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 derivatives 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 gives dimethyl phenylphosphonite:

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". doi:10.1351/goldbook.P04565
  3. T. V. (Babu) Rajanbabu “Phosphinite and Phosphonite Ligands” in Phosphorus(III) Ligands in Homogeneous Catalysis: Design and Synthesis Paul C. J. Kamer and Piet W. N. M. van Leeuwen, Eds., John Wiley & Sons 2012. doi:10.1002/9781118299715.ch5
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