Isolation and characterization of a two-coordinate phosphinidene oxide

Nitroso compounds, R–N=O, are common intermediates in organic synthesis, and are typically amenable to storage and manipulation at ambient temperature under aerobic conditions. By contrast, phosphorus-containing analogues, such as R–P=O (R = OH, CH3, OCH3, Ph), are extremely reactive and need to be studied in inert gas matrices at ultralow temperatures (3–15 K). These species are believed to be key intermediates in the degradation/combustion of organic phosphorus compounds, a class of chemicals that includes chemical warfare agents and flame retardants. Here we describe the isolation of a two-coordinate phosphorus(III) oxide under ambient conditions, enabled by the use of an extremely bulky amine ligand. Reactivity studies reveal that the phosphorus centre can be readily oxidized, and that in doing so, the P–O bond remains intact, an observation that is of interest to the proposed reactivity of transient phosphorus(III) oxides. Phosphinidene oxides are intermediates in the combustion of organic phosphorus compounds; however, they are highly unstable and their observation requires ultralow temperatures. Now it has been shown that a combination of steric bulk and electronic stabilization enables the isolation and manipulation of a two-coordinate phosphorus(III) oxide compound at room temperature.