CRYSTAL ENGINEERING IN [(12C4)(2)NA][CD(SCN)(3)] - FIRST EXAMPLE OF AN ANIONIC CADMIUM THIOCYANATE COORDINATION SOLID WITH A SANDWICH [(12C4)(2)NA](+) CATION AS SPACER CONTROLLER, RESULTING IN A HEXAGONAL ARRANGEMENT OF ANTIPARALLEL ZIGZAG [CD(SCN)(3)(-)]INFINITY CHAINS/

This paper reports the synthesis, characterization, and structure of [ (12C4)(2)Na][Cd(SCN)(3)] (3). The title compound 3 represents the firs t example of an anionic cadmium thiocyanate coordination solid in whic h a sandwich [(12C4)(2)Na](+) monocation serves as the spacer/controll er, giving rise to a hexagonal array of antiparallel infinite zigzag [ Cd(SCN)3(-)](infinity) chains with the cations occupying the triangula r channels. The title compound 3 crystallizes in a monoclinic unit cel l of P2(1)/n space group symmetry with lattice parameters of 13.204(2) Angstrom, 10.692(2) Angstrom, 21.036(1) Angstrom, 95.520(8)degrees, a nd Z = 4. A detailed comparison of the title structure (3) with that o f [(18C6)(2)Na-2(H2O)(2)](1/2)[Cd(SCN)(3)] (1) and [(18CG)K][Cd(SCN)(3 )] (2) revealed that the arrangement and the alignment of the infinite anionic [Cd(SCN)(3)(-)](infinity) zigzag chains are dictated by the d imensions and symmetry, respectively, of the cations. The infinite ani onic [Cd(SCN)(3)(-)](infinity) chains in 1 and 2 form an approximate t etragonal array, creating square channels which are filled with the di meric [(18C6)(2)Na-2(H2O)(2)](2+) (in 1) or with two monomeric [(18C6) K](+) (in 2) cations while the infinite anionic [Cd(SCN)(3)(-)](infini ty) chains in 3 adopt an approximate hexagonal arrangement with the tr iangular channels filled by the smaller [(12C4)(2)Na](+) cations (the dimension effect). The relative alignment (either parallel or antipara llel) of the anionic chains is dictated by the symmetry or approximate symmetry of the cations. Thus, both the dimeric cation in 1 and the s andwich cation in 3 give rise to antiparallel alignment of the anionic [Cd(SCN)(3)(-)](infinity) chains with the centrosymmetric space group P2(1)/n whereas the disklike cation in 2 gives rise to parallel align ment of [Cd(SCN)(3)(-)](infinity) chains with noncentrosymmetric space group Cmc2(1) (the symmetry effect).