Immobilization of oxomolybdenum species in a layered double hydroxide pillared by 2,2 '-bipyridine-5,5 '-dicarboxylate anions
authors Gago, S; Pillinger, M; Valente, AA; Santos, TM; Rocha, J; Goncalves, IS
nationality International
journal INORGANIC CHEMISTRY
keywords ALKENE EPOXIDATION CATALYSTS; MESOPOROUS MCM-41 MATERIALS; HYDROTALCITE-LIKE COMPOUNDS; CURVED-WAVE THEORY; DIOXOMOLYBDENUM(VI) COMPLEXES; EXAFS CALCULATIONS; AIR OXIDATION; INTERCALATION; MOLYBDENUM; CHEMISTRY
abstract A Zn,Al layered double hydroxide (LDH) with Zn/Al = 1.45 and containing nitrate anions was prepared by coprecipitation and characterized by powder X-ray diffraction, Zn K-edge extended X-ray absorption fine structure spectroscopy (EXAFS), thermogravimetric analysis, FTIR and FT Raman spectroscopy, and 27Al MAS NMR spectroscopy. Three Zn... O and four Zn... M (M = Zn, Al) shells could be fitted to the low-temperature (40 K) EXAFS spectrum, in accordance with a model for an ordered cationic sheet. The nitrate anions were easily exchanged by 2,2'-bipyridine-5,5'-dicarboxylate anions, resulting in an increase in the basal spacing from 9 to 18 A. The basal spacing of the pillared derivative indicates that the anions are arranged with their longest dimension nearly perpendicular to the host layers. This material exhibits a high encapsulating ability, as evidenced by its interaction with a dichloromethane solution of the dioxomolybdenum(VI) complex MoO(2)Cl(2)(THF)(2). A material with a metal loading of 11.2 wt % was obtained. Molybdenum K-edge EXAFS analysis could not substantiate the formation of a supported complex of the type MoO(2)Cl(2)(N-N) but instead indicated the formation of unidentate-bridged entities of the type [O(2)MO-O-MoO(2)] with a metal-metal separation of 3.29 Angstrom. The molybdenum-containing LDH was active as a catalyst for the liquid-phase epoxidation of cis-cyclooctene, 1-octene, and trans-2-octene using tertbutyl hydroperoxide as the oxygen source, yielding the corresponding epoxides as the only products. For reactions carried out with no additional solvent (other than n-decane) or in the presence of 1,2-dichloroethane, the solid catalyst could be recycled with no major loss of activity. Other tests confirmed that the systems functioned as true heterogeneous catalysts.
publisher AMER CHEMICAL SOC
issn 0020-1669
year published 2004
volume 43
issue 17
beginning page 5422
ending page 5431
digital object identifier (doi) 10.1021/ic049755n
web of science category Chemistry, Inorganic & Nuclear
subject category Chemistry
unique article identifier WOS:000223397100037
  ciceco authors
  impact metrics
journal analysis (jcr 2019):
journal impact factor 4.825
5 year journal impact factor 4.501
category normalized journal impact factor percentile 92.222
dimensions (citation analysis):
altmetrics (social interaction):



 


Sponsors

1suponsers_list_ciceco.jpg