39 results on '"Ya Fan Lin"'
Search Results
2. Chiral Tetra-coordinate Aluminum Cation in Catalysis
- Author
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Ching-Pei Hsu, Yi-Hung Liu, Ching-Wen Chiu, Ya-Fan Lin, Rong-Jie Chein, and Ramalingam Boobalan
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biology ,010405 organic chemistry ,Chemistry ,Organic Chemistry ,Cationic polymerization ,chemistry.chemical_element ,010402 general chemistry ,biology.organism_classification ,01 natural sciences ,0104 chemical sciences ,Catalysis ,Inorganic Chemistry ,Aluminum Cation ,Aluminium ,Polymer chemistry ,Tetra ,Physical and Theoretical Chemistry - Abstract
Although the application of cationic aluminum complexes in catalysis has been extensively investigated, the incorporation of an aluminum cation into a chiral environment is less explored. In this s...
- Published
- 2021
3. Mechanistic Insight into the Ring-Opening Polymerization of ε-Caprolactone and L-Lactide Using Ketiminate-Ligated Aluminum Catalysts
- Author
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Ya-Fan Lin and Nai-Yuan Jheng
- Subjects
DFT calculation ,ring-opening polymerization ,L-lactides ,ε-caprolactone ,aluminum complexes ,ketiminate ligands ,Organic chemistry ,QD241-441 - Abstract
The reactivity and the reaction conditions of the ring-opening polymerization of ε-caprolactone (ε-CL) and L-lactide (LA) initiated by aluminum ketiminate complexes have been shown differently. Herein, we account for the observation by studying the mechanisms on the basis of density functional theory (DFT) calculations. The calculations show that the ring-opening polymerization of ε-CL and LA are rate-determined by the benzoxide insertion and the C−O bond cleavage step, respectively. Theoretical computations suggest that the reaction temperature of L−LA polymerization should be higher than that of ε-CL one, in agreement with the experimental data. To provide a reasonable interpretation of the experimental results and to give an insight into the catalyst design, the influence of the electronic, steric, and thermal effects on the polymerization behaviors will be also discussed in this study.
- Published
- 2019
- Full Text
- View/download PDF
4. Physical organic studies and dynamic covalent chemistry of picolyl heterocyclic amino aminals
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Ji-Ming Ciou, Ya-Fan Lin, Hong-Feng Zhu, Chia-Wen Chang, and Jing-Yun Chen
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010405 organic chemistry ,General Chemical Engineering ,Imine ,Substituent ,Dynamic covalent chemistry ,General Chemistry ,010402 general chemistry ,01 natural sciences ,0104 chemical sciences ,chemistry.chemical_compound ,chemistry ,Covalent bond ,Polymer chemistry ,Polar effect ,Aminal ,Hemiaminal ,Moiety - Abstract
A dynamic covalent system of the picolyl heterocyclic amino aminals has been studied. The aminals are characterized as a metastable species and easily switch to other forms via external stimuli. The solvent, temperature, acid–base and substituent effects have been examined to evaluate the dynamic covalent system. The results reveal that a more polar solvent, a lower temperature, basic conditions and an electron-withdrawing moiety contribute to the stabilities of aminals. The existence of the n → π* interaction between acetonitrile and the CN moiety makes the N-pyrimidyl imine (4c and 4d) yield higher in CD3CN. In a similar fashion, all aminals tend to convert to the corresponding hemiaminal ethers in a methanol environment. According to these findings, we successfully synthesized the following species: (a) N-2-picolylpyrimidin-2-amine 6c obtained by reduction using acetonitrile as the specific solvent; (b) a picolyl aromatic amino aminal 3e prepared from 2-pyridinecarboxaldehyde and the electron withdrawing 2-methoxy-5-nitroaniline.
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- 2020
5. [η5-Cp*B-Mes]+: A Masked Potent Boron Lewis Acid
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Ding-Nan Shih, Shigehiro Yamaguchi, Ya-Fan Lin, Kentaro Matsumoto, Yi-Hung Liu, Hsi-Ching Tseng, Chao-Tang Shen, Shie-Ming Peng, and Ching-Wen Chiu
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Inorganic Chemistry ,chemistry ,Organic reaction ,Organic Chemistry ,chemistry.chemical_element ,Organic chemistry ,Lewis acids and bases ,Physical and Theoretical Chemistry ,Boron ,Stoichiometry ,Catalysis - Abstract
The chemistry of the boron cation has been revitalized in the past decade due to its newfound application in stoichiometric and catalytic organic reactions. To extend the frontier of boron cation c...
- Published
- 2019
6. Chiral Aluminum Cation in Catalysis
- Author
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Ching-Wen Chiu, Rong-Jie Chein, Ya-Fan Lin, Ramalingam Boobalan, Yi-Hung Liu, Chao-An Liu, and Ching-Pei Hsu
- Published
- 2021
7. Novel aluminum complexes bearing 2-(aminomethylene)malonate ligands with high efficiency and controllability in ring-opening polymerization of ε-caprolactone
- Author
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Wei Yi Lu, Kuo Hui Wu, Chi Chi Chang, Yung Chi Chang, Yi Chun Lai, Hsuan-Ying Chen, and Ya Fan Lin
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Steric effects ,Polymers and Plastics ,Organic Chemistry ,General Physics and Astronomy ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Ring-opening polymerization ,Medicinal chemistry ,0104 chemical sciences ,Catalysis ,chemistry.chemical_compound ,Malonate ,chemistry ,Polymerization ,Materials Chemistry ,Chelation ,Methylene ,0210 nano-technology ,Caprolactone - Abstract
A series of Al complexes bearing diethyl 2-((arylamino)methylene)malonate and diethyl 2-((alkylamino)methylene)malonate ligands (AMM ligands) were synthesized and their application in the ring-opening polymerization of e-caprolactone was studied. All the Al complexes bearing AMM ligands exhibited higher catalytic activity (approximately 2.8–16.5 fold) than those Al complexes bearing ketiminate ligands did, except OiPrAlMe2 (2 fold lower catalytic activity). In addition, Al complexes with steric hindrance or electron-withdrawing groups in the ligands revealed the greater catalytic activity, and the chelating effect reduced the reactivity of ring-opening polymerization.
- Published
- 2019
8. Kinetics, Mechanism and Theoretical Studies of Norbornene-Ethylene Alternating Copolymerization Catalyzed by Organopalladium(II) Complexes Bearing Hemilabile α-Amino–pyridine
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Kuo-Hsuan Yu, Shou-Ling Huang, Yi-Hung Liu, Yu Wang, Shiuh-Tzung Liu, Yuan-Chung Cheng, Ya-Fan Lin, and Jwu-Ting Chen
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Norbornene–ethylene alternating copolymerization ,hemilabile ,amino–pyridine ,palladium ,geometrical isomerism ,kinetics ,mechanism. ,Organic chemistry ,QD241-441 - Abstract
Cationic methylpalladium complexes bearing hemilabile bidentate α-amino–pyridines can serve as effective precursors for catalytic alternating copolymerization of norbornene (N) and ethylene (E), under mild conditions. The norbornyl palladium complexes in the formula of {[RHNCH2(o-C6H4N)]Pd(C7H10Me)(NCMe)}(BF4) (R = iPr (2a), tBu (2b), Ph (2c), 2,6-Me2C6H3 (2d), 2,6-iPr2C6H3 (2e)) were synthesized via single insertion of norbornene into the corresponding methylpalladium complexes 1a–1e, respectively. Both square planar methyl and norbornyl palladium complexes exhibit facile equilibria of geometrical isomerization, via sterically-controlled amino decoordination–recoordination of amino–pyridine. Kinetic studies of E-insertion, N-insertion of complexes 1 and 2, and the geometric isomerization reactions have been examined by means of VT-NMR, and found in excellent agreement with the results estimated by DFT calculations. The more facile N-insertion in the cis-isomers, and ready geometric isomerization, cooperatively lead to a new mechanism that accounts for the novel catalytic formation of alternating COC.
