Organogold chemistry. XVII. Synthesis and reactions of the gold(I)-dimethylphosphonium-bis-methylid dimer

From the reaction of (CH₃)₃PCH₂ and (CH₃)₃ PAuCl in the ration 2:1 a cyclic dimer of the formula [(CH₃)₂P(CH₂)₂Au]₂ is obtained, containing two liner CAuC and two tetrahedral PC₄ units as components of an eight-membered ring Oxidative addition of one or two moles of halogen leads to products, for which structures with a transannular metal-metal bond in the first case and with two halogen atoms at both gold atoms in a trans configuration in the second case are proposed. Methyl iodide was found to add to the title compound only in a 1:1 ratio across the heterocycle. Methylation of the halogen adducts with CH₃Li exclusively yields the trans-dimethyl derivative with one of the gold atoms solely being in the +III oxidation state. Thermally induced reductive elimination of ethane converts this material to the title compound in the original configuration.