Phosphaalkene

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title: "Phosphaalkene" type: doc version: 1 created: 2026-02-28 author: "Wikipedia contributors" status: active scope: public tags: ["organophosphanes", "functional-groups", "unsaturated-compounds"] topic_path: "general/organophosphanes" source: "https://en.wikipedia.org/wiki/Phosphaalkene" license: "CC BY-SA 4.0" wikipedia_page_id: 0 wikipedia_revision_id: 0

::figure[src="https://upload.wikimedia.org/wikipedia/commons/b/b9/Mesityldiphenylmethylenephosphine-from-xtal-1986-3D-balls.png" caption="[[Ball-and-stick model]] of mesityldiphenylmethylenephosphine, a phosphaalkene"] ::

Phosphaalkenes (IUPAC name: alkylidenephosphanes) are organophosphorus compounds with double bonds between carbon and phosphorus(III) with the formula R2C=PR. In the compound phosphorine one carbon atom in benzene is replaced by phosphorus. The reactivity of phosphaalkenes is often compared to that of alkenes and not to that of imines because the HOMO of phosphaalkenes is not the phosphorus lone pair (as in imines the amine lone pair) but the double bond. Therefore like alkenes, phosphaalkenes engage in Diels-Alder reactions and Wittig and Cope rearrangements.

The first phosphaalkene discovered was a phosphabenzene, by Mërkl in 1969. The first localized phosphaalkene was reported in 1976 by Gerd Becker as a keto-enol tautomerism akin a Brook rearrangement: ::[[Image:Becker Reaction.svg|300px|Becker reaction to phosphaalkenes (R = [[methyl]] or [[phenyl]])]] Becker's method continues to see use in, e.g., a phosphorus analogue to poly(para-phenylene vinylene): ::[[Image:Poly(p-phenylenephosphaalkene).svg|800px|Poly(p-phenylenephosphaalkene)]].

In 1976, Harold Kroto also established spectroscopically that thermolysis of Me2PH generates CH2=PMe. A general method for the synthesis of phosphaalkenes is by 1,2-elimination of suitable precursors, initiated thermally or by base such as DBU, DABCO or triethylamine:Synthesis of mesityldiphenylmethylenephosphine: a stable compound with a localized phosphorus:carbon bond T. C. Klebach, R. Lourens, F. Bickelhaupt J. Am. Chem. Soc., 1978, 100 (15), pp 4886–4888 ::[[Image:PhosphaalkeneGeneral.png|400px|Phosphaalkene general method]]

The reduction or oxidation of phosphaalkenes can produce radical phosphorus ions.

References

References

  1. ''Bildung und Eigenschaften von Acylphosphinen. I. Monosubstitutionsreaktionen an substituierten Disilylphosphinen mit Pivaloylchlorid'' Gerd Becker, Zeitschrift für anorganische und allgemeine Chemie '''1976''', 423, pp 242 - 254
  2. ''Phosphorus Copies of PPV: π-Conjugated Polymers and Molecules Composed of Alternating Phenylene and Phosphaalkene Moieties'' Vincent A. Wright, Brian O. Patrick, Celine Schneider, and Derek P. Gates [[J. Am. Chem. Soc.]]; '''2006'''; 128(27) pp 8836 - 8844; (Article) {{doi. 10.1021/ja060816l

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organophosphanesfunctional-groupsunsaturated-compounds