Cyclic ruthenium-alkylidene catalysts for ring-expansion metathesis polymerization.
Cyclic ruthenium-alkylidene catalysts for ring-expansion metathesis polymerization.
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DOI：
10.1021/ja8037849
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发表时间：
2008-09-24
影响因子：
15
通讯作者：
Grubbs, Robert H.
中科院分区：
文献类型：
--
作者：
Boydston, Andrew J.;Xia, Yan;Kornfield, Julia A.;Gorodetskaya, Irina A.;Grubbs, Robert H.
制备了一系列环状Ru-亚烷基催化剂，并评价了它们在扩环复分解聚合（REMP）中的效率。催化剂结构的特征在于从咪唑基配体的一个N-原子延伸到Ru金属中心的螯合系链。催化剂设计本质上是模块化的，这提供了获得具有不同系链长度以及电子上不同的NHC配体的Ru络合物的途径。通过1H NMR光谱以及单晶X射线分析揭示了系链长度的结构影响。通过环辛烯的聚合反应，催化剂的活性进行了评价，并提供了关键数据的增长率，分子内链转移，催化剂的稳定性，三个领域所需的有效合成环状聚（烯烃）s通过REMP。从这些研究中确定，虽然增加催化剂的系链长度导致聚合速率提高，但发现较短的系链促进分子内链转移和催化剂从聚合物中释放。电子修饰的NHC通过主链饱和被发现，以提高聚合速率在更大程度上比同源的系链。总体而言，环状钌配合物轴承5-或6-碳系链和饱和NHC配体被发现是容易合成的，工作台稳定的，高活性的催化剂的REMP。
A series of cyclic Ru-alkylidene catalysts have been prepared and evaluated for their efficiency in ring-expansion metathesis polymerization (REMP). The catalyst structures feature chelating tethers extending from one N-atom of an imidazolylidine ligand to the Ru metal center. The catalyst design is modular in nature, which provided access to Ru-complexes having varying tether lengths, as well as electronically different NHC ligands. Structural impacts of the tether length were unveiled through 1H NMR spectroscopy as well as single-crystal X-ray analyses. Catalyst activities were evaluated via polymerization of cyclooctene and key data are provided regarding propagation rates, intramolecular chain-transfer, and catalyst stabilities, three areas necessary for the efficient synthesis of cyclic poly(olefin)s via REMP. From these studies, it was determined that while increasing the tether length of the catalyst leads to enhanced rates of polymerization, shorter tethers were found to facilitate intramolecular chain-transfer and release of catalyst from the polymer. Electronic modification of the NHC via backbone saturation was found to enhance polymerization rates to a greater extent than did homologation of the tether. Overall, cyclic Ru-complexes bearing 5- or 6-carbon tethers and saturated NHC ligands were found to be readily synthesized, bench-stable, and highly active catalysts for REMP.
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影响因子：
16.6
作者：
Berlin, Jacob M.;Goldberg, Steven D.;Grubbs, Robert H.
通讯作者：
Grubbs, Robert H.
影响因子：
5.2
作者：
Hansen, EC;Lee, D
通讯作者：
Lee, D
影响因子：
15
作者：
Funk, TW;Berlin, JM;Grubbs, RH
通讯作者：
Grubbs, RH
影响因子：
16.6
作者：
Hilf, Stefan;Berger-Nicoletti, Elena;Kilbinger, Andreas F. M.
通讯作者：
Kilbinger, Andreas F. M.
影响因子：
5.5
作者：
Alberty, KA;Tillman, E;Feast, WJ
通讯作者：
Feast, WJ