1-Dimensional coordination polymers 1 ∞ [CuX(μ-pydz)] 1 - 3 (X = Cl, Br, I; pydz = pyridazine) may be prepared by self-assembly in acetonitrile solution at 120 °C (1) or room temperature (2, 3). Individual chains contain (CuX)2 rings and dimeric [Cu(μ-pydz)]2 substructures. At a 2:1 molar ratio treatment of CuI with pydz in acetonitrile affords the lamellar complex 2 ∞[(Cul)2(μ-pydz)] (4) whose novel 2 ∞[(Cul)2] sheets contain fused 4-, 6- and 8-membered (Cul)n rings and are stabilized by pydz bridging between adjacent Cu atoms. In contrast,2 ∞[(CuBr)2(μ-pym)2] (5) (pym = pyrimidine) contains separated 1 ∞[CuBr] chains and (CuBr)2 rings as participating building units.