Halides quaternary ammonium halide hydrates

It is worth noting, in passing, that Mootz s work is predated by that of G. A. Jeffrey and coworkers who, in a series of papers [669, 670], have described an extensive series of quaternary ammonium halide hydrates with low-melting points. A number of these have been structurally characterised, but as they melt to give liquids that are not conprised solely of ions (indeed, they are aqueous solutions), they are only briefly mentioned in the following text. 

In the case of Type 1 and 11 eutectics the potential window is limited at high potentials by chlorine gas evolution and at low potentials by the metal ion reduction with metal deposition from the melt. Type I eutectics have been prepared using Zn, Sn, Fe, Al, Ge and Cu chlorides. Their reduction potential is shifted towards more electronegative values as the metal halide is closer by Lewis acid. Because the reduction potential is associated with Lewis acidity, the corresponding proportions of metal and quaternary ammonium salts affect the potential window. Type 11 eutectics have been developed in order to extend the range of metals able to be electrodeposited from ionic liquids and Cr electrodeposition with good characteristics has been reported (Abbott et al., 2004 Abbott et al., 2004 Benaben Sottil, 2006). Hydration water plays a significant role on the stability and fluidity of choline chloride based ionic liquids. In this case water behaviour is different compared to the case of aqueous electrolytes and the potential window is limited rather by the metallic species... 

Moreover, both aliphatic and aromatic unactivated alkynes can be hydrated with a catalyst generated from PtCl4 and CO at 40-110°C. This powerful catalyst is able to operate under homogeneous conditions in wet THF or, under phase-transfer conditions, in CHCI3/H2O in the presence of a quaternary ammonium salts [127, 128]. The active species is a Pt(II) compound [PtH(CO)Cl(L)] (L = CO, H2O, THF) and the reaction mechanism parallels that reported for platinum(II) halides and Zeise s catalyst. The reactions work with internal and terminal alkynes, following in the latter case the Markovnikov rule. Scarce reproducibility and erratic yields are the main drawbacks in these reactions. 

---