TETRAHEDRAL-ATOM 3-RING GROUPINGS IN 1-DIMENSIONAL INORGANIC CHAINS - BE2ASO4OH.4H2O AND NA2ZNPO4OH.7H2O

The hydrothermal syntheses and X-ray single-crystal structures of Be2AsO4OH.4H2O and Na2ZnPO4OH.7H2O, two phases which contain 3-ring groupings of tetrahedra as part of 1-dimensional chains Of MXO4 (M = Zn, Be; X = P, As) groups, are reported. MAS NMR and TGA data are reported for these phases, and the structures of these two materials are briefly compared with those of some other known extended tetrahedral species. Crystal data for Be2AsO4OH.4H2O (BAO): M(r) = 246.01; monoclinic, space group P2(1)/a, with a = 7.2349(8) angstrom, b = 12.686(2) angstrom, c = 8.6546(9) angstrom, and beta = 98.439(3)degrees; Z = 4. Final residuals of R = 4.49% and R(w) = 4.79% were obtained for 2333 observed reflections [I > 3sigma(I)]. BAO contains 1-dimensional stacks of interconnected BeO4 and AsO4 tetrahedra, including alternating 4-rings and 3-rings, the latter ring system containing Be-(OH)-Be bonds. The tetrahedral columns are held together by water molecules, via a network of H-bonds. Crystal data for Na2ZnPO4-OH.7H2O (NZPO): M(r) = 349.43; monoclinic, space group P2(1)/a, with a = 6.4212(6) angstrom, b = 21.612(2) angstrom, c = 8.6813(6) angstrom, and beta = 109.899(3)degrees; Z = 4. R = 5.85% and R(w) = 5.61% for 2654 observed reflections [I > 3sigma(I)]. NZPO also contains 1-dimensional tetrahedral stacks (ZnO4 and PO4 moieties) made up only of 3-rings which include Zn-(OH)-Zn connections. Adjacent stacks are interconnected via a complex arrangement of sodium cations and water molecules.