Language：English   Publishing type：Research paper (scientific journal)   Publisher：Wiley  

DOI： 10.1002/chem.201905830

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Springer Nature America, Inc  

DOI： 10.1038/s41929-018-0140-3

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Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1038/s41557-018-0153-1

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：American Chemical Society ({ACS})  

© 2018 American Chemical Society. A saturated N-heterocyclic carbene-phenolate bidentate ligand, 3,3a,4,5-tetrahydroimidazo[1,5-a]quinolin-9-olate-1-ylidene (SIzQO), was synthesized and characterized. The SIzQO ligand was then treated with PdClMe(pyridine)2 and [Pd(μ-Cl)Me(2,6-lutidine)]2, which afforded C,C-cis-(SIzQO)PdMe(pyridine) and the thermodynamically unstable trans isomer C,C-trans-(SIzQO)PdMe(2,6-lutidine), respectively. The latter isomerizes at 40 °C into the corresponding cis isomer via a dissociative mechanism. These palladium/SIzQO complexes catalyze the polymerization of ethylene at 100-120 °C, although the catalytic activity is lower than that of a previously reported palladium/imidazo[1,5-a]quinolin-9-olate-1-ylidene (IzQO) system.

DOI： 10.1021/acs.organomet.8b00263

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：American Chemical Society ({ACS})  

© 2018 American Chemical Society. Coordination-insertion copolymerization of ethylene with 1,1-disubstituted ethylenes bearing a polar functional group, such as methyl methacrylate (MMA), is a long-standing challenge in catalytic polymerization. The major obstacle for this process is the huge difference in reactivity of ethylene versus 1,1-disubstituted ethylenes toward both coordination and insertion. Herein we report the copolymerization of ethylene and 1,1-disubstituted ethylenes by using an imidazo[1,5-a]quinolin-9-olate-1-ylidene-supported palladium catalyst. Various types of 1,1-disubstituted ethylenes were successfully incorporated into the polyethylene chain. In-depth characterization of the obtained copolymers and mechanistic inferences drawn from stoichiometric reactions of alkylpalladium complexes with methyl methacrylate and ethylene indicate that the copolymerization proceeds by the same coordination-insertion mechanism that has been postulated for ethylene.

DOI： 10.1021/jacs.7b12593

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ROYAL SOC CHEMISTRY  

We report the synthesis and characterisation of palladium complexes bearing an N-heterocyclic carbene-phosphine oxide bidentate ligand and their use as catalysts for ethylene polymerisation and ethylene/polar monomer copolymerisation.

DOI： 10.1039/c7cc00002b

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PubMed

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

The mechanism of linear polyethylene formation catalyzed by palladium/phosphine sulfonate and the effect of the ligand structure on the catalytic performance, such as linearity and molecular weight of the polyethylene, were reinvestigated theoretically and experimentally. We used dispersion-corrected density functional theory (DFT-D3) to study the entire mechanism of polyethylene formation from (R2PC6H4SO3)PdMe(2,6-lutidine) (R = Me, t-Bu) and elucidated the key steps that determine the molecular weight and linearity of the polyethylene. The alkylpalladium ethylene complex is the key intermediate for both linear propagation and fi-hydride elimination from the growing polymer chain. On the basis of the key species, the effects of substituents on the phosphorus atom (R = t-Bu, i-Pr, Cy, Men, Ph, 2-MeOC6H4, biAr) were further investigated theoretically to explain the experimental results in a comprehensive manner. Thus, the experimental trend of molecular weights of polyethylene could be correlated to the AA G* value between (i) the transition state of linear propagation and (ii) the transition state of the path for ethylene dissociation leading to fi-hydride elimination. Moreover, the experimental behavior of the catalysts under varied ethylene pressure was well explained by our computation on the small set of key species elucidated from the entire mechanism. In our additional experimental investigations, [o-Ani(2)PC(6)H(4)SO(3)]PdH[P(t-Bu)(3)] catalyzed a hydrogen/ deuterium exchange reaction between ethylene and Me0D. The deuterium incorporation from Me0D into the main chain of polyethylene, therefore, can be explained by the incorporation of deuterated ethylene formed by a small amount of Pd H species. These insights into the palladium/phosphine sulfonate system provide a comprehensive understanding of how the phosphine sulfonate ligands function to produce linear polyethylene.

DOI： 10.1021/acscatal.6b00911

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Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1002/anie.201510077

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

Palladium catalysts bearing imidazo[1,5-a]quinolin-9-olate-1-ylidene (IzQO) ligands polymerize alpha-olefins while incorporating polar monomers. The steric environment provided by N-heterocyclic-carbene (NHC) enables regioselective insertion of alpha-olefins and polar monomers, yielding polypropylene, propylene/allyl carboxylate copolymers, and propylene/methyl acrylate copolymer. Known polymerization catalysts bearing NHC-based ligands decompose rapidly, whereas the present catalyst is durable because of structural confinement, wherein the NHC-plane is coplanar to the metal square plane. The present catalyst system enables facile access to a new class of functionalized polyolefins and helps conceive a new fundamental principle for designing NHC-based ligands.

DOI： 10.1021/jacs.5b06948

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Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：NATURE PUBLISHING GROUP  

Although carbon dioxide has attracted broad interest as a renewable carbon feedstock, its use as a monomer in copolymerization with olefins has long been an elusive endeavour. A major obstacle for this process is that the propagation step involving carbon dioxide is endothermic; typically, attempted reactions between carbon dioxide and an olefin preferentially yield olefin homopolymerization. Here we report a strategy to circumvent the thermodynamic and kinetic barriers for copolymerizations of carbon dioxide and olefins by using a metastable lactone intermediate, 3-ethylidene-6-vinyltetrahydro-2H-pyran-2-one, which is formed by the palladium-catalysed condensation of carbon dioxide and 1,3-butadiene. Subsequent free-radical polymerization of the lactone intermediate afforded polymers of high molecular weight with a carbon dioxide content of 33 mol% (29 wt%). Furthermore, the protocol was applied successfully to a one-pot copolymerization of carbon dioxide and 1,3-butadiene, and one-pot terpolymerizations of carbon dioxide, butadiene and another 1,3-diene. This copolymerization technique provides access to a new class of polymeric materials made from carbon dioxide.

DOI： 10.1038/NCHEM.1882

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PubMed

Other Link： http://orcid.org/0000-0002-3705-0381

Event date： 2022.3

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Language：English   Presentation type：Poster presentation  

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Event date： 2020.3

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：東京理科大学野田キャンパス  

Event date： 2020.3

Language：English   Presentation type：Oral presentation (general)  

Event date： 2020.3

Language：English   Presentation type：Oral presentation (general)  

Event date： 2020.3

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：東京理科大学野田キャンパス  

Event date： 2019.10

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Event date： 2019.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：大阪国際交流センター  

Event date： 2019.3

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：甲南大学　岡本キャンパス