Tris(2-aminoethyl)amine

Synthesis

In a 2000 mL glass reactor, 120.5 g of nickel hydroxide and 146.2 g of tris(2-aminoethyl)amine were added to 2000 mL of H₂O. The solution was stirred at 50°C for 8.5 h. Excess nickel hydroxide was removed by centrifugation (30 min, 4400 rpm). The solution was recovered by decantation to obtain the title compound tris(2-aminoethyl)amine. The exact concentration of nickel was determined by inductively coupled plasma optical emission spectrometry (ICP-OES). The synthetic route is shown in Figure

Figure: Synthetic Route of Tris(2-aminoethyl)amine

Chemical Properties

Colorless liquid

Uses

Tris(2-aminoethyl)amine is a tetradentate chelating ligand and forms stable complexes with transition metals. It is also used as a carbon dioxide absorbent. Further, it acts as a reagent for cleavage of the fluorenylmethyloxycarbonyl (Fmoc) group in peptide synthesis. It reacts with aryl isocyanates and isothiocyanates to give tris-urea and -thiourea derivatives.

Definition

ChEBI: Tris(2-aminoethyl)amine is a tetramine.

General Description

Tris(2-aminoethyl)amine (TREN) is a water soluble tripodal ligand that is majorly used in co-ordination chemistry. It has three aminoethylgroups that attach with the surface atoms to provide a scaffold assembly.

Reactivity Profile

Tris(2-aminoethyl)amine (tren) is a commercially available tripodal amine, which has found wide application as a ligand in the preparation of metal complexes. Due to the tripodal arrangement of donor atoms, tren and various N-functionalised derivatives have been commonly employed in the preparation of trigonal bipyramidal metal complexes. More elaborate or extended tren ligands have been formed via substitution or condensation reactions with aldehydes. Metal complexes prepared therefrom have been employed in catalysis and oxygen binding studies. They have also been used to stabilise redox active oxoanions, such as thiosulfate, and to prepare cyano-bridged heteropolynuclear clusters with ferromagnetic properties. Less well explored are aryl-substituted tren ligand structures. However, some have been employed in the formation of transition metal amido complexes, which have been demonstrated to act as catalysts in dinitrogen reduction (Mo V and Cr complexes) and which have been tested in alkene epoxidation reactions (Fe and Mn complexes). Aryl-substituted tren-based ligands are generally synthesised via aryl substitution reactions using commercially available ArF compounds in 28– 99% yields. A different pathway to these aryl-substituted tren compounds involves Pd-mediated aromatic coupling, limited to commercially available ArBr compounds, affording the products 27–90% yields. More extended tren structures have been prepared via a two-step synthesis of the starting ArBr compound followed by Pd-mediated aromatic coupling in lower but acceptable overall yields of 36–45%. Given the versatility and demonstrated utility of these ligands, considerable benefit would be derived from new synthetic strategies that would broaden the range of accessible aryl-substituted tren ligands[2].

Hazard

A poison by ingestion and skin contact.

Safety Profile

A poison by ingestion and skin contact. When heated to decomposition it emits toxic vapors of NOx.

Purification Methods

For a separation from a mixture containing 62% TRIEN, see entry under triethylenetetramine. Also purify it by conversion to the hydrochloride (see below), recrystallise it and regenerate the free base [Xie & Hendrickson J Am Chem Soc 109 6981 1987]. [Beilstein 4 H 256, 4 II 695, 4 III 545, 4 IV 1250.]

References

[1] Bengang Zhang. “Highly Branched Tannin-Tris(2-aminoethyl)amine-Urea Wood Adhesives.” Polymers 15 4 (2023).
[2] Ann Almesker . “One-pot synthesis of tripodal tris(2-aminoethyl)amine derivatives from seven molecular components.” Tetrahedron Letters 50 16 (2009): Pages 1847-1850.