Diketonate ligands, polymeric metal complexes

Lanthanide(III) ions form three distinct types of complexes with 1,3-diketones (p-diketones) (a) tris complexes with a metal-to-ligand ratio of 1 3, (b) Lewis-base adducts of tris complexes, and (c) tetrakis complexes with a metal-to-ligand ratio of 1 4 (Binnemans, 2005a). It is very difficult to obtain pure monomeric tris complexes, because the coordination number of the lanthanide ion in this type of compounds is six and this is too low for saturation of the first coordination sphere of a trivalent lanthanide ion (except for tris complexes of very bulky 1,3-diketones). Therefore, most of the tris complexes form either dimeric (or even oligomeric or polymeric) complexes, or they form hydrates. The water molecules act as Lewis bases and by addition of... 

The decomposition of the transition complex (Scheme 12) at elevated temperatures causes the reduction of the metal cation, whereas the carbocation (Scheme 13) initiates the polymerization of the epoxy oligomers. In that way, the metal type and the stereochemistry of the mixed-ligand complexes as well as of the metal )S-diketonates bring about the reactivity... 

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