Some reactions of R3SnM（CO）5 （M = Mn, Re） with CH3CN or pyridine were investigated to give complexes R3SnMn（CO）3LL＇ or R3SnMn（CO）4L by a facile mild method. X-ray diffractions analyses show that, in contrast ...Some reactions of R3SnM（CO）5 （M = Mn, Re） with CH3CN or pyridine were investigated to give complexes R3SnMn（CO）3LL＇ or R3SnMn（CO）4L by a facile mild method. X-ray diffractions analyses show that, in contrast to the phosphine ligand occupying in axial position, nitrogen ligands occupy equatorial position.展开更多
The direct conversion of carbon dioxide(CO_(2))and propylene oxide(PO)into propylene carbonate(PC)offers a green way to utilize anthropogenic CO_(2).However,this reaction is limited by low conversion of PO and harsh r...The direct conversion of carbon dioxide(CO_(2))and propylene oxide(PO)into propylene carbonate(PC)offers a green way to utilize anthropogenic CO_(2).However,this reaction is limited by low conversion of PO and harsh reaction conditions.In this study,we solve this problem using ionic liquids(ILs)/metal oxide composites(ILs@MAO).The catalytic activity of MAO-500(500?annealing temperature)is poor evidenced by its low conversion of PO(24.94%).However,ILs@MAO-500 has a high conversion of PO(97.54%)under similar reaction conditions(2 h at 1.5 MPa CO_(2) pressure,90℃,and 0.85 g catalyst).The ILs consist of imidazolium cation with weak coordinated[NTf_(2)]^(-)anion leading to outward movement of anion resulting in the formation of“heterodinuclear complex”.This complex generates an amorphous-crystalline intermediate with balanced acidbase sites that activate PO and stabilize the catalytic intermediate.In large part,the high PO conversion is theorized to be primarily due to the abundant reactive sites in the ILs that are covalently immobilized on the MAO-500 carrier.Furthermore,even after multiple recycling,ILs@MAO-500 remains stable and exhibits high yield and selectivity.The proposed solvent-free catalytic system is mild,kinetically fast,and naturally safe for coupling CO_(2) and PO into PC synthesis.展开更多
Hydrogenases are enzymes that can reversibly split molecular hydrogen. Study on the structure of the active site and the mechanism of catalysis has drawn great attention because the results may be useful for the desig...Hydrogenases are enzymes that can reversibly split molecular hydrogen. Study on the structure of the active site and the mechanism of catalysis has drawn great attention because the results may be useful for the design of cheap biomimetic hydrogen catalysts for fuel cells, or as model for the photoproduction of H\-2. At one time the active site was generally considered to be composed of mononuclear nickel complex with ligands from the polypeptide. A breakthrough in the understanding of the structure of Hases occurred with the resolution crystal structure of D. gigas Hases in 1995. The unexpected result challenged the previously reported spectroscopic studies and caused some academic arguments. Some methods and results used for insight into Hases have to be reconsidered. Different viewpoints concerning the structure of active site of Hases in different periods and some remaining questions will be presented.展开更多
基金supported by the National Natural Science Foundation of China(No.29672018).
文摘Some reactions of R3SnM（CO）5 （M = Mn, Re） with CH3CN or pyridine were investigated to give complexes R3SnMn（CO）3LL＇ or R3SnMn（CO）4L by a facile mild method. X-ray diffractions analyses show that, in contrast to the phosphine ligand occupying in axial position, nitrogen ligands occupy equatorial position.
基金supported by the National Research Foundation(NRF)grants funded by the Ministry of Education(2020R1A6A1A03038817),Republic of Korea.
文摘The direct conversion of carbon dioxide(CO_(2))and propylene oxide(PO)into propylene carbonate(PC)offers a green way to utilize anthropogenic CO_(2).However,this reaction is limited by low conversion of PO and harsh reaction conditions.In this study,we solve this problem using ionic liquids(ILs)/metal oxide composites(ILs@MAO).The catalytic activity of MAO-500(500?annealing temperature)is poor evidenced by its low conversion of PO(24.94%).However,ILs@MAO-500 has a high conversion of PO(97.54%)under similar reaction conditions(2 h at 1.5 MPa CO_(2) pressure,90℃,and 0.85 g catalyst).The ILs consist of imidazolium cation with weak coordinated[NTf_(2)]^(-)anion leading to outward movement of anion resulting in the formation of“heterodinuclear complex”.This complex generates an amorphous-crystalline intermediate with balanced acidbase sites that activate PO and stabilize the catalytic intermediate.In large part,the high PO conversion is theorized to be primarily due to the abundant reactive sites in the ILs that are covalently immobilized on the MAO-500 carrier.Furthermore,even after multiple recycling,ILs@MAO-500 remains stable and exhibits high yield and selectivity.The proposed solvent-free catalytic system is mild,kinetically fast,and naturally safe for coupling CO_(2) and PO into PC synthesis.
文摘Hydrogenases are enzymes that can reversibly split molecular hydrogen. Study on the structure of the active site and the mechanism of catalysis has drawn great attention because the results may be useful for the design of cheap biomimetic hydrogen catalysts for fuel cells, or as model for the photoproduction of H\-2. At one time the active site was generally considered to be composed of mononuclear nickel complex with ligands from the polypeptide. A breakthrough in the understanding of the structure of Hases occurred with the resolution crystal structure of D. gigas Hases in 1995. The unexpected result challenged the previously reported spectroscopic studies and caused some academic arguments. Some methods and results used for insight into Hases have to be reconsidered. Different viewpoints concerning the structure of active site of Hases in different periods and some remaining questions will be presented.
