[reaction: see text] Hydroxy-pentaoxy-phosphoranes are transient intermediates formed during the hydrolysis of various phosphoesters. Kinetic analyses support the existence of such compounds, although they are not isolated. In an attempt to create a stable example, 2 equiv of a ligand possessing a very high effective molarity were attached to a central phosphorus. Instead of obtaining a hydroxyphosphorane, analysis by (31)P and (19)F NMR spectroscopy and X-ray crystallography showed the product to be a phosphotriester. The reason for this is discussed.