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- 2017
- Full Text
- View/download PDF
9. Neferine, a bisbenzylisoquinoline alkaloid of Nelumbo nucifera, inhibits glutamate release in rat cerebrocortical nerve terminals through 5-HT
- Author
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Kun Chieh, Yeh, Chi Feng, Hung, Ya Fan, Lin, Der Chen, Chang, Ming Shang, Pai, and Su Jane, Wang
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Cerebral Cortex ,Male ,Nerve Endings ,Dose-Response Relationship, Drug ,Glutamic Acid ,Nelumbo ,Benzylisoquinolines ,Protein Structure, Secondary ,Rats ,Molecular Docking Simulation ,Rats, Sprague-Dawley ,Alkaloids ,Receptor, Serotonin, 5-HT1A ,Animals ,Excitatory Amino Acid Antagonists ,Drugs, Chinese Herbal - Abstract
Neferine, a bisbenzylisoquinoline alkaloid present in Nelumbo nucifera, has been reported to exhibit neuroprotective effects. Because reduced glutamatergic transmission through inhibition of glutamate release has been proposed as a mechanism of neuroprotection, we investigated whether and how neferine inhibits glutamate release in the nerve terminals of the cerebral cortex of rats. The results demonstrated that neferine inhibits the glutamate release that is evoked by the potassium channel blocker 4-aminopyridine, doing so in a dose-dependent manner. This effect was prevented by removing extracellular calcium and blocking vesicular transporters or N- and P/Q-type calcium channels but not by blocking glutamate transporters. Neferine decreased the 4-aminopyridine-stimulated elevation in intrasynaptosomal calcium concentration; however, it had no effect on the synaptosomal membrane potential. The inhibition of glutamate release by neferine was also eliminated by the selective 5-hydroxytryptamine 1A (5HT
- Published
- 2020
10. N‐Heterocyclic Carbene Complexes of Cp*–Aluminum Triflate
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Ching-Wen Chiu, Ya-Fan Lin, Shie-Ming Peng, Chen‐Hao Wang, Gene‐Shiang Lee, and Hsi-Ching Tseng
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Inorganic Chemistry ,Aluminum triflate ,chemistry.chemical_compound ,010405 organic chemistry ,Chemistry ,Polymer chemistry ,010402 general chemistry ,01 natural sciences ,Carbene ,0104 chemical sciences - Published
- 2018
11. Improvement in titanium complexes supported by Schiff bases in ring-opening polymerization of cyclic esters: ONO-tridentate Schiff bases
- Author
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Wei-Yi Lu, Chu-Chieh Lin, Hsiu-Wei Ou, Hsuan-Ying Chen, Ya-Fan Lin, and Jaya Kishore Vandavasi
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Polymers and Plastics ,010405 organic chemistry ,Organic Chemistry ,chemistry.chemical_element ,010402 general chemistry ,01 natural sciences ,Ring-opening polymerization ,0104 chemical sciences ,Catalysis ,chemistry.chemical_compound ,Monomer ,chemistry ,Polymerization ,Polymer chemistry ,Materials Chemistry ,Electronic effect ,Titanium - Abstract
A series of titanium (Ti) complexes bearing ONO-tridentate Schiff bases were synthesized and their application to the ring-opening polymerization of L-lactide and e-caprolactone was studied. Ti complexes bearing ONO-tridentate Schiff bases revealed a greater catalytic activity compared to other previously synthesized Ti complexes bearing multi-dentate phenolate ligands. We hypothesize that using ONO-tridentate Schiff bases as ligands reduces the occupied space and increases the monomer coordination around the Ti center, thereby increasing catalytic activity. The electronic effect of the phenolate group on the polymerization rate was also studied, showing that electron-donating substituents on the ligands could drastically increase polymerization activity.
- Published
- 2018
12. N-Heterocyclic Silylene Coordinated Dialkyl Borenium Equivalent
- Author
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Ya-Fan Lin, Hsiu-Chen Tsai, Gene-Hsiang Lee, Ching-Wen Chiu, Shie-Ming Peng, and Wei-Chun Liu
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chemistry.chemical_classification ,Double bond ,010405 organic chemistry ,Ligand ,Organic Chemistry ,Silylene ,chemistry.chemical_element ,010402 general chemistry ,Photochemistry ,01 natural sciences ,0104 chemical sciences ,Ion ,Inorganic Chemistry ,chemistry.chemical_compound ,chemistry ,Polymer chemistry ,Nucleophilic substitution ,Reactivity (chemistry) ,Physical and Theoretical Chemistry ,Boron ,Trifluoromethanesulfonate - Abstract
In an attempt to prepare the heavier analogue of NHC-stabilized borenium cation, we have prepared a silylene-coordinated borenium equivalent (1a), which can be viewed as a contact ion pair of borenium and triflate. The triflate anion coordinates to the oxophilic silicon center, leaving the boron center existing in a trigonal-planar geometry in the solid state and in solution. Nucleophilic substitution reactions of 1a all result in the release of free silylene ligand, demonstrating the borenium-ion-like reactivity of 1a. Chemical reduction of 1a leads to a neutral radical possessing a partial Si–B double bond.
