Syntheses and structures of dinuclear gold(I) dithiophosphonate complexes and the reaction of the dithiophosphonate complexes with phosphines: Diverse coordination types

Article abstract of DOI:10.1021/ic034114y

The dinuclear gold(I) dithiophosphonate complex, [Au₂(dtp) ₂] (1), where dtp = [S₂P(R)(OR′)]^- with R = p-C₆H₄-OCH₃; R′ = c-C ₅H₉, has been synthesized and its reaction studied with the phosphine ligands PPh₃ and Ph₂P(CH₂) _n-PPh₂ (n = 1-4). Compound 1 contains two gold atoms homobridged by the anionic dithiophosphonate ligand, forming an eight-membered ring complex in a chair form. After the reaction of 1 with diphosphine ligands, the dinuclear open-ring complexes Au₂(dppm)(dtp)₂ (2), Au₂(dppe)(dtp)₂ (3), Au₂(dppp)(dtp) ₂ (4), Au₂(dppb)(dtp)₂ (5) were formed (dppm = diphenylphosphinomethane; dppe = diphenylphosphinoethane; dppp = diphenylphosphinopropane; dppb = diphenylphosphinobutane). The reaction with dppm is stoichiometry-dependent. Thus, when 1 reacts with 2 equiv of dppm, the ionic complex [Au₂(dPPM)₂(dtp)]dtp forms. This dtp counterion was exchanged with tetrafluoroborate to yield [Au ₂(dppm)₂(dtp)]BF₄, the crystallization of which afforded two interconvertible isomers, 6-yellow and 7-white. Reaction of 1 with PPh3 affords the tetracoordinate mononuclear complex [Au(dtp)(PPh ₃)₂] (8). The molecular structures of 1-8 were confirmed by X-ray crystallography and show multiple coordination modes and geometries. The crystal structures of 1 and its reaction products with dppm (2, 6, 7) show short intramolecular Au...Au aurophilic bonding interactions of 2.95-3.10 A while no intermolecular interactions were discernible. However, reaction products of 1 with longer-chain Ph₂P(CH₂) _nPPh₂ ligands, n = 2-4, exhibit structures that lack both intra- and intermolecular Au...Au interactions.