A new version of this entry is available:
Loading...
Article
2023
Exo‐endo Isomerism of carboranes: Unusual geometries of C2B5X7 (X=Cl, Br) and C2B7Cl9 with exo‐skeletal BCl2 groups on carbon revealed by joint spectroscopic/computational studies
Exo‐endo Isomerism of carboranes: Unusual geometries of C2B5X7 (X=Cl, Br) and C2B7Cl9 with exo‐skeletal BCl2 groups on carbon revealed by joint spectroscopic/computational studies
Abstract (English)
Reexamination of the co‐pyrolysis reactions of B2Cl4 with C2Cl4 at 350 °C and of B2Br4 with CBr4 at 300 °C in vacuo confirmed the carboranes C2B5Cl7 (1), C2B7Cl9 (2), and C2B5Br7 (3) as low‐yield products. While 1 only could be concentrated by repeated vacuum fractionation, 2 and 3 could now be isolated from the conglomerate mixtures for a full spectroscopic characterization and the compounds were verified in their geometries by detailed DFT computations. Surprisingly, the perhalogenated carboranes do not adopt the expected “all‐endo”‐geometries with cluster sizes derived by the sum of the n boron and two carbon atoms (n+2) as known from the syntheses of the parent closo‐carboranes C2BnHn+2. Instead, DFT/GIAO(ZORA)/NMR (GIAO for X=Cl, ZORA for X=Br) computations revealed that the perhalogenated carboranes favor structures with BX2 groups as exo‐skeletal ligands attached to both cage‐carbon atoms yielding the five‐vertex closo‐1,5‐(CBX2)2B3X3 (1: X=Cl; 3: X=Br) and the seven‐vertex closo‐2,4‐(CBCl2)2B5Cl5 for 2. In contrast to these perhalogenated carboranes, analogous computations on the hydrogen substituted carboranes C2BnHn+2, silaboranes Si2BnHn+2 and Si2BnXn+2 (n=5, 7) show in all cases a thermodynamic favorization of structures where all boron atoms of the formula are endo‐skeletally incorporated into the cluster frameworks.
File is subject to an embargo until
This is a correction to:
A correction to this entry is available:
This is a new version of:
Notes
Publication license
Publication series
Published in
ChemistrySelect, 8 (2023), 24, e202301653.
https://doi.org/10.1002/slct.202301653.
ISSN: 2365-6549
Faculty
Institute
Examination date
Supervisor
Edition / version
Citation
DOI
ISSN
ISBN
Language
English
Publisher
Publisher place
Classification (DDC)
540 Chemistry
Collections
Original object
Standardized keywords (GND)
Sustainable Development Goals
BibTeX
@article{Keller2023,
url = {https://hohpublica.uni-hohenheim.de/handle/123456789/16279},
doi = {10.1002/slct.202301653},
author = {Keller, Willi and Conrad, Jürgen and Hofmann, Matthias et al.},
title = {exo‐endo Isomerism of Carboranes: Unusual Geometries of C2B5X7 (X=Cl, Br) and C2B7Cl9 with exo‐Skeletal BCl2 Groups on Carbon Revealed by Joint Spectroscopic/Computational Studies},
journal = {ChemistrySelect},
year = {2023},
volume = {8},
number = {24},
}