Reaction of N-heterocyclic carbene (NHC) with different HF sources and ratios – A free fluoride reagent based on imidazolium fluoride.

Treatment of N-heterocyclic carbene (1,3-Bis(2,6-diisopropylphenyl)-1,3-dihydro-2H-imidazol-2-ylidene; (L Dipp )) with different sources of hydrofluoric acid (Et 3 N∙3HF, anhydrous hydrofluoric acid and KHF 2 ) in 1:1, 1:2, 1:3 ratios affords [(L Dipp )H] + [F] − ( 1 ), [(L Dipp )H] + [(HF)F] − ( 2 ) and [(L Dipp )H] + [(HF) 2 F] − ( 3 ) salts respectively. Different fluoride sources all yield the same products, but ease of manipulation and isolation can influence the choice in the future use. Compound ( 1 ), which shows characteristics of a free fluoride reagent, can be obtained with good yield and without the contaminants usually present in such compounds. All products were characterized by X-Ray crystallography, NMR spectroscopy and free fluoride (F f − ) chemical analysis. [ABSTRACT FROM AUTHOR]