This paper describes a new archetypal 3D framework with a honeycomb structure containing hexagonal channels, which provides a potentially useful model for the future construction of related materials with larger channels and with possible catalytic applications. Reaction between Cd(CN)2 and hexamethylenetetramine provides two crystalline products, Cd-(CN)2.1/3(C6H12N4) and Cd(CN)5/3(OH)1/3.1/3(C6H12N4) (C6H12N4 = hexamethylenetetramine), which have been studied by single-crystal X-ray diffraction. Cd(CN)5/3(OH)1/3.1/3(C6H12N4): monoclinic, space group P2(1)/a (No. 14), Z = 12; a = 11.358 (2), b = 12.619 (2), c = 12.366 (2) angstrom; beta = 104.05 (1)degrees; R = 0.023 and R(w) = 0.044 for 4446 reflections with I greater-than-or-equal-to 3-sigma(I). The extended 3D network consists of three types of Cd (6-coordinate, 5-coordinate, and intermediate between 4- and 5-coordinate) interconnected by mu-2-CN groups, mu-3-OH groups, and mu-2-C6H12N4 units. A third N of each C6H12N4 coordinates weakly to a Cd center that otherwise would be 4-coordinate and a fourth N is involved in H bonding to OH. Cd(CN)2.1/3(C6H12N4): orthorhombic, space group Cmcm (No. 63), Z = 12; a = 21.274 (4), b = 7.782 (1), c = 13.272 (5) angstrom; R = 0.029 and R(w) = 0.043 for 1447 reflections with I greater-than-or-equal-to 3-sigma(I). The structure consists of an infinite [Cd(CN)2]n framework in which all Cd centers are coordinated by four mu-2-CN groups. The framework generates two sorts of channels running in the b direction; all the C6H12N4 units are found in the smaller channels of roughly square cross section with all four N's coordinated to Cd's, while the larger channels of hexagonal cross section are vacant. Recrystallization of Cd(CN)2 from aqueous tBuOH gives crystals of Cd(CN)2.2/3H2O.tBuOH, which have been studied by single-crystal X-ray diffraction: orthorhombic, space group Amm2 (No. 38), Z = 6; a = 8.695 (1), b = 8.548 (1), c = 21.092 (4) angstrom; R = 0.033 and R(w) = 0.044 for 761 reflections with I greater-than-or-equal-to 3-sigma(I). The [Cd(CN)2]n network provides the first example of a new type of extended 3D structure that is particularly simple, consisting essentially of interconnected square-planar centers and tetrahedral centers in 1:2 proportions. The ''square-planar'' Cd's carry, in addition, two trans water ligands (which from the point of view of framework structure can be regarded as mere appendages), which project into hexagonal channels filled with disordered tBuOH. The [Cd(CN)2]n frameworks in Cd-(CN)2.1/3(C6H12N4) and Cd(CN)2.2/3(H2O).tBuOH are topologically identical (if the difference between the two ends of the cyano group is ignored) thought, at first sight, geometrically very different. The geometrical relationship between the two frameworks is described in terms of sliding alternate hexagonal sheets of Cd's in the bc plane in Cd(CN)2.2/3H2O.tBuOH in the b direction to generate the less regular arrangement seen in Cd(CN)2.1/3(C6H12N4).
