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Media type:
E-Article
Title:
Synthesis of N‐Heterocyclic Carbenes and Their Complexes by Chloronium Ion Abstraction from 2‐Chloroazolium Salts Using Electron‐Rich Phosphines
Contributor:
Böhme, Matthias D.;
Eder, Tobias;
Röthel, Maike B.;
Dutschke, Patrick D.;
Wilm, Lukas F. B.;
Hahn, F. Ekkehardt;
Dielmann, Fabian
Published:
Wiley, 2022
Published in:
Angewandte Chemie International Edition, 61 (2022) 28
Language:
English
DOI:
10.1002/anie.202202190
ISSN:
1433-7851;
1521-3773
Origination:
Footnote:
Description:
AbstractN‐Heterocyclic carbenes (NHCs) are commonly prepared by deprotonation of azolium salts using strong anionic bases. This reaction is often unselective, yielding alkali metal NHC complexes or dimerized NHCs. Alternatively, free NHCs are obtained by the dechlorination of 2‐chloroazolium salts using electron‐rich phosphines. PPh3, PCy3, and PtBu3 are unsuitable for Cl+ abstraction, while the sterically encumbered tris(1,3‐tert‐butylimidazolidin‐2‐ylidenamino)phosphine 1 selectively removes Cl+ from 2‐chloroazolium salts. Since bulky 1 does not bind to metal complexes, it was used for the preparation of NHC complexes via in situ Cl+ abstraction from 2‐chloroazolium salts. The dechlorination was employed for the site‐selective monometallation with IrI, IrIII, RhI, RhIII, and RuII of a bis‐NHC precursor composed of a 2‐chlorobenzimidazolium and a 2‐chlorobenzimidazole group, followed by the preparation of the heterobimetallic IrIII/PdII complex [18](BF4)2 by a dechlorination/oxidative addition reaction sequence.