N‐Heterocyclic Carbenes with a Nido‐C₂B₉ Carborane Backbone

Abstract

Main observation and conclusion The steric and electronic properties of N‐heterocyclic carbenes (NHCs) can be modified by the exocyclic substituents at the nitrogen atoms, by 1—3 atoms’ replacements of the five‐membered imidazolium skeleton and by the changes of the backbones. Herein, we report the usage of nido‐C2B9 carborane anions as the backbones of NHCs. Stirring the mixture of secondary amino o‐carboranes (1b—1e), triethyl orthoformate and HBF4∙Et2O results in the unexpected cage‐opening of o‐carboranes to afford the nido‐C2B9 carborane anions supported N‐heterocyclic carbene precursors (4b—4e). Deprotonation of 4b with sodium hexamethyldisilazide at −78 oC affords the N‐heterocyclic carbene ligand, which was used to form an Au(I) NHC complex (5). DFT calculations revealed a high‐lying lone pair orbitals of the carbene ligands, predicting their strong σ‐donating abilities.

A 12-Vertex Metallacarborane of Silver(I)

“…Both of them made metallacarborane of Ag the most difficult to synthesize in this group. In an ongoing project, we detailed the synthesis of nido -C 2 B 9 carborane anion-supported N -heterocyclic carbene, elucidating its transformation into gold–NHC complexes. Additionally, we explored its conversion into nickelacarborane-supported bis-NHCs and their corresponding complexes.…”

Nickelacarborane-Supported Bis-N-heterocyclic Carbenes

“…They have emerged as a privileged class of ligands owing to their ability to stabilize diverse transition metal complexes, nanoparticles, or main-group elements, thus exhibiting an extensive range of applications across the chemical sciences . This ever-growing success is primarily attributed to their distinctive stereoelectronic properties, which can be easily modulated by changing the heterocyclic backbone or exocyclic substituents at the nitrogen atoms . These strategies have resulted in a significant alteration in the electronic properties of the carbene unit.…”

Anionic N-heterocyclic carbenes featuring weakly coordinating perfluoroalkylphosphorane moieties

“…40,43,44 Beside II, only few examples of other WCA-NHCs are known. [45][46][47][48][49][50][51][52] Especially noteworthy are carboranyl-functionalized NHCs developed by Lavallo and coworkers, which contain one or two anionic {closo-1-CB 11 } or {closo-1-CB 9 } clusters attached via C cluster -N imidazole bonds to the imidazole ring. [48][49][50][51] However, dianionic WCA-NHCs with two very weakly coordinating, i.e.…”