Dicarboxylic adds chelate coordination

Complexes containing unidentate coordination have depended for their characterization upon physicochemical methods rather than structural determinations. The monomeric octahedral co-balt(III) complex [Co(en)2X(ox)], where X = halogen or OH, provides one of the few examples of unidentate oxalate coordination the conformation was determined from IR data, By contrast, there are numerous examples of structurally characterized chelating dicarboxylate systems. There are several structural determinations of different forms of oxalic acid and its ions but the most useful for comparative purposes are those of a-oxalic acid and anhydrous sodium oxalate. Using the planar (Z>2a) oxalate ion and add as benchmarks it can be seen (Table 4) that the tf oxalate ligand (bite = 265 pm) has two long and two short C—O bonds. The coordinated C—0(M) bond resembles the C—O bond of the add while the free C=0 bonds are similar to those in the oxalate... 

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