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Triazolylidene-Iridium Complexes with a Pendant Pyridyl Group for Cooperative Metal-Ligand Induced Catalytic Dehydrogenation of Amines.
Journal article

Triazolylidene-Iridium Complexes with a Pendant Pyridyl Group for Cooperative Metal-Ligand Induced Catalytic Dehydrogenation of Amines.

  • Valencia M Department of Chemistry and Biochemistry, University of Bern, Freiestrasse 3, 3012, Bern, Switzerland.
  • Pereira A School of Chemistry, University College Dublin, Belfield, Dublin 4, Ireland.
  • Müller-Bunz H School of Chemistry, University College Dublin, Belfield, Dublin 4, Ireland.
  • Belderraín TR Laboratorio de Catálisis Homogénea, Unidad Asociada al CSIC, Centro de Investigación en Química Sostenible, Departamento de Química, Universidad de Huelva, 21007, Huelva, Spain.
  • Pérez PJ Laboratorio de Catálisis Homogénea, Unidad Asociada al CSIC, Centro de Investigación en Química Sostenible, Departamento de Química, Universidad de Huelva, 21007, Huelva, Spain.
  • Albrecht M Department of Chemistry and Biochemistry, University of Bern, Freiestrasse 3, 3012, Bern, Switzerland.
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  • 2017-04-07
Published in:
  • Chemistry (Weinheim an der Bergstrasse, Germany). - 2017
amine dehydrogenation
hydrogen bonding
iridium
ligand-metal cooperativity
triazolylidene
English Two iridium(III) complexes containing a C,N-bidentate pyridyl-triazolylidene ligand were prepared that are structurally very similar but differ in their pendant substituent. Whereas complex 1 contains a non-coordinating pyridyl unit, complex 2 has a phenyl group on the triazolylidene substituent. The presence of the basic pyridyl unit has distinct effects on the catalytic activity of the complex in the oxidative dehydrogenation of benzylic amines, inducing generally higher rates, higher selectivity towards formation of imines versus secondary amines, and notable quantities of tertiary amines when compared to the phenyl-functionalized analogue. The role of the pyridyl functionality has been elucidated from a set of stoichiometric experiments, which demonstrate hydrogen bonding between the pendant pyridyl unit and the amine protons of the substrate. Such Npyr ⋅⋅⋅H-N interactions are demonstrated by X-ray diffraction analysis, 1 H NMR, and IR spectroscopy, and suggest a pathway of substrate bond-activation that involves concerted substrate binding through the Lewis acidic iridium center and the Lewis basic pyridyl site appended to the triazolylidene ligand, in agreement with ligand-metal cooperative substrate activation.
Language
  • English
Open access status
closed
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Persistent URL
https://folia.unifr.ch/global/documents/285910
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