The course of oxidative addition reactions of haloalkynes and haloalkenes to dimethyl- and dialkynylaurate(I) anions [RAuR]−

The reactions of halo-alkynes Cl–CCH, C–lCC–Cl or PhCC–I with solutions of Li+[MeAuMe]− in diethylether containing Ph3P do not give the expected oxidative addition products Me2(RCC)Au(PPh3) with R = H, Cl, Ph. A mixture of other complexes is obtained instead which are generated in secondary reactions involving reductive elimination of ethane and/or dialkyne. However, addition of the halo-alkene H(Cl)CCCl2 to the same substrate solution affords trans-Me2[trans-H(Cl)CC(Cl)]Au(PPh3) in good yield. Its molecular structure with pseudo-Cs symmetry has been determined by the solution NMR spectra and a single-crystal X-ray diffraction study. The reaction of methyl iodide with solutions of Li+[RCCAuCCR]− in diethylether containing PPh3 give the quaternary salts Ph3PMe+ [RCCAuCCR]− as the main products and only small amounts of cis-Me2(RCC)Au(PPh3) complexes probably formed in a series of oxidative addition, reductive elimination, and substitution reactions. The structure of Ph3PMe+ [PhCCAuCCPh]− has been determined.

The reactions of haloalkynes RCC–X with solutions of Li[MeAuMe] in diethylether containing tertiary phosphines do not give the expected complexes of the type [Me2(RCC)AuPR3]. Products of substitution and reductive elimination are obtained instead. However, addition of the alkene H(Cl)CCCl2 affords trans-Me2[trans-H(Cl)CC(Cl)]Au(PPh3). The reaction of methyl iodide with solutions of Li[RCCAuCCR]/PR3 gives quaternary salts R3PMe[RCCAuCCR] and low yields of cis-Me2(RCC)Au(PR3) complexes.Figure optionsDownload as PowerPoint slide