Hydrogen/Deuterium‐Exchange Reactions of Methane with Aromatics and Cyclohexane Catalyzed by a Nanoscopic Aluminum Chlorofluoride

Abstract

H/D-exchange reactions between methane and deuterated solvents such as [D 6 ]benzene and [D 12 ]cyclohexane were heterogeneouslyc atalyzed by nanoscopic aluminum chlorofluoride (ACF = AlCl x F 3Àx , x % 0.05-0.3) under very mild conditions. 13 CNMR spectroscopy experiments at labeled methane revealed the formationo fa ll isotopologues. AlCl 3 ,A lBr 3 ,H S-AlF 3 , g-Al 2 O 3 ,a nd g-Al 2 O 3 preheated at 700 8Cd id not show any H/D-exchange reactionofmethane or [D 6 ]benzene. Mechanistically,e lectrophilic activation of methane was suggesteda tt he ACF surface.

Theoretical Study on the Lewis Acidity of the Pristine AlF3 and Cl-Doped α-AlF3 Surfaces

“…In the past two decades, metal fluoride catalysts, especially high-surface aluminium fluoride, HS-AlF 3 and amorphous ACF (aluminiumchlorofluoride, AlCl x F 3−x , x = 0.05−0.3), have shown high activity in several reactions such as C-H and C-F bond activation or hydroarylation reactions [1][2][3][4][5][6]. In selected reactions, these catalysts show comparable activity with the homogeneous catalyst SbF 5 [2].…”

“…In the past two decades, metal fluoride catalysts, especially high-surface aluminium fluoride, HS-AlF 3 and amorphous ACF (aluminiumchlorofluoride, AlCl x F 3−x , x = 0.05−0.3), have shown high activity in several reactions such as C-H and C-F bond activation or hydroarylation reactions [1][2][3][4][5][6]. In selected reactions, these catalysts show comparable activity with the homogeneous catalyst SbF 5 [2]. To get more insight into the chemistry of these heterogenous catalysts, the Lewis acidity of the active sites, which describes their potential to bind to electron rich compounds, can be compared [7].…”

“…In different experimental investigations, the Lewis acidity of milled α-AlF 3 , β-AlF 3 , high-surface AlF 3 (HS-AlF 3 ) and ACF were previously determined by the adsorption of CO and the corresponding IR spectra (see Table 1) [2,3,17,18]. Additionally Bailey et al [19,20] performed theoretical studies at four-and fivefold coordinated aluminium centres of the β-AlF 3 (001), α-AlF 3 -(0001) and α-AlF 3 -(01 12) surfaces with adsorbed CO, which show blue shifts comparable to the available experimental values.…”

A HF Loaded Lewis‐Acidic Aluminium Chlorofluoride for Hydrofluorination Reactions

“…Among them, aluminium chlorofluoride (ACF, AlCl x F 3− x , x= 0.05–0.3, patented by Dupont) is of high interest, in part because of its large surface area and high Lewis acidity, which is comparable to the one of SbF 5 . Its properties and reactivity have been intensely investigated, showing that a variety of reactions can be mediated . For instance, H/D or Cl/F exchange reactions were reported at ACF .…”

“…Its properties and reactivity have been intensely investigated, showing that a variety of reactions can be mediated . For instance, H/D or Cl/F exchange reactions were reported at ACF . In the presence of a hydrogen source, such as triethylsilane and triethylgermane, hydrodehalogenation, or dehydrohalogenation of C−F bonds or C−Cl bonds were achieved .…”