Oxidation of substituted phenols using copper(II) metallatriangles formed through ligand sharing.

Abstract Reaction of N 2 , N 2′ - bis -[(1-butyl-benzimidazol-2yl)methyl]biphenyl-2,2′-dicarboxamide ( L ) with CuX 2 ⋅nH 2 O in methanol leads to the assembly of four trinuclear Cu(II) complexes with the general formula [Cu 3 ( L ) 3 X 3 ]⋅3 X ⋅nH 2 O⋅mMeCN, where X  = Cl − , Br − , NO 3 − and C 6 H 5 COO − and n  = 0–5, m  = 0–8 (compounds 1–4 , respectively). The structure of one of the complex contains three Cu(II) metal ions at the corners of an equilateral triangle. Each of the copper(II) are coordinated through two benzimidazolyl imine N -atoms and two amide carbonyl O -atoms and the apical position is occupied by an anionic nitrate ion, leading to a distorted square pyramidal environment. The magnetic susceptibility data were analyzed through Hamiltonian H = − J ( S 1 S 2  +  S 2 S 3  +  S 1 S 3 ) obtaining − J  = 0.16, 0.12, 0.15 and 0.14 cm −1 for 1–4 , respectively. X-Band EPR spectra typically show a broad single line at 120 K with g  ∼ 2.11. Oxidation of phenols was studied homogeneously using copper(II) metallatriangles ( 1 – 3 ) as catalyst in acetonitrile. The oxidation of 2,4,6-tri- tert -butyl phenol yields the corresponding quinone after oxidative dealkylation. The oxidation of 2-amino-5-methyl phenol yields the corresponding phenoxazinone while the oxidation of 2-amino-4- tert -butyl phenol yields the phenoxazine instead of phenoxazinone. The products so obtained were analyzed by NMR and X-ray single crystallography.