Tris(2-aminoethyl)amine

Tris(2-aminoethyl)amine is the organic compound with the formula N(CH2CH2NH2)3. This colourless liquid is soluble in water and is highly basic, consisting of a tertiary amine center and three pendant primary amine groups. Abbreviated tren, it is the archetypal tripodal ligand of interest in coordination chemistry.

Tris(2-aminoethyl)amine
Names
IUPAC name
N,N-Bis(2-aminoethyl)-1,2-ethanediamine
Other names
  • 2,2′,2′′-Nitrilotriethylamine
  • 2,2′,2′′-Triaminotriethylamine
  • TAEA
Identifiers
3D model (JSmol)
1739626
ChEBI
ChEMBL
ChemSpider
ECHA InfoCard 100.021.689
EC Number
  • 223-857-4
27074
MeSH Tris(2-aminoethyl)amine
RTECS number
  • KH8587082
UN number 2922
Properties
C6H18N4
Molar mass 146.238 g·mol−1
Appearance Colorless liquid
Odor Ichtyal, ammoniacal
Density 0.976 g/mL (20 °C)[1]
Melting point −16 °C (3 °F; 257 K)
Boiling point 265 °C (509 °F; 538 K)
Miscible
log P −2.664
Vapor pressure 3 Pa (at 20 °C)
1.497[1]
Thermochemistry
Std enthalpy of
formation (ΔfH⦵298)
 −74.3–−72.9 kJ mol−1
Std enthalpy of
combustion (ΔcH⦵298)
 −4860.6–−4859.2 kJ mol−1
Hazards
Safety data sheet fishersci.com
GHS pictograms
GHS Signal word Danger
GHS hazard statements
 H301, H310, H314
P280, P302+350, P305+351+338, P310
Flash point 113 °C (235 °F; 386 K)
Lethal dose or concentration (LD, LC):
  • 117 mg kg−1 (dermal, rabbit)
  • 246 mg kg−1 (oral, rat)
Related compounds
Related amines
Related compounds
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

Tren is a C3-symmetric, tetradentate chelating ligand that forms stable complexes with transition metals, especially those in the 2+ and 3+ oxidation states. Tren complexes exist with relatively few isomers, reflecting the constrained connectivity of this tetramine. Thus, only a single achiral stereoisomer exists for [Co(tren)X2]+, where X is halide or pseudohalide.[2] In contrast, for [Co(trien)X2]+ five diastereomers are possible, four of which are chiral. In a few cases, tren serves as a tridentate ligand with one of the primary amine groups non-coordinated. Tren is a common impurity in the more common triethylenetetramine ("trien"). As a trifunctional amine, tren forms a triisocyanate when derivatized with COCl2.

Structures of trigonal bipyramidal and octahedral complexes of the formulae M(tren)X (left, C3v symmetry) and M(tren)X2 (right, Cs symmetry).

N-methylated trens

The permethylated derivative of tren has the formula N(CH2CH2NMe2)3. "Me6tren" forms a variety of complexes but, unlike tren, does not stabilize Co(III). Related amino-triphosphines are also well developed, such as N(CH2CH2PPh2)3 (m.p. 101-102 °C). This species is prepared from the nitrogen mustard N(CH2CH2Cl)3.[3]

N,N,N-trimethyltren, N(CH2CH2NHMe)3 is also available.[4]

Safety considerations

(H2NCH2CH2)3N, like other polyamines, is corrosive.[5] It causes severe skin burns and eye damage, is harmful if inhaled due to the destruction of respiratory tissues, is toxic if swallowed, and can be fatal in contact with skin. Its median lethal dose is 246 mg/kg, oral (rat), and 117 mg/kg, dermal (rabbit). It is also combustible.[6]

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References
  1. "Tris(2-aminoethyl)amine". Sigma-Aldrich.
  2. Donald A. House "Ammonia & N-donor Ligands" in Encyclopedia of Inorganic Chemistry John Wiley & Sons, 2006. doi:10.1002/0470862106.ia009.
  3. R. Morassi, L. Sacconi "Tetradentate Tripod Ligands Containing Nitrogen, Sulfur, Phosphorus, and Arsenic as Donor Atoms" Inorganic Syntheses 1976, vol. 16 p. 174-180. doi:10.1002/9780470132470.ch47
  4. Schmidt, H.; Lensink, C.; Xi, S. K.; Verkade, J. G. (1989). "New Prophosphatranes: Novel intermediates to five-coordinate phosphatranes". Zeitschrift für Anorganische und Allgemeine Chemie. 578: 75–80. doi:10.1002/zaac.19895780109.
  5. The Physical and Theoretical Chemistry Laboratory Oxford University MSDS
  6. "Safety Data Sheet". Sigma-Aldrich. July 1, 2014. Retrieved April 7, 2019.
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