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Access to High-Molecular-Weight Polyethylenes through High Temperature Ethylene Polymerization Catalysed by Ethylene-Bridged ansa-(3-R-Cyclopentadienyl)(Fluorenyl) Zirconocene Complexes

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Chinese Journal of Polymer Science 2024年第1期42卷 42-51,I0007页

作者： Bo Li Haiyan Ma Jiling Huang Shanghai Key laboratory of Functional Materials Chemistry and laboratory of organometallic Chemistry School of Chemistry and Molecular EngineeringEast China University of Science and TechnologyShanghai 200237China

A series of C1-symmetric ethylene-bridged ansa-(3-R-cyclopentadienyl)(fluorenyl) metallocene complexes(Zr: 1-5;Hf: 6) have been synthesized, characterized and investigated as catalyst precursors for the high temperature ethylene polymerization. Using methylaluminoxane(MAO) as the cocatalyst, zirconium complexes 1-5 bearing a bulky substituent on the 3-position of the cyclopendienyl ring showed high catalytic activities up to 1.48×10^(7) g PE·mol_(Zr)^(-1)·h^(-1) toward the polymerization of ethylene and afforded polyethylenes with high molecular weights(1.49×10^(5)-6.31×10^(5) g/mol), meanwhile exhibting great thermal stability at high temperatures up to 120 ℃ together with a long catalytic life time up to 2 h. By adopting low Al/Zr ratios, such as 125, polyethylenes with ultra high molecular weights up to 2.86×106 g/mol were obtained. It is worthy of noting that zirconium complexes 1-4 bearing a substituent with an aryl pendant showed temperature-dependent activities, which increased rapidly with the increase of polymerization temperature, thus weak interaction of the pendent aryl group with the cationic active center is proposed to account for the very low activities displayed at low temperatures. In contrast to zirconocene complexes 1-5, hafnocene complex 6 only displayed very low catalytic activities toward the polymerization of ethylene and afforded polyethylenes with molecular weights ten times smaller than those obtained by zirconocene complexes 1-5. Zirconocene complexes 1-5 were also able to catalyse the polymerization of propylene at high temperatures, but only afforded waxes with low molecular weights.

关键词： ansa-Metallocene Ethylene Propylene Polymerization High temperature

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Polyethylene to gasoline via a self-supplied hydrogen strategy

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Science China Chemistry 2024年第10期67卷 3187-3188页

作者： Yong Tang State Key laboratory of organometallic Chemistry Shanghai Institute of Organic ChemistryChinese Academy of SciencesShanghai 200032China

Polyethylenes(PEs)are one of the most widely used plastics in almost every aspect of modern life and are produced on a huge scale(a market volume of 110.13 million metric tons worldwide in 2022)[1].A large portion of the PEs are used once and discarded as waste,which caused severe problems such as plastic pollution as well as a waste of the fossoil resource.

关键词： pollution plastics strategy

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Recent advances in the synthesis and application of N-heterocyclic carbene-based molecular cages

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Science China Chemistry 2024年第5期67卷 1510-1523页

作者： Qiongjie Chai Lixin Duan Yanzhe Ma Tianheng Hou Tao Tu Shanghai Key laboratory of Molecular Catalysis and Innovative Materials Department of ChemistryFudan UniversityShanghai 200438China State Key laboratory of organometallic Chemistry Shanghai Institute of Organic ChemistryChinese Academy of SciencesShanghai 200032China

N-Heterocyclic carbene(NHC)-based cages have emerged as a prominent and dynamic research area within the research field of chemistry. Leveraging the distinctive electronic and steric properties of NHC ligands, the design, synthesis, and application of these corresponding cages have garnered substantial scholarly interest. In recent years, we have witnessed the successful fabrication of diverse NHC-based cages through a range of synthetic methodologies, which hold significant potential for applications in molecular recognition and catalysis. In this review, we delve into the foundational synthetic strategies that underlie the creation of NHC-based cages, employing approaches encompassing metal–NHC chelation, coordination assembly,and covalent bonding. Additionally, we compile the diverse applications of these cages within catalytic processes and molecular recognition. Lastly, we shed light on the current limitations of synthesis and outline future trends in the development of NHCbased cages.

