Polymerization of Isoprene Promoted by Aminophosphine(ory)-Fused Bipyridine Cobalt Complexes: Precise Control of Molecular Weight and cis-1,4- alt-3,4 Sequence.
Polymerization of Isoprene Promoted by Aminophosphine(ory)-Fused Bipyridine Cobalt Complexes: Precise Control of Molecular Weight and cis-1,4- alt-3,4 Sequence.
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DOI：
10.1021/acs.inorgchem.8b00270
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发表时间：
2018-03
影响因子：
4.6
通讯作者：
Junyi Zhao;Huafeng Chen;Wenxin Li;X. Jia;Xuequan Zhang;Dirong Gong
中科院分区：
文献类型：
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作者：
Junyi Zhao;Huafeng Chen;Wenxin Li;X. Jia;Xuequan Zhang;Dirong Gong
配体N-（二烷基或芳基膦基）-（2，2 '-联吡啶）-6-胺（L1，芳基= Ph; L2，烷基= tBu; L3，烷基=金刚烷基（Ad））以及相应的氧化的N-（2，2 '-联吡啶-6-基）- P，P-二烷基或芳基次膦酰胺（L4，芳基= Ph; L5，烷基= tBu; L 6，烷基= Ad）同系物被设计并配位到二氯化钴。通过元素分析、红外光谱和X射线衍射对配合物Co 4和Co 6的结构进行了表征，结果表明，配合物中钴中心以五配位的扭曲三角双锥构型存在，并存在一个延长的Co-O（N-P）键。配合物Co_2与MMAO配合后，对cis-1，4- alt-3，4链聚合具有较高的催化活性。O P的半不稳定性质可能是由于η4- cis-1，4和η2- 3，4配位交替，并随后插入金属-碳键。在与AlEt 2Cl组合时，配合物Co 4、Co 5和Co 6中的每一个都能够以控制模式将异戊二烯转化为聚异戊二烯，其中观察到聚合速率常数（kobs = 0.1531 L mol-1 min-1（Co 4）、0.1382 L mol-1 min-1（Co 5）和0.0902 L mol-1 min-1（Co 6））。通过测定0、30和50 °C下的kobs值，Co 4福尔斯聚合的活化能落在27-31 kJ/mol的范围内。所得聚异戊二烯的13 C NMR分析表明，配合物Co 4、Co 5和Co 6具有86.6-93.4%的顺式-1，4选择性和6.6- 13.4%的3，4选择性。该催化剂体系也可用于异戊二烯和月桂烯的活性顺式-1，4嵌段共聚合，从而得到了一种新型的生物源单体基弹性体。
Ligands N-(dialkyl or arylphosphino)-(2,2'-bipyridin)-6-amine (L1, aryl = Ph; L2, alkyl = tBu; L3, alkyl = adamantyl (Ad)) as well as the corresponding oxidized N-(2,2'-bipyridin-6-yl)- P, P-dialkyl or aryl phosphinic amide (L4, aryl = Ph; L5, alkyl = tBu; L6, alkyl = Ad) congeners were designed and coordinated to cobalt dichloride. The structures of formed complexes were characterized by IR and elemental analyses, as well as characterizations of the X-ray diffractions for complexes Co4 and Co6, which revealed the cobalt center is expectedly pentacoordinated in a distorted trigonal bipyramidal configuration with a prolonged Co-O(═P) bond . In combination with MMAO, complex Co2 was highly active in cis-1,4- alt-3,4 enchained polymerization. The hemilabile nature of O═P is possible for the alternating η4- cis-1,4 and η2-3,4 coordination, and insertion at the metal-carbon bond ensued. In combination with AlEt2Cl, each of complexes Co4, Co5, and Co6 was capable of converting isoprene to polyisoprene in a control mode with observed polymerization rate constants ( kobs = 0.1531 L mol-1 min-1 (Co4), 0.1382 L mol-1 min-1 (Co5), and 0.0902 L mol-1 min-1 (Co6)). The activation energy of the polymerization by Co4 falls in the range of 27-31 kJ/mol by determining kobs values at 0, 30, and 50 °C. The 13C NMR analyses of the obtained polyisoprene revealed that complexes Co4, Co5, and Co6 have a cis-1,4 selectivity of 86.6-93.4% with a 3,4 selectivity of 6.6-13.4%. This catalyst system can also be applied to block copolymerization of isoprene and myrcene in a living cis-1,4 fashion; therefore, a new biosourced monomer-based elastomer has been achieved.