- Published
- 2017
13. Quercetin inhibits histamine-induced calcium influx in human keratinocyte via histamine H4 receptors
- Author
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Su-Jane Wang, Yen-Ling Hung, Chi-Ming Pu, Chi-Feng Hung, Der-Chen Chang, Chung-Chi Yang, Ya-Fan Lin, and Hsin-Ju Li
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Keratinocytes ,0301 basic medicine ,Agonist ,Indoles ,medicine.drug_class ,Primary Cell Culture ,Immunology ,TRPV Cation Channels ,Pharmacology ,Piperazines ,03 medical and health sciences ,chemistry.chemical_compound ,Histamine receptor ,0302 clinical medicine ,Piperidines ,medicine ,Animals ,Choline Kinase ,Humans ,Immunology and Allergy ,heterocyclic compounds ,Enzyme Inhibitors ,Receptor ,Protein kinase C ,Receptors, Histamine H4 ,Mice, Inbred BALB C ,Behavior, Animal ,Molecular Structure ,Chemistry ,Pruritus ,Interleukin-8 ,Molecular Docking Simulation ,030104 developmental biology ,medicine.anatomical_structure ,Type C Phospholipases ,030220 oncology & carcinogenesis ,Quinolines ,Calcium ,Quercetin ,Capsaicin ,Keratinocyte ,Capsazepine ,Histamine - Abstract
Histamine is released from mast cells when tissues are inflamed or stimulated by allergens. Activation of histamine receptors and calcium influx via TRPV1 could be related to histamine-induced itch and skin inflammation. Quercetin is known to have anti-inflammatory and anti-itching effects. This study aims to understand whether quercetin can directly affect histamine-induced calcium influx in human keratinocyte. In it, we investigated quercetin, which acts on histamine-induced intracellular free calcium ([Ca2+]i) elevation in human keratinocyte. Changes in [Ca2+]i were measured using spectrofluorometry and confocal Imaging. We detected the expression of IL-8 after treatment of quercetin using qRT-PCR and evaluated its anti-itching effect in BALB/c mice. We also performed a docking study to estimate the binding affinity of quercetin to H4 receptors. We found that quercetin pretreatment decreased histamine-induced [Ca2+]i elevation in a concentration-dependent manner. The inhibitory effect of quercetin on histamine-induced [Ca2+]i elevation was blocked by JNJ7777120, a selective H4 antagonist, as well as by U73122, a PLC inhibitor, and by GF109203X, a PKC inhibitor. We also found that H4 agonist (4-methylhistamine)-induced [Ca2+]i elevation could be inhibited by quercetin. Moreover, the selective TRPV1 blocker capsazepine significantly suppressed the quercetin-mediated inhibition of histamine-induced [Ca2+]i elevation, whereas the TRPV4 blocker GSK2193874 had no effect. Last, quercetin decreased histamine and H4 agonist-induced IL-8 expression in keratinocyte and inhibited the scratching behavior-induced compound 48/80 in BALB/c mice. The molecular docking study also showed that quercetin exhibited high binding affinities with H4 receptors (autodock scores for H4 = −8.7 kcal/mol). These data suggest that quercetin could decrease histamine 4 receptor-induced calcium influx through the TRPV1 channel and could provide a molecular mechanism of quercetin in anti-itching, anti-inflammatory, and unpleasant sensations.
- Published
- 2021
14. Mono- and Polynuclear Boron Dications
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Ya-Fan Lin and Ching-Wen Chiu
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inorganic chemicals ,010405 organic chemistry ,Chemistry ,Inorganic chemistry ,chemistry.chemical_element ,Molecular electronics ,General Chemistry ,010402 general chemistry ,01 natural sciences ,0104 chemical sciences ,Catalysis ,Reagent ,Organic chemistry ,Reactivity (chemistry) ,Lewis acids and bases ,Boron ,Stoichiometry - Abstract
As the synthetic applications of boron monocations as stoichiometric reagents or catalysts have expanded significantly in the past decade, investigation on the molecular electronics and reactivity of the related boron dications remains in its infancy. This mini-review highlights the recent advancements in boron polycations consisting of one or multiple boron centers. The structure–reactivity relationship of these dicationic species will also be discussed.
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- 2017
15. Improvement in Aluminum Complexes Bearing Schiff Bases in Ring-Opening Polymerization of ε-Caprolactone: A Five-Membered-Ring System
- Author
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Michael Y. Chiang, Jaya Kishore Vandavasi, Yi-Chun Lai, Wei-Yi Lu, Man-Ting Jiang, Hsuan-Ying Chen, Chieh-Ling Lee, Ya-Fan Lin, and Li-Fang Wang
- Subjects
Schiff base ,010405 organic chemistry ,Organic Chemistry ,chemistry.chemical_element ,010402 general chemistry ,Photochemistry ,01 natural sciences ,Ring-opening polymerization ,0104 chemical sciences ,Steric repulsion ,Catalysis ,Inorganic Chemistry ,chemistry.chemical_compound ,chemistry ,Polymerization ,Aluminium ,Polymer chemistry ,Density functional theory ,Physical and Theoretical Chemistry ,Caprolactone - Abstract
A series of five- and six-membered-ring Al complexes bearing Schiff bases was synthesized and their application to the ring-opening polymerization of e-caprolactone (CL) was studied. The five-membered-ring Al complexes have been shown to have a significantly higher polymerization rate than six-membered-ring Al complexes (2–3 fold for CL polymerization). The X-ray data revealed that the Al center of a five-membered-ring Al complex is farther from the Schiff base ligand than is that of a six-membered-ring Al complex. The results of density functional theory calculations also suggest that more space around the Al center of five-membered-ring Al complexes may reduce the steric repulsion in CL polymerization and increase the catalytic activity of five-membered-ring Al complexes.
- Published
- 2017
16. Neferine, a bisbenzylisoquinoline alkaloid of Nelumbo nucifera, inhibits glutamate release in rat cerebrocortical nerve terminals through 5-HT1A receptors
- Author
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Der Chen Chang, Chi-Feng Hung, Kun Chieh Yeh, Ming Shang Pai, Su-Jane Wang, and Ya Fan Lin
- Subjects
0301 basic medicine ,Pharmacology ,Voltage-dependent calcium channel ,Glutamate receptor ,chemistry.chemical_element ,Calcium ,Pertussis toxin ,Adenylyl cyclase ,Vesicular transport protein ,03 medical and health sciences ,chemistry.chemical_compound ,030104 developmental biology ,0302 clinical medicine ,chemistry ,Receptor ,Protein kinase A ,030217 neurology & neurosurgery - Abstract
Neferine, a bisbenzylisoquinoline alkaloid present in Nelumbo nucifera, has been reported to exhibit neuroprotective effects. Because reduced glutamatergic transmission through inhibition of glutamate release has been proposed as a mechanism of neuroprotection, we investigated whether and how neferine inhibits glutamate release in the nerve terminals of the cerebral cortex of rats. The results demonstrated that neferine inhibits the glutamate release that is evoked by the potassium channel blocker 4-aminopyridine, doing so in a dose-dependent manner. This effect was prevented by removing extracellular calcium and blocking vesicular transporters or N- and P/Q-type calcium channels but not by blocking glutamate transporters. Neferine decreased the 4-aminopyridine-stimulated elevation in intrasynaptosomal calcium concentration; however, it had no effect on the synaptosomal membrane potential. The inhibition of glutamate release by neferine was also eliminated by the selective 5-hydroxytryptamine 1A (5HT1A) receptor antagonist WAY100635, Gi/o protein inhibitor pertussis toxin, adenylyl cyclase inhibitor MDL12330A, and protein kinase A inhibitor H89. Moreover, immunocytochemical analysis revealed the presence of 5-HT1A receptor proteins in the vesicular transporter of glutamate type 1 positive synaptosomes. The molecular docking study also demonstrated that neferine exhibited the highest binding affinity with 5-HT1A receptors (Autodock scores for 5-HA1A = −11.4 kcal/mol). Collectively, these results suggested that neferine activates 5-HT1A receptors in cortical synaptosomes, which decreases calcium influx and glutamate release through the activation of Gi/o protein and the inhibition of adenylyl cyclase/cAMP/protein kinase A cascade.
- Published
- 2020
17. Non-chelating polydentate N-heterocyclic carbenes through assembly approaches
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Chung-Hao Hu, Ching-Wen Chiu, Ya-Fan Lin, and Chih-Hsun Liu
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Denticity ,010405 organic chemistry ,Chemistry ,Ligand ,Organic Chemistry ,010402 general chemistry ,01 natural sciences ,Biochemistry ,Combinatorial chemistry ,0104 chemical sciences ,Inorganic Chemistry ,chemistry.chemical_compound ,Chelation ,Carbene - Abstract
Bridging-type polydentate N-heterocyclic carbene (NHC) ligands are valuable building blocks for organometallic supramolecules. In order to quickly expand the ligand library of poly-NHC, we have ass...
