Cu(ii) complexes of N-rich aroylhydrazone: magnetism and catalytic activity towards microwave-assisted oxidation of xylenes.

The new aroylhydrazone N'-(di(pyridin-2-yl)methylene)pyrazine-2-carbohydrazide (HL) species, rich in N-donor sites, has been used to synthesize Cu(ii) compounds with different nuclearities, viz. the binuclear [Cu2(μ-1κN3,2κN2O-L)(Cl)3(MeOH)] (1), the octanuclear [Cu4(μ-1κN3,2κN2O-L)2(μ-Cl)3(Cl)3]2 (2) and the 1D coordination polymer [Cu3(μ3-1κN3,2κN2O,3κN-L)(μ-NO3)(NO3)3(H2O)3]n·nNO3 (3). They have been characterized by elemental analysis, FT-IR and single crystal X-ray diffraction. The magnetic properties of 2 and 3 have been explored using variable temperature magnetic measurements. The catalytic performances of the compounds were evaluated towards the peroxidative oxidation of o-, p- and m-xylenes under microwave irradiation, leading to the formation of the corresponding methyl benzyl alcohol, tolualdehyde and toluic acid as the major products. Complex 3 exhibits the best catalytic activity towards the oxidation of p-xylene with a total yield of 37% (4-methylbenzyl alcohol + p-tolualdehyde + p-toluic acid).