Mixed chloro-, NN-dialkyldithiocarbamato-, and S-alkyl NN-dialkyldithiocarbamate complexes of platinum(II). Crystal structure of [PtCl(S2CNEt2)(MeS2CNEt)]

Abstract

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).

Unique Pt5 metallacycle: [PtIICl(pyrrolidinedithiocarbamate)]5

“…Typical angle values for platinum are observed due to the chelation of the dithiocarbamate species. The internal chelate SPt-S angles are almost identical, ranging from 75.38 (14) • (S37-Pt3-S38) to 76.19 (14) • (S47-Pt4-S48). Analogous Pt-Cl and Pt-S bond distances and angles were found in the related species [PtCl(S 2 CNEt 2 )(MeS 2 CNEt 2 )].…”

THIO-LIGANDS in MONOMERIC Pt(II) COMPLEXES – STRUCTURAL ASPECTS

“…The fourth coordination site, trans to the N atom, is occupied by the S atom of a SCN group. The Pt-L bond distance elongates in the order: 66 and [Pt(η 3 -dmt)Cl](+1cation) 67 with PtS 3 Cl chromophore. In the first 65 , three monodentate S donor ligands plus the Cl atom form (PtS 3 Cl), with the mean Pt-S bond distance of 2.298 Å and Pt-Cl of 2.318(4)Å.…”

“…In the first 65 , three monodentate S donor ligands plus the Cl atom form (PtS 3 Cl), with the mean Pt-S bond distance of 2.298 Å and Pt-Cl of 2.318(4)Å. In the second 66 , a bidentate (S,S) ligand forms a four-membered ring with S-Pt-S "bite" angle of 74.1(1)º. The Pt-L bond distances are 2.300(2)Å (mono-S), 2.329(2)Å (η 2 -S) and 2.323(2)Å (Cl).…”

“…The sixmembered chelate rings have a mean S-.Pt-S "bite" angle of 93.6(2)º. The sum of all four (Pt-S(x3) plus Pt-Cl) bond distances increases in the order: 9.19Å 67 < 9.21Å 65 < 9.28Å 66 .…”

Tetra-n-butylammonium iodido(pyrrolidine-1-carbodithioato-κ2S,S′)(tris-tert-butoxysilanethiolato-κS)cadmate(II)

“…For related literature, see: Allen (2002); Battaglia & Corradi (1986); Clemente et al (1987); Kropidłowska et al (2006a,b); Kropidłowska, Chojnacki et al (2008); Kropidłowska, Rotaru et al (2008); Wojnowski et al (1992).…”