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

Abstract

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