COORDINATION OF OXOVANADIUM(IV) TO AMINOCARBOXYLIC ACIDS IN AQUEOUS-SOLUTION

The oxovanadium(IV) complexes formed in aqueous solutions by ethylened iaminetetraacetic (EDTA), N-(2-hydroxyethyl)ethylenediaminetriacetic ( HEDTA), ethylenebis(oxyethylenenitrilo)tetraacetic (EGTA), trans-(1,2- cyclohexylenedinitrilo)tetraacetic (CDTA), ethylenediamine-N,N'-diacet ic (EDDA), nitrilotriacetic (NTA), imino-diacetic (IDA), N-methylimino diacetic (MIDA), ethylenediamine-N,N'-dipropionic (EDDP) and N,N'-ethy lenedianthranilic (EDA) acids have been studied by EPR and electronic absorption spectroscopy. The species taking part in the complex format ion processes have been identified and structures proposed by previous equilibrium studies have been examined and discussed on the basis of the spectroscopic data. In particular, hydrolysis has been found to yi eld mononuclear and dinuclear hydroxo species. The dinuclear di-mu-hyd roxo species formed by iminodiacetate-like ligands exhibit EPR spectra indicative of the triplet state and have been assigned as involving i ntermolecular carboxylate binding and hydroxyl bridges. EPR-silent di- mu-hydroxo complexes have been substantiated by the intensity loss of the EPR signals.