Bimetallic catalysis for styrene homopolymerization and ethylene-styrene copolymerization. Exceptional comonomer selectivity and insertion regiochemistry
Bimetallic catalysis for styrene homopolymerization and ethylene-styrene copolymerization. Exceptional comonomer selectivity and insertion regiochemistry
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DOI：
10.1021/ja048761f
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发表时间：
2004-06-02
影响因子：
15
通讯作者：
Marks, TJ
中科院分区：
文献类型：
--
作者：
Guo, N;Li, LT;Marks, TJ
本文报道了共价键合的非限制几何构型催化剂的苯乙烯均聚行为和乙烯-苯乙烯共聚行为（μ-CH2CH2 - 3，3'）{（η 5-茚基）[1-Me2Si（tBuN）]（TiMe2）} 2（Ti 2），其是第一种不仅以高活性实现苯乙烯均聚，而且在宽的苯乙烯组成范围内（在20 ° C，1.0 atm乙烯压力下为0 - 76%）也是有效的乙烯-苯乙烯共聚。在苯乙烯均聚反应中，使用相同的三苯甲基硼酸酯助催化剂和聚合条件，与单核类似物Ti 1相比，Ti 2的聚合活性提高了50倍。在乙烯-苯乙烯共聚合反应中，在相同的反应条件下，Ti2比Ti1的苯乙烯链长多20%。13 C NMR谱表明，在Ti2 + Ph3C + B（C6F5）4-生成的共聚物主链中，有两个以上的苯乙烯单元被链长。对Ti_2 + Ph_3C + B（C_6F_5）_4~-引发苯乙烯均聚物的端基分析表明，在约50%的引发步骤中存在1，2-区域化学。这种不寻常的微观结构被认为与催化剂的结构有关。
This communication reports the styrene homopolymerization behavior and ethylene−styrene copolymerization behavior of the covalently linked bimetallic constrained geometry catalyst (μ-CH2CH2-3,3‘){(η5-indenyl)[1-Me2Si(tBuN)](TiMe2)}2(Ti2), which is the first single-site catalyst that effects not only styrene homopolymerization with high activity, but also efficient ethylene−styrene copolymerization over a broad styrene composition range (0−76% at 20 °C, 1.0 atm ethylene pressure). In styrene homopolymerization, a 50× increase in polymerization activity is achieved withTi2vs the mononuclear analogue,Ti1, using an identical trityl borate cocatalyst and polymerization conditions. In ethylene + styrene copolymerization,Ti2enchains ∼20% more styrene thanTi1under identical reaction conditions.13C NMR spectroscopy indicates that greater than two consecutive styrene units are enchained in the copolymer backbone produced byTi2+ Ph3C+B(C6F5)4-. End group analysis of the styrene homopolymer produced byTi2+ Ph3C+B(C6F5)4-suggests that 1,2-regiochemistry is installed in ∼50% of the initiation steps. This unusual microstructure is believed to be related to the bimetallic catalyst structure.