Trimethylolpropane phosphite

Trimethylolpropane phosphite, C2H5C(CH2O)3P, is a phosphite ester used as a ligand in organometallic chemistry. Trimethylolpropane phosphite is sometimes abbreviated to EtCage. It is a white solid that is soluble in organic solvents. It is also highly toxic.[1]

Trimethylolpropane phosphite
Names
Preferred IUPAC name
4-Ethyl-2,6,7-trioxa-1-phosphabicyclo[2.2.2]octane
Other names
EtCage; Ethyl bicyclic phosphite; Trishydroxymethylpropane bicyclic phosphite
Identifiers
3D model (JSmol)
ChemSpider
ECHA InfoCard 100.011.385
EC Number
  • 212-523-3
UNII
  • InChI=1S/C6H11O3P/c1-2-6-3-7-10(8-4-6)9-5-6/h2-5H2,1H3 ☒N
    Key: QRUSNTDXJQBKBI-UHFFFAOYSA-N ☒N
  • InChI=1/C6H11O3P/c1-2-6-3-7-10(8-4-6)9-5-6/h2-5H2,1H3
    Key: QRUSNTDXJQBKBI-UHFFFAOYAD
  • O1P2OCC(CC)(C1)CO2
Properties
C6H11O3P
Molar mass 162.125 g·mol−1
Appearance white waxy solid
Melting point 56 °C (133 °F; 329 K)
organic solvents
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

Preparation and reactions

It is prepared by reaction of trimethylolpropane with phosphorus trichloride or by transesterification with trimethylphosphite:[2]

P(OMe)3 + EtC(CH2OH)3 → 3 MeOH + EtC(CH2O)3P

The first member of this series was derived from trimethylolethane,[3] but these derivatives are often poorly soluble. For this reason, the ethyl derivative has received more attention.[4]

Reactions

The compound forms an isolable ozonide, which degrades above 0 °C to release singlet O2.[1]

Coordination chemistry

Several EtCage complexes are known, since the ligand is highly basic (for a phosphite) and has a small ligand cone angle (101°). Illustrative complexes include [(EtCage)2Mo(CO)4], [Ir4(CO)11(EtCage)] and (CpMe5)RuCl(EtCage)2, shown below.

Ball-and-stick model of the bis(trimethylolpropane phosphite)molybdenum tetracarbonyl complex Ball-and-stick model of the (trimethylolpropane phosphite)tetrairidium undecacarbonyl cluster

Safety

Trimethylolpropane phosphite is very toxic and is a convulsant. LD50 is 1.1 mg per kg bodyweight (mice, i.p.).[5][6]

References
  1. Ende, Christopher; Parker, Kathlyn (2014). "4-Ethyl-2,6,7-trioxa-1-phosphabicyclo[2.2.2]octane". e-EROS Encyclopedia of Reagents for Organic Synthesis. pp. 1–3. doi:10.1002/047084289X.rn01781. ISBN 9780470842898.
  2. Verkade, J. G. "Spectroscopic studies of metal-phosphorus bonding in coordination complexes" Coordination Chemistry Reviews 1972, vol. 9, 1-106. doi:10.1016/S0010-8545(00)80224-6
  3. Verkade, J. G.; Reynolds, L. T. "The synthesis of a novel ester of phosphorus and of arsenic" Journal of Organic Chemistry (1960), 25, 663-5. doi:10.1021/jo01074a622
  4. Huttemann, T. J., Jr.; Foxman, B. M.; Sperati, C. R.; Verkade, J. G. "Transition metal complexes of a constrained phosphite ester. IV. Compounds of cobalt(I), cobalt(III), nickel(II), and nickel(0)" Inorganic Chemistry (1965), 4(7), 950-3. doi:10.1021/ic50029a005
  5. Ralf Stöhr et al. Chemische Kampfstoffe und Schutz vor chemischen Kampfstoffen 2. Aufl. Militärverlag der DDR, 1985 (german)
  6. Milbrath, Dean S.; Engel, Judith L.; Verkade, John G.; Casida, John E. (1979). "Structure-toxicity relationships of 1-substituted-4-alkyl-2,6,7-trioxabicyclo[2.2.2.]octanes". Toxicology and Applied Pharmacology. 47 (2): 287–93. doi:10.1016/0041-008X(79)90323-5. PMID 452023.
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