关键词： N-heterocyclic carbene molecular cages supramolecular chemistry synthetic strategies applications

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Copper-catalyzed enantioselective desymmetrizing C(sp^(2))-H functionalization of azide-ynamides via α-imino copper carbenes

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Science China Chemistry 2024年第9期67卷 2982-2988页

作者： En-He Huang Li-Gao Liu You-Wei Yin Hao-Xuan Dong Ji-Jia Zhou Xin Lu Bo Zhou Long-Wu Ye Key laboratory for Chemical Biology of Fujian Province and State Key laboratory of Physical Chemistry of Solid Surfaces College of Chemistry and Chemical EngineeringXiamen UniversityXiamen 361005China State Key laboratory of organometallic Chemistry Shanghai Institute of Organic ChemistryChinese Academy of SciencesShanghai 200032China

α-Imino metal carbenes are versatile intermediates in organic synthesis,and have broad applications in the assembly of divergent ***,the catalytic enantioselective desymmetrization based onα-imino metal carbenes has not been developed to ***,we disclose an enantioselective desymmetrizing C(sp^(2))-H functionalization of azide-ynamides viaα-imino copper carbenes,leading to the efficient assembly of divergent chiral indoloazepines in generally moderate to excellent yields with high ***,this reaction represents the first enantioselective desymmetrization based onα-imino metal *** synthetic transformations and biological tests show the potential utility of this ***,computational studies are employed to elucidate the reaction mechanism and the origin of enantioselectivity.

关键词： enantioselective desymmetrization metal carbenes copper catalysis nitrene transfer alkynes

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Cobalt(Ⅲ)hydride HAT mediated enantioselective intramolecular hydroamination access to chiral pyrrolidines

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Science China Chemistry 2024年第6期67卷 2002-2008页

作者： Qi Meng Tao Qin Huanran Miao Ge Zhang Qian Zhang Jilin Province Key laboratory of Organic Functional Molecular Design&Synthesis Department of ChemistryNortheast Normal UniversityChangchun130024China State Key laboratory of organometallic Chemistry Shanghai Institute of Organic ChemistryChinese Academy of SciencesShanghai200032China

Enantioenriched pyrrolidines and derivatives are ubiquitous substructures in compounds of importance to medicinal and biological ***,we report an efficient cobalt-catalyzed intramolecular asymmetric hydroamination reaction that produces chiral pyrrolidines with good to excellent yield and *** with previously reported radicalinvolved methodologies for enantioenriched pyrrolidines,these conditions feature two elegant versatilities,enabling(1)the use of cobalt-catalyzed hydrogen atom transfer(HAT)to generate organocobalt intermediates that bring radical reaction to organometallic chemistry,and(2)enantioselective intramolecular C-N bond forging through an S_(N)2-like displacement involving dynamic kinetic resolution(DKR).This approach provides a new alternative and efficient methodology for enantioselective radical-involved C-N bond construction that can be used in the synthesis of both chiral pyrrolidines and homologous nitrogen heterocycles.

关键词： asymmetric catalysis radical hydroamination cobalt catalysis hydrogen atom transfer

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Synthesis and reactivity of cobalt dinitrogen complex supported by nonsymmetrical pincer ligand

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Chinese Chemical Letters 2024年第7期35卷 259-263页

作者： Yuanjin Chen Xianghui Shi Dajiang Huang Junnian Wei Zhenfeng Xi Beijing National laboratory for Molecular Sciences(BNLMS) Key Laboratory of Bioorganic Chemistry and Molecular Engineering of Ministry of EducationCollege of ChemistryPeking UniversityBeijing 100871China State Key laboratory of organometallic Chemistry Shanghai Institute of Organic ChemistryShanghai 200032China

