321-60-8Relevant articles and documents
Abnormal-NHC Palladium(II) Complexes: Rational Synthesis, Structural Elucidation, and Catalytic Activity
Rottsch?fer, Dennis,Schürmann, Christian J.,Lamm, Jan-Hendrik,Paesch, Alexander N.,Neumann, Beate,Ghadwal, Rajendra S.
, p. 3421 - 3429 (2016)
Reaction of a C2-arylated imidazolium iodide (IPrPh)I (1) (IPrPh = 1,3-bis(2,6-diisopropylphenyl)-2-phenyl-imidazolium) with PdCl2 in the presence of Ag2O affords abnormal N-heterocyclic carbene (aNHC) palladium complexes (aIPrPh)PdCl2 (2) and (aIPrPh)2PdCl2 (3) (aIPrPh = 1,3-bis(2,6-diisopropylphenyl)-2-phenyl-imidazol-4-ylidene). Treatment of 2 with a pyridine gives Pd-PEPPSI-type complexes (aIPrPh)PdCl2(L) (L = pyridine (py), 5; L = 3-chloropyridine (3Cl-py), 6). Compounds 5 and 6 are also accessible by a one-pot reaction of 1, PdCl2, and Ag2O in a pyridine solvent. While the use of a conventional base K2CO3 leads to the formation of mixed halide complexes (aIPrPh)Pd(Cl)I(L) (7, L = py; 8, L = 3Cl-py), iodide derivatives (aIPrPh)PdI2(L) (9, L = py; 10, L = 3Cl-py) can be selectively prepared with addition of an excess of KI to the reaction mixture. Albeit in a low yield, a putative transmetalation agent {(aIPrPh)2Ag}AgI2 (4) has been isolated and characterized. Compounds 2-10 are air stable crystalline solids and have been characterized by elemental analysis, mass spectrometry, and NMR spectroscopic studies. Molecular structures of 2-10 have been established by single crystal X-ray diffraction analyses. Catalytic activity of three representative compounds 2, 5, and 6 has been tested for the Suzuki-Miyaura cross-coupling reactions.
PEPPSI-effect on suzuki-miyaura reactions using 4,5-dicyano-1,3-dimesitylimidazol-2-ylidene-palladium complexes: A comparison between trans-ligands
Baier, Heiko,Kelling, Alexandra,Holdt, Hans-Jürgen
, p. 1950 - 1957 (2015)
The PEPPSI (Pyridine Enhanced Precatalyst Preparation, Stabilization and Initiation) complexes 12-15 with the structure [PdCl2{(CN)2IMes}(3-R-py)] (12: R = H; 13: R = Cl; 14: R = Br; 15: R = CN) bearing the maleonitrile-based N-heterocyclic carbene (NHC) (CN)2IMes ({(CN)2IMes}: 4,5-dicyano-1,3-dimesitylimidazol-2-ylidene) were prepared. Solid state structures of 14 and 15 were obtained. Complexes 14 and 15 adopt a slightly distorted square-planar coordination geometry in the solid state with the substituted pyridine ligand trans to the NHC. Catalytic activities of precatalysts 12-15 were studied and subsequently compared to complexes [PdCl2{(CN)2IMes}(PPh3)] (4) and [PdCl(dmba){(CN)2IMes}] (5) recently reported by our group in the Suzuki-Miyaura reaction of various aryl halides and phenylboronic acid. Reactions using previously reported [PdCl2(IMes)(py)] (IMes: 1,3-dimesitylimidazol-2-ylidene) (1) were also carried out and their results contrasted to those involving 12-15, 4 and 5. Differences in initiation rates and the catalytically active species related to the seven complexes in regards to the "throw away ligand" were investigated. Poisoning experiments with mercury show that palladium nanoparticles are responsible for the catalytic activity.
Efficient and Economical Preparation of Hypercrosslinked Polymers-palladium Based on Schiff Base as Recyclable Catalyst for Suzuki-Miyaura Reactions
Gao, Xiyue,Lin, Hongwei,Liu, Shasha,Luo, Qionglin,Ouyang, Yuejun,Xiang, Bailin,Xiang, Dexuan,Yao, Huan,Zhang, Li
supporting information, p. 1879 - 1882 (2021/10/29)
A novel hypercrosslinked polymer (HCP) was prepared via Friedel-Crafts alkylation reaction of Schiff base with benzene and formaldehyde dimethyl acetal (FDA) promoted by FeCl3. The HCP was then metalated with Pd(II) to form heterogeneous catalyst. The protocol featured low cost, mild conditions, readily available materials, easy separation and high yield. Physicochemical methods, including IR, N2 sorption, ICP, TGA, XPS, SEM, EDX, and TEM, were used to characterize the catalyst structure and composition. The results reveal that the heterogeneous catalyst possesses high specific surface area, large pore volume, good chemical and thermal stability, and highly dispersed palladium. The heterogeneous catalysts were applied in Suzuki-Miyaura coupling reaction to evaluate their catalytic performance. The experiments reflected that the HCPs-Pd(OAc)2 was an efficient catalyst for Suzuki-Miyaura reactions with the yield of biaryl up to 99%, while the TON could reach 2250. The reusability test showed the catalyst was easily recovered and reused for at least six times without obvious decrease in activity.
Functionalized chitosan as a novel support for stabilizing palladium in Suzuki reactions
Dong, Yahao,Bi, Jiajun,Ming, Shujun,Zhang, Shoute,Zhu, Dajian,Meng, Di,Li, Tao
, (2021/03/01)
Chitosan is a versatile polysaccharide in different domains due to facile modification and good biodegradability. In this paper, taking advantage of such functional properties, we have developed a stabilizer agent [OCMCS-SB] produced from chitosan, and palladium was successfully immobilized on this designed stabilizer [OCMCS-SB-Pd(II)]. The obtained complex was illuminated by 13C CP-MAS NMR, FT-IR, TGA, XRD, XPS, SEM, TEM and ICP-OES analyses. Due to the interactions of primary hydroxyl groups on chitosan, Schiff base and carboxy groups, the Pd complex showed excellent reactivity (up to 99 %) and stability towards Suzuki reactions in eco-friendly medium. Subsequently, the reusability experiments for OCMCS-SB-Pd(II) formed from chitosan were examined in five consecutive cycles, which showed no appreciable decrease in activity. Furthermore, a reasonably trifunctional complex structure was proposed. The present bio-based system offers a promising approach in utilizing such biopolymers in organic transformations.
