THE CRYSTAL CHEMISTRY OF THE ZIPPEITE GROUP

Abstract

Single crystals of eight zippeite-group compounds have obtained using mild hydrothermal synthesis techniques. The structure of each has been determined with single-crystal diffraction data collected using Mo K α X-radiation and an APEX CCD-based detector, and refined on the basis of F 2 for all unique data. The structure of zippeite, K 3 (H 2 O) 3 [(UO 2 ) 4 (SO 4 ) 2 O 3 (OH)], is mono-clinic, C 2, a 8.7524(4), b 13.9197(7), c 17.6972(8) A, β104.178(1)°, V 2090.39(17) A 3 , R 1 3.30%, D c 4.794 g/cm 3 . The structure of sodium-zippeite, Na 5 (H 2 O) 12 [(UO 2 ) 8 (SO 4 ) 4 O 5 (OH) 3 ], is monoclinic, P 2 1 / n , a 17.6425(11), b 14.6272(9), c 17.6922(11) A, β104.461(1)°, V 4421.0(5) A 3 , R 1 6.88%, D c 4.517 g/cm 3 . The structure of magnesium-zippeite, Mg(H 2 O) 3.5 [(UO 2 ) 2 (SO 4 )O 2 ], is monoclinic, C 2/ m , a 8.6514(4), b 14.1938(7), c 17.7211(9) A, β 104.131(1)°, V 2110.24(18) A 3 , R 1 2.39%, D c 4.756 g/cm 3 . The structure of zinc-zippeite, Zn(H 2 O) 3.5 [(UO 2 ) 2 (SO 4 )O 2 ], is monoclinic, C 2/ m , a 8.6437(10), b 14.1664(17), c 17.701(2) A, β 104.041(3)°, V 2102.7(4) A 3 , R 1 4.57%, D c 5.032 g/cm 3 . The structure of cobalt-zippeite, Co(H 2 O) 3.5 [(UO 2 ) 2 (SO 4 )O 2 ], is mono-clinic, C 2/ m , a 8.650(4), b 14.252(9), c 17.742(10) A, β 104.092(19)°, V 2122(2) A 3 , R 1 5.55%, D c 4.948 g/cm 3 . The structure of (NH 4 ) 4 (H 2 O)[(UO 2 ) 2 (SO 4 )O 2 ] 2 is monoclinic, C 2/ m , a 8.6987(15), b 14.166(2), c 17.847(3) A, β 104.117(4)°, V 2132.9(3) A 3 , R 1 4.31%, D c 4.442 g/cm 3 . The structure of (NH 4 ) 2 [(UO 2 ) 2 (SO 4 )O 2 ] is orthorhombic, Cmca , a 14.2520(9), b 8.7748(5), c 17.1863(10) A, V 2149.3(2) A 3 , R 1 5.11%, D c 4.353 g/cm 3 . The structure of Mg 2 (H 2 O) 11 [(UO 2 ) 2 (SO 4 )O 2 ] 2 is monoclinic, P 2 1 / c , a 8.6457(4), b 17.2004(8), c 18.4642(9) A, β 102.119(1)°, V 2684.6(2) A 3 , R 1 4.73%, D c 3.917 g/cm 3 . Each structure contains the zippeite-type sheet consisting of chains of edge-sharing uranyl pentagonal bipyramids that are cross-linked by vertex sharing with sulfate tetrahedra, although the compositional details of the sheet are varied. The interlayer configurations are diverse, and are related to the bonding requirements of the sheets.