Triosmium clusters on a support: Determination of structure by X-ray absorption spectroscopy and high-resolution microscopy

Shareghe Mehraeen, Apoorva Kulkarni, Miaofang Chi, Bryan W. Reed, Norihiko L. Okamoto, Nigel D. Browning, Bruce C. Gates

Research output: Contribution to journalArticle

7 Citations (Scopus)

Abstract

The structures of small, robust metal clusters on a solid support were determined by a combination of spectroscopic and microscopic methods: extended X-ray absorption fine structure (EXAFS) spectroscopy, scanning transmission electron microscopy (STEM), and aberration-corrected STEM. The samples were synthesized from [Os3(CO)12] on MgO powder to provide supported clusters intended to be triosmium. The results demonstrate that the supported clusters are robust in the absence of oxidants. Conventional high-angle annular dark-field (HAADF) STEM images demonstrate a high degree of uniformity of the clusters, with root-mean-square (rms) radii of 2.03±0.06Å The EXAFS Os-Os coordination number of 2.1±0.4 confirms the presence of triosmium clusters on average and correspondingly determines an average rms cluster radius of 2.02±0.04Å The high-resolution STEM images show the individual Os atoms in the clusters, confirming the triangular structures of their frames and determining Os-Os distances of 2.80±0.14Å, matching the EXAFS value of 2.89±0.06Å. IR and EXAFS spectra demonstrate the presence of CO ligands on the clusters. This set of techniques is recommended as optimal for detailed and reliable structural characterization of supported clusters.

Original languageEnglish
Pages (from-to)1000-1008
Number of pages9
JournalChemistry - A European Journal
Volume17
Issue number3
DOIs
Publication statusPublished - 2011 Jan 17
Externally publishedYes

Keywords

  • EXAFS spectroscopy
  • HAADF-STEM
  • MgO-supported clusters
  • aberration-corrected STEM
  • osmium carbonyls

ASJC Scopus subject areas

  • Catalysis
  • Organic Chemistry

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