CHEMISTRY OF CHELATE-STABILIZED ARYLOXOPALLADIUM(II) COMPLEXES - SYNTHESES, X-RAY CRYSTAL-STRUCTURES AND FORMATION OF C-H-CENTER-DOT-CENTER-DOT-CENTER-DOT-O HYDROGEN-BONDS

In this paper the synthesis, characterization and properties of variou s Pd(II) complexes with 2-acylphenolates as chelating ligands are repo rted. The compounds are easily accessible by stirring 2-acylphenoles w ith Pd(II) complexes in the presence of potassium tert-butoxide. Cyclo metallated tri(o-tolyl)phosphine derivatives and allyl palladium compl exes were chosen as palladium precursor. The solid state structures of the complexes olato-[o-(di-o-tolylphosphino)benzyl]palladium(II) (2), olato-[o-(di-o-tolylphosphino)benzyl]palladium(II) (4) and olato-[o-( di-o-tolylphosphino)benzyl]palladium(II) (6) were further studied by X -ray diffraction analyses. In all complexes the palladium center is co ordinated in a square planar fashion. Interestingly, coordination of t he 2-acylphenolates to palladium results in a significant perturbation of the delocalization within the aromatic ring. The strong hydrogen-b ond 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. (C) 1998 Elsevier S cience Ltd. All rights reserved.