Cation-aromatic bonding in group 14 organometallics

被引:12
作者
Basch, H
机构
[1] Department of Chemistry, Bar Ilan University
关键词
cation aromatic bonding; Group; 14; organometallics;
D O I
10.1016/0020-1693(95)04866-9
中图分类号
O61 [无机化学];
学科分类号
070301 ; 081704 ;
摘要
The geometric and electronic structure of (para)toluene-XY(3)(+) complexes have been determined by ab initio, gradient optimization methods at the MP2 level of theory in a valence double-zeta + polarization basis set. The Y substituents are CH3, H and Cl, and X is any one of the Group 14 atoms; carbon, silicon, germanium, tin and lead. Comparison is made with a recently reported crystal structure of the toluene-Si(Et)(3)(+) complex and gas phase mass spectrometry reactions of tert-butyl and silynium cations with arenes. The carbenium complexes have an essentially classical four-coordinate ring (ipso) carbon atom. In passing from X = Si to X = Pb the XY(3) group moves in tandem with the geminally bound hydrogen atom to a position where the X atom is almost directly above the ipso carbon atom and the hydrogen atom is almost coplanar with the benzene ring. In general, one X-Y bond lies parallel to the long axis of toluene to give approximate C-s symmetry complexes. The toluene-XY(3)(+) binding energies are found to increase from the Sn to the Pb complexes for each Y substituent, indicating a special stabilizing interaction for the lead complexes. The binding energies, geometric structures and charge distribution of the complexes are interpreted in terms of classical sigma-bonded and localized pi-bonding models.
引用
收藏
页码:191 / 200
页数:10
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