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Homogeneous oxidation reactions catalysed by in situ-generated triazolylidene copper(I) complexes

  • Siyabonga G. Mncube
  • Muhammad D. Bala
Article
  • 46 Downloads

Abstract

Four new Cu complexes bearing triazolylidene ligands 1-(R)-3-methyl-4-phenyl-1H-1,2,3-triazol-3-ium-5-yl: R = phenyl (2a), mesitylenyl (2b), propyl (2c), hexyl (2d) (NHC) were synthesised in high yields. Characterisation by spectroscopic and analytical methods confirmed the molecular composition of the complexes as NHC–Cu-I. The complexes 2(a–d) bearing NHC wingtip variations were tested as in situ-generated catalysts for homogeneous oxidation catalysis with H2O2 as oxidant. The in situ technique was adopted for ease of application and to circumvent the poor stability of the complexes in solution. The results showed that the NHC–Cu-I complexes are capable of initiating oxidation reactions, yielding ketones/aldehydes as dominant products for the oxidation of alkanes under optimised reaction conditions, with complexes bearing aliphatic N-substituents showing the highest catalytic activities. Oxidation of toluene with 2c resulted in a mixture of benzaldehyde and benzyl alcohol as the main products. Also, 2c catalysed the oxidation of n-octane, yielding a mixture of mainly C-8 oxidation products with over 75% selectivity for the isomeric octanones. Analysis of regioselectivity indicated that the internal \({\text{C}}_{{sp^{3} }}\)–H bonds of n-octane [especially C(2)] are more reactive than the terminal ones.

Graphical abstract

Notes

Acknowledgements

This project is generously supported by c*change PAR program, the National Research Foundation and the University of KwaZulu-Natal for which we are grateful (Grant No. PAR08).

Supplementary material

11243_2018_278_MOESM1_ESM.docx (1.5 mb)
Supplementary material 1 (DOCX 1493 kb)

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Copyright information

© Springer Nature Switzerland AG 2018

Authors and Affiliations

  1. 1.School of Chemistry and PhysicsUniversity of KwaZulu-NatalDurbanSouth Africa

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