Density functional theory calculations have been employed to model ethene hydroarylation using an [Ir(?2-OAc)(PMe3)Cp] + catalyst, 1. The reaction proceeds via: (i) an acetate-assisted C-H activation of benzene via an AMLA-6 transition state; (ii) rate-limiting insertion of ethene into the Ir-Ph bond; and (iii) protonolysis of the ß-phenylethyl species by HOAc. A range of competing processes are assessed, the most important of which are the C-H activation of ethene at 1 and trapping of the ß-phenylethyl intermediate with ethene. The former process gives rise to Ir-vinyl species which can then access further ethene insertion to give stable allyl by-products. A comparison with other ethene hydroarylation catalysts reported in the literature is presented. © 2010 The Royal Society of Chemistry.