Synthesis, Characterization, and Catalytic Reactivities of Novel Dinuclear Cu(II) Complexes : Efficient Ring Opening Reaction of Epoxide

摘要

Novel tridentate N2O-type ligands L1-L4 (((((X-benzyl)pyridine-2-yl)methylamino)methyl)phenol); L1 for X=4-CH3, L2 for X=H, L3 for X=2-F, L4 for X=4-CF3) and their dinuclear copper(II) complexes C1-C4 (C1 for [(L1)(2)Cu-2(NO3)(2)], C2 for [(L2)(2)Cu-2(NO3)(2)], C3 for [(L3)(2)Cu-2(NO3)(2)] and C4 for [(L4)(2)Cu-2(NO3)(2)]) was synthesized and verified by H-1 NMR, IR, and ESI-Mass. The structural forms of the copper complexes were determined by X-ray crystallography. The dinuclear copper complexes C1-C4 showed efficient ring-opening properties of epoxides with methanol under mild conditions. In particular, the copper complex C1 having electron-donating group in the ligand showed the most efficient reactivity in the ring opening of epoxides. The sole attack at the benzylic carbon of styrene oxide and the less steric preference in 1,2-epoxyhexane demonstrated that the regiochemistry of the ring opening catalyzed by dinuclear copper complexes might be dependent on the electronic feature of epoxide.