Density functional study on the regioselectivity of nucleophilic attack in 1,3-disubstituted (diphosphino) (η3-allyl)palladium cations

A density functional study has been performed to analyze the influence of electronic effects on the regioselectivity of the Tsuji-Trost reaction. Optimized geometries of model (diphosphino)(eta(3)-allyl)palladium cations 6 and 7 show that for unsymmetrical allyl ligands the shortest Pd-C(terminal) bond is the one closest to the most electron-withdrawing group. The calculated energy barriers for the attack of an ammonia molecule at each one of the terminal allyl carbon atoms of 7b-d predict that nucleophilic attack would take place preferentially on the carbon atom remote from the most electron-withdrawing group, in excellent agreement with experimental observations on allylic precursors of cations 4.