Chlorometallate(iii) ionic liquids as Lewis acidic catalysts – a quantitative study of acceptor properties

Abstract

The Gutmann Acceptor Number (AN), which is a quantitative measure of Lewis acidity, has been estimated using the (31)P NMR chemical shift of a probe molecule, triethylphosphine oxide, for a range of chlorometallate(III) ionic liquids, based on Group 13 metals (aluminium(III), gallium(III) and indium(III)) and the 1-octyl-3-methylimidazolium cation, at different compositions. The results were interpreted in terms of extant speciation studies of chlorometallate(III) ionic liquids, and compared with a range of standard molecular solvents and acids. The value of these data were illustrated in terms of the selection of appropriate ionic liquids for specific applications.

Elucidation of inorganic reaction mechanisms in ionic liquids: the important role of solvent donor and acceptor properties

“…The fundamental discrepancy between our ANs and the hydrogen-bond-donation ability, either expressed by the Kamlet-Taft-α value or by the HBD value, could originate from the completely different probe molecules and measurement techniques used for the determination of the ANs, α-and HBD-values. Seddon et al 43 already stated, "it must be remembered that a Lewis acidity scale can never be universal, and will depend on, inter alia, the nature of the probe molecule". Therefore, a detailed comparison requires a much larger set of data, most suitably also for ILs with different cations, to obtain a better view of the overall picture and closer insight into the cation dependence of the AN and α, and also the DN and β.…”

Lewis Superacidic Ionic Liquids with Tricoordinate Borenium Cations

“…[16,17] Borenium ionic liquids were prepared via a solventless procedure, analogous to that used for chlorometallate ionic liquids. [18] [19,20] In contrast, higher chlorogallate(III) anion homologues are known, [20,21] so gallium(III) chloride was used in 1-3 mol ratio.…”

“…The method is well established in Lewis acidity studies of both borenium cations [7,22] and of ionic liquids. [18,20] Unambiguous results could only be obtained for systems with N-donors, because the 31 P NMR signals from tepo (used in 1-3% quantity) were obscured by signals from the P888 ligand. AN values were calculated based on the signal originating from [BCl2L(tepo)] + (Table 2).…”

“…With three moles of GaCl3, a second signal appeared (δ31P 1%tepo = 93±1 ppm; AN = 118±1), at a slightly higher value than that reported for chlorogallate(III) ionic liquids with [Ga3Cl10] -anion (AN = 107). [18] Figure 2. 31 Comparing the AN values (Figure 3), for systems with pyridine-based donors (py, 3pic, 4pic), the same pattern was observed, with acidity dependent both on the molar ratio of MCl3, and on the metal (Al or Ga).…”

Diethyldisulfoammonium chlorometallates as heterogeneous Brønsted–Lewis acidic catalysts for one‐pot synthesis of 14‐aryl‐7‐(N‐phenyl)‐14H‐dibenzo[a,j]acridines

“…The anionic composition determines the properties of chlorometallates which again depend on the types of metal chloride and the ratios of metal chloride to parent organic chloride. [3][4][5] The various developments of such ionic salts over the last two decades have recognized these chlorometallates/halometallates as functional materials with unique and useful properties including photophysical, magnetic, catalytic and semiconducting properties [6][7][8] The catalytic performances of these chlorometallates were examined for the three-component synthesis of novel 14-aryl-7-(N-phenyl)-14H-dibenzo[a,j]acridine derivatives (1) from the reaction of an equimolar mixture of 2-naphthol, N-phenyl-2-naphthylamine and aromatic aldehyde under solvent-free conditions at 100°C. The benzoacridine derivatives have a wide range of pharmacological activities such as antitumour, antiviral, antimicrobial, antimalarial, analgesic and anti-inflammatory activities.…”