《Modulating the Bonding Properties of N-Heterocyclic Carbenes (NHCs): A Systematic Charge-Displacement Analysis》 was published in Chemistry – A European Journal in 2017. These research results belong to Gaggioli, Carlo Alberto; Bistoni, Giovanni; Ciancaleoni, Gianluca; Tarantelli, Francesco; Belpassi, Leonardo; Belanzoni, Paola. Product Details of 852445-84-2 The article mentions the following:
In view of their intensive use as ligands in many reactions catalyzed by transition-metal complexes, modulation of the bonding properties of N-heterocyclic carbenes (NHCs) on a rational basis is highly desirable, which should enable optimization of current applications or even promote new functions. In this paper, we provide a quant. anal. of the chem. bond between a metal fragment AuCl and a series of 29 different NHCs in [(NHC)AuCl] complexes. NHCs electronic properties are modified through: (i) variation of the groups attached to the NHC nitrogen atoms or backbone; (ii) change of unsaturation/size of the NHC ring; (iii) inclusion of paracyclophane moieties; or (iv) heteroatom substitution on the NHC ring. For evaluating the donation and back-donation components of the Dewar-Chatt-Duncanson (DCD) model in the NHC-AuCl bond, we apply the charge-displacement (CD) anal. within the NOCV (natural orbitals for chem. valence) framework, a methodol. that avoids the constraint of using symmetrized structures. We show that modulation of the NHC bonding properties requires substantial modification of their structure, such as, for instance, insertion of two ketone groups into the NHC backbone (which enhances the π back-donation bond component and introduces an effective electronic communication within the NHC ring) or replacement of a nitrogen atom in the ring with an sp3 or sp2 carbon atom (which increases and decreases the π back-donation bond component, resp.). We extend our investigation by quant. comparing the NHC electronic structures for a subset of 13 NHCs in [(NHC)PPh] adducts, the 31P NMR chem. shift values of which are exptl. available. The latter have been considered as a suitable tool for measuring the NHCs π acceptor properties [Bertrand et al., Angew. Chem. Int. Ed. 2013, 52, 2939-2943]. We show that information obtained using the metal fragment can be transferred to the PPh moiety and vice versa. However, the 31P NMR chem. shift values only qual. correlate with the π acceptor properties of the NHCs, with the stronger π acidic carbenes as the most outliners. The results came from multiple reactions, including the reaction of Chloro{1,3-bis[2,6-bis(1-methylethyl)phenyl]-4,5-dihydroimidazol-2-ylidene}gold(I)(cas: 852445-84-2Product Details of 852445-84-2)
Chloro{1,3-bis[2,6-bis(1-methylethyl)phenyl]-4,5-dihydroimidazol-2-ylidene}gold(I)(cas: 852445-84-2) belongs to imidazoles.Although other azole heterocycles are ubiquitous in a wide range of biologically active natural products, imidazole rings occur predominantly in the natural amino acid histidine. Product Details of 852445-84-2 In addition, imidazole rings are part of unnatural cyclic peptides and are used as ester isosteres in peptidomimetic studies.
Referemce:
Imidazole – Wikipedia,
Imidazole | C3H4N2 – PubChem