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Tricyanoborane‐Functionalized Anionic N‐Heterocyclic Carbenes: Adjustment of Charge and Stereo‐Electronic Properties
Author(s) -
Zapf Ludwig,
Peters Sven,
Bertermann Rüdiger,
Radius Udo,
Finze Maik
Publication year - 2022
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.202200275
Subject(s) - carbene , chemistry , deprotonation , adduct , ligand (biochemistry) , alkyl , medicinal chemistry , ion , acceptor , polymer chemistry , catalysis , organic chemistry , biochemistry , physics , receptor , condensed matter physics
The 1‐methyl‐3‐(tricyanoborane)imidazolin‐2‐ylidenate anion ( 2 ) was obtained in high yield by deprotonation of the B(CN) 3 ‐methylimidazole adduct 1 . Regarding charge and stereo‐electronic properties, anion 2 closes the gap between well‐known neutral NHCs and the ditopic dianionic NHC, the 1,3‐bis(tricyanoborane)imidazolin‐2‐ylidenate dianion ( IIb ). The influence of the number of N ‐bonded tricyanoborane moieties on the σ‐donating and π‐accepting properties of NHCs was assessed by quantum chemical calculations and verified by experimental data on 2 , IIb , and 1,3‐dimethylimidazolin‐2‐ylidene (IMe, IIa ). Therefore NHC 2 , which acts as a ditopic ligand via the carbene center and the cyano groups, was reacted with alkyl iodides, selenium, and [Ni(CO) 4 ] yielding alkylated imidazoles 3 and 4 , the anionic selenium adduct 5 , and the anionic nickel tricarbonyl complex 8 , respectively. The results of this study prove that charge, number of coordination sites, buried volume (% V bur ) and σ‐donor and π‐acceptor abilities of NHCs can be effectively fine‐tuned via the number of tricyanoborane substituents.