SYNTHESIS AND CRYSTAL-STRUCTURE OF A TUBULAR HYDROXYPHOSPHITE - ZN11-SQUARE(HPO3)8(OH)6

Zn11□(HPO3)8(OH)6 is hexagonal, space group P63mc, Z = 1, a = 12.872(1) Å, c = 4.9772(4) Å; R = 0.030 for 986 reflections from single-crystal X-ray diffraction data. This compound is unexpectedly isotypical with A3 Te2O6(OH)2 (A = Co, Ni) and related to that of dumortierite. It is built up from zigzag (pyroxene-like) octahedra-edge-shared chains which fuse by face-sharing to form double chains. Connection of these double chains by corner sharing of octahedra builds an open tridimensional framework delimiting two kinds of channels running parallel to c. The smaller channels are occupied by 2/8 of the HPO3 groups. On the walls of the largest tunnels are connected the remaining HPO3 groups, with their hydrogen atoms pointing toward the tunnel center, forming an unusual infinite chain of empty [H6] octahedra sharing faces along the c axis. Comparison with the tellurates and the dumortierite structures is given. © 1993 Academic Press, Inc.