A nonsymmetrical PNN pincer ligand[6-(^(t)Bu_(2)PNH)C_(5)H_(4)N-2-(3-Mes)C_(3)H_(2)N_(2)]and its corresponding cobalt-N_(2)complex were synthesized and *** the stoichiometric reaction of the PNN ligand lithium salt with CoCl_(2),the complex 3,(PNN)CoCl,was ***,reduction of 3 with NaBHEt3under a dinitrogen atmosphere yielded complex 5,(PNN)Co(Ⅰ)(η^(1)-N_(2)).Single-crystal X-ray analysis,IR spectrum,and DFT calculations revealed that the dinitrogen in 5 was only weakly reduced by the cobalt *** reactions of 5 with carbon monoxide and 2,6-dimethylphenyl isocyanide gave carbonyl and isocyanide complexes 6 and 7 with the release of N_(2),***,these cobalt complexes,especially complex 5,demonstrated the capacity to convert dinitrogen to N(TMS)_(3)with moderate efficiency.

关键词： Dinitrogen fixation Dinitrogen transformation Nonsymmetrical pincer ligand Cobalt complex Catalytic silylamine formation

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Palladium-catalyzed multi components oxy-aminofluorination and aminofluorination of gem-difluoroalkenes

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Chinese Chemical Letters 2024年第2期35卷 420-425页

作者： Fen Wu Xin Li Junbiao Chang Dachang Bai State Key laboratory of Antiviral Drugs NMPA Key Laboratory for Research and Evaluation of Innovative DrugKey Laboratory of Green Chemical Media and ReactionsMinistry of EducationSchool of Chemistry and Chemical EngineeringPingyuan LaboratoryHenan Normal UniversityXinxiang 453007China State Key laboratory of organometallic Chemistry Shanghai Institute of Organic ChemistryChinese Academy of SciencesShanghai 200032China

Organofluorine compounds are widely used in the realm of drug discovery and material ***,we developed palladium catalyzed intermolecular aminofluorination and oxy-aminofluorination of gem‑difluoroalkenes with N-fluorobenzenesulfonimide(NFSI),in which NFSI was used as the nitrogen source and *** reaction provides an efficient and straightforward synthesis route of a series ofα-trifluoromethyl benzylic ***,three/four components oxy-aminofluorination processes were realized to giveα-trifluoromethyl benzylic ether with a terminal amino group,which proceed through C(sp^(3))-O bond cleavage of easily available ether and simultaneous introduced a fluorine,an amino and an oxy substituent in one pot with excellent *** divergent reactivity not only included the incorporation of one ether molecular,but also much more challenged two ether insertion with excellent selectivity through succession C(sp^(3))-O bonds *** protocol allows for concise synthesis of high value amines with fluoroalkyl-substituents and selectively transformation of easily available ethers by high-valent palladium catalysis.

关键词： Palladium Multi components Aminofluorination Oxy-aminofluorination C(sp^(3))-O bond cleavage

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Selective control of secondary alcohols upgrading using Ir-catalyzed cross-coupling strategy

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Science China Chemistry 2024年第3期67卷 914-921页

作者： Siqi Yang Zeye Lu Jiale Ji Qingshu Zheng Tao Tu Shanghai Key laboratory of Molecular Catalysis and Innovative Materials Department of ChemistryFudan UniversityShanghai 200438China Frontiers Science Center for Transformative Molecules School of Chemistry and Chemical EngineeringShanghai Jiao Tong UniversityShanghai 200240China State Key laboratory of organometallic Chemistry Shanghai Institute of Organic ChemistryChinese Academy of SciencesShanghai 200032China

The selective coupling of alcohols is a fascinating yet challenging approach for upgrading alcohols. Herein, we accomplished the controlled production of β-disubstituted ketones or upgraded secondary alcohols via the Ir-catalyzed cross-coupling of secondary alcohols in excellent yields with broad substrate scopes. This selective control was achieved by using an in-situ generated monoNHC-Ir or a tris-NHC-Ir complex as the catalysts, respectively. Mechanistic studies revealed that the delicate balance between dehydrogenation and hydrogenation abilities of these bifunctional catalysts is crucial for achieving different selectivity. The tris-NHC-Ir complex effectively facilitated dehydrogenation of alcohols and hydrogenation of intermediates, leading to the desired upgraded secondary alcohols. Conversely, the high dehydrogenation ability of the mono-NHC-Ir complex promoted the conversion of formed secondary alcohols back to ketones.

