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

Abstract The reaction of Cu II acetate with the new sulfo‐functionalized arylhydrazone of β‐diketone 2‐[2‐(4,4‐dimethyl‐2,6‐dioxocyclohexylidene)hydrazinyl]benzenesulfonic acid (H 2 L, 1 ) in aqueous methanol solution led to the formation of the 2D coordination polymer {[Cu 4 (1κ 2 O ,κ N :2κ O ,κ N ‐L) 4 (μ‐OH 2 ) 2 ] · H 2 O} n ( 2 ). However, when the reaction was peformed in the presence of the N‐containing species cyanoguanidine (cyg), 3,5‐dimethyl‐1 H ‐pyrazole (dp), 2,2′‐bipyridine (bpy) or pyrazine (py), the mononuclear (H 3 O + ) 2 [Cu(κ 2 O ,κ N ‐L) 2 ] ( 4 ), [Cu(κ 2 O ,κ N ‐L)(dp) 2 ] ( 3 ) or [Cu(κ 2 O ,κ N ‐L)(κ 2 N‐bpy)] ( 5 ) or dinuclear [{Cu(κ 2 O ,κ N ‐L)(H 2 O)} 2 (κ‐py)] · CH 3 OH ( 6 ) complexes were obtained, respectively. The compounds were characterized by elemental analysis, IR spectroscopy, single‐crystal X‐ray diffraction analysis and, for 1 , by 1 H and 13 C NMR spectroscopy. The Cu II complexes 2 – 6 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.