Catalysis Letters

, Volume 38, Issue 1–2, pp 101–108 | Cite as

Structural characterization of photoreduced complete and incomplete cubane-type molybdenum oxide clusters in CO and their catalytic behavior in propene metathesis reaction

  • Yasunori Imada
  • Takafumi Shido
  • Ryuichiro Ohnishi
  • Kiyoshi Isobe
  • Masaru Ichikawa
Article

Abstract

SiO2-impregnated complete and incomplete cubane-type molybdenum oxide clusters such as [(RhCp*)4Mo4O16] (I) and [(RhCp*)2Mo3O9(OMe)4] (II) were photoreduced with a UHP-Hg lamp (> 365 nm) in CO, resulting in the formation of catalytically active species for propene metathesis at 300 K. The CO-photoreduced Mo oxide clusters were characterized by EXAFS, IR, XPS and TPD technique. The results suggest that the Mo-O4c (four-centered bridging oxygens) in I were specifically reduced with CO under the illumination to produce two sets of subcarbonyl species, e.g., those characteristic of the IR bands at 2061 and 2021 cm−1, which were thermally inactive for the13CO exchange reaction but very active under illumination at 300 K, possibly assignable to Mo(CO)x (x = 2, 3), whereas those at 2092 and 2035 cm−1 due to Rh(CO)2, which were readily exchangeable with13CO at 300 K in dark. Removal of both carbonyls attached on Rh and Mo in photoreduced I and II by evacuation at 375–440 K led to the formation of oxygen-deficient Mo4+/Mo5+ sites, which exhibited high catalytic activities in propene metathesis at 300 K to produce an equimolar mixture of ethene and 2-butenes. The CO-photoreduced incomplete cubane Mo oxide cluster (II) exhibited higher activities and higher trans/cis ratios of 2-butenes in the reaction, compared with those on the photoreduced I.

Keywords

cubane-type molybdenum oxide clusters CO-photoreduction propene metathesis reaction 

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Copyright information

© J.C. Baltzer AG, Science Publishers 1996

Authors and Affiliations

  • Yasunori Imada
    • 1
  • Takafumi Shido
    • 1
  • Ryuichiro Ohnishi
    • 1
  • Kiyoshi Isobe
    • 2
  • Masaru Ichikawa
    • 1
  1. 1.Catalysis Research CenterHokkaido UniversitySapporoJapan
  2. 2.Department of Chemistry, Faculty of ScienceOsaka City UniversityOsakaJapan

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