Mixing of aqueous solutions of the cluster anion [Re(6)Se(8)(CN)(6)](4-) and Zn(2+) in the presence of acetic acid (pH 3) leads to precipitation of (H(3)O)(2)Zn(3)[Re(6)Se(8)(CN)(6)](2). 20H(2)O having a three dimensional framework of {Zn(3)[Re(6)Se(8)(CN)(6)](2)}(2-) formed by Re-C=N-Zn covalent interactions. This framework occupies only 41.9% of the unit cell volume. The rest of the space is tilled by disordered water molecules and hydroxonium cations. (C) 2000 Published by Elsevier Science S.A. All rights reserved.