Halometallate Salts

Only a few recent examples of halogen bonding of halogenated TTFs with halometallate anions have been described and this most probably represents a broad development field in this area. Indeed, these halometallate salts offer a wide variety of complexes and specifically here a large variation of the ratio of anion charge vs number of halide atoms, as already discussed above in the comparison between Br and 13 salts. This point is illustrated by the superb structures of two salts of EDT-TTF-I2 with the polymeric one-dimensional PbV (Fig. 9) and two-dimensional (Pbs/eDi/eh) anions where shorter C -1- -Ianion contacts are observed with the linear Pbl3 chains... 

Solubility of metal salts in ILs is extremely important in electrodeposition. In this section, the solubility of metal salts in air stable ILs is summarized. The solubility of metal salts in halometalate type ILs has been summarized in previous reports [90, 91]. In addition, many IL systems have been reported as electrolytes for lithium-ion secondary batteries. Some metal salts were reported to be soluble above 50 mol%. However, these systems were obtained by mixing ILs with metal salts in organic solvent or water followed by removal of the solvent this may produce supersaturated solutions. In this section, these systems are omitted due to space limitations. 

Impurities are a lot less problematic for eutectic-based ionic liquids. The strong acid-base nature of these systems leads to predominantly halometallate species which tend to be unaffected by simple salts or other impurities such as water. The strong Lewis acids and bases coordinate well to water and even in the chloroa-luminate systems low amounts of water do not significantly affect voltammetric behavior or have a deleterious effect on deposit morphology. 

The ability of halometallates [38-40] (as well as cyano [41, 42] and thiocyanato [19] analogs) to act as halogen bond acceptors has been extensively explored [43], particularly by Brammer et al., and several series of salts with halo-pyridinium cations as halogen bond donors were reported. 

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