DFT Studies on Styrene Polymerization Catalyzed by Cationic Rare-Earth-Metal Complexes: Origin of Ligand-Dependent Activities
DFT Studies on Styrene Polymerization Catalyzed by Cationic Rare-Earth-Metal Complexes: Origin of Ligand-Dependent Activities
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DOI：
10.1021/acs.organomet.6b00558
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发表时间：
2016-09
期刊：
影响因子：
2.8
通讯作者：
Xingbao Wang;Feiyue Lin;Jingping Qu;Z. Hou;Yizhan Luo
中科院分区：
文献类型：
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作者：
Xingbao Wang;Feiyue Lin;Jingping Qu;Z. Hou;Yizhan Luo
五种类似阳离子稀土金属配合物[(RCH2-Py)Y(CH2SiMe3)]+ （R = C5Me4 （Cp′），1+）催化苯乙烯聚合的机理R = C9H6 (Ind), 2+；通过DFT计算研究了R = C13H8 (Flu), 3+), [(Flu - py)Y(CH2SiMe3)]+ (4+), [(Flu - ch2ch2 - nhc)Y(CH2SiMe3)]+(5+)。在活性差异和选择性上，理论与实验结果一致，发现苯乙烯聚合在动力学上更倾向于2,1插入而不是1,2插入。计算了迁移和固定两种插入方式下第二个单体分子的自由能分布，迁移和固定插入方式导致的共规链结显示出明显的动力学偏好。目前的研究结果表明苯乙烯与活性金属中心的配位可能对观察到的活性差异起重要作用。有趣的是，阳离子的中心金属上的电荷决定了1+，2+和3+的活性：
The mechanism of styrene polymerization catalyzed by five analogous cationic rare-earth-metal complexes [(RCH2–Py)Y(CH2SiMe3)]+ (R = C5Me4 (Cp′), 1+; R = C9H6 (Ind), 2+; R = C13H8 (Flu), 3+), [(Flu–Py)Y(CH2SiMe3)]+ (4+), and [(Flu–CH2CH2–NHC)Y(CH2SiMe3)]+ (5+) has been studied through DFT calculations. Having achieved an agreement between theory and experiment in the activity discrepancy and selectivity, it is found that styrene polymerization kinetically prefers 2,1-insertion to 1,2-insertion. The free energy profiles for the insertion of a second monomer molecule have been computed for both migratory and stationary insertion manners, and the former resulting in a syndiotactic enchainment indicates obvious kinetic preference. The current results suggest that the coordination of styrene to the active metal center could play an important role in the observed activity difference. Interestingly, the charge on central metal of the cationic species accounts for the activities of 1+, 2+, and 3+: the higher the ...