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

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.