Chemistry of chelate-stabilized aryloxopalladium(II) complexes: Syntheses, X-ray crystal structures and formation of C - H ... O hydrogen-bonds

Article abstract of DOI:10.1016/S0277-5387(97)00504-4

In this paper the synthesis, characterization and properties of various Pd(II) complexes with 2-acylphenolates as chelating ligands are reported. The compounds are easily accessible by stirring 2-acylphenoles with Pd(II) complexes in the presence of potassium tert-butoxide. Cyclometallated tri(o-tolyl)phosphine derivatives and ally1 palladium complexes were chosen as palladium precursor. The solid state structures of the complexes 2-acetylphenolato-[o-(di-o-tolylphosphino)benzyl]palladium(II) (2), 2-benzoylphenolato-[o-(di-o-tolylphosphino)benzyl]palladium(II) (4) and 2-acetyl-1 -naphtholato-[o-(di-o-tolylphosphino)benzyl] palladium(II) (6) were further studied by X-ray diffraction analyses. In all complexes the palladium center is coordinated in a square planar fashion. Interestingly, coordination of the 2-acylphenolates to palladium results in a significant perturbation of the delocalization within the aromatic ring. The strong hydrogen-bond acceptor behavior of the phenolic oxygen as well as the cis/trans-isomerisation is discussed in terms of the solid structure (2, 4 and 6) and the NMR shifts observed in various solvents.