@article{BaierKellingSchildeetal.2016,
  author    = {Baier, Heiko and Kelling, Alexandra and Schilde, Uwe and Holdt, Hans-J{\"u}rgen},
  title     = {Investigation of the Catalytic Activity of a 2-Phenylidenepyridine Palladium(II) Complex Bearing 4,5-Dicyano-1,3-bis(mesityl)imidazol-2-ylidene in the Mizoroki-Heck Reaction},
  series = {Zeitschrift f{\~A}¼r anorganische und allgemeine Chemie},
  volume    = {642},
  journal   = {Zeitschrift f{\~A}¼r anorganische und allgemeine Chemie},
  publisher = {Wiley-VCH},
  address   = {Weinheim},
  issn      = {0044-2313},
  doi       = {10.1002/zaac.201500625},
  pages     = {140 -- 147},
  year      = {2016},
  abstract  = {The phenylidenepyridine (ppy) palladacycles [PdCl(ppy)(IMes)] (4) [IMes = 1,3-bis(mesityl) imidazol-2-ylidene] and [PdCl(ppy){(CN)(2)IMes}] (6) [(CN)(2)IMes = 4,5-dicyano-1,3-bis(mesityl) imidazol-2-ylidene] were prepared by facile two step syntheses, starting with the reaction of palladium(II) chloride with 2-phenylpyridine followed by subsequent addition of the NHC ligand to the precatalyst precursor [PdCl(ppy)](2). Suitable crystals for the X-ray analysis of the complexes 4 and 6 were obtained. It was shown that 6 has a shorter NHC-palladium bond than the IMes complex 4. The difference of the palladium carbene bond lengths based on the higher pi-acceptor strength of (CN)(2)IMes in comparison to IMes. Thus, (CN)(2)IMes should stabilize the catalytically active central palladium atom better than IMes. As a measure for the pi-acceptor strength of (CN)(2)IMes compared to IMes, the selone (CN)(2)IMes center dot Se (7) was prepared and characterized by Se-77-NMR spectroscopy. The pi-acceptor strength of 7 was illuminated by the shift of its Se-77-NMR signal. The Se-77-NMR signal of 7 was shifted to much higher frequencies than the Se-77-NMR signal of IMes center dot Se. Catalytic experiments using the Mizoroki-Heck reaction of aryl chlorides with n-butyl acrylate showed that 6 is the superior performer in comparison to 4. Using complex 6, an extensive substrate screening of 26 different aryl bromides with n-butyl acrylate was performed. Complex 6 is a suitable precatalyst for para-substituted aryl bromides. The catalytically active species was identified by mercury poisoning experiments to be palladium nanoparticles.},
  language  = {en}
}
@article{SchwarzeTraegerKellingetal.2013,
  author    = {Schwarze, Thomas and Traeger, Juliane and Kelling, Alexandra and Schilde, Uwe and Holdt, Hans-J{\"u}rgen},
  title     = {Macrocyclic dithiomaleonitriles for an efficient PdCl2 coordination},
  series = {Inorganica chimica acta : the international inorganic chemistry journal},
  volume    = {408},
  journal   = {Inorganica chimica acta : the international inorganic chemistry journal},
  number    = {2},
  publisher = {Elsevier},
  address   = {Lausanne},
  issn      = {0020-1693},
  doi       = {10.1016/j.ica.2013.08.020},
  pages     = {53 -- 58},
  year      = {2013},
  abstract  = {We have synthesized a set of new unsaturated macrocyclic dithioethers with an increasing number of flexible methylene units 1-7 (Scheme 2) to investigate the correlation between the ring size of these ligands, the chelation effect and the consequences for an efficient PdCl2 coordination. The dithioethers 1-7 and the complex [PdCl2(4)]center dot CHCl3 were characterized by X-ray diffraction analysis. The crystal structures of 1-7 show that 2-7 are better preorganized chelating ligands for an exocyclic PdCl2 coordination than 1. The chelation effect of 1-7, the orientation of the sulfur atoms and the S center dot center dot center dot S donor distances, are influenced by the flexibility of the methylene units. In this series the unsaturated macrocyclic ligands 5 and 6 are the best chelating ligands for an efficient PdCl2 coordination. Comparative solvent extraction experiments with mn-12S(2)O(2) (mn = maleonitrile) reveal that the low interface activity of the new ligands reduces the extraction rate. However, a comparison with open-chain dithiomaleonitriles shows the impact of the macrocyclic effect of 4 and 5 on the extraction yield.},
  language  = {en}
}