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Issue 1, 2006
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(N-Benzyl-bis-N′,N″-salicylidene)-cis-1,3,5-triaminocyclohexane copper(II): a novel catalyst for the aerobic oxidation of benzyl alcohol

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Abstract

Reaction of Cu(BF4)2·6H2O with the N3O2 donor ligand H2L (where H2L = N-benzyl-N′,N″-di-tert-butyl-disalicyl-triaminocyclohexane) results in the formation of a novel CuIIL complex, 1. X-Ray crystallography of 1 shows the CuII 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 Å) in the axial position. EPR spectroscopy of 1 gives g values of g1 = 2.277, g2 = 2.100, g3 = 2.025, and A1 = 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 E½ = 0.89 V (ΔE = 81 mV, vs. Ag/AgCl) and the second at E½ = 1.13V (ΔE = 84 mV, vs. Ag/AgCl). Chemical oxidation of 1 results in the formation of a species, assigned as [1]+˙ which is EPR silent due to antiferromagnetic coupling between the CuII centre and the bound phenoxyl radical. The oxidised species catalyses the oxidation of benzyl alcohol to benzaldehyde.

Graphical abstract: (N-Benzyl-bis-N′,N″-salicylidene)-cis-1,3,5-triaminocyclohexane copper(ii): a novel catalyst for the aerobic oxidation of benzyl alcohol

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Publication details

The article was received on 30 Aug 2005, accepted on 14 Oct 2005 and first published on 28 Oct 2005


Article type: Paper
DOI: 10.1039/B512296C
Citation: Dalton Trans., 2006, 172-176
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    (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 and P. H. Walton, Dalton Trans., 2006, 172
    DOI: 10.1039/B512296C

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