Reactions and electrochemical behaviour of dithiocarbene complexes of platinum(II)

Abstract

The dithiocarbene complex trans[(PPh 3) 2PtH{C(SMe) 2}][BF 4] ( 1) was obtained from the reaction of trans-[(PPh 3) 2PtH(CF 3)] with CH 3SH in the presence of ethereal HBF 4. The reactions of 1 with different nucleophiles, such as Cl −, H − and CN − ions, P-donor ligands such as Ph 2PCH 2CH 2PPh 2, PPh 3, and PMe 3, have been investigated and these mostly lead to the decomposition of the dithiocarbene ligand with formation of different sulfured products. From the reaction of 1 with Ph 2PCH 2CH 2PPh 2 the complex [Pt{C(H)(SMe) 2}(PPh 3)(Ph 2PCH 2CH 2PPh 2)][BF 4] ( 2), containing an ins dithiocarbene ligand, was isolated in low yield. The electrochemical behaviour of trans-[PtH{C(SMe) 2}(PPh 3) 2][BF 4] and the related complexes trans-[(PPh 3) 2PtH{C(SPh) 2}][BF 4], , trans-[(PPh 3) 2PtH{ CS(CH 2) nS }][BF 4] ( n=2 or 3) and cis-[(PPh 3) 2Pt{ C(H)S(CH 2) 2S }][BF 4] (with an ‘inserted dithiocarbene’ ligand) was also investigated in 0.2 M [NBu 4][BF 4]/NCMe by cyclic voltammetry and controlled potential electrolysis, and shown to involve cathodic processes (at potentials dependent on the dithio ligand) with partial reduction of the S-containing ligands to hydrocarbons (ethylene or propylene, although detected in low yields), liberation of PPh 3 and dealkylation of the electrolyte, by the reduced metal centre, to give tributylamine, as indicated by GC-MS. The ‘inserted dithiocarbene’ complex also presents an anodic process which involves proton liberation. Evolution of any sulfur-containing product has not been detected electrochemically or by GC-MS. These behaviours are compared with those exhibited by related dioxy-, diamino- or aminooxy-carbene complexes.