- Published
- 2016
18. Mechanistic Studies on the Rearrangement of a Boron Cation: From a nido-Carborane to a Planar Boracycle
- Author
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Ching-Wen Chiu, Yi-Hung Liu, Ya-Fan Lin, Shie-Ming Peng, Chao-Tang Shen, and Yu-Ting Hsiao
- Subjects
Steric effects ,Pericyclic reaction ,010405 organic chemistry ,Hydride ,Borabenzene ,Organic Chemistry ,chemistry.chemical_element ,010402 general chemistry ,Photochemistry ,01 natural sciences ,0104 chemical sciences ,Inorganic Chemistry ,Crystallography ,chemistry.chemical_compound ,Deprotonation ,chemistry ,Carborane ,Borenium ion ,Physical and Theoretical Chemistry ,Boron - Abstract
The reaction mechanism of the [Et3BH]−-induced conversion of a dicationic boron compound ([Cp*B-IMes]2+, [1]2+) to a planar neutral carbene-coordinated borabenzene (2) is investigated experimentally and theoretically. Owing to the steric congestion around the boron center, bulky [Et3BH]− attacks the less encumbered carbon atom of Cp*, leading to a metastable 5-borabicyclo[2.1.1]hex-2-ene borenium cation ([3-CH]+) at low temperature. Upon raising the temperature, the bicyclic-borenium ion undergoes sequential pericyclic reactions, including suprafacial [1,3]-sigmatropic shift, two-electron electrocyclic ring opening, and then [1,2]-hydrogen shift to a planar cyclic borenium ion, [4-CH]+, which can then be deprotonated to yield the neutral aromatic borabenzene. The attack of hydride at the boron center of [1]2+ was excluded through the preparation and isolation of 6-borabicyclo[3.1.0]hexenylium, [3-BH]+, which could not be transformed into [3-CH]+ or [4-CH]+. The borenium ion rearrangement follows first-ord...
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- 2016
19. N-Heterocyclic olefin stabilized boron dication
- Author
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Ching-Wen Chiu, Shie-Ming Peng, Ya-Fan Lin, Wan-Hua Lee, and Gene-Hsiang Lee
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Steric effects ,Olefin fiber ,010405 organic chemistry ,Bent molecular geometry ,Substituent ,chemistry.chemical_element ,Nanotechnology ,010402 general chemistry ,Boron atom ,01 natural sciences ,0104 chemical sciences ,Dication ,Inorganic Chemistry ,Crystallography ,chemistry.chemical_compound ,chemistry ,Nucleophile ,Boron - Abstract
Boron mono- and di-cations featuring a nucleophilic N-heterocyclic olefin and the pentamethylcyclopentadienyl substituent have been prepared and structurally characterized. Experimental and theoretical investigations show that [η5-Cp*B-NHO]2+is considerably more Lewis acidic than [η5-Cp*B-IMes]2+due to the steric congestion imposed by the bent geometry of NHO around the central boron atom.
- Published
- 2016
20. Comparison of L-lactide polymerization by using magnesium complexes bearing 2-(arylideneamino)phenolate and 2-((arylimino)methyl)phenolate ligands
- Author
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Feng Jie Lai, Hsuan-Ying Chen, Shou Jie Chung, Yu Lun Chang, Shangwu Ding, Ya Fan Lin, Yen Tzu Huang, Chun Juei Chang, and Kuo Hui Wu
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Schiff base ,Polymers and Plastics ,Hydrogen bond ,Organic Chemistry ,General Physics and Astronomy ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Ring (chemistry) ,01 natural sciences ,Ring-opening polymerization ,0104 chemical sciences ,Catalysis ,Adduct ,chemistry.chemical_compound ,Polymerization ,chemistry ,Benzyl alcohol ,Polymer chemistry ,Materials Chemistry ,0210 nano-technology - Abstract
A series of magnesium complexes bearing 2-(arylideneamino)phenolate (forming 5-membered ring Mg complexes) and 2-((arylimino)methyl)phenolate (forming 6-membered ring Mg complexes) ligands were synthesized, and their application in the ring-opening polymerization of L-lactide (LA) was investigated. The Mg complexes with 5-membered rings exhibit a higher polymerization rate and controllability for polylactide production than those with 6-membered rings do (one-fold to three-fold for LA polymerization). The density function theory calculation results revealed that benzyl alcohol approaches LA through the hydrogen bond with phenolate oxygen, and then initiates LA, with the proton transferring to phenolate oxygen to form the LA-OBn adduct. The LA-OBn adduct was activated using the proton present on phenolate oxygen to open the ring of the LA-OBn adduct. Moreover, the LA polymerization using L5ThioMg as a catalyst needs to overcome a 17.7 kcal/mol activation free energy that is lower than that of L6ThioMg (21.0 kcal/mol)
- Published
- 2020
21. Structure and nitrite reduction reactivity study of bio-inspired copper(i)-nitro complexes in steric and electronic considerations of tridentate nitrogen ligands
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Michael Y. Chiang, Ya-Fan Lin, Manmath Narwane, Chai-Lin Kao, Hsing-Yin Chen, Yu-Lun Chang, Sodio C. N. Hsu, and Wan-Jung Chuang
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Steric effects ,010405 organic chemistry ,Ligand ,Tetrahedral molecular geometry ,chemistry.chemical_element ,010402 general chemistry ,01 natural sciences ,Medicinal chemistry ,Copper ,0104 chemical sciences ,Inorganic Chemistry ,chemistry.chemical_compound ,chemistry ,Nitro ,Reactivity (chemistry) ,Nitrite ,Stoichiometry - Abstract
Two copper(I)–nitro complexes [Tpm3-tBuCu(NO2)] (1) and [(Ph3P)2N][Tp3-tBuCu(NO2)] (2), containing steric bulky neutral tris(3-tert-butylpyrazolyl)methane and anionic hydrotris(3-tert-butylpyrazolyl)borate ligands, have been synthesized and characterized. Complex 2 adopts a unique κ2-binding mode of Tp3-tBu around the copper(I)–nitro environment in the solid state and shows a four-coordinated tetrahedral geometry surrounded by a nitro and three pz3-tBu groups in solution. Both complexes 1 and 2 allow for the stoichiometric reduction of NO2− to NO with H+ addition. The results of this effort show that increasing steric bulk and electron donation properties on the nitrogen ancillary ligand will improve the nitrite reduction ability of the copper(I)–nitro model complexes.
