STRUCTURE OF SR5(BO3)3CL

Pentastrontium chloride trisorthoborate, Sr5(BO3)3Cl, M(r) = 649.98, orthorhombic, C222(1), a = 10.000 (2), b = 14.202 (2), c = 7.421 (1) angstrom, V = 1053.9 (3) angstrom3, Z = 4, D(x) = 4.096 Mg m-3, lambda(Mo K-alpha) = 0.71069 angstrom, mu = 24.7 mm-1, F(000) = 1176, T = 295 K, R = 0.045 for 911 independent reflections with I > 3-sigma(I). The intricate three-dimensional framework consists of several Sr-atom coordination types - SrO5Cl2, SrO7Cl2 and SrO8- interconnected by sharing either faces, corners, or B03 triangles. Each Cl atom is surrounded by six Sr nearest neighbors, forming zigzag chains that propagate along the c axis. The plane of the B03 group centered by atom B2 is orthogonal to the twofold rotation b axis, and the vector normal of the B03 plane centered by atom B1 is only slightly canted from the 2(1) screw axis, portending a small propensity for optical second-harmonic generation.