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Dismutational and Global‐Minimum Isomers of Heavier 1,4‐Dimetallatetrasilabenzenes of Group 14
Author(s) -
Jana Anukul,
Huch Volker,
Repisky Michal,
Berger Raphael J. F.,
Scheschkewitz David
Publication year - 2014
Publication title -
angewandte chemie international edition
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.831
H-Index - 550
eISSN - 1521-3773
pISSN - 1433-7851
DOI - 10.1002/anie.201310475
Subject(s) - chemistry , homonuclear molecule , germanium , propellane , chemical shift , crystallography , tin , atomic orbital , stereochemistry , homo/lumo , nmr spectra database , spectral line , molecule , computational chemistry , organic chemistry , bicyclic molecule , silicon , electron , physics , quantum mechanics , astronomy
Abstract Aromatic species with heavier Group 14 elements show remarkable differences in terms of stability, structure, and reactivity. Herein we report our experimental and theoretical investigations regarding isomers of germanium‐ and tin‐containing benzene analogues E 2 Si 4 R 6 (E=Ge, Sn). The germanium‐substituted dismutational isomer with a tricyclic six‐membered scaffold is isolable, but unlike the homonuclear Si 6 analogue slowly rearranges even at room temperature to give the propellane‐type global minimum isomer. In case of E=Sn the dismutational isomer may be an intermediate on the pathway to the propellane‐type species obtained, but cannot be detected even at low temperature. Unprecedentedly large chemical shift anisotropies in the 29 Si NMR spectra that increase from the Si 6 species through Ge 2 Si 4 to Sn 2 Si 4 are rationalized by progressively larger paramagnetic‐term contributions to the chemical shift tensor as a result of diminishing HOMO–LUMO gaps, which are also reflected in the absorption spectra, as well as by appearance and symmetry of these frontier orbitals.

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