Bis( N -cyclopropenio)-imidazol-2-ylidene: An N -Heterocyclic Carbene Bearing Two N -Cationic Substituents - Archive ouverte HAL Access content directly
Journal Articles Organometallics Year : 2022

Bis( N -cyclopropenio)-imidazol-2-ylidene: An N -Heterocyclic Carbene Bearing Two N -Cationic Substituents

Abstract

Thanks to the onio-substitution strategy, tricationic imidazolium salt (1·H)(OTf)3 featuring two N-cyclopropenio substituents was readily prepared in a two-step procedure from 1H-imidazole. The influence of the two cyclopropenium moieties on the electronic properties of the related dicationic NHC 12+ was evaluated on the basis of the 1JCH, δ 77Se, and Tolman electronic parameter (TEP) values obtained, respectively, from NHC precursor (1·H)(OTf)3, NHC═Se adduct (5)(OTf)2, and NHC–Rh(CO)2 complex (7)(OTf)2, leading to the conclusion that carbene 12+ is one of the least-donating cationic NHCs reported to date. The coordinating ability of 12+ was extended to Pd(II) and Au(I) centers, providing dicationic [PdCl(allyl)(1)](OTf)2 (8)(OTf)2 and [AuCl(1)](OTf)2 (10)(OTf)2 complexes, respectively, which were fully characterized. While Pd complex (8)(OTf)2 was found to exhibit the lability of a cyclopropenium substituent upon the cleavage of a C+–N bond, Au complex (10)(OTf)2 was implemented in model Au-catalyzed intramolecular cyclization reactions, showing moderate activity.
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hal-03818692 , version 1 (18-10-2022)

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Ajay Padunnappattu, Carine Duhayon, Vincent César, Yves Canac. Bis( N -cyclopropenio)-imidazol-2-ylidene: An N -Heterocyclic Carbene Bearing Two N -Cationic Substituents. Organometallics, 2022, 41 (20), pp.2868-2878. ⟨10.1021/acs.organomet.2c00429⟩. ⟨hal-03818692⟩
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