(N-benzyl-bis-N ',N ''-salicylidene)-cis-1,3,5-triaminocyclohexane copper(II): a novel catalyst for the aerobic oxidation of benzyl alcohol

A K Nairn, S J Archibald, R Bhalla, B C Gilbert, E J MacLean, S J Teat, P H Walton

Research output: Contribution to journalArticlepeer-review

Abstract

Reaction of Cu(BF4)(2) center dot 6H(2)O with the N3O2 donor ligand H2L (where H2L = N-benzyl- N', N ''-di-tert-butyl-disalicyl- triaminocyclohexane) results in the formation of a novel (CuL)-L-II complex, 1. X-Ray crystallography of 1 shows the Cu-II centre coordinated by two phenolate oxygens and two imine nitrogens in a distorted square plane with an elongated bond to the amine nitrogen (2.512 angstrom) in the axial position. EPR spectroscopy of 1 gives g values of g(1) = 2.277, g(2) = 2.100, g(3) = 2.025, and A(1) = 15.6 mT which are consistent with the distorted square pyramidal coordination environment determined from the X-ray structure. UV/visible and electrochemical analysis of 1 shows that it undergoes two reversible processes assigned to the successive oxidation of the phenolate oxygens to phenoxyl radicals, the first at E-1/2 = 0.89 V (Delta E = 81 mV, vs. Ag/AgCl) and the second at E-1/2 = 1.13 V (Delta E = 84 mV, vs. Ag/AgCl). Chemical oxidation of 1 results in the formation of a species, assigned as [1](+center dot) which is EPR silent due to antiferromagnetic coupling between the Cu-II centre and the bound phenoxyl radical. The oxidised species catalyses the oxidation of benzyl alcohol to benzaldehyde.

Original languageEnglish
Pages (from-to)172-176
Number of pages5
JournalDalton Transactions
Volume1
Issue number1
DOIs
Publication statusPublished - 2006

Keywords

  • PHENOXYL RADICAL COMPLEXES
  • GALACTOSE-OXIDASE MODELS
  • N-PYRIDYL DERIVATIVES
  • OXIDIZED ACTIVE FORM
  • STRUCTURAL MODELS
  • ONE-ELECTRON
  • SITE MODELS
  • CHEMISTRY
  • MONONUCLEAR
  • REACTIVITY

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