reported various S-alkyl NN-dialkyldithiocarbamate complexes of platinum(1r) and palladium(1r) halides which were tested for in oitro cytostatic activity against KB cells,'.2 a line derived from a human epidermoid carcinoma of the mouth. In the complexes of general formula [PtX,L,] (L = R1S,CNRZ2; R', R 2 = Me or Et), the ligand was bound in a unidentate manner through the thiocarbonyl sulphur, whereas in the series [PtX,L] it was found to coordinate through both sulphur atoms. In synthesizing the 1 : 2 complexes, the formation of the side products containing the ~ S2CNR, group was occasionally observed. In particular, when platinum halides were dissolved in acetone solutions containing a large excess of MeS,CNEt,, small amounts of the species [PtX(S,CNEt,)(MeS,CNEt,)] (X = C1, Br, or I) separated in a few days, suggesting a slow S-demethylation process in the dithioester molecule.2 In this new class of mixed platinum(i1) complexes both ligands can potentially behave as uni-or bi-dentate. The versatile -S,CNR, ion can act either as a chelating species or, in the presence of strong donors, as ~n i d e n t a t e . ~-~ Moreover in a binuclear platinum(1i) compound the group -S,CNMe2 was found simultaneously to chelate one platinum atom and bridge (through one of the chelating sulphur atoms) a second platinum atom.6Therefore it was worthwhile to determine the bonding around platinum and to develop a general preparative procedure to be used also with S-ethyl dithioesters, which do not undergo S-de-ethylation in the presence of platinum halides, at least at room temperature. Our interest in such platinum(i1) complexes is due also to the detoxicant and immunopharmacological properties of Na(S,CNEt,) and MeS2CNEt,,' and to the protective effect of thiocarbonyl donors on platinuminduced nephrotoxicity.8 Moreover S-methyl transfer is of importance in biological systems.' This paper reports the preparation and characterization of the compounds [PtCI(S,-CNMe,)( EtS,CNEt,)] (l), [PtCI(S,CNEt,)(MeS,CNMe,)l (2), and [PtCI(S,CNEt,)(MeS,CNEt,)] (3) and the crystal and molecular structure of (3). t Chloro( diet h yldithiocarbamato-SS')( S-met h yl diet hyldit hiocarbamate-S')platinum( 11).
