McLachlan Lorna J, Hinchley Sarah L, Rankin David W H, Morrison Carole A, Robertson Heather E, Mitzel Norbert W, Rüdinger Christoph, Schmidbaur Hubert
School of Chemistry, University of Edinburgh, West Mains Road, Edinburgh, EH9 3JJ, UK.
Inorg Chem. 2003 Oct 6;42(20):6539-44. doi: 10.1021/ic034596d.
The molecular structures of trans-1,2-dichloro-1,2-disilylethene and 1-bromo-1-silylethene have been determined by gas-phase electron diffraction (GED) and ab initio molecular orbital calculations (MP2/6-311G). Both compounds were found to have highly asymmetric coordination around the carbon atoms with [ab initio (r(e))/GED (r(a))] C=C-Cl [117.0/117.0(2) degrees] and C=C-Si [126.2/128.1(1) degrees] in the C(2)(h) structure of trans-1,2-dichloro-1,2-disilylethene and C=C-Br [119.2/120.7(4) degrees] and C=C-Si [125.0/125.0(4) degrees] in the C(s) structure of 1-bromo-1-silylethene. Other important structural parameters for trans-1,2-dichloro-1,2-disilylethene are C=C [135.2/134.5(3) pm], C-Si [189.4/187.9(2) pm], and C-Cl [175.1/174.9(1) pm], and C=C [134.2/133.4(2) pm], C-Si [187.8/187.2(3) pm], and C-Br [191.3/191.0(3) pm] for 1-bromo-1-silylethene. Further ab initio calculations were carried out on CH(2)CRX and trans-(CRX)(2) (R = SiH(3), CH(3), or H; X = H, F, Cl, or Br) to gauge the effects of electron-withdrawing and electron-donating groups on the structures. They reveal some even more distorted structures. The asymmetric appearance of these molecules can largely be accounted for by valence shell electron pair repulsion theory.
通过气相电子衍射（GED）和从头算分子轨道计算（MP2/6 - 311G）确定了反式 - 1,2 - 二氯 - 1,2 - 二硅基乙烯和1 - 溴 - 1 - 硅基乙烯的分子结构。发现这两种化合物在碳原子周围具有高度不对称的配位，在反式 - 1,2 - 二氯 - 1,2 - 二硅基乙烯的(C_{2h})结构中，([从头算(r_e)/GED(r_a)]) (C = C - Cl)为([117.0/117.0(2)^{\circ}]) ，(C = C - Si)为([126.2/128.1(1)^{\circ}]) ；在1 - 溴 - 1 - 硅基乙烯的(C_s)结构中，(C = C - Br)为([119.2/120.7(4)^{\circ}]) ，(C = C - Si)为([125.0/125.0(4)^{\circ}]) 。反式 - 1,2 - 二氯 - 1,2 - 二硅基乙烯的其他重要结构参数为(C = C) ([135.2/134.5(3) pm]) ，(C - Si) ([189.4/187.9(2) pm]) ，(C - Cl) ([(175.1/174.9(1) pm]) ；1 - 溴 - 1 - 硅基乙烯的(C = C) ([134.2/133.4(2) pm]) ，(C - Si) ([187.8/187.2(3) pm]) ，(C - Br) ([191.3/191.0(3) pm]) 。对(CH_2CRX)和反式(-(CRX)_2)（(R = SiH_3)，(CH_3)或(H)；(X = H)，(F)，(Cl)或(Br)）进行了进一步的从头算计算，以评估吸电子和供电子基团对结构的影响。计算结果揭示了一些更加扭曲的结构。这些分子的不对称外观在很大程度上可以用价层电子对排斥理论来解释。
