Ionic liquids reactive methods

A further important aspect is how to handle reactive elements It was found in the Clausthal group that nanocrystalline aluminum and nanoscale silicon made in 1-butyl-l-methylpyrrolidinium bis(trifluoromethylsulfonyl)amide react even with the comparably low level of oxygen (<1 ppm) in an inert gas glove box. Under air the deposit can be oxidized on the time scale of a few days. Maybe in situ passivation methods will have to be developed. One could think about deposition of a reactive element in an ionic liquid, washing off the ionic liquid, followed by passivation in a different liquid. 

The Suzuki-Miyaura cross-coupling reaction is a standard method for carbon-carbon bond formation between an aryl halide or triflate and a boronic acid derivative, catalyzed by a palladium-metal complex. As with the Mizoroki-Heck reaction, this cross-coupling reaction has been developed in ionic liquids in order to recycle and reuse the catalyst. In 2000, the first cross-coupling of a halide derivative with phenylboronic acid in [bmim] [BF4] was described. As expected, the reaction proceeded much faster with bromobenzene and iodobenzene, whereas almost no biphenyl 91 was obtained using the chloride derivative (Scheme 36). The ionic liquid allowed the reactivity to be increased, with a turnover number between 72 and 78. Furthermore, the catalyst could be reused repeatedly without loss of activity, even when the reaction was performed under air. Cross-coupling with chlorobenzene was later achieved - although with only a moderate yield (42%) - using ultrasound activation. 

The other concern relating to the use of supported systems is that they are often, but not always, slower to react than their solution counterparts. This can be problematic, but can often be overcome by a number of methods. An obvious way to enhance reactivity is by improving the surface topology of the supported material. The use of focused microwaves, ultrasound, or novel solvents such as ionic liquids, or indeed combinations of these can also be useful in increasing reactivity and reaction rates. ... 

Detailed kinetic investigations of the reaction of cumene with propene in [C2mim]Cl—AICI3 (X(AlCl3) = 0.67) were conducted by Joni et al. in a liquid-liquid biphasic reaction mode [24]. Various products (di-, tri- and tetraisopropylbenzene) result from a series of consecutive alkylation reactions. It is necessary to take the solubility of these products into account to fit kinetic models to the data. A conductor-like screening model for real solvent (COSMO-RS) method was used to predict the relative solubilities of the products. Higher alkylated products are less soluble in the reactive ionic liquid phase, leading to an irtproved selectivity for the monoalkylated product. 

Ab initio MD methods are certain to gain popularity as computational power grows, but they are presently too expensive to use to obtain quantitative estimates of properties. Quantum MD is most useful for computing spectra, for helping validate and improve classical force fields, and for studying reactivity in ionic liquids, something classical simulations cannot do. 

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