title: (N-Benzyl-bis-N',N''-salicylidene)-cis-1,3,5-triaminocyclohexane copper(II): a novel catalyst for the aerobic oxidation of benzyl alcohol.
abstract: Reaction of Cu(BF(4))(2).6H(2)O with the N(3)O(2) donor ligand H(2)L (where H(2)L = N-benzyl-N',N''-di-tert-butyl-disalicyl-triaminocyclohexane) results in the formation of a novel Cu(II)L complex, 1. X-Ray crystallography of it 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 A) in the axial position. EPR spectroscopy 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 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 (DeltaE = 81 mV, vs. Ag/AgCl) and the second at E((1/2)) = 1.13V (DeltaE = 84 mV, vs. Ag/AgCl). Chemical oxidation results in the formation of a species, assigned as [1](+)(.) 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.
authors.affiliation: Department of Chemistry, University of York, Heslington, York, UK YO10 5DD.
authors.forename: Alison K
authors.initials: AK
authors.lastname: Nairn
authors.forename: Stephen J
authors.initials: SJ
authors.lastname: Archibald
authors.forename: Rajiv
authors.initials: R
authors.lastname: Bhalla
authors.forename: Bruce C
authors.initials: BC
authors.lastname: Gilbert
authors.forename: Elizabeth J
authors.initials: EJ
authors.lastname: Maclean
authors.forename: Simon J
authors.initials: SJ
authors.lastname: Teat
authors.forename: Paul H
authors.initials: PH
authors.lastname: Walton