The synthesis and characterization of a new cluster polymer with a sodium centered hexacopper(II) barrel portion, catena-[Nasubset ofCU(2){Cu(hpro)(2)}(4)(ClO4)(4)](ClO4).4H(2)O (hpro = 4-hydroxyL-prolinato) are described. The central sodium ion in the barrel portion is surrounded by eight carboxylate oxygen atoms from hpro ligands, which link the central metal to the copper atoms of four [Cu(hpro)(2)] units. These units are in turn connected to two further apical Cu-II centers. The central alkali ion is therefore octahedrally surrounded by six copper atoms. The hydroxyl oxygen atoms of two hpro groups are coordinated to the axial copper atoms of two neighboring barrel portions, so that a chain complex forms. Magnetic studies indicate weak ferromagnetic coupling between copper(II) ions within the complex leading to a high spin multiplicity in the ground state.