Yazar "Dixneuf, Pierre H." seçeneğine göre listele

Listeleniyor 1 - 4 / 4
  • Küçük Resim Yok
    Öğe
    Direct arylation of arene C-H bonds by cooperative action of NHCarbene-Ruthenium(II) catalyst and carbonate via proton abstraction mechanism
    (Amer Chemical Soc, 2008) Ozdemir, Ismail; Demir, Serpil; Cetinkaya, Bekir; Gourlaouen, Christophe; Maseras, Feliu; Bruneau, Christian; Dixneuf, Pierre H.
    Direct functionalization of sp(2) C-H bonds via ortho diarylation of 2-pyridyl benzene with arylbromides was achieved using ruthenium(II) catalysts containing a RuCl2(NHC) unit and generated from [RuCl2(arene)](2) and two types of NHC precursors, pyrimidinium and benzimidazolium salts, in the presence of Cs2CO3. DFT calculations from RuCl2(NHC)(2-pyridylbenzene) show that a proton abstraction mechanism, on cooperative actions of both the coordinated base and the Ru(II) center, is favoured via a 13.7 kcal mol(-1) exothermic process affording an orthometalated intermediate with a 2.009 angstrom Ru-C bond.
  • Küçük Resim Yok
    Öğe
    Ruthenium(n6,n1-arene-CH2-NHC) Catalysts for Direct Arylation of 2-Phenylpyridine with (Hetero)Aryl Chlorides in Water
    (Mdpi, 2018) Kaloglu, Nazan; Ozdemir, Ismail; Gurbuz, Nevin; Arslan, Hakan; Dixneuf, Pierre H.
    A series of new benzimidazolium halides were synthesized in good yields as unsymmetrical N-heterocyclic carbene (NHC) precursors containing the N-CH2-arene group. The benzimidazolium halides were readily converted into ruthenium(II)-NHC complexes with the general formula [RuCl2 (eta(6),eta(1)-arene-CH2-NHC)]. The structures of all new compounds were characterized by H-1 NMR (Nuclear Magnetic Resonance), C-13 NMR, FT-IR (Fourier Transform Infrared) spectroscopy and elemental analysis techniques. The single crystal structure of one benzimidazole ruthenium complex, 2b, was determined. The complex is best thought of as containing an octahedrally coordinated Ru center with the arene residue occupying three sites, the remaining sites being occupied by a (carbene)C-Ru bond and two Ru-Cl bonds. The catalytic activity of [RuCl2(eta(6),eta(1)-arene-CH2 -NHC)] complexes was evaluated in the direct (hetero)arylation of 2-phenylpyridine with (hetero)aryl chlorides in water as the nontoxic reaction medium. These results show that catalysts 2a and 2b were the best for monoarylation with simple phenyl and tolyl chlorides. For functional aryl chlorides, 2d, 2e, and 2c appeared to be the most efficient.
  • Küçük Resim Yok
    Öğe
    Synthesis of N-heterocyclic carbene-palladium-PEPPSI complexes and their catalytic activity in the direct C-H bond activation
    (Elsevier Science Sa, 2018) Kaloglu, Nazan; Kaloglu, Murat; Tahir, Muhammad Nawaz; Arici, Cengiz; Bruneau, Christian; Doucet, Henri; Dixneuf, Pierre H.
    A series of benzimidazolium salts having their two nitrogen atoms substituted by bulky groups have been synthesized. The benzimidazolium salts were readily converted into the corresponding palladium-NHC-PEPPSI complexes with general formula [PdBr2(NHC) (Py)], (NHC = N-heterocyclic carbene; PEPPSI = pyridine-enhanced precatalyst preparation, stabilisation, and initiation). The structures of all new compounds were characterized by NMR, IR spectroscopy and microanalysis techniques, which support the proposed structures. The molecular structure of complex 2g was determined by singlecrystal X-ray diffraction study. Next, the palladium-NHC-PEPPSI complexes were used as catalysts in the direct C5-arylation of 1-methylpyrrole-2-carboxaldehyde by aryl halides. These complexes exhibited moderate to high catalytic activities and gave C-H activation selectively at the C5-position of 1methylpyrrole- 2-carboxaldehyde. Both electron-donating and electron-withdrawing substituents were well tolerated with catalytic systems based on these complexes, even non-activated aryl chlorides such as chlorobenzene or 4-chlorotoluene were coupled with pyrrole in moderate yields. (C) 2017 Elsevier B.V. All rights reserved.
  • Küçük Resim Yok
    Öğe
    Synthesis, Characterization and Catalytic Activity of New N-Heterocyclic Bis(carbene)ruthenium Complexes
    (Wiley-V C H Verlag Gmbh, 2009) Ozdemir, Ismail; Demir, Serpil; Gurbuz, Nevin; Cetinkaya, Bekir; Toupet, Loic; Bruneau, Christian; Dixneuf, Pierre H.
    The reaction of RuCl2(PPh3)(3) with tBuOK-deprotonated ortho-xylyl-bis(N-imidazolinium) salts 1a-d yields RuCl2(PPh3)[bis(imidazolidin-2-ylidene)] complexes (2a-d). Under similar conditions, [RuCl2(p-cymene)](2) leads to the ruthenium complex 3 containing a tridentate eta(6)-arene-dicarbene ligand. All synthesized compounds were characterized by elemental analysis and NMR spectroscopy, and the molecular structures of 2a, 2b and 3 were determined by X-ray crystallography. The catalytic activity of RuCl2(PPh3)[bis(imidazolidin-2-ylidene)] complexes 2a-b was evaluated in the direct arylation of 2-phenylpyridine with chlorobenzene derivatives. ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)