Ionic liquids of superior thermal stability. Validation of PPh4+ as an organic cation of impressive thermodynamic durability

Abstract

Recent work by Wasserscheid, et al. suggests that PPh₄⁺ is an organic molecular ion of truly exceptional thermal stability. Herein we provide data that cements that conclusion: specifically, we show that aliphatic moieties of modified PPh₄⁺-based cations incorporating methyl, methylene, or methine C–H bonds burn away at high temperatures in the presence of oxygen, forming CO, CO₂, and water, leaving behind the parent ion PPh₄⁺. The latter then undergoes no further reaction, at least below 425 °C.