Tetrakis (Hydroxymethyl)Phosphonium Chloride for Crosslinking Polyethylenimine (PEI) to Improve Metal Ion Extraction

In memorium to my friend, the Professor M.A. Didi deceased in traffic accident in Oran (Algeria) on the 17 january 2023.

Abstract : Tetra (Hydroxymethyl) Phosphinium chloride (THPC) in aqueous solution wasobtained by A. Hoffman (1928) by reacting phosphine with hydrochloric formaldehyde solution¹. THPC is commercially available as a textile flamme retardant agent². It has been used in organometallic chemistry for the synthesis of aminomethylphosphines such as 3,5-triaza-7-phosphaadamantane (PTA), a water-soluble ligand of transition metal.

We previously showed that phosphonic PEIs obtained by the Irani reaction are metal ion complexing agents³. We first studied the reaction of THPC with piperidine⁴ as model of amine. In a second step, we used THPC for PEI crosslinking. THPC easily generate aminomethylphosphine or aminomethylphosphine oxide groups after hydrogen peroxide treatment into the PEI, improving the coordination properties of PEI to metal ions.

The synthesis of PEI crosslinked with aminomethylphosphine oxide groups was described and characterized by spectroscopy (IR,NMR). The metal extraction was tested on large variety metal ions. (Cu+2, Co+2, Fe+3, Sm+3, La+3, Ce+4...)

References :

1. A. Hoffman, J. Amer. Chem. Soc., 1921, 43, 1684 ; 1930, 52, 2995.

2 E.D. Weil, S.V. Levchik, J. Fire Sci. 2008, 26 (3): 243–281.

3.D. Villemin, C. Monteil, N. Bar, M. A. Didi, Phosphorous, Sulfur Silicone 2015, 190, 879-890

4. A. Jullien, Ph D thesis, University of Caen, 16 dec. 2004.