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Keywords:

  • Nitrogen heterocycles;
  • Oxidation;
  • Carbene ligands;
  • Ruthenium;
  • Osmium

Abstract

Hemilabile ligands are known to impart remarkable properties to their metal complexes. Herein, we present arene half-sandwich complexes of RuII, OsII, and IrIII with “click”-derived 1,2,3-triazole (L1) and 1,2,3-triazol-5-ylidene (L2) ligands containing a potentially hemilabile thioether donor. Structural elucidation of the complexes revealed localization of double bonds within the triazole in L1 and a delocalized situation within the triazolylidene ring of L2. For complexes with L1, unusual coordination occurs through the less basic nitrogen “N2” of the 1,2,3-triazole. All complexes were applied for the catalytic oxidation of benzyl alcohol to benzaldehyde using N-methylmorpholine N-oxide as sacrificial oxidant. Furthermore, oxidation of diphenylmethanol to benzophenone was also achieved by using low catalyst loadings in very good yields. These are rare examples of OsII–triazole, as well as of OsII–triazolylidene complexes with “click”-derived ligands.