Salts composed of ortho-phosphite anions have been produced through the mechanochemical reduction of phosphate compounds. Scientists emphasize the synthetic adaptability of ortho-phosphite, rendering it a viable substitute for the hazardous and combustible white phosphorus, which is presently the primary precursor for numerous phosphorus compounds.
Numerous phosphorus oxyanions are known, such as phosphate (PO₄³⁻) and phosphite (HPO₃²⁻). However, the ortho-phosphite (PO₃³⁻) anion—characterized by a central phosphorus atom bonded to three singly charged oxygen atoms—has proven hard to obtain, even though it is frequently used as a reference in Lewis structures within educational settings.
A team of researchers in the US has addressed this deficiency by fabricating various group 1 ortho-phosphite salts, thus expanding the catalog of heavier group 15 trioxyanions already identified.
Utilizing ball milling of phosphate sources with sodium, potassium, or caesium salts for durations of up to 36 hours resulted in a blend of reduced phosphorus species. Solid-state NMR and Raman spectroscopy identified significant peaks for the ortho-phosphite anion, closely aligning with calculated predictions. Consequently, it was demonstrated that ortho-phosphite salts represented a principal element of the mixture, together with phosphate, hypophosphate (P₂O₆⁴⁻), and phosphide (P³⁻) compounds.
The hydrolysis of ortho-phosphite produced phosphite, a valuable phosphorylating agent. The reaction of the crude mixture with trimethylsilyl chloride yielded tris(trimethylsilyl)phosphite, which serves as a precursor to various organophosphorus compounds. While efforts to alkylate ortho-phosphite succeeded, isolating the products from the mixture was challenging, resulting in low yields.
Researchers assert that the versatility of ortho-phosphite as a reagent may enable chemists to synthesize valuable organophosphorus compounds without resorting to white phosphorus, which remains the conventional reagent. The team is now advancing the synthesis of ortho-phosphite and investigating the complete range of its reactivity.