Alternative modes of bonding of C 4 F 8 units in mononuclear and binuclear iron carbonyl complexes
Alternative modes of bonding of C 4 F 8 units in mononuclear and binuclear iron carbonyl complexes
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单核和双核羰基铁络合物中 C 4 F 8 单元的替代键合模式
DOI：
10.1039/c9nj00882a
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发表时间：
2019
影响因子：
3.3
通讯作者：
Schaefer, Henry F.
中科院分区：
文献类型：
--
作者：
Huang, Liping;Li, Jing;Li, Guoliang;Xie, Yaoming;King, R. Bruce;Schaefer, Henry F.
密度泛函理论研究表明，最低能量的C4F8Fe(CO)4结构并不是由Fe(CO)12和四氟乙烯得到的实验已知的二环戊烷异构体(CF2CF2CF2CF2)Fe(CO)4。相反，来自全氟-2-丁烯、全氟-1-丁烯和全氟-2-甲基丙烯的异构体(全氟烯烃)Fe(CO)4结构是能量显著较低的结构，最高可达∼17kcal−1。然而，所需氟的活化能从一个碳原子转移到邻近的碳原子以形成这些来自四氟乙烯的(全氟烯烃)Fe(CO)4络合物(例如，∼70kcal−1)。因此，铁环戊烷异构体(CF2CF2CF2CF2)Fe(CO)4是动力学上最受欢迎的产物，它不需要进行氟转移就可以由Fe3(CO)12和四氟乙烯生成。双核(C4F8)2Fe2(CO)n(n=7，6)衍生物的最低能量结构是桥联全氟卡宾配体和末端全氟烯烃配体。
Density functional theory studies show that the lowest energy C4F8Fe(CO)4 structure is not the very stable experimentally known ferracyclopentane isomer (CF2CF2CF2CF2)Fe(CO)4 obtained from Fe(CO)12 and tetrafluoroethylene. Instead isomeric (perfluoroolefin)Fe(CO)4 structures derived from perfluoro-2-butene, perfluoro-1-butene, and perfluoro-2-methylpropene are significantly lower energy structures by up to ∼17 kcal mol−1. However, the activation energies for the required fluorine shifts from one carbon to an adjacent carbon atom to form these (perfluoroolefin)Fe(CO)4 complexes from tetrafluoroethylene are very high (e.g., ∼70 kcal mol−1). Therefore the ferracyclopentane isomer (CF2CF2CF2CF2)Fe(CO)4, which does not require a fluorine shift to form from Fe3(CO)12 and tetrafluoroethylene, is the kinetically favored product. The lowest energy structures of the binuclear (C4F8)2Fe2(CO)n (n = 7, 6) derivatives have bridging perfluorocarbene ligands and terminal perfluoroolefin ligands.