Oxalato-Bridged Coordination Ploymers

The oxalate ion is a good bridging ligand. Most of the insoluble transition-metal oxalates are actually coordination polymers, with the metal centers connected by bis-chelating oxalato groups. 

FIGURE 29. (a) The [Ni(bpca)2] building block (b) The heterobimetallic cationic chain in [ Ln(O2N0)(H20)3 Ni(bpca)2 ](NO3)2 3H2O. 

The reaction between [Cr(C204)3] complexes and trivalent lanthanide ions leads to chains, [Ln Cr (C204)3(H20)4] nH20, with a ladder-type motif. The rare earth ions are 10-coordinated six oxygen atoms from the three bis-chealting oxalato groups and four aqua ligands. 

Honeycomb anionic layers resulted by assembling Mn ions with tectons. 

FIGURE 31. Heterobimetallic chain resulted by assembling Mn ions and [Cr(bipy) (0204)2] tectons. 

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