(Ni-3-Mg-x(x))[B3P3O12(OH)(6)] center dot 6 H2O (x approximate to 1.5): A novel borophosphate-hydrate containing isolated six-membered rings of tetrahedra

A novel borophosphate-hydrate, (Ni3-xMgx)[B3P3O12(OH)(6)] . 16H(2)O (x appr oximate to 1.5), has been prepared by hydrothermal synthesis (T = 170 degre esC) from a mixture of NiCl2 . 6H(2)O, Mg(OH)(2), B2O3 and H3PO4. The cryst al structure was determined at 293 K from single-crystal X-ray diffraction data (trigonal, R(3) over barc (no.167), a = 14.957(10) Angstrom, c = 13.81 2(6) Angstrom, V = 2676(2) Angstrom (3), Z = 6, R-1 = 0.0276, wR(2) = 0.071 4 for 779 observed reflections with I > 2 sigma (I)). The crystal structure contains unbranched six-membered rings [B3P3O12(OH)(6)](6-) of alternating corner linked borate and phosphate tetrahedra, which are stacked along [00 1] and connected via (MO2)-O-II(OH)(2)(H2O)(2) coordination polyhedra. Hydr ogen bonding between the tetrahedral six-membered rings and (MO2)-O-II(OK)( 2)(H2O)(2) octahedra leads to a further cross-linking. With respect to the arrangement of isolated six-membered tetrahedral rings the crystal structur e of this borophosphate-hydrate is closely related to the cyclo-hexasilicat e dioptase, Cu-6[Si6O18] . 6 H2O.