The origin of living polymerization with an o-fluorinated catalyst: NMR spectroscopic characterization of chain-carrying species.
The origin of living polymerization with an o-fluorinated catalyst: NMR spectroscopic characterization of chain-carrying species.
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DOI：
10.1002/chem.201102408
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发表时间：
2012-01
期刊：
影响因子：
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通讯作者：
H. Möller;M. Baier;S. Mecking;E. P. Talsi;K. Bryliakov
中科院分区：
文献类型：
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作者：
H. Möller;M. Baier;S. Mecking;E. P. Talsi;K. Bryliakov
为了表征含邻氟芳基取代基的非茂钛催化剂活性聚合的起源，用多核核磁共振技术，以甲基铝氧烷(MAO)或AlMe(3)/CPH(3)B(C(6)F(5))(4)为活化剂，研究了邻氟双烯醇亚胺钛催化剂及其非氟代催化剂的乙烯聚合反应。观察到两种催化剂都形成了[TIL(2)Me][MeMAO]和[TIL(2)Me][B(C(6)F(5))(4)]型离子对。这些离子对分别与乙烯反应生成链增长物种[TIL(2)P][MeMAO]和[TIL(2)P][B(C(6)F(5))(4)](P=增长的聚合链)。对于第二类o-F-取代催化剂物种，核磁共振光谱提供了o-F取代基与金属中心相互作用的证据。这种相互作用通过抑制向AlMe(3)的链转移和β-氢转移过程来保持聚合催化剂的活性。
To characterize the origin of living polymerization with nonmetallocene titanium-based catalysts containing o-fluoroaryl substituents, ethene polymerization by an o-fluorinated bis(enolatoimine) titanium catalyst and its nonfluorinated counterpart has been studied by multinuclear NMR spectroscopy by using methylaluminoxane (MAO) or AlMe(3)/CPh(3)B(C(6)F(5))(4) as activators. Formation of ion pairs of the type [TiL(2)Me][MeMAO] and [TiL(2)Me][B(C(6)F(5))(4)] has been observed for both catalysts. These ion pairs react with ethene to afford the chain-propagating species [TiL(2)P][MeMAO] and [TiL(2)P][B(C(6)F(5))(4)], respectively (P = growing polymeryl chain). For the o-F-substituted catalyst species of the second type, NMR spectroscopy provides evidence that the o-F substituents interact with the metal center. This interaction is proposed to keep the polymerization catalysis living by suppressing chain transfer to AlMe(3) and β-hydrogen transfer processes.