Synthesis, characterization and X-ray structural determination of palladium(0)–olefin complexes containing pyridin-thioethers as ancillary ligands. Equilibria and rates of olefin and ligand exchange
The synthesis of Pd(0)–olefin complexes with pyridin-thioether ligands R′NSR is reported. X-raystructuredeterminations of selected species are described. The dynamic behavior was studied by variable-temperature 1H-NMR spectrometry. Equilibrium constants for olefin and chelate ligand exchange were determined by UV–vis spectrophotometry in chloroform at 25°C. The following metal–olefin stability order
NHC–phosphines or NHC–isocyanides Pd(0) olefin complexes that can potentially act as catalysts. The complexes were characterized by standard spectroscopic methods and elemental analysis and in two cases by SC-XRD technique. We have analyzed with particular care the thermodynamic and kinetic conditions governing the one-pot synthesis of the mixed complexes. In this respect we tried to validate our results
palladacyclopentadienyl complexes [Pd(C4(COOMe)4)(CNR)(PPh3)] and of the palladium(0) olefin complexes whose synthesis invariably yields the mixed [Pd(η2-olefin)(CNR)(PPh3)] derivatives. The paper includes studies on the reactivity toward allylamination in the case of the palladium(II) allyl complexes. A diffractometric investigation on the solid state structures of four different palladium isocyanide–phosphane
The interaction between heteroditopic pyridine–nitrogen NHC with novel sulfur NHC ligands in palladium(0) derivatives: Synthesis and structural characterization of a bis-carbene palladium(0) olefin complex and formation in solution of an alkene–alkyne mixed intermediate as a consequence of the ligands hemilability
We have synthesized a new class of heteroditopic chelating ligands bearing the phenylthiomethyl group and variously substituted imidazole derivatives and the corresponding complexes [Pd(eta(2)-ma)(R-NHC-CH2-SPh) (ma = maleic anhydride; R = methyl, mesityl, di-i-propylphenyl). We have compared their chemical characteristics and reactivity with those of similar palladium(0) complexes bearing the R-NHC-CH2-Py ligands.The hemilability of the above-mentioned moieties is apparent when their palladium derivatives react with an excess of the same or different heteroditopic ligands. In these cases, we obtained complexes bearing maleic anhydride and two mono-coordinated heteroditopic ligands bound to the same metal center. However, at variance with the generally accepted opinion, precipitation of AgBr does not warrant the quantitative formation of the bis-heteroditopic Pd(0) derivative and in some cases, a reaction involving a heterogeneous equilibrium is observed.The reaction of the palladium(0) carbene-sulfur or carbene-nitrogen complexes with the alkyne dimethyl-2-butynedioate (dmbd) to give palladacyclometallate derivatives is not always warranted and formation of the intermediate [Pd(eta(2)-ma)(eta(2)-dmdb)(kappa(1)-Mes-NHC-CH2-SPh)] is detected only in one case.Finally, we have carried out a diffractometric study on the solid-state structures of two derivatives and in particular we describe the configurations of the complex [Pd(eta(2)-ma)(kappa(1)-Me-NHC-CH2-SPh)(2)] and of [Pd(eta(2)-ma)(Me-NHC-CH2-SPh)]. (C) 2012 Elsevier B.V. All rights reserved.