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
CAS Number	824-11-3 Y
3D model (JSmol)	Interactive image
ChemSpider	12655 N
ECHA InfoCard	100.011.385
EC Number	212-523-3
PubChem CID	13210
UNII	1ND7080ZYD Y
CompTox Dashboard (EPA)	DTXSID10871809
InChI 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
SMILES O1P2OCC(CC)(C1)CO2
Properties
Chemical formula	C6H11O3P
Molar mass	162.125 g·mol−1
Appearance	white waxy solid
Melting point	56 °C (133 °F; 329 K)
Solubility in water	organic solvents
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). N verify (what is YN ?) 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.

Safety

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