Dendritic Zirconium-Peroxotungstosilicate Hybrids: Synthesis, Characterization, and Use as Recoverable and Reusable Sulfide Oxidation Catalysts

• Published in: European Journal of Inorganic Chemistry Vol. 2010; no. 10; pp. 1559 - 1566
• Main Authors: Jahier, Claire, Mal, Sib Sankar, Kortz, Ulrich, Nlate, Sylvain
• Format: Book Review Journal Article
• Language: English
• Published: Weinheim WILEY-VCH Verlag 01.04.2010; WILEY‐VCH Verlag; Wiley
• Subjects: Catalyst recovery; Chemistry; Chemistry, Inorganic & Nuclear; Dendrimers; Homogeneous catalysis; Oxidation; Physical Sciences; Polyoxometalates; Science & Technology; Zirconium; Catalyst recovery; ALKENES; Dendrimers; Polyoxometalates; Zirconium; POLYOXOTUNGSTATE; DENDRONS; Homogeneous catalysis; POLYOXOMETALATE; CHEMISTRY; Oxidation
• ISSN: 1434-1948; 1099-0682
• DOI: 10.1002/ejic.200901141

A series of dendrimer‐containing polyoxometalates(DENDRIPOMs) was synthesized by coupling zirconium‐peroxotungstosilicate [Zr2(O2)2(SiW11O39)2]12– with ammonium dendrons by electrostatic bonding. These DENDRIPOMs were successfully characterized by standard physicochemical techniques (e.g. IR and NMR spectroscopy and MS), and they represent the first examples of dendritic POMs based on zirconium‐substituted polytungstates. The data obtained are consistent with structures in which the anionic POM is surrounded by cationic ammonium dendrons. In contrast to the potassium salt of [Zr2(O2)2(SiW11O39)2]12–, the dendritic counterparts are soluble in common organic solvents, an important feature for the use of DENDRIPOMs in homogeneous catalysis. Our DENDRIPOMs are stable, efficient, recoverable, and reusable catalysts for the oxidation of sulfides in aqueous/CDCl3 biphasic media, with hydrogen peroxide as the oxidant, in contrast to their nondendritic n‐butyl ammonium counterpart. Two cycles of catalytic reactions were performed without any appreciable loss of activity. We also discovered that the reaction kinetics and selectivity of theDENDRIPOMs are influenced by the structure of the countercation used. A series of dendritic zirconium‐peroxotungstosilicate hybrids was synthesized and used as recoverable catalysts in the oxidation of sulfides with H2O2. These hybrids represent the first examples of DENDRIPOMs based on a zirconium‐containing polytungstate. The synthetic approach used is promising and elegant with respect to catalytic activity, selectivity (also enantioselectivity), and catalyst recovery.