CHAPTER 16. Noncovalent Interactions in Ionic Liquids

Ionic liquids (ILs) exhibit a wide range of noncovalent (NC) interactions, coulombic, van der Waals, H-bonding, halogen bonding and π interactions, giving rise to polar, lipophilic and fluorous domains. ILs also exhibit a variety of unique features and a high level of complexity in a single liquid environment. In this chapter, an understanding of the underlying NC interactions within ILs is developed. Catalysis in ILs is a well-established and diverse field, the IL normally playing the role of solvent, but the IL can also be an additive or the catalyst. The prevalence of NC interactions within ILs leads to NC interactions playing an important role in catalytic mechanisms and reactivity. Selected cases from the literature are used to highlight specific examples. However, in many cases the focus of reports on catalysis in ILs is on the performance and products and not on the mechanistic details. The range of interactions possible can make unravelling the effect of an IL on a reaction very difficult. The purpose of this chapter is to build a robust understanding of the NC interactions that occur between catalyst and IL, with the aim of being better able to conceptualize a potential mechanism.