BAV2P2O10, A NEW TETRAVALENT VANADIUM PHOSPHATE WITH A TUNNEL STRUCTURE

A new vanadium (IV) phosphate, BaV2P2O10, with a tunnel structure has been isolated. Its structure was solved by single crystal X-ray diffraction. It crystallizes in the monoclinic system with the space group P21c. The cell parameters are a = 5.2204(3), b = 9.1702(7), c = 16.3247(9)Å; β = 92.757(5)°; V = 780.6(3)Å3; Z = 4; Dm= 3.93(6); Dx = 3.92; R = 0.031 and Rw = 0.035 for 4039 unique reflections with I > 3σ(I). The three-dimensional framework [V2P2O10∞ can be described as the assemblage of [P2VO9 rows formed of VO5 pyramids and PO4 tetrahedra, linked to each other through VO6 octahedra. The existence of [V2O10 units involving one VO5 pyramid and one VO6 octahedron, already observed in other V(IV) phosphates is also considered, as well as the existence of [V2P2O14 units corresponding to the association of one [V2O10 unit with two PO4 tetrahedra and which allow the whole structure to be described. This host lattice delimits large elliptic tunnels running along a where double rows of barium cations are located. The particular coordination of vanadium (IV), which corresponds to the existence of vanadyl ion as well in VO5 pyramids, as in VO6 octahedra (coordination "5 + 1") is emphasized. © 1992 Academic Press, Inc.