Crystal structures of the ('maximally') hydrated scandium halides, ScX(3 center dot)nH(2)O (X = Cl,Br,I)

Low-temperature single-crystal X-ray structure determinations are recorded for the ('maximally') hydrated scandium( III) trihalides, ScX(3 .)nH(2)O (X = Cl, Br, I). The chloride and bromide are isomorphous heptahydrates (n = 7), ScX(3 .)7H(2)O [Sc(OH2)(7)]X-3, monoclinic, space group P2/n, a similar to 7.6, b similar to 7.7, c similar to 9.6 Angstrom, beta similar to 99 de grees, Z = 2, R 0.051, 0.039 for N-o 1253, 1339 'observed' (F > 4 sigma (F) ) reflections, respectively, the metal atom disposed in a homoleptic enviro nment of seven water molecule oxygen atoms arranged in an essentially penta gonal-bipyramidal disposition, site symmetry 2, Sc-O(axial) 2.09(5) Angstro m, Sc-O(eq) 2.157(3)-2.209(4) Angstrom. The iodide is an octahydrate, ScI3. 8H(2)O = [Sc(OH2)(7)]I3 .H2O, monoclinic P2(1)/c, Z = 4, R 0.022 for N-o 3 243; the seven-coordinate metal atom environment here is well distorted fro m the pentagonal-bipyramidal norm, the largest angle in the coordination sp here being 162.4(1)degrees, subtended by Sc-O 2.109(3), 2.128(3) Angstrom, the remaining Sc-O ranging between 2.157(3)-2.219(3) Angstrom.