The influence of electron delocalization upon the stability and structure of potential N-heterocyclic carbene precursors with 1,3-diaryl-imidazolidine-4,5-dione skeletons
Hobbs, M., Forster, T., Borau-Garcia, J., Knapp, C., Tuononen, H., & Roesler, R. (2010). The influence of electron delocalization upon the stability and structure of potential N-heterocyclic carbene precursors with 1,3-diaryl-imidazolidine-4,5-dione skeletons. New Journal of Chemistry, 34(7), 1295-1308. https://doi.org/10.1039/B9NJ00771G
Published in
New Journal of ChemistryAuthors
Date
2010Copyright
© Royal Society of Chemistry 2010. This is a final draft version of an article whose final and definitive form has been published by RSC. Published in this repository with the kind permission of the publisher.
Targeting N-heterocyclic carbenes (NHCs) with increased π-acceptor character featuring N-fluorophenyl substituents, the molecular 2-chloro-1,3-bis(fluorophenyl)imidazolidine-4,5-diones (1a–c) were isolated from the condensation of the corresponding formamidine with oxalyl chloride. These formal adducts of NHCs with hydrogen chloride demonstrated reactivity akin to that of alkyl halides: 1,3,1′,3′-tetrakis(2,6-dimethylphenyl)-[2,2′]diimidazolidinyl-4,5,4′,5′-tetraone (2b) was formed via the reductive coupling of 1b, while 1,3-bis(2,6-diisopropylphenyl)-4,5-dioxoimidazolidin-2-yl acetate (3c) was formed as the result of a metathesis reaction with mercury(II) acetate. Chloride abstraction resulted in the formation of imidazolium-4,5-dione salts (4a–c) that decomposed rapidly, except in the case of the kinetically-stabilized 1,3-bis(2,6-diisopropylphenyl)imidazolium-4,5-dione hexafluorophosphate 4c. All imidazolium-4,5-dione hexafluorophosphate salts decomposed to neutral 2-fluoro-1,3-bis(aryl)imidazolidine-4,5-diones (5a–c) via fluoride abstraction. 2-Methoxy-1,3-di(aryl)imidazolidine-4,5-diones (6a–c) were also prepared and they failed to undergo thermolysis and yield the free NHCs. Computational analyses revealed that the instability of NHCs with an oxalamide skeleton, as well as that of imidazolium-4,5-diones, results from a π-framework which extends over both carbonyl moieties and gives rise to a very low energy LUMO, rendering the compounds in question highly electrophilic.
...
Publisher
RSCISSN Search the Publication Forum
1144-0546Publication in research information system
https://converis.jyu.fi/converis/portal/detail/Publication/20144657
Metadata
Show full item recordCollections
Related items
Showing items with similar title or keywords.
-
N-Heterocyclic Carbenes with Inorganic Backbones: Electronic Structures and Ligand Properties
Kausamo, Anna; Tuononen, Heikki; Krahulic, Kelly; Roesler, Roland (ACS, 2008)The electronic structures of known N-heterocyclic carbenes (NHCs) with boron, nitrogen, and phosphorus backbones are examined using quantum chemical methods and compared to the experimental results and to the computational ... -
A σ-Donor with a Planar Six-π-Electron B2N2C2 Framework: Anionic N-Heterocyclic Carbene or Heterocyclic Terphenyl Anion?
Forster, Taryn; Krahulic, Kelly; Tuononen, Heikki; McDonald, Robert; Parvez, Masood; Roesler, Roland (Wiley, 2006)NB! The anionic ligand 2 was synthesized through deprotonation of a planar, formally zwitterionic diazadiborine precursor, isolated as a lithium salt, and structurally characterized. According to experimental evidence and ... -
Electronic Structures of Main-Group Carbene Analogues
Tuononen, Heikki; Roesler, Roland; Dutton, Jason; Ragogna, Paul (ACS, 2007)The electronic structures of 15 group 13−16 carbene analogues are analyzed using various quantum chemical methods and compared to the data obtained for the parent N-heterocyclic carbene (NHC), imidazol-2-ylidene. The results ... -
Ammonia Activation by a Nickel NCN-Pincer Complex featuring a Non-Innocent N-Heterocyclic Carbene: Ammine and Amido Complexes in Equilibrium
Brown, Rudy M.; Garcia, Javier Borau; Valjus, Juuso; Roberts, Christopher; Tuononen, Heikki; Parvez, Masood; Roesler, Roland (Wiley - VCH Verlag GmbH & Co. KGaA, 2015)A Ni0-NCN pincer complex featuring a six-membered N-heterocyclic carbene (NHC) central platform and amidine pendant arms was synthesized by deprotonation of its NiII precursor. It retained chloride in the square-planar ... -
Isolation of Free Phenylide-like Carbanions with N-Heterocyclic Carbene Frameworks
Krahulic, Kelly; Tuononen, Heikki; Parvez, Masood; Roesler, Roland (ACS, 2009)A series of 1,3-bis(2,6-diisopropylphenyl)-5-methyl-1,3-diaza-4,6-diborabenzenes with methyl, phenyl, and dimethylamino substituents on the ring boron atoms were prepared using the cyclocondensation reaction between ...