Ordered bimetallic coordination networks featuring rare earth and silver cations

Abstract

Three lanthanide complexes of the ditopic ligand 3-cyanopentane-2,4-dionate (acacCN) have been synthesized and structurally characterized. Longer intermolecular contacts result in ninefold coordination of the cation in Ce(acacCN)₃(H₂O)₂, whereas mononuclear complexes of the same stoichiometry with coordination number eight are obtained for the smaller Eu(III) and Yb(III) cations. Reaction of these labile compounds with AgPF₆ leads to re-organization of the coordination sphere of the rare earth cations: neutral extended structures are formed in which the peripheric –CN moieties of Ln(acacCN)₄ anions coordinate to silver cations. The initially formed heterometallic networks show additional coordination of water or inclusion of solvent molecules; three different structure types, two of them as isomorphous pairs, have been characterized. In the case of Eu(III) and Yb(III), these solids are instable when stored in their mother liquor and undergo a slow aging process, finally resulting in phase pure stable and solvent-free 3D networks Ln(acacCN)₄Ag.