Metal Directed Synthesis Involving Formaldehyde and Nitroethane, and Crystal Structure of the Copper(II) Complex of the 14-Membered Macrocycle 6-Methyl-6-Nitro-1,4,8,11-Tetraazacyclotetradecane

Abstract

The condensation reaction of (3,7-diazanonane-1,9-diamine)copper(II) with formaldehyde and nitroethane in basic methanol is highly specific, producing the macromonocyclic complex (6-methyl-6-nitro-1,4,8,11-tetraazacyclotetradecane)copper(II) as the only product. However, under conditions employed, the reaction cannot be readily driven to completion, and an intermediate consisting of equimolar amounts of precursor and product complexes can be crystallized preferentially. The intermeciate crystallizes in the monoclinic space group P 2₁/c, a 16.11 5(10), b 8 825(6), c 25.970(13)Å, β 104.30(4)º, and consists of a linear polymer of the two alternating copper(II) complexes bridged by perchlorate anions; 3372 'observed' reflections were refined to a residual of 0.049. Each copper ion is surrounded by a square-planar arrangement of four nitrogen donors, with perchlorate oxygens from bridging ions occupying the axial sites. The Cu-N distances in the precursor tetraamine unit (1.991 to 2.006 Å) and the product macromonocycle unit (1.995 to 2.017 Å) are similar; apparently the copper ion is readily accommodated in both the precursor and the 14-membered macrocycle. Reduction of the nitro group of the macrocycle by zinc/aqueous acid produces the corresponding ligand with a pendant primary amine group, isolated as the copper(II) complex. Complexes were characterized by infrared and electronic spectroscopy, and voltammetry.