Two new pyrazine-bridged, linear chain complexes of Cu(II) of formula [Cu(pzdo)2(H2O)2(pz)](A)2·nH2O [pzdo = pyrazine-N,N′-dioxide; pz = pyrazine; A = BF4− (1), ClO4− (2)] have been prepared. Single-crystal X-ray diffraction shows the Cu ions to be six-coordinate, pyrazine-bridged chains with trans-pairs of ancillary ligands. The pzdo molecules are coordinated through their oxygen atoms. The ClO4− and BF4− anions are each two-site disordered in the lattice. Further, there are partial occupancy water molecules in the lattice which are very weakly bound. The structures are stabilized by hydrogen bonds between the coordinated water molecules and the non-coordinated pzdo oxygen atoms as well as the anions. Variable temperature magnetic susceptibility data show antiferromagnetic interactions and the data were fit to the uniform chain model yielding J/kB = −13.0(2) K and −11.8(2) K for 1 and 2, respectively []. In addition, the structure of the serendipitously prepared compound [Cu(pz)(pzdo)(H2O)2](ClO4)2 (3) is described. The compound crystallizes as rectangular layers of Cu(II) ions bridged by pzdo (parallel to the a-axis) and pyrazine (parallel to the b-axis) with water molecules coordinated in the axial sites.