Halides ionic

For all research carried out with commercial ionic liquids we recommend a serious quality check of the product prior to work. As already mentioned, a good commercial ionic liquid may be colored and may contain some traces of water. However, it should be free of organic volatiles, halides (if not an halide ionic liquid), and all ionic impurities. 

The charged species were in all cases found to concentrate at the surface of the liquid under vacuum conditions. Little surface separation of the anions and cations was observed. For the [PFg] and [BFJ ions, the cation ring was found to prefer a perpendicular orientation to the surface, with the nitrogen atoms closest to the surface. An increase in the alkyl chain length caused the cation to rotate so that the alkyl chain moved into the bulk liquid, away from the surface, forcing the methyl group closer to the surface. For halide ionic liquids, the data were less clear and the cation could be fitted to a number of orientations. 

The transition states (27) calculated at the B3LYP/6-31+-l-G and B3LYP/6-31G levels of theory for the alkylation of 1-methylimidazole (26) by alkyl bromides and chlorides, forming imidazolium halide ionic liquids (28),110 had a hydrogen bond between the incipient halide ion and the hydrogen on C(2) of the substrate. 

Most simple halides, ionic or covalent, melt unchanged on heating. Crystal defects have been identified as being important in the decompositions of C0F3 [48] and Cdlj [49]. Barret [50] studied the decomposition of CuBrj - CuBr + /2BT2 and discussed the role of diffusion within the mass of reactant particles on the overall kinetic behaviour. HF.LiF and HF.NaF decompose [51] before melting, in a single... 

Purification of halide ionic melts from oxide-ion admixtures... 

Scheme 7.1. Synthes is of 1,3-diall

Many ionic liquids, including the still widely used tetrafluoroborate and hexaflu-orophosphate systems, are synthesized in a two-step synthesis. In the first step a nucleophile, such as a tertiary amine or phosphine, is alkylated to form the cation. For this reaction alkyl halides are frequently used as alkylating agents, forming the halide salts of the desired cation. To obtain a non-halide ionic liquid, the halide anion is exchanged in a second reaction step. This can either be realized by addition of the alkali salt of the desired anion (with precipitation of the alkali halide salt) or by reaction with a strong acid (with removal of the corresponding hydrohalic... 

In this context it should be noted that there is quite a difference between an ionic liquid made in a metathesis step from a halide ionic Hquid, with subsequent removal of residual halide by washing, and one where no alkyl halide was involved during the course of its synthesis. 

The authors of this study demonstrated that similar species, along with an unidentified one, were present during the Mizoroki-Heck reaction. It was proved that isolated trans-90 behaved as an efficient catalyst for this reaction. Finally, when [bmim] [BF4] was used as the starting material, no palladium carbene complex was obtained. This observation might explain why Mizoroki-Heck reactions proceed more quickly in halide ionic liquids than in non-coordinating ones such as PFe salts. Ultrasound-promoted formation of carbene palladium complexes can also allow their in situ preparation at room temperature. ... 

Direct evidence for toe stabilisation of carbenium ions formed from simple olefins on zeolitic Broensted sites is not extensive. Comparison of bands in toe uv-vis spectra for olefins, and their oligomeric products, sorbed in acid zeolites wito bands for appropriate carbenium ions, in acid solution, provides su[ rt for the existoice of carbenium-ion surface species. A recent pqrer describes a UV-vis study using aromatics as basic probes. In toe presence of strxHig Broensted acids or of Lewis acid/hydrogen halides, ionic complexes wito aromatics may be formed as shown below. 

Gaseous alkali metal halides ionic bonds... 

GASEOUS ALKALI METAL HALIDES IONIC BONDS... 

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