- Published
- 2018
22. Disproportionation of Bis(phosphaethenyl)pyridine Iron(I) Bromide Induced by tBuNC
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Yumiko Nakajima, Ya-Fan Lin, Nobuko Ichihara, and Fumiyuki Ozawa
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Ligand ,Organic Chemistry ,Disproportionation ,Photochemistry ,Toluene ,Square pyramidal molecular geometry ,Inorganic Chemistry ,chemistry.chemical_compound ,Crystallography ,Trigonal bipyramidal molecular geometry ,chemistry ,Bromide ,Pyridine ,Phosphaalkene ,Physical and Theoretical Chemistry - Abstract
Redox behavior of Fe(I) complexes bearing a PNP-pincer-type phosphaalkene ligand, 2,6-bis[1-phenyl-2-(2,4,6-tri-tert-butylphenyl)-2-phosphaethenyl]pyridine (BPEP-Ph), is reported. The four-coordinate Fe(I) complex [FeBr(BPEP-Ph)] (1) readily reacts with 1 equiv of tBuNC in toluene at −35 °C to give [FeBr(tBuNC)(BPEP-Ph)] (2) with a 17e configuration. Complex 2 is fairly stable in neat benzene at room temperature, but smoothly undergoes disproportionation in the presence of added tBuNC to afford the Fe(0) complex [Fe(tBuNC)2(BPEP-Ph)] (3) and the Fe(II) complex [FeBr2(tBuNC)4] (4) along with free BPEP-Ph. The single-crystal X-ray diffraction studies of 3 and 4 reveal distorted trigonal bipyramidal and square pyramidal arrangements around Fe, respectively. The yield of 3 increases up to 50%/2 when 2 equiv of tBuNC is added to the system. A disproportionation process involving a 19e intermediate is proposed.
- Published
- 2014
23. Cp*-Substituted Boron Cations: The Effect of NHC, NHO, and CAAC Ligands
- Author
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Ching-Wen Chiu, Jih-Sheng Huang, Ya-Fan Lin, Yi-Hung Liu, Shie-Ming Peng, Wan-Hua Lee, and Chao-Tang Shen
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Addition reaction ,010405 organic chemistry ,Hydride ,Ligand ,chemistry.chemical_element ,Electron deficiency ,010402 general chemistry ,Photochemistry ,01 natural sciences ,Medicinal chemistry ,0104 chemical sciences ,Dication ,Inorganic Chemistry ,chemistry.chemical_compound ,chemistry ,Electrophile ,Physical and Theoretical Chemistry ,Boron ,Carbene - Abstract
The effect of a ligand on the electron deficiency and Lewis acidity of the Cp*-substituted boron dication has been investigated experimentally and theoretically. In addition to the reported IMes- and N-heterocyclic olefin (NHO)-stabilized boron dications, the related cyclic alkylamino carbene (CAAC)-coordinated boron mono- and dications have also been synthesized and structurally characterized. An electrochemical study of dications [3a–3c]2+ confirms the higher electron deficiency of the dicationic system than the related boron monocations. Moreover, the presence of a π-acidic CAAC ligand is critical for realizing stable radical species generated from the chemical reduction of boron cations. The nature of the axial ligand also significantly affects the selectivity of the hydride addition reaction of boron dications. While bulky superhydride reacts with [3a–3c]2+ in the same manner to give the cyclic boreniums, [BH4]− attacks three different electrophilic sites of boron dications: the sp2 carbon of Cp* of ...
- Published
- 2016
24. Mechanistic Insight into the Ring-Opening Polymerization of ɛ-Caprolactone and L-Lactide Using Ketiminate-Ligated Aluminum Catalysts
- Author
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Ya-Fan Lin and Nai-Yuan Jheng
- Subjects
Steric effects ,Materials science ,Polymers and Plastics ,ring-opening polymerization ,DFT calculation ,Ring-opening polymerization ,Article ,L-lactides ,Catalysis ,lcsh:QD241-441 ,chemistry.chemical_compound ,lcsh:Organic chemistry ,Computational chemistry ,Reactivity (chemistry) ,ε-caprolactone ,Bond cleavage ,ɛ-caprolactone ,aluminum complexes ,General Chemistry ,ketiminate ligands ,Polymerization ,chemistry ,Density functional theory ,Caprolactone - Abstract
The reactivity and the reaction conditions of the ring-opening polymerization of ɛ-caprolactone (ɛ-CL) and L-lactide (LA) initiated by aluminum ketiminate complexes have been shown differently. Herein, we account for the observation by studying the mechanisms on the basis of density functional theory (DFT) calculations. The calculations show that the ring-opening polymerization of ɛ-CL and LA are rate-determined by the benzoxide insertion and the C&ndash, O bond cleavage step, respectively. Theoretical computations suggest that the reaction temperature of L&ndash, LA polymerization should be higher than that of ɛ-CL one, in agreement with the experimental data. To provide a reasonable interpretation of the experimental results and to give an insight into the catalyst design, the influence of the electronic, steric, and thermal effects on the polymerization behaviors will be also discussed in this study.
- Published
- 2019
25. Electrospray mass spectrometry studies of purified aluminum tridecamer in a 50:50 water/acetonitrile mixture
- Author
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Ya-Fan Lin and Duu-Jong Lee
- Subjects
Mass spectrometry -- Usage ,Aluminum -- Chemical properties ,Aluminum -- Electric properties ,Acetonitrile -- Chemical properties ,Acetonitrile -- Electric properties ,Organometallic compounds -- Structure ,Organometallic compounds -- Chemical properties ,Organometallic compounds -- Electric properties ,Chemicals, plastics and rubber industries - Published
- 2010
26. Dense membranes precoated with aluminium tridecamer (Al13) for water treatment
- Author
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Ya-Fan Lin, Justin Chun-Te Lin, Wan-Mu Guo, Duu-Jong Lee, and An-Chi Cheng
- Subjects
chemistry.chemical_classification ,Chromatography ,Mechanical Engineering ,General Chemical Engineering ,chemistry.chemical_element ,General Chemistry ,Membrane ,chemistry ,Chemical engineering ,Aluminium ,Coagulation (water treatment) ,Humic acid ,Surface modification ,General Materials Science ,Water treatment ,Nanofiltration ,Reverse osmosis ,Water Science and Technology - Abstract
Coagulation or dense membrane processes, i.e. nanofiltration (NF) and reverse osmosis (RO), are intensively used in surface water treatment. Conventional coagulation process is used to remove colloids and particles, while the dense membrane processes are used to remove trace dissolved contaminants. This paper applied an in-situ surface modification technique by directly depositing the laboratory synthesized coagulant, aluminium tridecamer ([AlO4Al12(OH)24(H2O)12]Cl7, Al13), as a coating solution for two NF and one RO membranes. The dense membranes can completely reject the Al13 compounds; while the coated membranes were effectively removing humic acid and 17β-estradiol (E2) from waters. The coated Al13 layer revealed structural stability subjected to salt (NaCl), acid (pH 5) and base (pH 9) challenges.
- Published
- 2012
27. Electrospray mass spectrometry studies of purified aluminum tridecamer in 50:50 water/methanol mixture
- Author
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Ya-Fan Lin and Duu-Jong Lee
- Subjects
chemistry.chemical_classification ,Ligand ,Chemistry ,General Chemical Engineering ,Electrospray ionization ,Analytical chemistry ,Salt (chemistry) ,General Chemistry ,Sample preparation in mass spectrometry ,Adduct ,chemistry.chemical_compound ,Mass spectrum ,Molecule ,Methanol ,Nuclear chemistry - Abstract
This study conducted electrospray ionization mass spectrometry (ESI-MS) tests on 90–95% pure aluminum tridecamer (Al13) salt dissolved in a 50:50 (v/v) water/methanol mixture. The mass spectra for water/methanol mixture revealed no major characteristic peaks for Al13, but showed a few series with incremental difference of 32u, 18u (or 9u), and 14u in the m/z = 200–500 regime. The methanol molecule typically replaces one by one the ligated aqua ligand and adducts to the aluminum center to destruct aluminum tridecamer into smaller, singly or doubly charged polymeric species. A species network with ligand substitution and addition reactions was for the first time revealed.
