Tris(hydroxymethyl)phosphine

Tris(hydroxymethyl)phosphine is the organophosphorus compound with the formula P(CH₂OH)₃. It is a white solid. The compound is multifunctional, consisting of three alcohol functional groups and a tertiary phosphine. It is prepared by treating tetrakis(hydroxymethyl)phosphonium chloride with strong base:^[2][3]

[P(CH₂OH)₄]Cl + NaOH → P(CH₂OH)₃ + H₂O + H₂C=O + NaCl

Tris(hydroxymethyl)phosphine

Identifiers
CAS Number	2767-80-8 Y
3D model (JSmol)	Interactive image
ChEMBL	ChEMBL279546
ChemSpider	68500
ECHA InfoCard	100.018.587
EC Number	220-445-6
PubChem CID	76001
UNII	Y6TG7WF7OQ
CompTox Dashboard (EPA)	DTXSID0062634
InChI InChI=1S/C3H9O3P/c4-1-7(2-5)3-6/h4-6H,1-3H2 Key: JMXMXKRNIYCNRV-UHFFFAOYSA-N
SMILES C(O)P(CO)CO
Properties
Chemical formula	C3H9O3P
Molar mass	124.076 g·mol−1
Appearance	white solid
Density	1.16 g/cm3
Melting point	51–53 °C (124–127 °F; 324–326 K)
Boiling point	decomposes
Solubility in water	alcohols, dmf
Hazards
GHS labelling:[1]
Pictograms
Signal word	Danger
Hazard statements	H301, H315, H318, H335
Precautionary statements	P261, P264, P264+P265, P270, P271, P280, P301+P316, P302+P352, P304+P340, P305+P354+P338, P317, P319, P321, P330, P332+P317, P362+P364, P403+P233, P405, P501
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Infobox references

The compound can be prepared on a large scale using triethylamine as base and as solvent.^[4]

Reactions

The compound forms complexes with a variety of metals. These complexes display some solubility in water but more so in methanol.^[4] The compound decomposes violently to phosphine and formaldehyde upon attempted distillation. In air, it oxidizes to the oxide.

Upon heating with hexamethylenetetramine, it converts to the water-soluble ligand 1,3,5-triaza-7-phosphaadamantane (PTA).^[5][6]

Tris(hydroxymethyl)phosphine can also be used to synthesize the heterocycle, N-Boc-3-pyrroline by ring-closing metathesis using Grubbs' catalyst (bis(tricyclohexylphosphine)benzylidineruthenium dichloride). N-Boc-diallylamine is treated with Grubbs' catalyst, followed by tris(hydroxymethyl)phosphine. The carbon-carbon double bonds undergo ring closure, releasing ethene gas, resulting in N-Boc-3-pyrroline.^[2] The hydroxymethyl groups on THPC undergo replacement reactions when THPC is treated with α,β-unsaturated nitrile, acid, amide and epoxides. For example, base induces condensation between THPC and acrylamide with displacement of the hydroxymethyl groups. (Z = CONH₂)

[P(CH₂OH)₄]Cl + NaOH + 3CH₂=CHZ → P(CH₂CH₂Z)₃ + 4CH₂O + H₂O + NaCl

Similar reactions occur when THPC is treated with acrylic acid; only one hydroxymethyl group is displaced, however.^[7]