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General ester of phosphonous acid
Not to be confused with phosphinite (formula P(OR)R2).

Phosphonites are organophosphorus compounds with the formula P(OR)2R. They are found in some pesticides and are used as ligands.[1]


Although they are derivivatives of phosphonous acid (RP(OH)2),[2] they are not prepared from such precursors. Phosphonites are prepared by alcoholysis of organophosphinous chlorides. For example, treatment of dichlorophenylphosphine with methanol and base give methyl diphenylphosphonite:

Cl2PPh + 2 CH3OH → (CH3O)2PPh + 2 HCl


Oxidation of phosphonites gives phosphonates:

2 P(OR)2R + O2 → 2 OP(OR)2R

Phosphonites can function as ligands in homogeneous catalysis.[3]


  1. ^ D. E. C. Corbridge "Phosphorus: An Outline of its Chemistry, Biochemistry, and Technology" 5th Edition Elsevier: Amsterdam 1995. ISBN 0-444-89307-5.
  2. ^ IUPAC, Compendium of Chemical Terminology, 2nd ed. (the "Gold Book") (1997). Online corrected version:  (2006–) "phosphonous acids".
  3. ^ Detlef Selent, Klaus-Diether Wiese, Dirk Röttger, Armin Börner "Novel Oxyfunctionalized Phosphonite Ligands for the Hydroformylation of Isomeric n-Olefins" Angewandte Chemie International Edition 2000, vol. 39, pp. 1639–1641.