Is there really a diagnostically useful relationship between the carbon–oxygen stretching frequencies in metal carboxylate complexes and their coordination mode?

Abstract

An investigation into the relationship between the asymmetric and symmetric stretching modes of ancillary carboxylate ligands and their mode of binding in a family of manganese(III) complexes of tetradentate N₂O₂ Schiff base ligands, which includes comparison of an ¹⁸O isotopically labelled derivative, has been undertaken. The results suggest that caution should be employed in using this technique to assign the binding mode of the carboxylate ligands in these complexes despite its very extensive use in the literature.