- Published
- 2011
28. Purification of aluminum tridecamer salt using organic solvent precipitation
- Author
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Duu-Jong Lee and Ya-Fan Lin
- Subjects
chemistry.chemical_classification ,Base (chemistry) ,Precipitation (chemistry) ,Electrospray ionization ,Inorganic chemistry ,Salt (chemistry) ,Filtration and Separation ,Mass spectrometry ,Chloride ,Analytical Chemistry ,chemistry.chemical_compound ,chemistry ,medicine ,Titration ,Sulfate ,medicine.drug - Abstract
Aluminum tridecamer (Al 13 ) salt of 70% purity can be yielded by slowly adding base to a mixed aluminum chloride solution with sodium chloride as the primary byproduct. The purity of the so-produced Al 13 solution is typically increased to >90% using sulfate precipitation and nitrate metathesis reactions (the SO 4 2− /Ba 2+ separation method). However, the presence of excess sulfate and, as demonstrated in this study, excess chloride ions can destabilize Al 13 clusters. This study applied the organic solvent precipitation technique to purify crude Al 13 salt. The solution and solid-state 27 Al nuclear magnetic resonance (NMR) spectra indicate that Al 13 purity was >95%. The infrared adsorption spectra had clear Al 13 characteristic bands. The electrospray ionization mass spectrometry (ESI-MS) tests identified Al 13 7+ species. The organic solvent precipitation method purified Al 13 clusters with minimal free Cl − ions.
- Published
- 2010
29. Kinetics, Mechanism and Theoretical Studies of Norbornene-Ethylene Alternating Copolymerization Catalyzed by Organopalladium(II) Complexes Bearing Hemilabile α-Amino–pyridine
- Author
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Jwu-Ting Chen, Kuo-Hsuan Yu, Ya-Fan Lin, Shiuh-Tzung Liu, Yuan-Chung Cheng, Shou-Ling Huang, Yu Wang, and Yi-Hung Liu
- Subjects
Magnetic Resonance Spectroscopy ,Denticity ,Pyridines ,Norbornene–ethylene alternating copolymerization ,Stereochemistry ,mechanism ,Pharmaceutical Science ,chemistry.chemical_element ,010402 general chemistry ,01 natural sciences ,Catalysis ,Article ,Polymerization ,Analytical Chemistry ,lcsh:QD241-441 ,chemistry.chemical_compound ,Isomerism ,lcsh:Organic chemistry ,Drug Discovery ,Pyridine ,Polymer chemistry ,Molecule ,geometrical isomerism ,Physical and Theoretical Chemistry ,Norbornene ,Molecular Structure ,010405 organic chemistry ,Organic Chemistry ,hemilabile ,Cationic polymerization ,Ethylenes ,Models, Theoretical ,palladium ,Norbornanes ,amino–pyridine ,kinetics ,0104 chemical sciences ,chemistry ,Chemistry (miscellaneous) ,Organopalladium ,Molecular Medicine ,Isomerization ,Palladium - Abstract
Cationic methylpalladium complexes bearing hemilabile bidentate α-amino–pyridines can serve as effective precursors for catalytic alternating copolymerization of norbornene (N) and ethylene (E), under mild conditions. The norbornyl palladium complexes in the formula of {[RHNCH2(o-C6H4N)]Pd(C7H10Me)(NCMe)}(BF4) (R = iPr (2a), tBu (2b), Ph (2c), 2,6-Me2C6H3 (2d), 2,6-iPr2C6H3 (2e)) were synthesized via single insertion of norbornene into the corresponding methylpalladium complexes 1a–1e, respectively. Both square planar methyl and norbornyl palladium complexes exhibit facile equilibria of geometrical isomerization, via sterically-controlled amino decoordination–recoordination of amino–pyridine. Kinetic studies of E-insertion, N-insertion of complexes 1 and 2, and the geometric isomerization reactions have been examined by means of VT-NMR, and found in excellent agreement with the results estimated by DFT calculations. The more facile N-insertion in the cis-isomers, and ready geometric isomerization, cooperatively lead to a new mechanism that accounts for the novel catalytic formation of alternating COC.
- Published
- 2017
30. N-Heterocyclic Silylene Coordinated Dialkyl Borenium Equivalent.
- Author
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Hsiu-Chen Tsai, Ya-Fan Lin, Wei-Chun Liu, Gene-Hsiang Lee, Shie-Ming Peng, and Ching-Wen Chiu
- Subjects
- *
SILYLENES , *HETEROCYCLIC compounds , *BORENIUM ions , *ION pairs , *NUCLEOPHILIC substitution reactions - Abstract
In an attempt to prepare the heavier analogue of NHC-stabilized borenium cation, we have prepared a silylene-coordinated borenium equivalent (1a), which can be viewed as a contact ion pair of borenium and triflate. The triflate anion coordinates to the oxophilic silicon center, leaving the boron center existing in a trigonal-planar geometry in the solid state and in solution. Nucleophilic substitution reactions of 1a all result in the release of free silylene ligand, demonstrating the borenium-ion-like reactivity of 1a. Chemical reduction of 1a leads to a neutral radical possessing a partial Si-B double bond. [ABSTRACT FROM AUTHOR]
- Published
- 2017
- Full Text
- View/download PDF
31. Electrospray mass spectrometry studies of purified aluminum tridecamer in a 50:50 water/acetonitrile mixture
- Author
-
Duu-Jong Lee and Ya-Fan Lin
- Subjects
chemistry.chemical_classification ,Electrospray ionization ,Inorganic chemistry ,Salt (chemistry) ,Decomposition ,Chloride ,Adduct ,chemistry.chemical_compound ,chemistry ,Mass spectrum ,medicine ,Molecule ,Physical and Theoretical Chemistry ,Acetonitrile ,medicine.drug - Abstract
This study conducted electrospray ionization mass spectrometry (ESI-MS) tests on 90-95% pure [AlO(4)Al(12)(OH)(24)(H(2)O)(12)]Cl(7) (Al(13)) salt dissolved in a 50:50 v/v water/acetonitrile solution. Acetonitrile typically replaces the ligated aqua ligands and adducts to the aluminum center, leading to aluminum tridecamer breakdown. The chloride anions cannot coordinate with the aluminum center in the presence of acetonitrile molecules. The acetonitrile deconstructs the "cagelike" aluminum tridecamer structure into smaller polymeric species, which are further transformed into a brucite-like structure. The present work obtained the mass spectra of incremental difference of 18u for fresh solution and of 9u for aged solution in the m/z = 200-900 regime, providing support to the occurrence of water ligand exchange reaction during aluminum tridecamer decomposition.
- Published
- 2010
32. Improvement in Aluminum Complexes Bearing Schiff Bases in Ring-Opening Polymerization of ε-Caprolactone: A Five-Membered-Ring System.
