Two-electron homoaromatics with heteroatom bridges

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• 作者：Sahin ; Y&uuml ; ksel ; Ziegler ; Andreas ; Happel ; Thorsten ; Meyer ; Harald ; Bayer ; Michael J. ; Pritzkow ; Hans ; et. al.
• 关键词：Ab initio computations ; Boron heterocycles ; Homoaromaticity ; Three-center two-electron bonds ; Zwitterions
• 刊名：Journal of Organometallic Chemistry
• 出版年：2003
• 出版时间：August 29, 2003
• 年：2003
• 卷：680
• 期：1-2
• 页码：244-256
• 全文大小：535 K

文摘

Zwitterionic mono- and bis-homoaromatics 2a–f and 5a comprised of positively charged NMe₂, P(C₆H₅)₂ or As(C₆H₅)₂ bridges and anionic three-center two-electron (3c2e) delocalized boron heterocyclic units, were prepared and characterized by NMR as well as by X-ray structure analyses. The boron chemical shifts of the trishomoaromatic dianion 12a with an oxygen bridge compare well with those computed ab initio for model 12b. Analysis of the electronic structure of the bishomoaromatic 5u and its anionic analog 11u gives insight into the origin of the trend of increasing effectiveness of BC₂, B₂C and B₃ 3c2e bonds: higher electronegativity of carbon vs boron prevents symmetric delocalization in rings with B₂C and especially BC₂ centers.