Water-Soluble Copper(II) Complexes with a Sulfonic-Functionalized Arylhydrazone of ß-Diketone and Their Application in Peroxidative Allylic Oxidation of Cyclohexene

The reaction of CuII acetate with the new sulfo-functionalized arylhydrazone of beta-diketone 2-[2-(4,4-dimethyl-2,6-dioxocyclohexylidene)hydrazinyl]benzenesulfonic acid (H2L, 1) in aqueous methanol solution led to the formation of the 2D coordination polymer {[Cu4(1?2O,?N:2?O,?N-L)4(mu-OH2)2].H2O}n (2). However, when the reaction was peformed in the presence of the N-containing species cyanoguanidine (cyg), 3,5-dimethyl-1H-pyrazole (dp), 2,2'-bipyridine (bpy) or pyrazine (py), the mononuclear (H3O+)2[Cu(?2O,?N-L)2] (4), [Cu(?2O,?N-L)(dp)2] (3) or [Cu(?2O,?N-L)(?2N-bpy)] (5) or dinuclear [{Cu(?2O,?N-L)(H2O)}2(?-py)].CH3OH (6) complexes were obtained, respectively. The compounds were characterized by elemental analysis, IR spectroscopy, single-crystal X-ray diffraction analysis and, for 1, by 1H and 13C NMR spectroscopy. The CuII complexes 26 act as catalyst precursors for the selective peroxidative (with TBHP) allylic oxidation of cyclohexene to cyclohex-2-enol (Cy-ol) and cyclohex-2-enone (Cy-one), formed in a Cy-one/Cy-ol ratio of up to 9 with total yields of around 70?% and TONs of up to 350.