Liquid chlorocuprates

Of interest is the use of this system as both solvent and reactant in a voltaic cell. If two platinum gauze electrodes are immersed in liquid chlorocuprates and a potential is applied, the cell begins charging- At less than 1/of full charge, the potential stabilizes at 0.85 V and remains at that value until the cell is fully charged. The half-reactions for charging are... 

These features can be exploited in synthesis and catalysis. Acidic ionic liquids have proved to be particularly useful as they strip away halide ligands attached to catalysts thereby generating coordinatively unsaturated species that are more reactive towards the substrates. Ionic liquids based on chlorocuprates are prepared in a similar manner from the direct reaction of... 

It is of course essential that the ionic liquid is stable in the presence of the oxidant, which excludes ionic liquids with metallic anions such as chlorocuprates. In many oxidation reactions water is present as co-solvent, reagent or it is produced in the course of the reaction, which further eliminates the use of chloroaluminates. However, less care has to be taken with respect to drying the ionic liquid compared to other catalytic reactions when aqueous oxidants are used. Common imidazolium and ammonium based ionic liquids are neither water-nor oxygen sensitive and thus well suited and may even act as co-catalyst in the oxidation reaction. Some anions like [BF4] and [PF6] are, however, susceptible towards hydrolysis. Where the ionic liquid is highly viscous, a co-solvent such as dichloromethane might be necessary to afford acceptable reaction rates, especially when molecular oxygen is used as reagent. 

Chlorocuprate based ionic liquids have also been quite widely studied.20 Like the chloroaluminates they also contain a complex mixture of anions that include species such as [CuCl2], [Cu2Cl3r and [Cu3Cl4]. ... 

Room Temperature Fused Salts Liquid Chlorocuprates(I)... 

Tn studies of copper(I) coordination about 12 years ago (I), Yoke and co-workers observed that the crystalline solids copper(I) chloride and triethylammonium chloride react quickly when brought into contact to produce a light green oil. The oil is quite oxygen sensitive, and it was assumed that the compound triethylammonium dichlorocuprate(I) had been formed which was liquid because of the low lattice energy inherent to the bulky cation. Many previous preparations of polyalkylammonium chlorocuprates (2, 3, 4, 5), however, had yielded only crystalline solids. Consequently, the unusual liquid nature of the system inspired structural studies and the synthesis of comparable compounds. 

Our preliminary examination of these two applications seems to confirm the molten-salt interpretation of the liquid chlorocuprate(I) structure. There may be circumstances in which this property may find other application, or in which a liquid copper (I) compound might be useful in organic syntheses designed to use a solid copper(I) halide as a reductant or hydride acceptor see Refs. 14 and 15 and the references cited therein). Our aim in presenting this report is to encourage others to take advantage of this series of inorganic compounds with an unusual property. 

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