Co-ordination chemistry of electron-rich poly(organosulphur) compounds. Part 2. Comparative data on reactions of di-µ-chloro-bis[chloro(triethylphosphine)platinum(II)], and the crystal and molecular structure of cis-µ-2,2-bis(methylthio)ethene-1,1-dithiolato-SS″ : S′S‴-bis[chloro(triethylphosphine)platinum(II)]

Abstract

The tetrakis(alkylthio)-olefins C₂(SR)₄(R = Me or Et) react with [{PtCl₂(PEt₃)}₂] in hot xylene to yield cis- and trans-[(Et₃P)Cl[graphic omitted]tCl(PEt₃)]; with C₂(SEt)₄ there is spectroscopic evidence for intermediates, cis- and trans-[(Et₃P)Cl₂[graphic omitted](RS)CC(SR)([graphic omitted]tCl₂(PEt₃)](R = Et). In contrast, the cyclic olefin [:[graphic omitted]]₂ forms the SS″-bonded cis-[PtCl(PEt₃)(olefin)][PtCl₃(PEt₃)]; similar behaviour is found with C₂(NMe₂)₄ and o-C₆H₄(NMe₂)₂, the corresponding cations being [PtCl{C₂(NMe₂)₄-NN″}(PEt₃)]⁺(6) and [PtCl{o-C₆H₄(NMe₂)₂-NN′}(PEt₃)]⁺, respectively. The salt [PtCl{C₂(NMe₂)₄-NN″}(PEt₃)][PtCl₃(PEt₃)] readily transforms into [C₂(NMe₂)₄][Pt^IICl₃(PEt₃)]₂ on dissolution in dimethylformamide. A single-crystal X-ray analysis of the title complex shows that it has approximate C₂ symmetry with each platinum atom bound to a chelating ligand attached at one end by a thiolate sulphur atom and at the other by a thioether S atom; the average bond lengths are 2.25(1) and 2.33(1)Å, respectively. Interaction of Pt with the CC π orbitals is unlikely because the distance of closest approach is ca. 3.1 Å. The average Pt–P and Pt–Cl distances are 2.26(1) and 2.34(1)Å, respectively. Bond lengths [1.34(4)(CC) and 1.75(3)(CS)Å] in the 2,1,1-dithiolate ligand indicate essentially localised double and single bonds.