Synthesis and structural characterization of copper complexes of N4 tetradentate Schiff bases derived from N-alkylated 2-aminobenzaldehyde.: Effects of cyclization, oxidation, and dinucleation

The structures of the copper complexes of 7,8,15,16,17,18-hexahydro-dibenzo[e,m][1,4,8,11]tetraazacyclotetradecine (Cu(2,2 mac)) 7,8,15,18-tetrahydro-dibenzo[e,m][1,4,8,11]tetraazacyclotetradecine-16,17-dionato (Cu(2,2 oxomac)) and Cu(N-CH3 amben) and Cu(2,2 oxomac)Ni(hfa)(2) are reported. The three copper complexes containing a 14-membered macrocycle are essentially square planar complexes and exhibit no short axial interactions. The analogous acyclic complex, Cu(N-CH3 amben), exhibits an average tetrahedral distortion of 34.35 degrees which appears to be due to steric repulsion between the two methyl groups. The dinuclear complex, which exhibits a planar exchange coupled oxamido core, was prepared by reaction of Cu(2,2 oxomac) with Ni(hfa)(2). The analogous complex, Cu(2,2 oxomac)Cu(hfa)(2). can be prepared by the same procedure or by reaction of Cu(2,2 mac) with Cu(hfa)(2). The former method is a general synthetic route while the latter is specific for Cu(hfa)(2) relying on its ability to catalyze the oxidization of the ethylene unit between the anilino nitrogen atoms to the oxamide (N-CH2-CH2-N- to N-CO-CO-N-) under ambient conditions. (C) 2001 Elsevier Science B.V. All rights reserved.