Reactions of the Cyclic Platinum(II) Thiolate Complex (PPh3)2> with Electrophiles, and the Single-crystal Structure of (PPh3)2*HgBr2>2>

Article abstract of DOI:10.1039/DT9940002489

The cyclic thiolato complex <(PPh3)2> 1 reacted with alkyl halides RX (MeI, EtBr or PhCH2Cl) giving the thioether complexes <X(PPh3)> with the triphenylphosphine ligand trans to the thioether group. 31P-<1H> NMR spectroscopy revealed that the alkylation reactions proceed through a cationic thioether intermediate of the type <(PPh3)2>(1+)X(1-), the rate of formation of which is highly dependent on the reactivity of the alkyl halide.Reaction of 1 with dimethyl sulfate rapidly produced an analogous intermediate which is rather stable in the presence of an excess of dimethyl sulfate as a result of the low nucleophilicity of the methyl sulfate anion.Proton NMR spectroscopy of the complexes <X(PPh3)> is consistent with the presence of a rigid metallacycle in solution with the SMe group adopting an axial position.Complex 1 also forms sulfur-donor adducts with 'soft' metal centres such as Hg(II) and Ag(I).Adduct formation is readily monitored by the influence on the 1H NMR shifts of the metallacyclic CH2 groups.A single-crystal X-ray diffraction study on the mercury(II) bromide adduct reveals the presence of a 1:1 dimeric complex <<(PPh3)2*HgBr2>2>.The complex contains bridging thiolate ligands with a BrHg(μ-Br)2HgBr unit and distorted tetrahedrally co-ordinated mercury centres.

Full text of DOI:10.1039/DT9940002489

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