Copper(II) complex of the 2-pyridinecarbaldehyde aminoguanidine Schiff base: Crystal structure and catalytic behaviour in mild oxidation of alkanes

The new neutral dichloro-copper(II) Schiff base complex [CuCl2L]center dot dmf2, where L results from condensation of 2pyridinecarbaldehyde and aminoguanidine, was prepared, while the ligand itself was isolated in its protonated form as the dinitrate salt (H2L)(NO3)(2) 1. Extended conjugation is responsible for the planarity of the H2L2+ cation in 1. On coordination, L forms two fused 5-membered chelate rings occupying three equatorial positions of the distorted square pyramidal copper polyhedron in 2. The catalytic investigations disclosed a prominent activity of the copper compound 2 towards oxidation of cyclohexane with hydrogen peroxide in the presence of various promoters (nitric and acetic acids, pyridine and pyrrole), showing overall yields of products (cyclohexanol and cydohexanone) up to 21% based on the substrate. (C) 2017 Elsevier B.V. All rights reserved.