DEDICATED TO PROFESSOR J. M. HONIG (V IV O) 2 (H 2 O){O 3 P+(CH 2 ) 3 +PO 3 } ' 2H 2 O was hydrothermally synthesized from a mixture of VOSO 4 ' 5H 2 O : H 2 PO 3 + (CH 2 ) 3 +PO 3 H 2 : H 2 O in a molar ratio 1 : 0.5 : 250 and heated for 72 hours to 1703C. Its structure was determined from powder X-ray di4raction data. It crystallizes in the orthorhombic space group Immm (No. 71) with a ؍ 16.8210(5) A s , b ؍ 9.3790(3) A s , c )2(8654.7؍ A s , V ؍ 1176.4(1) A s 3 , Z ؍ 4. The pillared framework is built up from inorganic layers covalently linked via P+C+C+C+P bonds. The inorganic layers are similar to those encountered in a VO(HPO 4 ) ' 0.5H 2 O bidimensional compound described previously. The dimers of face-shared VO 5 (H 2 O) octahedra are linked by PO 3 C phosphonate groups instead of PO 3 (OH) groups in the vanadyl hydrogenphosphate. The terminal hydroxyl groups in the latter are substituted by the carbons of the organic chains which link two layers, giving the threedimensional character of the structure. The magnetic behaviors of the two compounds are compared.