Transition state symmetries and theoretical activation enthalpies for chloride exchange at planar [PdCl4]2−

Density functional theory is applied to associatively activated and dissociative chloride exchange on planar [PdCl4]2−. It is shown generally that the highest possible transition state symmetry for associative activation is C2v. However, for [PdCl5]3−, the rigorously trigonal bipyramidal (D3h) geometry has virtually the same energy and geometry. Enthalpic corrections have little effect on the DFT energy barriers although DFT alone predicts dissociation to be preferred due to the more favourable electrostatic interactions. Inclusion of solvation enthalpies establishes associative activation as the lower energy pathway in agreement with experimental assignments for related processes.