Cationic gold(I) π-complexes of terminal alkynes and their conversion to dinuclear σ,π-acetylide complexes

Treatment of a suspension of (IPr)AuCl [IPr = 1,3-bis(2,6- diisopropylphenyl)imidazol-2-ylidene] and AgSbF6 with terminal arylacetylenes led to the formation of thermally unstable gold π-alkyne complexes of the form [(IPr)Au(η ²-HC≡ CAr)]+SbF 6^- in ≥86 ± 5% yield, which were characterized by spectroscopy without isolation. Warming these complexes to 0 °C led to C(sp)-H bond cleavage and formation of dinuclear gold(I) σ,π-acetylide complexes of the form {[(IPr)Au]2(η 1,η ²-C≡ CAr)}+SbF6^-, three of which were isolated in 99% yield and one of which was characterized by X-ray crystallography. 1H NMR analysis of the conversion of gold π-arylacetylene complexes to σ,π-acetylide complexes established protonation of free arylacetylene, indicating the generation of a strong Brønsted acid under reaction conditions. © 2011 American Chemical Society.

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Author Ross A. Widenhoefer Chemistry