Wen Limei, Li Guoliang, Xie Yaoming, King R Bruce, Schaefer Henry F
Key Laboratory of Theoretical Chemistry of Environment, Ministry of Education, Center for Computational Quantum Chemistry, School of Chemistry, South China Normal University, Guangzhou 510006, P. R. China.
Phys Chem Chem Phys. 2020 Apr 14;22(14):7616-7624. doi: 10.1039/c9cp06685c. Epub 2020 Mar 30.
Fluorocarbons have been shown experimentally by Baker and coworkers to combine with the cyclopentadienylcobalt (CpCo) moiety to form fluoroolefin and fluorocarbene complexes as well as fluorinated cobaltacyclic rings. In this connection density functional theory (DFT) studies on the cyclopentadienylcobalt fluorocarbon complexes CpCo(L)(CF) (L = CO, PMe; n = 3 and 4) indicate structures with perfluoroolefin ligands to be the lowest energy structures followed by perfluorometallacycle structures and finally by structures with perfluorocarbene ligands. Thus, for the CpCo(L)(CF) (L = CO, PMe) complexes, the perfluoropropene structure has the lowest energy, followed by the perfluorocobaltacyclobutane structure and the perfluoroisopropylidene structure less stable by 8 to 11 kcal mol, and the highest energy perfluoropropylidene structure less stable by more than 12 kcal mol. For the two metal carbene structures Cp(L)Co[double bond, length as m-dash]C(CF) and Cp(L)Co[double bond, length as m-dash]CF(CF), the former is more stable than the latter, even though the latter has Fischer carbene character. For the CpCo(L)(CF) (L = CO, PMe) complexes, the perfluoroolefin complex structures have the lowest energies, followed by the perfluorometallacycle structures at 10 to 20 kcal mol, and the structures with perfluorocarbene ligands at yet higher energies more than 20 kcal mol above the lowest energy structure. This is consistent with the experimentally observed isomerization of the perfluorinated cobaltacyclobutane complexes CpCo(PPhMe)(-CFR-CF-CF-) (R = F, CF) to the perfluoroolefin complexes CpCo(PPhMe)(RCF[double bond, length as m-dash]CF) in the presence of catalytic quantities of HN(SOCF). Further refinement of the relative energies by the state-of-the-art DLPNO-CCSD(T) method gives results essentially consistent with the DFT results summarized above.
贝克及其同事通过实验表明，碳氟化合物可与环戊二烯基钴（CpCo）部分结合，形成氟代烯烃和氟卡宾配合物以及氟化钴环。在此方面，对环戊二烯基钴碳氟化合物配合物CpCo(L)(CF)（L = CO、PMe；n = 3和4）的密度泛函理论（DFT）研究表明，具有全氟烯烃配体的结构是能量最低的结构，其次是全氟金属环结构，最后是具有全氟卡宾配体的结构。因此，对于CpCo(L)(CF)（L = CO、PMe）配合物，全氟丙烯结构能量最低，其次是全氟钴环丁烷结构，全氟异亚丙基结构稳定性低8至11千卡/摩尔，能量最高的全氟亚丙基结构稳定性低超过12千卡/摩尔。对于两种金属卡宾结构Cp(L)Co═C(CF)和Cp(L)Co═CF(CF)，前者比后者更稳定，尽管后者具有费舍尔卡宾特征。对于CpCo(L)(CF)（L = CO、PMe）配合物，全氟烯烃配合物结构能量最低，其次是能量比最低能量结构高10至20千卡/摩尔的全氟金属环结构，以及能量更高、比最低能量结构高20千卡/摩尔以上的具有全氟卡宾配体的结构。这与实验观察到的在催化量的HN(SOCF)存在下，全氟钴环丁烷配合物CpCo(PPhMe)(-CFR-CF-CF-)（R = F、CF）异构化为全氟烯烃配合物CpCo(PPhMe)(RCF═CF)一致。通过最先进的DLPNO-CCSD(T)方法对相对能量进行进一步细化，得到的结果与上述DFT结果基本一致。
