Anisotropic Templating Effect in the Formation of Two-Dimensional Anionic Cadmium−Thiocyanate Coordination Solids [(12C4)₂Cd][Cd₂(SCN)₆] and [(12C4)₂Cd][Cd₃(SCN)₈] with Checkerboard and Herringbone Patterns, Respectively

Abstract

This paper reports the syntheses, characterization, and structures of two new two-dimensional cadmium-thiocyanate coordination solids [(12C4)(2)Cd][Cd(2)(SCN)(6)] (1) and [(12C4)(2)Cd][Cd(3)(SCN)(8)] (2), where 12C4 denotes 12-crown-4, C(8)H(16)O(4). 1 crystallizes in a monoclinic unit cell, space group C2/c with lattice parameters a = 16.297(3) Å, b = 26.267(3) Å, c = 16.296(2) Å, beta = 90.20(1) degrees, and Z = 8. 2 crystallizes in a monoclinic unit cell, space group P2(1)/n with lattice parameters a = 11.604(7) Å, b = 11.366(7) Å, c = 15.736(4) Å, beta = 92.84(3) degrees, and Z = 2. The structure of 1 exhibits a two-dimensional tetragonal motif consisting of Cd(2) units arranged in a checkerboard pattern with the dimeric [Cd(2)(SCN)(6)](2)(-) complex as the building block. The crystal structure of 2 can be described as a two-dimensional hexagonal array of linear trimeric Cd(3) units arranged in a herringbone pattern with the [Cd(3)(SCN)(8)](2)(-) complex as the building block. In both 1 and 2, the [(12C4)(2)Cd](2+) dications are housed in cavities within and between the anionic cadmium-thiocyanate layers but with different orientations ("upright" in 1 and "sideways" in 2) with respect to the cadmium-thiocyanate layers, giving rise to an anisotropic templating effect.