A new bimetallic selenite compound, Cd(VO 2 ) 4 (SeO 3 ) 3 ' H 2 O, with vanadium and cadmium metals was synthesized from hydrothermal reactions of V 2 O 5 , Cd(NO 3 ) 2 ' 2H 2 O, and SeO 2 in water at 2303C. This compound crystallizes in a triclinic unit cell with the space group P1 (No. 2) and the lattice parameters a ؍ 6.2999(4) A > , b ؍ 7.4078(4) A > , c ؍ 15.7525(9) A > , ؍ 100.881(1)3, ؍ 98.796(1)3, ؍ 93.690(1)3, V ؍ 710.14(7) A > 3 , Z ؍ 2. The crystal structure was determined by X-ray singlecrystal di4raction techniques and was re5ned with R ؍ 0.0336 and wR 2 ؍ 0.0819 for all 3175 re6ection data. The structure can be described as layers with pillars between the layers. The layer is composed of dimers of VO 5 square pyramids and dimmers of CdO 7 decahedra connected to one another by sharing corner and/or edge oxygen atoms, and the pillars are composed of VO 6 distorted octahedra connected to one another with capping SeO 2؊ 3 selenite groups. The coordination number of Cd atom in the structure shows a rare example of hepta-coordination with only oxygen donor atoms 2001 Academic Press