NMR Spectroscopic Studies of Palladium(II) Complexes of Bidentate Diphenylphosphane Ligands with Acetate and Tosylate Anions: Complex Formation and Structures

The synthetic pathways towards Pd-II complexes of functionalized bidentate diphenylphosphane ligands of the type [Pd(ligand)(anion)(2)] and [Pd(ligand)(2)](anion)(2) have been investigated. Eighteen different ligands have been used in combination with strongly (acetate, OAc-) or weakly (tosylate, OTs-) coordinating anions, The solid-state structure of some representative complexes was determined with X-ray crystallography. It is shown that the solid-state structures are fully retained in solution, The formation of [Pd(ligand)-(anion)(2)]-type complexes was studied in detail by H-1- and P-31-NMR spectroscopy. Depending on the Ligand structure, the complex is formed instantaneously, via a polynuclear intermediate or is not formed at all. Complex formation is demonstrated to depend on the length and rigidity of the ligand backbone and on the steric bulk at the ortho position of the phenyl rings on phosphorus, It was also found that the coordinating ability of the anions can alter the structure of the kinetic and/or thermodynamic product.