Bäcktorp and Norrby investigated the entire reaction paths for both the neutral and cationic mechanisms of styrene and phenyl chloride catalysed by Pd(PPh 3 ) 2 , including the two neutral paths depending on whether the chloride is cis or trans to the phenyl ring (Ph) when complexed with the catalyst (Figure ). The computed barrier heights for the insertion steps of the neutral path (where the chloride is trans to Ph) and the cationic path match the experimentally observed regioselectivities of predominately β and a roughly equal mix of α and β, respectively. Their results suggest that under some relatively common reaction conditions both reaction mechanism may contribute to the regioselectivity. As the authors note the relative importance of each path can, in principle, be computed using DFT but the difference in charge makes the results very sensitive to the solvent model and it is not clear whether the accuracy is sufficient to be used in practice.