Syntheses and Structures of Dinuclear Gold(I) Dithiophosphonate Complexes and the Reaction of the Dithiophosphonate Complexes with Phosphines: Diverse Coordination Types

The dinuclear gold(I) dithiophosphonate complex, [Au2(dtp)2] (1), where dtp = [S2P(R)(ORʹ)]^- with R = p-C6H4OCH3; Rʹ= c-C5H9, has been synthesized and its reaction studied with the phosphine ligands PPh3 and Ph2P(CH2)nPPh2 (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 [Au2(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)(PPh3)2] (8). The molecular structures of 1-8 were confirmed by Xray 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.