METAL-ION SEQUESTERING BY BORATE (AMINO)POLYHYDROXY OXIME SYSTEMS IN AQUEOUS-SOLUTION - A B-11, C-13 AND CD-113 NMR-STUDY

Cu(II) and Cd(II) coordination to mixtures of (amino)polyhydroxy oximes and borate has been studied using B-11, C-13 and Cd-113 NMR and titration procedures. The (amino)polyhydroxy oximes have strong Cu(II) coordinating properties, also in the absence of borate. The polyhydroxy oximes, on the contrary, have only low Cd(II) sequestering abilities. The metal ion complexing abilities of D-glucosamine oxime can be enhanced by the addition of borate. D-Glucosamine oxime forms borate diesters in which the borate is bound to the threo-3,4 diol functions. This species coordinates Cd(II) via the E isomers of both ligands by two oxime (or oximato) and two amino groups, while probably also two borate oxygens assist in the Cd(II) complexation. Factors determining metal ion coordination by borate diesters are discussed.