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Norimasa Yoza, Miki Okamatsu, Noriko Tokushige, Tohru Miyajima, Yoshinobu Baba, Nucleophilic Substitution Reactions between Diphosphonate and Orthophosphate Characterized by High-Performance Liquid Chromatography and 31P NMR Spectroscopy, Bulletin of the Chemical Society of Japan, Volume 64, Issue 1, January 1991, Pages 16–20, https://doi.org/10.1246/bcsj.64.16
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Abstract
Inorganic diphosphonate with phosphorus of an oxidation number +3 was found to react with orthophosphate (oxidation number +5) at 50 °C to give phosphonylated compounds; dimeric isohypophosphate (oxidation numbers +3 and +5) and a novel trimeric compound (oxidation numbers +3 and +5). Orthophosphate ion is considered to act as a ligand with two or three nucleophilic sites that were phosphonylated stepwise by diphosphonate. Kinetic processes of the nucleophilic reactions were monitored by HPLC and 31P NMR. Two products, the dimer having one P–H bond and the trimer with two P–H bonds, were well-resolved by HPLC and their yields, based on orthophosphate applied, were 85% (dimer) and 3% (trimer) when a mixed solution of 0.5 M diphosphonate and 0.1 M orthophosphate was incubated at 50 °C for 21 h. A complicated 31P NMR spectrum that indicated a large coupling constant(JPH=650 Hz) and grew with incubation time is reasonably assigned to the unsymmetrical isohypophosphate composed of both a phosphate group and a phosphonate group. Apparent formation constants of the dimer and trimer were evaluated.