Zhai F, Xin T, Geeson MB, Cummins CC. Sustainable Production of Reduced Phosphorus Compounds: Mechanochemical Hydride Phosphorylation Using Condensed Phosphates as a Route to Phosphite.
ACS CENTRAL SCIENCE 2022;
8:332-339. [PMID:
35350608 PMCID:
PMC8949633 DOI:
10.1021/acscentsci.1c01381]
[Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/09/2021] [Indexed: 05/07/2023]
Abstract
In pursuit of a more sustainable production of phosphorous acid (H3PO3), a versatile chemical with phosphorus in the +3 oxidation state, we herein report that condensed phosphates can be employed to phosphorylate hydride reagents under solvent-free mechanochemical conditions to furnish phosphite (HPO3 2-). Using potassium hydride as the hydride source, sodium trimetaphosphate (Na3P3O9), triphosphate (Na5P3O10), pyrophosphate (Na4P2O7), fluorophosphate (Na2PO3F), and polyphosphate ("(NaPO3) n ") engendered phosphite in optimized yields of 44, 58, 44, 84, and 55% based on total P content, respectively. Formation of overreduced products including hypophosphite (H2PO2 -) was identified as a competing process, and mechanistic investigations revealed that hydride attack on in-situ-generated phosphorylated phosphite species is a potent pathway for overreduction. The phosphite generated from our method was easily isolated in the form of barium phosphite, a useful intermediate for production of phosphorous acid. This method circumvents the need to pass through white phosphorus (P4) as a high-energy intermediate and mitigates involvement of environmentally hazardous chemicals. A bioproduced polyphosphate was found to be a viable starting material for the production of phosphite. These results demonstrate the possibility of accessing reduced phosphorus compounds in a more sustainable manner and, more importantly, a means to close the modern phosphorus cycle.
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