- Author
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Chieh-Ling Lee, Ya-Fan Lin, Man-Ting Jiang, Wei-Yi Lu, Vandavasi, Jaya Kishore, Li-Fang Wang, Yi-Chun Lai, Chiang, Michael Y., and Hsuan-Ying Chen
- Subjects
- *
ALUMINUM , *METAL complexes , *CHEMICAL synthesis , *POLYMERIZATION , *CAPROLACTONES , *SCHIFF bases , *LIGANDS (Chemistry) , *CATALYTIC activity - Abstract
A series of five- and six-membered-ring Al complexes bearing Schiff bases was synthesized and their application to the ring-opening polymerization of ε-caprolactone (CL) was studied. The five-membered-ring Al complexes have been shown to have a significantly higher polymerization rate than six-membered-ring Al complexes (2-3 fold for CL polymerization). The X-ray data revealed that the Al center of a five-membered-ring Al complex is farther from the Schiff base ligand than is that of a six-membered-ring Al complex. The results of density functional theory calculations also suggest that more space around the Al center of five-membered-ring Al complexes may reduce the steric repulsion in CL polymerization and increase the catalytic activity of five-membered-ring Al complexes. [ABSTRACT FROM AUTHOR]
- Published
- 2017
- Full Text
- View/download PDF
33. Cp*-Substituted Boron Cations: The Effect of NHC, NHO, and CAAC Ligands.
- Author
-
Jih-Sheng Huang, Wan-Hua Lee, Chao-Tang Shen, Ya-Fan Lin, Yi-Hung Liu, Shie-Ming Peng, and Ching-Wen Chiu
- Published
- 2016
- Full Text
- View/download PDF
34. Reduction of an Fe(i) mesityl complex induced by π-acid ligands
- Author
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Ya-Fan Lin, Fumiyuki Ozawa, and Yumiko Nakajima
- Subjects
Inorganic Chemistry ,chemistry.chemical_compound ,Energy profile ,Radical trapping ,Chemistry ,Stereochemistry ,Yield (chemistry) ,Pyridine ,Medicinal chemistry ,Homolysis - Abstract
Treatment of the Fe(I) mesityl complex [Fe(Mes)(BPEP-Ph)] (BPEP-Ph = 2,6-bis[1-phenyl-2-(2,4,6-tri-tert-butylphenyl)-2-phosphaethenyl]pyridine) with π-acid ligands (L = CO, RNC) leads to one-electron reduction via Mes group migration from Fe to P, followed by homolytic elimination of the 2,4,6-tBu3C6H2 group, to afford Fe(0) complexes of the formula [Fe(L)2(BPEP-Ph*)] (BPEP-Ph* = 2-[1-phenyl-2-mesityl-2-phosphaethenyl]-6-[1-phenyl-2-(2,4,6-tri-tert-butylphenyl)-2-phosphaethenyl]pyridine). This reduction process is supported by radical trapping experiments and theoretical studies. The 2,4,6-tBu3C6H2˙ radical is captured by 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) in high yield. DFT calculations reveal the mechanism of Mes group migration with a reasonable energy profile.
- Published
- 2014
35. Mechanistic Studies on the Rearrangement of a Boron Cation: From a nido-Carborane to a Planar Boracycle.
- Author
-
Ya-Fan Lin, Chao-Tang Shen, Yu-Ting Hsiao, Yi-Hung Liu, Shie-Ming Peng, and Ching-Wen Chiu
- Subjects
- *
REACTION mechanisms (Chemistry) , *REARRANGEMENTS (Chemistry) , *BORON compounds , *CATIONS , *CARBORANES , *ETHYL group - Abstract
The reaction mechanism of the [Et3BH]--induced conversion of a dicationic boron compound ([Cp*B-IMes]2+, [1]2+) to a planar neutral carbene-coordinated borabenzene (2) is investigated experimentally and theoretically. Owing to the steric congestion around the boron center, bulky [Et3BH]- attacks the less encumbered carbon atom of Cp*, leading to a metastable 5-borabicyclo[2.1.1]hex-2-ene borenium cation ([3-CH]+) at low temperature. Upon raising the temperature, the bicyclic-borenium ion undergoes sequential pericyclic reactions, including suprafacial [1,3]-sigmatropic shift, two-electron electrocyclic ring opening, and then [1,2]-hydrogen shift to a planar cyclic borenium ion, [4-CH]+, which can then be deprotonated to yield the neutral aromatic borabenzene. The attack of hydride at the boron center of [1]2+ was excluded through the preparation and isolation of 6-borabicyclo[3.1.0]hexenylium, [3-BH]+, which could not be transformed into [3-CH]+ or [4-CH]+. The borenium ion rearrangement follows first-order kinetics with activation parameters of ΔH- = 19.6 (±0.31) kcal/mol and ΔS- = -2.03 (±1.15) cal/mol·K. The observed kinetic isotope effect of 0.87 at 265 K is consistent with the DFT-calculated reaction mechanism, which predicts an overall KIE value of 0.90. These results show that [1]2+ reacts with [Et3BH]- as a carbon-based electrophile and the formation of an electron-deficient borenium center is responsible for the skeletal rearrangement of the nido-cluster. [ABSTRACT FROM AUTHOR]
- Published
- 2016
- Full Text
- View/download PDF
36. Synthesis, structures of (aminopyridine)nickel complexes and their use for catalytic ethylene polymerization
- Author
-
Kuo-Hsuan Yu, Ya-Chi Lin, Yu Wang, Shiuh-Tzung Liu, Ya-Fan Lin, Jwu-Ting Chen, and Gene-Hsiang Lee
- Subjects
Inorganic Chemistry ,Nickel ,Crystallinity ,chemistry ,Ligand ,Ethylene polymerization ,Stereochemistry ,chemistry.chemical_element ,Branching (polymer chemistry) ,Medicinal chemistry ,Catalysis - Abstract
A series of α-aminopyridines in the form of (2,6-C(6)H(3)N)(R(1))(CHR(2)NR(3)R(4)) (R(1) = R(2) = H R(3) = H R(4) = (i)Pr (L1a), R(4) = (t)Bu (L1b), R(4) = Ph (L1c), R(4) = 2,6-Me(2)C(6)H(3) (L1d), R(4) = 2,6-(i)Pr(2)C(6)H(3) (L1e), R(1) = R(2) = H R(3) = R(4) = Et (L1f), R(1) = H R(2) = Me R(3) = H R(4) = (i)Pr (L2a), R(4) = Ph (L2c), R(4) = 2,6-Me(2)C(6)H(3) (L2d), R(4) = 2,6-(i)Pr(2)C(6)H(3) (L2e), R(1) = Me R(2) = H R(3) = H R(4) = 2,6-(i)Pr(2)C(6)H(3) (L3e)) and β-aminopyridines in the form of (2-C(6)H(4)N)(CH(2)CH(2)NR(1)R(2)) (R(1) = H R(2) = (i)Pr (4a), R(2) = (t)Bu (L4b), R(1) = R(2) = Et (L4f)) have been prepared. Their corresponding halonickel complexes 1a-4f are synthesized by ligand substitution from (DME)NiBr(2) and the molecular structures are characterized. Four types of coordination modes include four-coordinate mononuclear species with one ligand, five-coordinate mononuclear species with two ligands, five-coordinate dinuclear species with two ligands, and a six-coordinate polymeric framework were determined by X-ray crystallography. Using methylaluminoxanes (MAO) as the activator, the nickel complexes can catalyze ethylene polymerization under moderate pressure and ambient temperature. The activity reaches 10(5) g PE mol(-1) Ni h. The PE products with high branching and high crystallinity have M(n) ~ 10(3) with PDI2.
