Hydrothermal scandium fluoride chemistry: syntheses and crystal structures of [C 2N 2H 10][ScF 5], [NH 4] 2[Sc 3F 11] and [H 3O][C 6N 2H 16][ScF 6]⋅H 2O

Abstract

The hydrothermal syntheses and crystal structures of three new scandium fluorides are reported. [enH 2][ScF 5] 1 exhibits continuous chains of vertex linked ScF 6 octahedra, which adopt two differing conformations (eclipsed and staggered). [NH 4] 2[Sc 3F 11] 2, displays a three-dimensional framework structure composed of edge and corner-shared ScF 7 pentagonal bipyramids interlinked via octahedral scandium centres. This structure encloses ‘butterfly’-shaped channels, and may be regarded as an ‘expanded’ version of the KSc 2F 7 structure, derived by insertion of the additional octahedral unit between neighbouring pentagonal bipyramidal chains. [H 3O][C 6N 2H 16][ScF 6]⋅H 2O 3 is composed of isolated ScF 6 octahedra hydrogen-bonded to trans-1,4-diaminocyclohexane cations and water molecules/hydronium cations. Crystal data for 1: tetragonal, space group P4/ncc, a = 13.035 ( 2 ) Å , c = 8.142 ( 2 ) Å ; for 2: orthorhombic, space group Cmmm, a = 18.501 ( 12 ) Å , b = 6.613 ( 5 ) Å , c = 4.025 ( 3 ) Å ; for 3: monoclinic, space group P2 1/n, a = 9.543 ( 2 ) Å , b = 6.704 ( 1 ) Å , c = 9.873 ( 2 ) Å , β = 90.349 ( 5 ) ° .