Reversible, Room-Temperature Ionic Liquids. Amidinium Carbamates Derived from Amidines and Aliphatic Primary Amines with Carbon Dioxide

摘要

Interest in ionic liquids (ILs), especially room-temperature ionic liquids (RTILs), has increased enormously during the past decade because, among other applications, they may be used to replace less environmentally friendly ("green") solvents. Supercritical carbon dioxide has also been employed as a green solvent, although it requires specialized equipment and reaction vessels. Here, we report a new class of solvents which can be cycled between a RTIL state and a non-ionic solvent by exposing the liquid mixtures sequentially to 1 atm of carbon dioxide and molecular nitrogen (Scheme 1). These systems obviate the necessity of employing specialized equipment, including maintaining absolutely dry atmospheres, and offer the distinct advantage of creating environments which can be made either to dissolve or phase separate solutes and added liquid components depending on their polarity.