Abstract: The reaction between phosphorus oxychloride and bifunctional alkoxy Grignard reagents gives stable pentacoordinate magnesium phosphoranoxides, such as 9. The less basic of these, the fluoro-substituted anion of 9, is not protonated by aqueous ammonium chloride and is isolated as a crystalline salt. Protonation of the phosphoranoxide anions of 4 and 9 gives hydroxyphosphoranes 6 and 10. While 6 equilibrates in solution with its open- ...