Theoretical Calculations, Microwave Spectroscopy, and Ring-Puckering Vibrations of 1,1-Dihalosilacyclopent-2-enes
Theoretical Calculations, Microwave Spectroscopy, and Ring-Puckering Vibrations of 1,1-Dihalosilacyclopent-2-enes
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1,1-二卤硅环戊-2-烯的理论计算、微波光谱和环褶皱振动
DOI：
10.1021/acs.jpca.0c07250
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发表时间：
2020
期刊：
影响因子：
--
通讯作者：
Grubbs, Garry S.
中科院分区：
文献类型：
--
作者：
McFadden, Thomas M.;Marshall, Frank E.;Ocola, Esther J.;Laane, Jaan;Guirgis, Gamil A.;Grubbs, Garry S.
采用CCSD/cc-pVTZ方法对1，1-二氟硅杂环戊二烯（2SiCPF 2）和1，1-二氯硅杂环戊二烯（2SiCPCl 2）的结构和皱环势能函数进行了高水平的理论计算.用从头算MP2/cc-pVTZ方法计算了1，1-二溴硅杂环戊二烯-2-烯（2SiCPBr 2）的结构和峰值电场.母体硅杂环戊二烯-2-烯（2SiCP）具有49 cm-1的平面性势垒，2SiCPF 2具有平面环系统，2SiCPCl 2具有计算的微小4 cm-1势垒，但基本上是平面的，并且二溴化物具有计算的36 cm-1势垒。用啁啾脉冲傅里叶变换微波（CP-FTMW）谱仪在6-18 GHz范围内记录了2SiCPF 2的7种同位素的微波谱。观察到a型和b型转变。测定了母体、29 Si、30 Si和天然丰度的所有单取代13 C同位素的转动常数和三个四次离心畸变常数。这允许确定环的重原子结构，并表明环是平面的。实验测定的转动常数和几何参数与理论值吻合得很好，证实了五元环的平面性。硅烷和三种二卤化物的PEF的比较显示硅烷具有最硬的起皱运动，而二溴化物具有最小的刚性。
High-level theoretical CCSD/cc-pVTZ computations have been carried out to calculate the structures and ring-puckering potential energy functions (PEFs) for 1,1-difluorosilacyclopent-2-ene (2SiCPF2) and 1,1-dichlorosilacyclopent-2-ene (2SiCPCl2). The structure and PEF for 1,1-dibromosilacyclopent-2-ene (2SiCPBr2) were obtained by ab initio MP2/cc-pVTZ computations. The parent silacyclopent-2-ene (2SiCP) is puckered with a 49 cm–1barrier to planarity, 2SiCPF2has a planar ring system, 2SiCPCl2has a calculated tiny 4 cm–1barrier but is essentially planar, and the dibromide has a calculated barrier of 36 cm–1. Microwave spectra of seven isotopic species of 2SiCPF2were recorded on a chirped pulse, Fourier transform microwave (CP-FTMW) spectrometer in the 6–18 GHz region. Thea-type andb-type transitions were observed. The rotational constants and three quartic centrifugal distortion constants were determined for the parent,29Si,30Si, and all singly substituted13C isotopologues in natural abundance. This allowed for the determination of the heavy-atom structure of the ring and showed the ring to be planar. The experimentally determined rotational constants and geometrical parameters agree very well with the theoretical values and confirm the planarity of the five-membered ring. A comparison of the PEFs for the silane and the three dihalides shows the silane to have the stiffest puckering motion and the dibromide to be the least rigid.