The pentadentate macrobicyclic ligand 1,5,8,12,15-pentaazabicyclo[10.5.2]nonadecane (L3), in which 1,4,7-triazacyclononane and cyclam (1,4,8,11 -tetraazacyclotetradecane) are “fused”, has been synthesized. The reactions involve condensation of [N,N'-bis(aminopropyl)-1,4,7-triazacyclononane]copper(II), [Cu(L)]2+, with glyoxal followed by reduction and demetalation. This process represents one of the few successful ring-closure condensations of this type at a copper center. A detailed mechanism, involving two unusual intermediates that have been isolated and characterized, is provided. The condensation results in the formation of the imidate complex [Cu(L1)]2+ via MeOH addition across a C=N bond. This imidate is unusual in that it is extremely resistant to acid hydrolysis, but it does undergo base hydrolysis to yield the first example of an amide formed by the condensation of a diamine with glyoxal. Incomplete reduction of the imidate (BH4-) affords a complexed enamine cation, [Cu(L2)]2+. The perchlorate salt of [Cu(L1)]2+ crystallized in the monoclinic space group P21/c (a = 8.492 (2), b = 17.240 (6), c = 15.696 (4) Å; β = 96.47 (2)°). Refinement converged at R = 0.0855 for 286 parameters with 1626 reflections with I > 3σ(I). The complex is square-pyramidal and contains an imidate group (C=N = 1.28 (2) Å). One of the perchlorate anions was disordered along the C3 axis, with occupancy factors of 0.45 and 0.55 for the two resolved configurations. The perchlorate salt of [Cu(L2)]2+ crystallized in the orthorhombic space group Pbca (a = 14.144 (5), b = 16.815 (6), c = 18.236 (5) Å). Refinement converged at R = 0.0619 for 283 parameters with 2658 reflections with I > 2σ(I). The complex is square-pyramidal with an enamine group showing a very short carbon-carbon double bond (1.213 (14) Å). © 1993, IEEE. All rights reserved. © 1990, American Chemical Society. All rights reserved.
