Interaction of the Gold(I) Cation Au(PMe3)+ with Unsaturated Hydrocarbons

Abstract

The binding energies of unsaturated hydrocarbons (benzene, styrene, 1-pentene, 1-pentyne, 2-pentyne, phenylacetylene, cyclooctene, 1,5-cyclooctadiene, 1,3-cyclooctadiene) with the (trimethylphosphino)gold cation have been investigated by means of mass spectrometry and density functional theory. It is shown that the interactions of the gold(I) cation with C–C triple bonds are stronger than those with C–C double bonds or with an aromatic ring. Further, the gold cation preferentially interacts with the isolated C–C double bonds in 1,5-cyclooctadiene and cyclooctene in comparison to the conjugated double bonds in 1,3-cyclooctadiene. In contrast to these results, the binding energies of Au(PMe3)+ to the simplest unsaturated hydrocarbons increase in the order acetylene < ethylene < butadiene. The effect of the alkyl and aryl substitution and the consequence of these results for the gold-catalyzed reactions of unsaturated hydrocarbons are discussed.