关键词： cross-coupling hydrogen-borrowing NHC-Ir complexes selectivity control upgrading of alcohols

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Palladium(Ⅱ)-Catalyzed Markovnikov Hydroalkynylation of Unactivated Terminal Alkenes

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Chinese Journal of Chemistry 2024年第1期42卷 29-34页

作者： Chuanqi Hou Pinhong Chen Guosheng Liu Sstate Key laboratory of organometallic Chemistry and Shanghai Hongkong Joint Laboratory in Chemical SynthesisCenter for Excellence in Molecular SynthesisShanghai Institute of Organic ChemistryUniversity of Chinese Academy of SciencesChinese Academy of SciencesShanghai 200032China Chang-Kung Chuang Institute East China Normal UniversityShanghai 200062China

Alkynes are versatile synthons in organic synthesis,as well as important structural moieties in bioactive ***,transition metal-catalyzed hydroalkynylation of alkenes has been developed with reactive alkenes and alkenes bearing directing ***,the regioselective hydroalkynylation of simple alkenes is still ***,we have developed a palladium-catalyzed Markovnikov hydroalkynylation of unactivated terminal alkenes,which provides an efficient approach for the synthesis of branched alkynyl compounds under mild *** reaction features excellent functional group tolerance,good reaction yields and excellent ***,the asymmetric hydroalkynylation reaction has also been achieved with moderate enantioselectivity by introducing a sterically bulky chiral Pyox ligand.

关键词： Palladium catalysis Alkynylpalladation Unactivated terminal alkenes Markovnikov hydroalkynylation

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Generation,bonding and reactivity of transient zinc-substituted silylenes

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Science China Chemistry 2024年第4期67卷 1256-1262页

作者： Cheng Xu Thayalan Rajeshkumar Laurent Maron Xuebing Leng Yaofeng Chen State Key laboratory of organometallic Chemistry Shanghai Institute of Organic ChemistryUniversity of Chinese Academy of SciencesChinese Academy of SciencesShanghai 200032China Spin-X Institute School of Chemistry and Chemical EngineeringState Key Laboratory of Luminescent Materials and DevicesGuangdong-Hong Kong-Macao Joint Laboratory of Optoelectronic and Magnetic Functional MaterialsSouth China University of TechnologyGuangzhou 510641China LPCNO CNRS&INSAUniversitéPaul SabatierToulous 31077France

The metal-substituted silylenes are of high interest,as the theoretical studies indicated that the silylenes with electropositive substituents have a small ΔE_(S-T)(singlet-triplet energy gap)or even the ground-state ***,such compounds are highly unstable,and only two transient alkali metal-substituted silylenes M(^(t)Bu_(3)Si)Si:(M=Li,K)were generated by photoextrusion of the alkali metal-substituted silacyclopropenes and merely studied by spectroscopic method(EPR)at low temperature(14 to 50 K).Herein,we report the generation of transient zinc-substituted silylenes from zinc silacyclopropanyl complexes under very mild and convenient *** generated transient zinc-substituted silylenes are highly reactive and undergo intermolecular cycloaddition with alkenes for the synthesis of zinc-substituted Si-heterocyclic *** there is no substrate,the zinc-substituted silylenes attack the C-C bonds of the β-diketiminato ligands and break the C-C *** studies further highlight the silylene nature of the zinc-substituted silylene and a very small ΔE_(S-T)(4.4 kcal/mol).

关键词： zinc complex silylene C-C bond cleavage cycloaddition DFT calculations

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