Imidazolium Hydroxides and Catalysis

Abstract

This chapter focuses on imidazolium hydroxides and their role in various catalytic transformations as one of the most studied classes of the ionic liquids (ILs). It outlines approaches to the synthesis of these salts and their effect on the properties and identity of the resultant material, given how strongly impurities are intertwined with IL chemistry generally and imidazolium hydroxide in particular. The synthesis of imidazolium hydroxides has been conducted through conventional ion metathesis from the corresponding imidazolium halide salt in an organic solvent, the use of an anion exchange resin, or a combination of both methods. Imidazolium hydroxides have clearly been shown to be useful for a range of catalytic transformations, both as a solvent and diluted by another solvent. Nonetheless, the inherent instability of these compounds is currently underreported and casts doubt on the active catalytic species, particularly the role of carbenes, and the actual identity of the material used for many of the investigations.