Synthesis of highly stable intermediates in Michael-type additions to the double bond in (SPPh2)2CCH2

Abstract

Treatment of vinylidenebis(diphenylphosphine) with elemental sulfur under reflux led to vinylidenebis(diphenylphosphine) disulfide, (SPPh₂)₂CCH₂, in good yields. Its co-ordination to a gold(III) centre activates the carbon–carbon double bond. Thus, the chelate complex [Au(C₆F₅)₂{(SPPh₂)₂CCH₂}]ClO₄ reacted rapidly with carbon- or oxygen-donor nucleophiles (Nu^–), such as acac^– (acetylacetonate), CN^–, C₅H₅^– or OEt^–, forming methanide-type derivatives [Au(C₆F₅)₂{(SPPh₂)₂CCH₂Nu}]. These products can be considered as intermediates in Michael-type additions of HNu to the CC bond, which in this particular case display high stabilities, allowing their isolation as solids. The crystal structure of the cyclopentadienyl derivative has been established by X-ray crystallography and displays a square-planar gold(III) centre with a cis disposition of the pentafluorophenyl groups and sulfur atoms of the chelating ligand, and sp² hybridization of the endocyclic carbon atom with partial P–C double-bond character.