4705-34-4Relevant articles and documents
Synthesis, crystal structure, and catalytic activity of bridged-bis(N-heterocyclic carbene) palladium(II) complexes in selective Mizoroki-Heck cross-coupling reactions
El Ali, Bassam,Fettouhi, Mohammed,Iali, Wissam,Mansour, Waseem,Suleiman, Rami
, (2021/08/09)
A series of three 1,3-propanediyl bridged bis(N-heterocyclic carbene)palladium(II) complexes (Pd-BNH1, Pd-BNH2, and Pd-BNH3), with + I effect order of the N-substituents of the ligand (isopropyl > benzyl > methoxyphenyl), was the subject of a spectroscopic, structural, computational and catalytic investigation. The bis(NHC)PdBr2 complexes were evaluated in Mizoroki-Heck coupling reactions of aryl bromides with styrene or acrylate derivatives and showed high catalytic efficiency to produce diarylethenes and cinnamic acid derivatives. The X-ray structure of the most active palladium complex Pd-BNH3 shows that the Pd(II) center is bonded to the two carbon atoms of the bis(N-heterocyclic carbene) and two bromide ligands in cis position, resulting in a distorted square planar geometry. The NMR data of Pd-BNH3 are consistent with a single chair-boat rigid conformer in solution with no dynamic behavior of the 8-membered ring palladacycle in the temperature range 25–120 °C. The catalytic activities of three Pd-bridged bis(NHC) complexes in the Mizoroki-Heck cross-coupling reactions were not found to have a direct correlation with +I effect order of the N-substituents of the ligand. However, a direct correlation was found between the DFT calculated absolute softness of the three complexes with their respective catalytic activity. The highest calculated softness, in the case of Pd-BNH3, is expected to favor the coordination steps of both the soft aryl bromides and alkenes in the Heck catalytic cycle.
Synthesis of ethylene bis [(2-hydroxy-5,1,3-phenylene) bis methylene] tetraphosphonic acid and their anticorrosive effect on carbon steel in 3%NaCl solution
Sait,Aliouane,Toukal,Hammache,Al-Noaimi,Helesbeux,Duval
, (2021/01/25)
The inhibition performance of the newly synthesized Ethylene bis [(2-hydroxy-5,1,3-phenylene) bis methylene] tetraphosphonic acid (ETPA) toward carbon steel in 3% NaCl was investigated at different concentrations using potentiodynamic polarization (PDP) and impedance spectroscopy (EIS) methods. It was found that the inhibition capability was increased with increasing inhibitor dose and reach 92% at 10?3 mol/L. Also, Polarization curves showed that ETPA acts as a mixed type inhibitor with predominantly control of anodic reaction. The new inhibitor was investigated by different spectroscopic methods such as 1H, 13C and 31PNMR. The quantum parameters such as absolute electronegativity (χ), energy gap ΔE (EHOMO-ELUMO), global softness (σ), global hardness (η), electrophilicity index (ω) and the number of transfer electrons (ΔN) are calculated by density functional theory (DFT). The experimental also correlated with density functional theory results. The calculations show that ETPA has high density of negative charge located on the oxygen atoms of the phosphonate group facilitating the adsorption of ETPA on the surface of carbon steel. The inhibition efficiency of ETPA was discussed in terms of blocking of electrode surface by adsorption of ETPA molecules through active centers. The adsorption of ETPA on the surface of carbon steel obeyed the Langmuir isotherm paradigm.
Palladium Complexes with Phenoxy- And Amidate-Functionalized N-Heterocyclic Carbene Ligands Based on 3-Phenylimidazo[1,5- a]pyridine: Synthesis and Catalytic Application in Mizoroki-Heck Coupling Reactions with Ortho-Substituted Aryl Chlorides
Hung, Cheng-Hau,Zheng, Wei-Yuan,Lee, Hon Man
, p. 702 - 713 (2021/04/02)
Mononuclear and tetranuclear palladium complexes with functionalized "abnormal"N-heterocyclic carbene (aNHC) ligands based on 3-phenylimidazo[1,5-a]pyridine were synthesized. All of the new complexes were structurally characterized by single-crystal X-ray diffraction studies. The new complexes were applied in the Mizoroki-Heck coupling reaction of aryl chlorides with alkenes in neat n-tetrabutylammonium bromide (TBAB). The mononuclear palladium complex with a tridentate phenoxy- and amidate-functionalized aNHC ligand displayed activity superior to that of the palladium complex with a bidentate amidate-functionalized aNHC ligand. The new tetranuclear complex with the tridentate ligand displayed the best activities, capable of the activation of deactivated aryl chlorides as substrates with a low Pd atom loading. Even challenging sterically demanding ortho-substituted aryl chlorides were successfully utilized as substrates. The studies revealed that the robustness of the catalyst precursor is crucial in delivering high catalytic activities. Also, the promising use of tetranuclear palladium complexes with functionalized aNHC ligands as the catalyst precursors in the Mizoroki-Heck coupling reaction in neat TBAB was demonstrated.
