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    Ring-expanded iridium and rhodium N-heterocyclic carbene complexes: a comparative DFT study of heterocycle ring size and metal center diversity
    (Taylor & Francis Ltd, 2017) Karaca, E. O.; Akkoc, M.; Oz, E.; Altin, S.; Dorcet, V.; Roisnel, T.; Gurbuz, N.
    A new series of ring-expanded six-and seven-membered N-heterocyclic carbene precursors (re-NHCs) and their transition metal complexes were synthesized. The basic properties of the synthesized materials were investigated by density functional theory (DFT). The six- and seven-membered re-NHCs were synthesized in good yield via reaction of the corresponding alkyldibromides or alkyldiiodides with N,N'-bis-(2-phenylbenzene)formamidine in the presence of K2CO3 under aerobic conditions. Complexes, represented by the formula [ML1,2(COD)Cl] (where M = Ir or Rh and L is a ring-expanded N-heterocyclic carbene ligand), were synthesized in the presence of the corresponding free carbene and iridium or rhodium metal precursors in tetrahydrofuran. All new re-NHC complexes were characterized by different analytical techniques, including NMR spectroscopy, X-ray diffraction, UV spectroscopy and elemental analysis. According to molecular electrostatic potential calculations, the electrophilic properties of the complexes were aligned, from highest to lowest, as Ir-6-DiPh, Rh-6-DiPh and Ir-7-DiPh. The HOMO, LUMO and energy gaps of the complexes were calculated by DFT. On the basis of the DFT analysis, it can be predicted that Rh-6-DiPh is the most stable complex and Ir-7-DiPh is more reactive than Ir-6-DiPh. [GRAPHICS] .
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    Synthesis and catalytic applications of palladium N-heterocyclic carbene complexes as efficient pre-catalysts for Suzuki-Miyaura and Sonogashira coupling reactions
    (Royal Soc Chemistry, 2017) Boubakri, L.; Yasar, S.; Dorcet, V.; Roisnel, T.; Bruneau, C.; Hamdi, N.; Ozdemir, I.
    A new palladium complex series with N-heterocyclic carbene (NHC), pyridine and phosphine ligands, PdCl2(L)NHC (2a-c)(L = NHC), PdCl2(L-1)NHC(3a-c)(L-1 = pyridine), PdCl2(L-2)NHC(4a-c)(L-2 = triphenyl-phosphine) was synthesised and fully characterized. The catalytic activities of these complexes were screened for the Sonogashira and Suzuki-Miyaura reactions between arylhalides and phenylacetylene, and phenylboronic acid, respectively. The results pointed out that the carbene/phosphine complexes 4a-c exhibited excellent catalytic activities as compared to 2a-c, 3a-c, and the well-known systems for the palladium-catalysed Sonogashira reaction. The reactivity of 4a-c in these preliminary Sonogashira coupling tests seems to be higher than that of previously reported catalytic systems based on Pd(NHC) moieties. These new palladium NHC complexes are among the first reported palladium catalysts that are efficient for catalysing the Sonogashira reaction from arylchloride substrates.