Study of the interaction between oxovanadium(IV) and hydroxamic acids

Péter Buglyó, Norbert Pótári

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The interaction between oxovanadium(IV) and primary hydroxamic acids (aceto- (HAha), benzohydroxamic acid (HBha) or N-hydroxy-N′-[3-(N-hydroxy-carbamoyl)-propyl]-heptane-1,7-dicarboxamide (H2Diha)) as well as the corresponding N-methyl substituted hydroxamic acids (HMeAha, HMeBha, H2MeDiha) was studied by pH-potentiometric and pH-stat methods in aqueous solution. Stoichiometry and stability constants of the VO(IV) complexes formed in the pH range 2.0-5.0 were determined and the effect of the substituents on the C or N atoms of the hydroxamic group is discussed. The dihydroxamic acids are more effective oxovanadium(IV) binders than the monohydroxamic ones. Above pH = 4.5-5.0 (depending upon ligand excess), slow redox reaction was found in all the systems studied. During this process, beside the oxidation of VO(IV) to the appropriate V(V)-hydroxamate complex, formation of amides as reduction products was detected under anaerobic conditions. The same reaction can also take place when stirring sparingly soluble VOA2 type complexes (A: Bha or MeBha) in water in the absence of oxygen. The exact stoichiometry of the redox reaction was determined by pH-stat measurements and found to be 2VO(R 1CON(R2)O)2 + R1CON(R 2)OH + H2O = 2[VO2(R1CON(R 2)O)2]- + 2H+ + R 1CON(R2)H (R1: CH3, C 6H5; R2: H, CH3) for the monohydroxamates. The N-methyl hydroxamic acids tend to oxidise VO2+ significantly slower than the corresponding primary ones.

Original languageEnglish
Pages (from-to)837-845
Number of pages9
Issue number7
Publication statusPublished - May 12 2005



  • Amide formation
  • Hydroxamic acids
  • Oxovanadium(IV) complexes
  • Stability constants
  • Vanadium(V)
  • pH-potentiometry

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Inorganic Chemistry
  • Materials Chemistry

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