Partially biobased polysilylethers(PSEs)are synthesized via dehydrocoupling polymerization catalyzed by an anionic iridium complex.Different types(AB type or AA and BB type)of monomers are suitable.Levulinic acid(LA)a...Partially biobased polysilylethers(PSEs)are synthesized via dehydrocoupling polymerization catalyzed by an anionic iridium complex.Different types(AB type or AA and BB type)of monomers are suitable.Levulinic acid(LA)and succinic acid(SA)have been ranked within the top 10 chemicals derived from biomass.BB type monomers(diols)derived from LA and SA have been applied to the synthesis of PSEs.The polymerization reactions employ an air-stable anionic iridium complex bearing a functional bipyridonate ligand as catalyst.Moderate to high yields of polymers with number-average molecular weights(Mn)up to 4.38×104 were obtained.A possible catalytic cycle via an Ir-H species is presented.Based on the results of kinetic experiments,apparent activation energy of polymerization in the tempe rature range of 0-10℃is about 38.6 kJ/mol.The PSEs synthesized from AA and BB type monomers possess good thermal stability(T5=418℃to 437℃)and low glass-transition temperature(Tg=49.6℃).展开更多
The development of efficient method to prepare poly(silyl ether)s(PSEs)is highly desirable.Herein,an environmentally sustainable copper-catalyzed dehydrocoupling polymerization was developed with good yields and high ...The development of efficient method to prepare poly(silyl ether)s(PSEs)is highly desirable.Herein,an environmentally sustainable copper-catalyzed dehydrocoupling polymerization was developed with good yields and high molecular weight(up to 48,400 of Mn and up to 97%yield).Monomers of different types(AB type or AA and BB type)are suitable to afford PSEs.The PSEs show good thermal stability and low glass-transition temperature.展开更多
The scandocene alkyl complex(C_(5)Me_(5))_(2)ScCH_(2)SiMe_(3)was found to be an efficient catalyst for the dehydrocoupling of the non-cyclic boranes, dicyclohexylborane and thexylborane, with amines under mild conditi...The scandocene alkyl complex(C_(5)Me_(5))_(2)ScCH_(2)SiMe_(3)was found to be an efficient catalyst for the dehydrocoupling of the non-cyclic boranes, dicyclohexylborane and thexylborane, with amines under mild conditions. The reactions afforded the corresponding aminoboranes in high yields with good functional group tolerance. The stoichiometric reaction of scandium alkyl with amine led to the isolation of a scandium amide complex, which was shown to be an active species during the catalysis. Although a boranecoordinated scandium hydride was also obtained from the stoichiometric experiment, it was not involved in the catalytic cycle. In addition, kinetic studies provided insight into this intermolecular dehydrogenation reaction.展开更多
The photocatalytic oxidation of 1-phenylethanol coupling with hydrogen evolution represents a promising strategy for the full utilization of the photogenerated electrons and holes to accomplish the maximum conversion ...The photocatalytic oxidation of 1-phenylethanol coupling with hydrogen evolution represents a promising strategy for the full utilization of the photogenerated electrons and holes to accomplish the maximum conversion of solar energy into chemical energy.To date,however,the controllable of reaction path and product distribution has yet not to be unrevealed.Herein,we report an efficient coupled catalytic system composed of ZnIn_(2)S_(4)/WO_(3)S-scheme heterojunction and Ni-containing polyoxometalate([Ni_(4)(H_(2)O)_(2)(PW_(9)O_(34))_(2)]^(10-)(Ni_(4)P_(2))),which exhibited excellent photocatalytic activities towards the oxidation valorization of 1-phenylethanol coupling with hydrogen evolution.The addition of Ni_(4)P_(2)can efficiently control the product distribution.Specifically,1-phenylethanol was preferentially converted to pinacol(86.0% selectivity)via C-C coupling over ZnIn_(2)S_(4)/WO_(3)S-scheme heterojunction accompanied by hydrogen production(202.4μmol),whereas it would be converted to acetophenone(93.8% selectivity)by photogenerated holes with concomitant hydrogen formation(183.1μmol)over the coupled Ni_(4)P_(2)/ZnIn_(2)S_(4)/WO_(3) catalytic system.Mechanism studies revealed that the hydrogen evolution cocatalyst Ni4P2,with its excellent electron storage capacity,can compete with the oxidation product acetophenone for electrons,and thus its addition can significantly inhibit the reduction of acetophenone,resulting in the inability to generate the coupling product pinacol.展开更多
基金Financial support from the National Natural Science Foundation of China(No.21690074)Dalian Bureau of Science and Technology(No.2016RD07)Chinese Academy of Sciences(No.XDB17020300)。
文摘Partially biobased polysilylethers(PSEs)are synthesized via dehydrocoupling polymerization catalyzed by an anionic iridium complex.Different types(AB type or AA and BB type)of monomers are suitable.Levulinic acid(LA)and succinic acid(SA)have been ranked within the top 10 chemicals derived from biomass.BB type monomers(diols)derived from LA and SA have been applied to the synthesis of PSEs.The polymerization reactions employ an air-stable anionic iridium complex bearing a functional bipyridonate ligand as catalyst.Moderate to high yields of polymers with number-average molecular weights(Mn)up to 4.38×104 were obtained.A possible catalytic cycle via an Ir-H species is presented.Based on the results of kinetic experiments,apparent activation energy of polymerization in the tempe rature range of 0-10℃is about 38.6 kJ/mol.The PSEs synthesized from AA and BB type monomers possess good thermal stability(T5=418℃to 437℃)and low glass-transition temperature(Tg=49.6℃).
