TY - JOUR
T1 - Mixed-addenda vanadium-substituted polyfluorooxometalates
T2 - Synthesis, characterization, and catalytic aerobic oxidation
AU - Khenkin, Alexander M.
AU - Neumann, Ronny
PY - 2000/8/7
Y1 - 2000/8/7
N2 - For the first time, mixed-addenda vanadium-substituted polyfluorooxometalates, PFOMs, have been synthesized. Depending on the workup procedure used, two types of compounds were prepared. The first PFOM was a quasi Wells-Dawson type compound, [H2F6NaV(V)W17O56]8-, and the second a mixture of vanadium-substituted polyfluorooxometalates of the Keggin structure, XV(IV)W11F(n)O(40-n) (X = H2, V, W; n = 1-4). From the X-ray diffraction analysis, [H2F6NaV(V)W17O56]8- has an elliptic (egg) shape with a central sodium atom surrounded by six fluorine atoms in a trigonal prism coordination. One may differentiate between two types of addenda atoms to be found in belt and capped positions. According to 1H, 19F, and 51V NMR analysis, it is concluded that vanadium is isomorphically substituted in both the belt and capped position of [H2F6NaV(V)W17O56]8-. The mixture of vanadium-substituted PFOMs of the Keggin structure was shown, by HPLC and ESR, to contain at least two species of different charge and of a different vanadium environment. The [H2F6NaV(V)W17O56]8- PFOM was active for the catalytic aerobic oxidation of alkyl aromatic compounds in biphasic (water-catalyst and substrate) media. The reaction selectivity (autoxidation versus oxydehydrogenation) depended on the substrate and reaction conditions such as temperature and oxygen pressure. The selectivity to oxydehydrogenation was significantly higher compared to the prototypical cobalt acetate catalytic system.
AB - For the first time, mixed-addenda vanadium-substituted polyfluorooxometalates, PFOMs, have been synthesized. Depending on the workup procedure used, two types of compounds were prepared. The first PFOM was a quasi Wells-Dawson type compound, [H2F6NaV(V)W17O56]8-, and the second a mixture of vanadium-substituted polyfluorooxometalates of the Keggin structure, XV(IV)W11F(n)O(40-n) (X = H2, V, W; n = 1-4). From the X-ray diffraction analysis, [H2F6NaV(V)W17O56]8- has an elliptic (egg) shape with a central sodium atom surrounded by six fluorine atoms in a trigonal prism coordination. One may differentiate between two types of addenda atoms to be found in belt and capped positions. According to 1H, 19F, and 51V NMR analysis, it is concluded that vanadium is isomorphically substituted in both the belt and capped position of [H2F6NaV(V)W17O56]8-. The mixture of vanadium-substituted PFOMs of the Keggin structure was shown, by HPLC and ESR, to contain at least two species of different charge and of a different vanadium environment. The [H2F6NaV(V)W17O56]8- PFOM was active for the catalytic aerobic oxidation of alkyl aromatic compounds in biphasic (water-catalyst and substrate) media. The reaction selectivity (autoxidation versus oxydehydrogenation) depended on the substrate and reaction conditions such as temperature and oxygen pressure. The selectivity to oxydehydrogenation was significantly higher compared to the prototypical cobalt acetate catalytic system.
UR - http://www.scopus.com/inward/record.url?scp=0034617624&partnerID=8YFLogxK
U2 - 10.1021/ic990606s
DO - 10.1021/ic990606s
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C2 - 11196802
AN - SCOPUS:0034617624
SN - 0020-1669
VL - 39
SP - 3455
EP - 3462
JO - Inorganic Chemistry
JF - Inorganic Chemistry
IS - 16
ER -