Department of Chemistry, University of Missouri-Kansas City, Kansas City, Missouri 64110, USA.
J Chem Phys. 2012 Jan 28;136(4):044306. doi: 10.1063/1.3673889.
The microwave spectrum (6500-18 ,500 MHz) of 1-fluoro-1-silacyclopentane, c-C(4)H(8)SiHF has been recorded and 87 transitions for the (28)Si, (29)Si, (30)Si, and (13)C isotopomers have been assigned for a single conformer. Infrared spectra (3050-350 cm(-1)) of the gas and solid and Raman spectrum (3100-40 cm(-1)) of the liquid have also been recorded. The vibrational data indicate the presence of a single conformer with no symmetry which is consistent with the twist form. Ab initio calculations with a variety of basis sets up to MP2(full)/aug-cc-pVTZ predict the envelope-axial and envelope-equatorial conformers to be saddle points with nearly the same energies but much lower energy than the planar conformer. By utilizing the microwave rotational constants for seven isotopomers ((28)Si, (29)Si, (30)Si, and four (13)C) combined with the structural parameters predicted from the MP2(full)/6-311+G(d,p) calculations, adjusted r(0) structural parameters have been obtained for the twist conformer. The heavy atom distances in Å are: r(0)(SiC(2)) = 1.875(3); r(0)(SiC(3)) = 1.872(3); r(0)(C(2)C(4)) = 1.549(3); r(0)(C(3)C(5)) = 1.547(3); r(0)(C(4)C(5)) = 1.542(3); r(0)(SiF) = 1.598(3) and the angles in degrees are: [angle]CSiC = 96.7(5); [angle]SiC(2)C(4) = 103.6(5); [angle]SiC(3)C(5) = 102.9(5); [angle]C(2)C(4)C(5) = 108.4(5); [angle]C(3)C(5)C(4) = 108.1(5); [angle]F(6)Si(1)C(2) = 110.7(5); [angle]F(6)Si(1)C(3) = 111.6(5). The heavy atom ring parameters are compared to the corresponding r(s) parameters. Normal coordinate calculations with scaled force constants from MP2(full)/6-31G(d) calculations were carried out to predict the fundamental vibrational frequencies, infrared intensities, Raman activities, depolarization values, and infrared band contours. These experimental and theoretical results are compared to the corresponding quantities of some other five-membered rings.
1-氟-1-硅杂环戊烷，c-C(4)H(8)SiHF 的微波光谱（6500-18500MHz）已被记录，对于单个构象体，87 个（28）Si、（29）Si、（30）Si 和（13）C 同位素的跃迁已被分配。气体和固体的红外光谱（3050-350cm(-1))和液体的拉曼光谱（3100-40cm(-1))也已被记录。振动数据表明，存在一个具有单一非对称构象的构象体，这与扭曲构象一致。利用各种基组至 MP2(full)/aug-cc-pVTZ 的从头算计算预测了包络-轴向和包络-赤道构象体为鞍点，具有几乎相同的能量，但比平面构象体的能量低得多。通过利用七种同位素（（28）Si、（29）Si、（30）Si 和四个（13）C）的微波旋转常数，并结合 MP2(full)/6-311+G(d,p)计算预测的结构参数，获得了扭曲构象的调整 r(0)结构参数。Å 中的重原子距离为：r(0)(SiC(2))=1.875(3)；r(0)(SiC(3))=1.872(3)；r(0)(C(2)C(4))=1.549(3)；r(0)(C(3)C(5))=1.547(3)；r(0)(C(4)C(5))=1.542(3)；r(0)(SiF)=1.598(3)，角度为：[angle]CSiC=96.7(5)；[angle]SiC(2)C(4)=103.6(5)；[angle]SiC(3)C(5)=102.9(5)；[angle]C(2)C(4)C(5)=108.4(5)；[angle]C(3)C(5)C(4)=108.1(5)；[angle]F(6)Si(1)C(2)=110.7(5)；[angle]F(6)Si(1)C(3)=111.6(5)。重原子环参数与相应的 r(s)参数进行了比较。利用 MP2(full)/6-31G(d)计算的缩放力常数进行了正则坐标计算，以预测基本振动频率、红外强度、拉曼活性、退偏值和红外带轮廓。这些实验和理论结果与其他一些五元环的相应数量进行了比较。
