Syntheses and structures of three new scandium selenites: Sc-2(SeO3)(3) center dot H2O, Sc-2 (SeO3)(3) center dot 3H(2)O and CsSc3(SeO3)(4) (HSeO3)(2) center dot 2H(2)O

Three new hydrated scandium selenites have been hydrothermally synthesized as single crystals and structurally and physically characterized. Sc-2(SeO3)(3).H2O crystallizes as a new structure type containing novel ScO7 pentagonal bipyramidal and ScO6+1 capped octahedral coordination polyhedra. Sc-2(SeO3)(3).3H(2)O contains typical ScO6 octahedra and is isostructural with its M-2(SeO3)(3).3H(2)O (M = Al, Cr, Fc, Ga) congeners. CsSc3(SeO3)(4)(HSeO3)(2).2H(2)O contains near-regular ScO6 octahedra and has essentially the same structure as its indium-containing analogue. All three phases contain the expected. pyramidal [SeO3](2-) selenite groups. Crystal data: Sc-2(SeO3)(3).3H(2)O, M-r = 524.85, trigonal, R3c (No. 161), a = 9.6481 (5) Angstrom, c = 20.7832(12) Angstrom, V = 1675.45(16) Angstrom(3), Z=6, R(F)=0.018, wR(F-2) = 0.036; Sc-2(SeO3)(3).H2O, M-r = 488.82, orthorhombic, P2(1)2(1)2(1) (No. 19), a = 6.5913 (6) Angstrom, b = 11.1596(11) Angstrom, c = 12.1368(11) Angstrom, V = 892.74(14) Angstrom(3), Z = 4, R(F) = 0.051, wR(F-2) = 0.086; CsSc3(SeO3)(4)(HSeO3)(2).2H(2)O, M-r = 1067.60, orthorhombic, Pnma (No. 62), a = 16.670 (3) Angstrom, b = 13.167(3) Angstrom, c = 9.575(2) Angstrom, V = 2101.6(7) Angstrom(3), Z = 4, R(F) = 0.035, wR(F-2) = 0.070. (C) 2004 Elsevier Inc. All rights reserved.