Yu Kuo-Hsuan, Huang Shou-Ling, Liu Yi-Hung, Wang Yu, Liu Shiuh-Tzung, Cheng Yuan-Chung, Lin Ya-Fan, Chen Jwu-Ting
Department of Chemistry, National Taiwan University, Taipei 10617, Taiwan.
Department of Medicinal and Applied Chemistry, Kaohsiung Medical University, Kaohsiung 80708, Taiwan.
Molecules. 2017 Jun 30;22(7):1095. doi: 10.3390/molecules22071095.
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(-C₆H₄N)]Pd(C₇HMe)(NCMe)}(BF₄) (R = Pr (), Bu (), Ph (), 2,6-Me₂C₆H₃ (), 2,6-Pr₂C₆H₃ ()) were synthesized via single insertion of norbornene into the corresponding methylpalladium complexes -, 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 and , 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 -isomers, and ready geometric isomerization, cooperatively lead to a new mechanism that accounts for the novel catalytic formation of alternating COC.
带有半不稳定双齿α-氨基吡啶的阳离子甲基钯配合物可作为在温和条件下催化降冰片烯（N）和乙烯（E）交替共聚的有效前体。式为{[RHNCH₂(-C₆H₄N)]Pd(C₇HMe)(NCMe)}(BF₄)（R = Pr（）、Bu（）、Ph（）、2,6-Me₂C₆H₃（）、2,6-Pr₂C₆H₃（））的降冰片基钯配合物分别通过降冰片烯向相应的甲基钯配合物 - 中单次插入合成。平面正方形的甲基和降冰片基钯配合物均通过空间控制的氨基吡啶的氨基去配位 - 再配位表现出几何异构化的易平衡。通过变温核磁共振（VT-NMR）研究了配合物 和 的乙烯插入、降冰片烯插入以及几何异构化反应，发现与密度泛函理论（DFT）计算估计的结果非常吻合。 - 异构体中更易发生的降冰片烯插入以及易于进行的几何异构化共同导致了一种新机制，该机制解释了交替COC的新型催化形成。
