ChemInform Abstract: Experimental and Theoretical Studies of Dinuclear Gold(I) and Gold(II) Phosphorus Ylide Complexes.

ChemInform Abstract

The reactions of the dinuclear phosphorus ylide gold(I) complexes (II) with the alkyl halides RZX, yielding the Au(II) alkyl halide adducts (I), are studied. The Au(II) dihalide adduets (III) are also synthesized. It is observed by ¹H NMR spectroscopy that equilibrium is rapidly achieved between (II), RZX and (I). This appears to be the first example of a reversible twocenter two-electron oxidative addition of an alkyl halide to a dinuclear complex. The MeI adduct reductively eliminates alkyl halide when the solid is heated. When CDCI; solutions of the Au(II) adducts (I) are heated or exposed to light, the Au(II) dihalide dimers (III), along with other products, are formed. Catalytic halogen exchange between CH₃Br and CD₃I is observed in solution in the presence of (II) (R′ : Ph). Halogen exchange between (IIIb) (X: Br) and MeI is also observed only in the presence of (II) (R′ : Ph). Mechanisms involving the adducts (I) as intermediates are discussed. Cyclic voltammetry of (II) (R′ : Ph) and the dihalide adducts (III) suggests that consecutive one-electron steps are involved in the electrochemical oxidations and reductions. MO calculations are used to indicate the character of the bonding in the alkyl halide and dihalide Au(II) complexes. The structures of the title compounds (II) (R′ : Ph; space group P2l/n; Z=2) and (Ib) (space group Cc, Z=4) are determined by a single-crystal X-ray diffraction study.