Binuclear Copper Complexes and Their Catalytic Evaluation
Résumé
Two binuclear copper complexes [{CuI(L1)}2][OTf]2 (1) and [{CuII(L2)Cl}2] (2) have been synthesized and structurally characterized. The reaction of [{(5,7-dimethyl-1,8-naphthyridin-2-yl)amino}carbonyl]ferrocene (L1) with [Cu(CH3CN)4][OTf] in dichloromethane afforded complex 1 in high yield and the dicopper(II) complex 2 was obtained by the overnight treatment of N-(5,7-dimethyl-1,8-naphthyridin-2-yl)-1-methylpyrrolidine-2-carboxamide (L2H) with [Cu(CH3CN)4][BF4] in dichloromethane. The two copper atoms in complex 1 are bridged by two L1 ligands in a trans disposition; the naphthyridine nitrogen atoms bridge two copper centers and the carbonyl oxygen atoms occupy sites trans to the Cu***Cu vector. The metal***metal distance is 2.4594(6) Å. In contrast, in complex 2, each of the two L2 ligands bind to the two copper atoms through one naphthyridine nitrogen, a deprotonated amide, and a proline nitrogen atom to form an open-book geometry. Both dicopper complexes have been shown to be excellent catalysts for the cyclopropanation of various olefins with ethyl diazoacetate (EDA), with catalyst 1 found to be marginally superior to 2.