phosphine oxides

https://doi.org/10.1351/goldbook.P04552

Compounds having the structure R₃P=O↔︎ R₃P⁺–O⁻ (analogously, phosphine imides and phosphine sulfides).

See: imides

Source:
PAC, 1995, 67, 1533. 'Use of immunoassays for the analysis of pesticides and some other organics in water samples (Technical Report)' on page 1537 (https://doi.org/10.1351/pac199567081533)