The copper(II) complex [Cu(C9H19N4O2)]2(ClO4)2.2H2O (1) is binuclear, the bridging being provided by O-H-O hydrogen bonds. The oxygen-oxygen distance of 2.459 angstrom is comparable to that of other binuclear copper(II) complexes with hydrogen-bonded bridges, but the copper-copper separation of 4.555 angstrom in this complex is the shortest observed. The complex exhibits weak antiferromagnetic coupling between the copper(II) centers with a triplet energy of 4.09 cm-1, unlike other hydrogen-bonded copper(II) dimers which exhibit values in the range 56-94 cm-1. This difference between the magnetic properties of complex 1 and those studied earlier is attributed to a tetrahedral distortion (tau = 11.5-degrees) at the copper centers in 1.