Thiolato-Ligand Substitution Reaction with Halide Ions of Five-Coordinate Trigonal-Bipyramidal Palladium(II) Complexes with Tris(2-(diphenylphosphino)ethyl)phosphine. Electronic and Steric Effects on the Reaction Mechanism

Mononuclear and dinuclear thiolato complexes with five-coordinate trigonal-bipyramidal palladium(II), [Pd(pt or tt)(pp3)](BF4) and [Pd2(pdt)(pp3)2](BF4)2 (pp3 = tris(2-(diphenylphosphino)ethyl)phosphine, pt = 1-propanethiolate, tt = α-toluenethiolate, pdt = 1,3-propanedithiolate) have been synthesized. The solid-state structure of the dinuclear pdt complex was confirmed by an X-ray crystal structure analysis and the structures of the pt, tt, and pdt complexes in solution were characterized by 31P NMR spectroscopy. It is indicated from the 31P NMR chemical shifts of the bound pp3 ligand that the axially coordinated thiolato ligands are strong σ and π donors compared with the halo ligands in the axial position of the corresponding trigonal-bipyramidal palladium(II) complexes, [PdX(pp3)]+ (X- = Cl-, Br-, I-). The kinetic parameters for the one-step and successive two-step thiolato-ligand substitution reactions with halide ions in chloroform were obtained for the mononuclear and dinuclear complexes, respectiv...