Catalysis in POM Chemistry

Oxidation-Catalysis

The oxygenase activity of natural metallo-enzymes offers a unique paradigm of what is the Holy Grail of oxidation chemistry. An innovative approach to the design of oxygenase functional mimics is the adoption of a totally inorganic ligand system derived from polyoxometalates (POMs), as an alternative to organic or organometallic coordination complexes. Bio-inspired activity of transition- metal-substituted POMs (TMSP, with TM being Fe, Mn, Ru) has been proposed in the recent literature. However, due to the severe mechanistic complexity, which is frequently associated with metal-mediated aerobic oxidations, it is a major challenge to unravel the catalyst’s role along oxygen-transfer pathways. Therefore, in the realm of POM-based oxygenase mimics, the adherence to bio-inspired mechanistic features is often a matter of debate and retains a fundamental interest. Among the class of Fesubstituted polyoxotungstates some structucatalysisral types are known, where the coordination geometry of the iron center exhibits a striking oxygenase synzyme motif. In particular, the tetrasubstituted Krebs-type polyanions with general formula [Fe4(H2O)10(β-XW9O33)2]n- (Fe4X2W18, X=AsIII, SbIII ; n=6; X=SeIV, TeIV; n=4), display two of the four iron sites with three terminal, substitution-labile coordination positions, typical of non-heme dioxygenase enzymes. The latter are responsible for the catabolism/ biodegradation of dihydroxylated aromatic compounds. While several functional models have been designed with coordination complexes using polydentate organic ligands, very few examples deal with POM-based systems, and FeIII framework-incorporated POMs as multi-turnover catalysts for the aerobic cleavage of catechols are unprecedented.

Selected Publications

  • Organo-Ruthenium Supported Heteropolytungstates: Synthesis, Structure, Electrochemistry and Oxidation Catalysis
    Bi, L.-H.; Al-Kadamany, G.; Chubarova, E. V.; Dickman, M. H.; Chen, L.; Gopala, D. S.; Richards, R. M.; Keita, B.; Nadjo, L.; Jaensch, H.; Mathys, G.; Kortz, U. Inorg. Chem. 2009, 48, 10068-10077. [Read Online]
  • Unique Catalytic Performance of the Polyoxometalate [Ti2(OH)2As2W19O67(H2O)]8-: The Role of 5-Coordinated Titanium in H2O2 Activation
    Kholdeeva, O. A.; Donoeva, B. G.; Trubitsina, T. A.; Al-Kadamany, G.; Kortz, U. Eur. J. Inorg. Chem. 2009, 5134-5141. [Read Online]
  • Iron Substituted Polyoxotungstates as Inorganic Synzymes: Evidence for a Biomimetic Pathway in the Catalytic Oxygenation of Catechols
    Sartorel, A.; Carraro, M.; Scorrano, G.; Bassil, B. S.; Dickman, M. H.; Keita, B.; Nadjo, L.; Kortz, U.; Bonchio, M., Chem. Eur. J 2009, 15, 7854-7858. [Read Online]
  • Heterogeneous wheel shaped Cu20-tungstophosphate ([Cu20Cl(OH)24(H2O)12(P8W48O184])25-) catalyst for solvent-free aerobic oxidation of n-hexadecane
    Chen, L.; Hu, J.; Mal, S. S.; Kortz, U.; Jaensch, H.; Mathys, G.; Richards, R. M. Chem. Eur. J. 2009, 15, 7490-7497. [Read Online]
  • Complete List of Publications