Salts and Ionic Liquids of Resonance Stabilized Amides

Abstract

The synthesis, structure, and bonding of alkali salts of resonance stabilized amides, such as diformylamide (dfa), formylcyanoamide (fca), nitrocyanoamide (nca), and for comparision, the well-known dicyanoamide (dca), are discussed on the basis of experimental and theoretical data. The first structural reports of K(18-crown-6)+dfa-, K(18-crown-6)+fca-, Na+nca-, and Li(TMEDA)+dca- are presented. Examination of the X-ray data reveals almost planar anions with strong cation-anion interactions resulting in network-like structures in the solid state. For comparison, the X-ray structures of covalently bound phenyldicyanoamide and diformamide are also discussed. The thermal behavior of the alkali salts of these amides is studied by thermoanalytical experiments. Moreover, several novel ionic liquids based on resonance stabilized amides have been prepared and were fully characterized, namely the dfa, fca, and nca salts of EMIM (1-ethyl-3-methyl-imidazolium), BMIM (1-butyl-3-methyl-imidazolium), and HMIM (1-hexyl-3-methyl-imidazolium). Most of them are liquid at room temperature, except BMIM+fca- that melts at 32 degrees C. These ionic liquids are neither heat nor shock sensitive, are thermally stable up to over 200 degrees C, and can be prepared easily in large quantities.

Crystal structure of ammonium triiodide – N-formyl-formamide (1:1), NH4I3 · C2H3NO2

“…Ammonium triiodide N-formyl-formamide adduct is an ew example of ac ompound containing N-formylformamide as neutral molecule. The bond lengths and angles agree very well with those found for the free acid [3]. …”

“…In contrast, only recently, in course of their investigations on resonance stabilized amides, the crystal structure determination, DFT calcualtions and vibrational spectroscopy analysis of diformamide and one of its complex alkali metal salts were published [3]. Ammonium triiodide N-formyl-formamide adduct is an ew example of ac ompound containing N-formylformamide as neutral molecule.…”

Chemical Variants of the Dicyanamide Anion, and a Landscape for Basic and Superbasic Ionic Liquids

“…The preparation of the ionic liquid 1-butyl-3-methyl imidazolium diformylamide, BMIM-DFA, using a solution route, has been reported previously. 33 Elsewhere, 20 we have given a simple thermodynamic route to the assignment of pK a values for well-known anhydrous acids, and bases, on the water scale, and only those results will be used in this paper. The metathetical reaction that produces the new ionic liquid is…”

Pseudo Halide Chemistry in Ionic Liquids with Decomposable Anions

“…Syntheses of pseudohalide‐containing ionic liquids (IL) are usually carried out in biphasic systems, in which different solubilities of salts are utilized, or via salt metathesis reactions, in which a highly insoluble salt (often a silver halide) precipitates . Incomplete cation exchange and dissolved traces of metal halides in the ionic liquid are known problems for this synthetic route.…”

“…[6] Syntheses of pseudohalide-containing ionic liquids (IL) [7] are usually carried out in biphasic systems, in which different solubilities of salts are utilized, or via salt metathesis reactions, in which a highly insoluble salt (often a silver halide) precipitates. [8][9][10][11][12][13] Incomplete cation exchange and dissolved traces of metal halides [14] in the ionic liquid are known problems for this synthetic route. In addition, long drying times at elevated temperatures are necessary to remove residual water or solvents, often resulting in darkening of the ionic liquid caused by traces of decomposition products.…”