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.
Preparation and reactions It is prepared by reaction of trimethylolpropane with phosphorus trichloride or by transesterification with trimethylphosphite:Verkade, J. G. "Spectroscopic studies of metal-phosphorus bonding in coordination complexes" Coordination Chemistry Reviews 1972, vol. 9, 1-106. P(OMe)3 + EtC(CH2OH)3 → 3 MeOH + EtC(CH2O)3P The first member of this series was derived from trimethylolethane,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. but these derivatives are often poorly soluble. For this reason, the ethyl derivative has received more attention.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.
Reactions The compound forms an isolable ozonide, which degrades above 0 °C to release singlet O2.
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.).Ralf Stöhr et al. Chemische Kampfstoffe und Schutz vor chemischen Kampfstoffen 2. Aufl. Militärverlag der DDR, 1985 (german)
References