Reactions of elemental sulfur with tetrakis(triphenylphosphine)platinum(0). Formation of a complex containing very nucleophilic bridging sulfido ligands

Abstract

The reactions of Pt(PPh3)4 with elemental sulfur in ratios S/Pt = 3, 4, 5, and 6 give a mixture of compounds identified as [PtS(PPh3)2]2 and PtS4(PPh3)2; PtS2(PPh3)2 is not detected. The dimeric complex also forms on reaction of PtS4(PPh3)2 with 3 mol of Pt(C2H4)(PPh3)2. It is alkylated at one bridging sulfido ligand by CH2Cl2 and CHCl3 to give cations [Pt2(μ-S)-(μ-SR)(PPh3)4]+, R = CH2Cl and CHCl2, respectively, which are characterized as their hexafluorophosphate salts. The cations give extreme AA′BB′X 31Pmr spectra since their cis-phosphorus atoms (A,B) have very similar chemical shifts but different coupling constants to 195Pt(X); spectral features are broadened by thiolate inversion processes. Reactions of bridging sulfido ligands with other electrophiles are discussed.