Crystal Structures of the ('Maximally') Hydrated Scandium Halides, ScX3.nH2O (X = Cl, Br, I)

Abstract

Low-temperature single-crystal X-ray structure determinations are recorded for the (‘maximally’) hydrated scandium(III) trihalides, ScX₃.nH₂O (X = Cl, Br, I). The chloride and bromide are isomorphous heptahydrates (n =7), ScX₃.7H₂O =[Sc(OH₂)₇]X₃, monoclinic, space group P2/n, a ~ 7.6, b ~ 7.7, c ~ 9.6 Å, β ~ 99˚, Z = 2, R 0.051, 0.039 for N_o 1253, 1339 ‘observed’ (F > 4σ (F)) reflections, respectively, the metal atom disposed in a homoleptic environment of seven water molecule oxygen atoms arranged in an essentially pentagonal-bipyramidal disposition, site symmetry 2, Sc–O(axial) 2.09₅ Å, Sc–O(eq) 2.157(3)–2.209(4) Å. The iodide is an octahydrate, ScI₃.8H₂O =[Sc(OH2)₇]I₃.H₂O, monoclinic P2₁/c, Z = 4, R 0.022 for N_o 3243; the seven-coordinate metal atom environment here is well distorted from the pentagonal-bipyramidal norm, the largest angle in the coordination sphere being 162.4(1)˚, subtended by Sc–O 2.109(3), 2.128(3) Å, the remaining Sc–O ranging between 2.157(3)–2.219(3) Å.