MTO Schiff-base complexes: Synthesis, structures and catalytic applications in olefin epoxidation

Ming Dong Zhou, Jin Zhao, Jun Li, Shuang Yue, Chang Nian Bao, Janos Mink, Shu Liang Zang, Fritz E. Kühn

Research output: Contribution to journalArticle

63 Citations (Scopus)

Abstract

Several Schiff-base ligands readily form complexes with methyltrioxorhenium(VII) (MTO) by undergoing a hydrogen transfer from a ligand-bound OH group to a ligand N atom. The resulting complexes are stable at room temperature and can be handled and stored in air without problems. Due to the steric demands of the ligands they display distorted trigonal-bipyramidal structures in the solid state, as shown by X-ray crystallogra phy. with the O- moiety binding to the Lewis acidic Re atom and the Rebound methyl group being located either in cis or trans position to the Schiff base. In solution, however, the steric differences seem not to be maintained, as can be deduced from 17O NMR spectroscopy. Furthermore, the Schiff-base ligands exchange with donor ligands. Nevertheless, the catalytic behaviour is influenced significantly by the Schiff bases coordinated to the MTO moiety, which lead either to high selectivities and good activities or to catalyst decomposition. A large excess of ligand, in contrast to the observations with aromatic N-donor ligands, is detrimental to the catalytic performance as it leads to catalyst decomposition.

Original languageEnglish
Pages (from-to)158-166
Number of pages9
JournalChemistry - A European Journal
Volume13
Issue number1
DOIs
Publication statusPublished - Jan 8 2007

Keywords

  • Epoxidation
  • Homogeneous catalysis
  • Rhenium
  • Schiff bases
  • Structure-activity relationships

ASJC Scopus subject areas

  • Catalysis
  • Organic Chemistry

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