Poly[[diaquadi-μ(2)-cyanido-bis-(μ(2)-pyrazine-2-carboxyl-ato)dicopper(I)copper(II)] dihydrate].

In the title compound, {[Cu(II)Cu(I) (2)(C(5)H(3)N(2)O(2))(2)(CN)(2)(H(2)O)(2)]·2H(2)O}(n), the Cu(II) atom lies on an inversion centre and is octa-hedrally coordinated by two N atoms and two O atoms from opposing pyrazine-2-carboxyl-ate (2-pac) ligands and two water O atoms. The Cu(I) atom has a triangular geometry, coordinated by one N atom and one C atom from two bridging cyanide ligands, and another N atom from the 2-pac ligand. The three-dimensional structure features a succession of two-dimensional sheets containing [Cu(CN)](n) chains linked by Cu(2-pac)(2)(H(2)O)(2) groups. The coordinated and free water mol-ecules are involved in an extended three-dimensional hydrogen-bond network with the 2-pac ligands.