The literature contains few references to the reactions of phosphonate esters with iron salts. Guilbaultet al.1recently studied the infrared spectrs of diisopropyl methylphosphonate (DIMP) and dimethyl methylphosphonate (DIMP) chemisorbed on solid FeCl3and made infrared band assignments. We wish to report the results of a study of the products of the homogeneous reaction of DIMP, DMMP and diethyl ethylphosphonate (DEEP) with ferric chloride. On the basis of elemental analysis and infrared absorption data, the products isolated were identified as tris (methylmethylphosphonate) iron (III), tris (ethyl ethylphosphonate) iron (III), and tris (isopropyl methylphosphonate) iron (III).