A TRIVALENT VANADIUM MONOPHOSPHATE WITH A TUNNEL STRUCTURE - CD3V4(PO4)6

A new vanadium(III) monophosphate, Cd3V4(PO4)6, has been isolated and its structure has been determined from single-crystal X-ray diffractio n data. It crystallizes in the monoclinic space group C2/c with a = 12 .446(1) angstrom, b = 12.547(1) angstrom, c = 6.487(1) angstrom, and b eta = 115.66-degrees(1). The three-dimensional framework [V4P6O24]infi nity is built from bi-octahedral V2O10 units linked through monophosph ate groups. It can be described as the stacking of [V2P2O12]infinity l ayers, parallel to (100) connected through layers of PO4 tetrahedra. T he [V2P2O12]infinity layers are themselves formed of [VPO8]infinity ch ains running along c, connected through the comers of their polyhedra and the edges of the VO6 octahedra alternately. This structure forms s mall tunnels running along [001], [110], and [110BAR], where the cadmi um ions are located with distorted octahedral and trigonal prismatic c oordinations. In fact, the [Cd3V4P6O24]infinity framework forms large empty tunnels running along [001]. (C) 1994 Academic Press, Inc.