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The Distribution of Charge Density of Hypervalent Organic Sulfur Compounds

高价有机硫化合物的电荷密度分布

基本信息

批准号：
03453161
负责人：
IWASAKI Fujiko
金额：
$ 4.48万
依托单位：
The University of Electro-Communications
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (B)
财政年份：
1991
资助国家：
日本
起止时间：
1991 至 1993
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-03453161/
关键词：
Crystal Structure Analysis Electron-density Distribution Low Temperature X-ray Diffraction Multipole Expansion Method Sulfur Compounds Hypervalent Bond Heteroatom Chemistry X線低温実験

项目摘要

Hypervalent compounds such as sigma-sulfuranes and thiathiophthenes are of great interest in structural chemistry and organic synthesis. Electron-density distributions of two tetraazathiapentalene derivatives, I and II,with typical hypervalent S-N bonds of 1.90 - 1.96 A were investigated in order to shed light on the character of hypervalent bonds and to compare electronic features of these sulfur atoms. Electron-density distributions of dibenzothiophene derivative, III,with a weak intramolecular S・・・S contact of 3.012 A were also investigated. Intensities of X-ray diffraction were measured at 143K up to 2rhetamax=100ﾟ (88ﾟ for III) and the structure refinements were performed using multipole expansion atomic scattering factors up to the hexadecapole expansion for S atom. In model-deformation maps of the tetraazathiapentalene planes, positive electron densities along S-N bonds are observed near the nitrogen atoms, not in the center of the bonds. The net atomic charges derived from the multipole refinement suggest a polarized character of S-N bond. For each compound, two lone-pair electron densities are observed in the section perpendicular to the pentalene plane through the S-C bonds. The angles of C-S-L,C-S-L' and L-S-L' (L and L' = peaks of lone-pair densities) are about 120ﾟ.Structure around the hypervalent S atom is a trigonal bipyramid with equatorial sp^2 hybrid of S-C bond and lone-pair electrons and apical polarized S-N bonds. In III lone-pair electron densities are observed perpendicular to the thiophene ring and the C-S-C sulfide planes. Lobes of lone-pair electrons of two sulfide groups are orthonormal with each other to avoid a steric hindrance between lone pairs of two S atoms.

超价化合物如σ-硫烷和硫杂噻吩在结构化学和有机合成中具有重要意义。本文研究了两种具有1.90 - 1.96 A超价S-N键的四氮硫并环戊二烯衍生物I和II的电子密度分布，以揭示超价键的性质并比较这些硫原子的电子特征。还研究了具有3.012 A的弱分子内S···S接触的二苯并噻吩衍生物III的电子密度分布。在143 K下测量了X射线衍射强度，直到2 rhetamax =100 μ m（III为88 μ m），并使用多极展开原子散射因子对S原子进行了结构细化，直到十六极展开。在四氮杂硫杂环戊二烯平面的模型变形图中，在氮原子附近观察到沿沿着S-N键的正电子密度，而不是在键的中心。由多极精细化得到的原子净电荷表明了S-N键的极化特征。对于每种化合物，在通过S-C键垂直于并环戊烯平面的截面上观察到两个孤对电子密度。C-S-L、C-S-L'和L-S-L'（L和L'为孤对电子密度的峰值）的夹角约为120 °。超价S原子周围的结构是一个三角双锥，由S-C键和孤对电子的赤道sp^2杂化和顶端极化的S-N键组成。在III孤对电子密度观察垂直于噻吩环和C-S-C硫化物平面。两个硫化物基团的孤对电子的瓣彼此正交，以避免两个S原子的孤对电子之间的空间位阻。