CYPHOS® Phosphonium Ionic Liquids

Chemfiles Volume 5 Article 6

The phosphonium cation, with the generic formula [PR3R]+ and with a judicious selection of the appropriate anion, forms many phosphonium salts that are liquid at room temperature and many have melting points below 100 °C.

Phosphonium-based Ionic Liquids offer the following advantages:

  • Phosphonium salts are thermally more stable than the corresponding ammonium salts and imidazolium salts. This is very important for processes which operate at temperatures higher than 100 °C (e.g., removal of reaction products by distillation). Furthermore, prevention of contaminations by decomposition products is a prerequisite for multiple recycle use of solvents.
  • Phosphonium cations lack acidic protons. Thus, they are stable under basic conditions, which can be problematic for several imidazolium-based Ionic Liquids (carbene formation).
  • Phosphonium salts are, in general, less dense than water, which might be beneficial in product work-up steps.

Sigma-Aldrich offers, in collaboration with Cytec Industries, Inc., a new class of Ionic Liquids based on phosphonium cations.

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  1. Bradaric, C. J.; Downard, A.; Kennedy, C.; Robertson A. J.; Zhou, Y. Green Chem. 2003, 5, 143

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