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Dendritic Zirconium‐Peroxotungstosilicate Hybrids: Synthesis, Characterization, and Use as Recoverable and Reusable Sulfide Oxidation Catalysts
Author(s) -
Jahier Claire,
Mal Sib Sankar,
Kortz Ulrich,
Nlate Sylvain
Publication year - 2010
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/ejic.200901141
Subject(s) - chemistry , catalysis , dendrimer , zirconium , cationic polymerization , polyoxometalate , hydrogen peroxide , salt (chemistry) , inorganic chemistry , sulfide , aqueous solution , ammonium , homogeneous catalysis , polymer chemistry , organic chemistry
A series of dendrimer‐containing polyoxometalates(DENDRIPOMs) was synthesized by coupling zirconium‐peroxotungstosilicate [Zr 2 (O 2 ) 2 (SiW 11 O 39 ) 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 [Zr 2 (O 2 ) 2 (SiW 11 O 39 ) 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/CDCl 3 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.