Ionic liquids of superior thermal stability. Validation of PPh 4 + as an organic cation of impressive thermodynamic durability.

Recent work by Wasserscheid, et al. suggests that PPh 4 + 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 PPh 4 + -based cations incorporating methyl, methylene, or methine C-H bonds burn away at high temperatures in the presence of oxygen, forming CO, CO 2 , and water, leaving behind the parent ion PPh 4 + . The latter then undergoes no further reaction, at least below 425 °C.