Windmill-type mixed-metal clusters containing Schiff-base ligands as an efficient catalyst for cyclohexene oxidation

Two new mixed-metal clusters {CuM 2 (H 2 O) 2 [Cu(C 14 H 16 N 2 O 3 )Cl] 6 }·H 2 O (M = Mn 1 , Zn 2 ) based on Schiff-base ligands were designed and synthesized by the reaction of 1,2-cyclohexanediamine- N , N ′-bis-(3-carboxylsalicylide), copper chloride and zinc chloride or manganese chloride under solvothermal conditions. They were characterized by various techniques including single-crystal X-ray diffraction, powder X-ray diffraction (XPRD), elemental analysis, TG analysis, IR and UV-visible spectroscopy. Compounds 1 and 2 are isostructural, and display an interesting windmill-type structure built from a trinuclear mixed-metal center [CuM 2 (CO 2 ) 6 (H 2 O) 2 ] (M = Mn 1 , Zn 2 ) linked with six [CuLCl] (L = C 14 H 16 N 2 O 3 ) units. The oxidation of cyclohexene catalysed by 1 and 2 as heterogeneous catalysts was investigated and showed high activity. In addition, a magnetic study indicates that antiferromagnetic interactions exist in compound 1 .