Syntheses and rearrangements of tris(hydroxymethyl)phosphine and tetrakis(hydroxymethyl)phosphonium salts

Abstract

Tetrakis(hydroxymethyl)phosphonium (HOCH₂)₄P⁺ salts, particularly the chloride (THPC) and sulfate (THPS), are among the most accessible organophosphorus compounds that can be made quantitatively from PH₃ and formaldehyde in aqueous media under ambient conditions. These phosphonium salts are air-stable, and are widely used as reactants in organic syntheses, as well as in textile or oil industries. Synthesis of tris(hydroxymethyl)phosphine (THP), an active component of the salts, is more complicated because direct synthesis from PH₃ and CH₂O requires either pressure and high temperature, at which THP rearranges into bis(hydroxymethyl)methylphosphine oxide, CH₃P(O)(CH₂OH)₂, or a metal catalyst that is usually difficult or impossible to recover. Syntheses of THP based on neutralization of the salts are more convenient but require pH control and additional steps to separate THP from CH₂O. This review summarizes literature data on syntheses and purification of the salts and THP, and side reactions such as thermal rearrangement and oxidation.

Graphical Abstract

Keywords:

• Hydroxymethyl phosphines
• water-soluble phosphines
• rearrangement
• autoxidation

Acknowledgments

We are indebted to Drs. Yulia B. Malysheva and Elena A. Zaburdaeva from the Nizhniy Novgorod State University, and Dr. Vladmir Malakhov from Ludwig-Maximilians-Universität München, for their help in the literature search.

Additional information

Funding

This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.