Synthesis of trans-Isotactic Poly(norbornene)s through Living Ring-Opening Metathesis Polymerization Initiated by Group VI Imido Alkylidene N-Heterocyclic Carbene Complexes
Synthesis of trans-Isotactic Poly(norbornene)s through Living Ring-Opening Metathesis Polymerization Initiated by Group VI Imido Alkylidene N-Heterocyclic Carbene Complexes
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DOI：
10.1021/acs.macromol.9b00422
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发表时间：
2019-06-11
期刊：
影响因子：
5.5
通讯作者：
Buchmeiser, Michael R.
中科院分区：
文献类型：
--
作者：
Benedikter, Mathis J.;Schowner, Roman;Buchmeiser, Michael R.
用核磁共振氢谱和碳谱研究了钼和钨的亚氨基烷叉氮杂环卡宾配合物在对映体纯的内，外-2，3-二甲氧羰基降冰片-5-烯（DCMNBE）开环易位聚合（ROMP）中的选择性.除了一个例外，所有复合物都显示出强烈的倾向于形成反式全同立构聚合物，一些产生基于>98%反式全同立构重复单元的聚合物。这种高选择性被成功地扩展到其它单体的ROMP，例如内和外-N-（R）-（+）-α-甲基苄基-5-异戊烯-2，3-二甲酰亚胺、2，3-双[（孟氧基）羰基]降冰片二烯和甲基-N-（S）-（-）-α-甲基苄基-2-氮杂双环[2.2.1]庚-5-烯-3-羧酸酯。阳离子引发剂[Mo（NAr）（5（i）Pr）-（CHCMe2Ph）（X）][B（Ar-F）（4）]（Ar = 2-（BuC 6 H4）-Bu-t，2，6-Me 2C 6 H3，2，6-（Pr 2C 6 H3）-Pr-i; 5（i）Pr = 1，3-二异丙基咪唑-2-亚基; X =吡咯烷，O-2，6-发现（2，4，6-Me 3C 6 H2）（2）C6 H3; B（ArF）（4）= B（3，5-（CF 3）（2）C6 H3）（4））是最具反应性的，同时也保持非常高的等选择性。最后，一个大的亚氨基配体提高立体特异性，而NHC配体的选择只有很小的影响。聚合反应可以终止与2-甲氧基苯乙烯，如由基质辅助激光解吸飞行时间质谱证明。
The selectivity of several molybdenum and tungsten imido alkylidene N-heterocyclic carbene (NHC) complexes in the ring opening metathesis polymerization (ROMP) of enantiomerically pure endo,exo-2,3-dicarbomethoxynorborn-5-ene (DCMNBE) was examined by H-1- and C-13 NMR spectroscopy. With one exception, all complexes showed a strong bias toward the formation of trans-isotactic polymers, some yielding polymers based on >98% trans-isotactic repeat units. This high selectivity was successfully extended to the ROMP of other monomers such as endo and exo-N-(R)-(+)-alpha-methylbenzyl-5-norbornene-2,3-dicarboximide, 2,3-bis[(menthyloxy)carbonyl]norbornadiene, and methyl-N-(S)-(-)-alpha-methylbenzyl-2-azabicyclo[2.2.1]hept-5-ene-3-carboxylate. The cationic initiators [Mo(NAr)(5(i)Pr)-(CHCMe2Ph)(X)][B(Ar-F)(4)] (Ar = 2-(BuC6H4)-Bu-t, 2,6-Me2C6H3, 2,6-(Pr2C6H3)-Pr-i; 5(i)Pr = 1,3-diisopropylimidazol-2-ylidene; X = pyrrolide, O-2,6-(2,4,6-Me3C6H2)(2)C6H3; B(ArF)(4) = B(3,5-(CF3)(2)C6H3)(4)) were found to be the most reactive ones, while also maintaining very high isoselectivity. Finally, a large imido ligand improved stereospecificity, while the choice of the NHC ligand had only a minor influence. Polymerizations can be terminated with 2-methoxystyrene, as evidenced by matrix-assisted laser-desorption time-of flight mass spectrometry.