Reaction of K-3[Cu(CN)(4)] with Me3SnCl and 4,4'-bipyridine (bpy) affords the novel ternary adduct [CuCN . Me3SnCN . 0.5bpy], 2, as yellow, cubelike crystals. The supramolecular architecture of 2 consists, according to a single-crystal X-ray study, of remarkably porous, approximately planar sheets held together by almost perpendicular bpy pillars. Basic building blocks of the sheets are {Cu-2(mu-ChT)(2)(CN)(2)} fragments whose N atoms are connected, via Me3Sn bridges, with the N atoms of adjacent fragments. 2 crystallizes in space group P2(1)/c with (at 20 degrees C) a 10.035(4) Angstrom, b = 11.980(3) Angstrom, c = 12.425(5) Angstrom beta = 110.94(3)degrees, and Z = 4. The dinuclear building blocks resemble strongly those of the long known, but chemically more labile, layered coordination polymer [CuCN . NH3], 1. Although the lattice of 2 consists of two equivalent, ideally interpenetrating 3D frameworks, spacious, straight channels of a cross section of ca. 10 Angstrom x 5 Angstrom persist in this unprecedented structure. The likewise polymeric new adduct [CuCN . Me3SnCN . H2O] (3) obtained from K-3[Cu(CN)(4)] and Me3SnCl in the absence of bpy may be considered as a formal precursor of 2.