Kinetic studies on thiolato-ligand substitution reactions with halide ions of square-planar palladium(II) complex with bis(2-(diphenylphosphino)ethyl)phenylphosphine

The square-planar thiolato palladium(II) complex with a terdentate phosphine bound ligand, [Pd(pt)(p3)](BF4) (p3=bis(2-(diphenylphosphino)ethyl)phenylphosphine, pt=1-propanethiolate) has been synthesized and characterized by 31P NMR spectroscopy. The solid state structure of [PdI(p3)]I was determined by an X-ray crystal structure analysis. The kinetic parameters for the thiolato-ligand substitution reactions with halide ions, [Pd(pt)(p3)]++X−→[PdX(p3)]++pt− (X−=Cl−, Br−, I−), in chloroform were obtained as follows: k298=7.22, 1.68 and 10.1×10−4 s−1, ΔH‡=67±2, 56±2 and 63±3 kJ mol−1 and ΔS‡=−80±7, −128±6 and −92±11 J mol−1 K−1, respectively. These kinetic results are compared with those for the corresponding reactions of the trigonal-bipyramidal complex with an analogous phosphine bound ligand, [Pd(pt)(pp3)](BF4) (pp3=tris(2-(diphenylphosphino)ethyl)phosphine).