- Published
- 2012
37. Nickel catalysts bearing bidentate α-aminoaldimines for ethylene polymerization—independent and cooperative structure/reactivity relationship resulting from unsymmetric square planar coordination
- Author
-
Jwu-Ting Chen, Shiuh-Tzung Liu, Ya-Fan Lin, Yi-Hung Liu, Yi-Chun Chen, Feng-Zhao Yang, Kuo-Hsuan Yu, and Yu Wang
- Subjects
Denticity ,Ethylene ,Imine ,chemistry.chemical_element ,Photochemistry ,Branching (polymer chemistry) ,Catalysis ,Inorganic Chemistry ,chemistry.chemical_compound ,Nickel ,Monomer ,chemistry ,Polymerization ,Polymer chemistry - Abstract
Ethylene polymerization catalyzed by Ni(ii) complexes that bear new bidentate ligands with a functional hybrid of amine and imine has been studied. A class of new alpha-aminoaldimines and their nickel complexes [R(1)R(2)NCMe(2)CH[double bond, length as m-dash]N(2,6-R(3)(2)C(6)H(3))]NiBr(2) (R(1) = R(2) = Me, R(3) = Me (Ni-); R(3) = (i)Pr (Ni-); R(1) = R(2) = Et, R(3) = H (Ni-); Me (Ni-); (i)Pr (Ni-); R(1) = R(2) = (n)Pr, R(3) = (i)Pr (Ni-); (R(1)R(2)) = c-C(3)H(6) R(3) = (i)Pr (Ni-); (R(1)R(2)) = c-C(4)H(8), R(3) = (i)Pr (Ni-)) were synthesized. The molecular structures of six nickel complexes were determined by X-ray crystallography, showing distorted tetrahedral configurations. The SQUID data of Ni- confirms its ground state of triplet spin. Using methylaluminoxanes (MAO) as the activator, the nickel complexes are found to catalyze ethylene polymerization under moderate pressure and ambient temperature. The activity reaches to 10(6) g PE mol Ni(-1) h(-1), and increases with the ethylene pressure in the range of 14-28 bar. The highly branching PE products have M(n) approximately 10(5) with PDI2. The amine and imine functionalities demonstrate independent control to the polymerization reactions, wherein the activity appears to be facilitated by using the catalysts installed with bulky imino substituents as well as with less sterically hindered amino substituents. This is ascribed to the C(2) unsymmetric coordination in the square planar resting state in which the bulky polymer chain prefers cis to the imine and the small ethylene monomer is cis to the amine.
- Published
- 2009
38. Nickel catalysts bearing bidentate α-aminoaldimines for ethylene polymerization--independent and cooperative structure/reactivity relationship resulting from unsymmetric square planar coordination.
- Author
-
Feng-Zhao Yang, Yi-Chun Chen, Ya-Fan Lin, Kuo-Hsuan Yu, Yi-Hung Liu, Yu Wang, Shiuh-Tzung Liu, and Jwu-Ting Chen
- Subjects
NICKEL catalysts ,ALDIMINES ,POLYMERIZATION ,ASYMMETRY (Chemistry) ,COORDINATION compounds ,METAL complexes ,MOLECULAR structure ,ORGANIC synthesis - Abstract
Ethylene polymerization catalyzed by Ni(II) complexes that bear new bidentate ligands with a functional hybrid of amine and imine has been studied. A class of new α-aminoaldimines and their nickel complexes [R
1 R2 NCMe2 CH=N(2,6-R3 2 C6 H3 )]NiBr2 (R1 = R2 = Me, R3 = Me (Ni-1b); R3 =i Pr (Ni-1c);1 = R2 = Et, R3 = H (Ni-2a); Me (Ni-2b);i Pr (Ni-2c); R1 = R2 =n Pr, R3 =i Pr (Ni-3c); (R1 R2 ) = c-C3 H6 R3 =t Pr (Ni-4c); (R1 R2 ) = c-C4 H8 , R3 =i Pr (Ni-5c)) were synthesized. The molecular structures of six nickel complexes were determined by X-ray crystallography, showing distorted tetrahedral configurations. The SQUID data of Ni-1c confirms its ground state of triplet spin. Using methylaluminoxanes (MAO) as the activator, the nickel complexes are found to catalyze ethylene polymerization under moderate pressure and ambient temperature. The activity reaches to 106 g PE mol Ni-1 h-1 , and increases with the ethylene pressure in the range of 14-28 bar. The highly branching PE products have Mn ∼ 105 with PDI < 2. The amine and imine functionalities demonstrate independent control to the polymerization reactions, wherein the activity appears to be facilitated by using the catalysts installed with bulky imino substituents as well as with less sterically hindered amino substituents. This is ascribed to the C2 unsymmetric coordination in the square planar resting state in which the bulky polymer chain prefers cis to the imine and the small ethylene monomer is cis to the amine. [ABSTRACT FROM AUTHOR]- Published
- 2009
- Full Text
- View/download PDF
39. Unsymmetrical bidentate ligands of α-aminoaldimines leading to sterically controlled selectivity of geometrical isomerism in square planar coordinationCCDC reference numbers 682281, 683783–683791 (3c, 4a, 4c, 5b, 5c, 6c, 7a, 7c, 8cand 10c). For crystallographic data in CIF or other electronic format see DOI: 10.1039/b805674a
- Author
-
Jen-Jeh Lee, Feng-Zhao Yang, Ya-Fan Lin, Ya-Chun Chang, Kuo-Hsuan Yu, Mu-Chieh Chang, Gene-Hsiang Lee, Yi-Hung Liu, Yu Wang, Shiuh-Tzung Liu, and Jwu-Ting Chen
- Subjects
HYDROGEN-ion concentration ,ACIDITY function ,BUFFER solutions ,SOIL acidity ,PH effect - Abstract
New α-aminoaldimines with the formula of Et2NCMe2CHNR (R = iPr, tBu, Ph) and their dichloro or diacetato complexes of Ni, Pd, Pt are prepared and structurally characterized. A nickel complex is in a distorted tetrahedral configuration, and the Pd and Pt complexes (4–6) are of square planar form. The α-aminoaldimines can chelate to the metal in a C2-unsymmetric bidentate motif through the hetero functionalities of amine and imine, which show comparable transinfluence. Square planar organometallic palladium derivatives bearing α-aminoaldimines, including Pd–methyl, Pd–acetyl, and Pd–(η2-acetylnorboryl) (7–10), are also synthesized. The latter two species are a result of CO-insertion into Pd–methyl complexes and ensuing norbornene-insertion, respectively. The geometrical isomerism is found in the transconfiguration in most studied cases. Such a stereoselectivity results from the thermodynamic stability governed predominantly by steric control. The stereoselectivity is also supported by DFT calculations. [ABSTRACT FROM AUTHOR]
- Published
- 2008
- Full Text
- View/download PDF
Catalog
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