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Bond Stretch Isomerism in Bicyclo[1.1.0]tetrasilanes. Contrasts Between Strained Silicon and Carbon Ring Systems
Author(s) -
Schleyer Paul von Ragué,
Sax Alexander F.,
Kalcher Josef,
Janoschek Rudolf
Publication year - 1987
Publication title -
angewandte chemie international edition in english
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.831
H-Index - 550
eISSN - 1521-3773
pISSN - 0570-0833
DOI - 10.1002/anie.198703641
Subject(s) - bond length , ring (chemistry) , bond order , maxima and minima , silicon , crystallography , ab initio , carbon fibers , molecular geometry , bicyclic molecule , single bond , chemistry , order (exchange) , ab initio quantum chemistry methods , bond energy , computational chemistry , materials science , molecular physics , stereochemistry , molecule , crystal structure , group (periodic table) , mathematics , organic chemistry , composite material , mathematical analysis , composite number , finance , economics
Is bicyclotetrasilane expected to exhibit a markedly short or a markedly long central SiSi bond? Ab initio calculations at different levels of accuracy all gave two potential minima. The corresponding structures differ in the length of the central bond (by about 0.5 Å), the interflap angle (120 and 140°), and the HSiSi angle at the bridgehead atoms (140 and 90°). In all calculations, the structure with the long SiSi bond proved to be lower in energy. This order can be reversed, however, in derivatives with bulky substituents at the bridgehead atoms.