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Combined Experimental and Theoretical Approach for Living and Isoselective Propylene Polymerization
ACS Catalysis ( IF 11.3 ) Pub Date : 2017-09-14 00:00:00 , DOI: 10.1021/acscatal.7b02107 Gregory J. Domski 1 , James M. Eagan 1 , Claudio De Rosa 2 , Rocco Di Girolamo 2 , Anne M. LaPointe 1 , Emil B. Lobkovsky 1 , Giovanni Talarico 2 , Geoffrey W. Coates 1
ACS Catalysis ( IF 11.3 ) Pub Date : 2017-09-14 00:00:00 , DOI: 10.1021/acscatal.7b02107 Gregory J. Domski 1 , James M. Eagan 1 , Claudio De Rosa 2 , Rocco Di Girolamo 2 , Anne M. LaPointe 1 , Emil B. Lobkovsky 1 , Giovanni Talarico 2 , Geoffrey W. Coates 1
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The controlled polymerization of propylene with living catalysts in an isoselective fashion with high activities is a continuing challenge for catalysis, with at least one of these properties suffering in most existing systems. Through experimental and theoretical studies, the pyridylamidohafnium olefin polymerization catalysts have been optimized for living behavior, isoselectivity, and activity of propylene polymerization (Đ = 1.2, [m4] = 91%, TOF = 25 000 h–1). Substitution of the bridgehead position with geminal dimethyl substituents forces the stereoselective elements of the catalyst into closer proximity with the active site through a “buttressing effect” while simultaneously preserving symmetry in the catalyst after activation and the first monomer insertion into the Hf–Caryl bond of the ligand. Propagation was shown to be favored over termination through beta-hydrogen transfer to the monomer through a combination of theoretical modeling and experimental monitoring of the reaction which showed a linear increase in molecular weight as a function of polymer yield. Furthermore, through computational and 13C labeling NMR studies, a different mechanism of stereocontrol involving a direct ligand–monomer interaction was confirmed.
中文翻译：
活性和等选择性丙烯聚合的实验和理论相结合的方法
丙烯与活性催化剂以等选择性的方式以高活性进行受控的聚合反应一直是催化的挑战，这些特性中的至少一种在大多数现有系统中都存在问题。通过实验和理论研究，对吡啶基lam基ha烯烃聚合催化剂进行了优化，以提高其丙烯的活性，等选择性和活性（Đ = 1.2，[ m 4 ] = 91％，TOF = 25 000 h –1）。用双甲基二甲基取代基取代桥头位置，通过“支撑效应”迫使催化剂的立体选择性元素更接近活性位，同时在活化和第一批单体插入Hf-C芳基键后保持催化剂的对称性配体。通过理论模型和反应的实验监测相结合，显示了比通过β-氢转移至单体的终止更有利于传播，反应的分子量随聚合物收率的增加而线性增加。此外，通过计算和13 C标记NMR研究，证实了涉及直接配体-单体相互作用的立体控制机理。
更新日期：2017-09-15
中文翻译：
活性和等选择性丙烯聚合的实验和理论相结合的方法
丙烯与活性催化剂以等选择性的方式以高活性进行受控的聚合反应一直是催化的挑战，这些特性中的至少一种在大多数现有系统中都存在问题。通过实验和理论研究，对吡啶基lam基ha烯烃聚合催化剂进行了优化，以提高其丙烯的活性，等选择性和活性（Đ = 1.2，[ m 4 ] = 91％，TOF = 25 000 h –1）。用双甲基二甲基取代基取代桥头位置，通过“支撑效应”迫使催化剂的立体选择性元素更接近活性位，同时在活化和第一批单体插入Hf-C芳基键后保持催化剂的对称性配体。通过理论模型和反应的实验监测相结合，显示了比通过β-氢转移至单体的终止更有利于传播，反应的分子量随聚合物收率的增加而线性增加。此外，通过计算和13 C标记NMR研究，证实了涉及直接配体-单体相互作用的立体控制机理。
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