Synthesis and crystal structure of Ba[V2(HPO4)4](H2O)

A new vanadium(III) phosphate, Ba[VIII2(HPO4)4](H2O), has been synthesized by hydrothermal methods, and its structure solved by single-crystal X-ray diffraction. This vanadium phosphate crystallizes in the monoclinic system, space group P21. The cell parameters are a = 9.441(2), b = 7.913(2), c = 9.521(2) Å; β = 117.91(2)°; V= 628.5(3)Å3; Z = 2; Dcalc = 3.387 mg mm−3; R = 0.055 and Rw = 0.065 for 1885 reflections with F > 6.0σ(F). The threedimensional [V2(HPO4)4(H2O)]2− lattice can be described as being built up of chains of eight-membered rings along the c axis, formed by corner-shared VO6 octahedra and HPO4 tetrahedra (-V-O-P-O-), which are crosslinked via interchain V-O-P bonding to produce a three-dimensional lattice. The crosslinking interaction produces 16-membered rings. Contrary to other low-valent vanadium phosphates, cavities are found in the solid,rather than tunnels. The Ba2+ and H2O are located in these cavities.