Phosphonium ionic liquids (PhosILs), most notably tetradecyl(trihexyl)phosphonium decanoate (PhosIL-C
9H
19COO), are solvents for bases such as Grignard reagents, isocyanides, Wittig reagents (phosphoranes),and
N-heterocyclic carbenes (NHCs). The stability of the organometallic species in PhosIL solution isanion dependent. Small bases, such as hydroxide, react with the phosphonium ions and promote C-Hexchange as suggested by deuterium-labeling studies. A method to dry and purify the ionic liquids isdescribed and this step is important for the successful use of basic reagents in PhosIL. NHCs have beengenerated in PhosIL, and these persistent solutions catalyze organic transformations such as the benzoincondensation and the
Kumada-Corriu cross-coupling reaction. Phosphoranes were generated in PhosIL,and their reactivity with various organic reagents was also tested. Inter-ion contacts involvingtetraal
kylphosphonium ions have been assessed, and the crystal structure of [(
n-C
4H
9)
4P][CH
3CO
2·CH
3CO
2H] has been determined to aid the discussion. Decomposition of organometallic compounds mayalso proceed through electron-transfer processes that,
inter alia, may lead to decomposition of the IL,and hence the electrochemistry of some representative phosphonium and imidazolium ions has beenstudied. A radical derived from the electrochemical reduction of an imidazolium ion has been characterizedby electron paramagnetic resonance spectroscopy.
