Hofmann-H2O-type and Hofmann-H2O-Td-type host structures accommodating 1,4-dioxane: Crystal structures of trans-bis(morpholine-N)cadmium(II) tetracyanonickelate(II), trans-diaquacadmium(II) tetracyanonickelate(II)-(1,4-dioxane)(1/2) and trans-diaquacadmium(II) tetracyanocadmate(II) (1,4-dioxane)(1/2)

In order to stabilise six-membered alicyclic ether guests through a hydrogen bond with an H2O ligand in the host, Hofmann-H2O-type [Cd(H2O)(2)Ni(CN)(4)] and Hofmann-H2O-Td-type [Cd(H2O)(2)Cd(CN)(4)] hosts were examined for accommodating 1,4-dioxane and morpholine as probable guests. The single crystal structures of the eventually obtained morpholine-ligated complex [Cd(C4H9NO)(2)Ni(CN)(4)] (1) and 1,4-dioxane-guest clathrates, [Cd(H2O)(2)Ni(CN)(4)].2C(4)H(8)O(2) (2) and [Cd(H2O)(2)Cd(CN)(4)].2C(4)H(8)O(2) (3), are closely related in topology with previously known [Cd(py)(2)Ni(CN)(4)], [Cd(NH3)(2)Ni(CN)(4)].2C(4)H(8)O(2) and [Cd(NH3)(2)Cd(CN)(4)].2C(6)H(6), respectively, but involve hydrogen bonds between the morpholine ligands in 1, and between the aqua ligand of the host and the guest 1,4-dioxane in 2 and 3. Complex 1 crystallises in the orthorhombic system, Pmna, a = 7.985(1), b = 6.695(2), c = 14.314(2) Angstrom, Z = 2, R = 0.048 for 1240 reflections; clathrate 2: monoclinic, P2/m, a = 7.3980(8), b = 7.6454(6), c = 8.0639(9) Angstrom, beta = 93.703(9)degrees, Z = 1, R = 0.041 for 1040; 3: monoclinic, C2/c, a = 12.054(5), b = 11.334(6), c = 15.249(2) Angstrom, beta = 91.62(2)degrees, Z = 4, R = 0.043 for 2129. The structure of a Hofmann-H2O-type hydrate [Fe(H2O)(2)Ni(CN)(4)].4H(2)O, orthorhombic Pnma, a = 12.200(2), b = 14.028(2), c = 7.2327(9) Angstrom, Z = 4, R = 0.042 for 710, is also reported.