基金support from National Natural Science Foundation of China(No.21690074)Chinese Academy of Sciences(Nos.XDB17020300,DICP I202015)is acknowledged.
文摘The development of efficient method to prepare poly(silyl ether)s(PSEs)is highly desirable.Herein,an environmentally sustainable copper-catalyzed dehydrocoupling polymerization was developed with good yields and high molecular weight(up to 48,400 of Mn and up to 97%yield).Monomers of different types(AB type or AA and BB type)are suitable to afford PSEs.The PSEs show good thermal stability and low glass-transition temperature.
基金supported by the National Natural Science Foundation of China (No. 21871204)。
文摘The scandocene alkyl complex(C_(5)Me_(5))_(2)ScCH_(2)SiMe_(3)was found to be an efficient catalyst for the dehydrocoupling of the non-cyclic boranes, dicyclohexylborane and thexylborane, with amines under mild conditions. The reactions afforded the corresponding aminoboranes in high yields with good functional group tolerance. The stoichiometric reaction of scandium alkyl with amine led to the isolation of a scandium amide complex, which was shown to be an active species during the catalysis. Although a boranecoordinated scandium hydride was also obtained from the stoichiometric experiment, it was not involved in the catalytic cycle. In addition, kinetic studies provided insight into this intermolecular dehydrogenation reaction.
基金the financial support from the National Natural Science Foundation of China(Nos.22008012 and 22471019)the Hebei Natural Science Foundation(No.B2024105003)+2 种基金Development and Reform Commission Project of Jilin Province(No.2024C020-2)the Recruitment Program of Global Experts(Young Talents)BIT Excellent Young Scholars Research Fund.
文摘The photocatalytic oxidation of 1-phenylethanol coupling with hydrogen evolution represents a promising strategy for the full utilization of the photogenerated electrons and holes to accomplish the maximum conversion of solar energy into chemical energy.To date,however,the controllable of reaction path and product distribution has yet not to be unrevealed.Herein,we report an efficient coupled catalytic system composed of ZnIn_(2)S_(4)/WO_(3)S-scheme heterojunction and Ni-containing polyoxometalate([Ni_(4)(H_(2)O)_(2)(PW_(9)O_(34))_(2)]^(10-)(Ni_(4)P_(2))),which exhibited excellent photocatalytic activities towards the oxidation valorization of 1-phenylethanol coupling with hydrogen evolution.The addition of Ni_(4)P_(2)can efficiently control the product distribution.Specifically,1-phenylethanol was preferentially converted to pinacol(86.0% selectivity)via C-C coupling over ZnIn_(2)S_(4)/WO_(3)S-scheme heterojunction accompanied by hydrogen production(202.4μmol),whereas it would be converted to acetophenone(93.8% selectivity)by photogenerated holes with concomitant hydrogen formation(183.1μmol)over the coupled Ni_(4)P_(2)/ZnIn_(2)S_(4)/WO_(3) catalytic system.Mechanism studies revealed that the hydrogen evolution cocatalyst Ni4P2,with its excellent electron storage capacity,can compete with the oxidation product acetophenone for electrons,and thus its addition can significantly inhibit the reduction of acetophenone,resulting in the inability to generate the coupling product pinacol.
