Copper(II) and Cobalt(III) Complexes of a Mixed Secondary and Tertiary Nitrogen Donor Tetraaza Macrocycle. Crystal Structure of Aqua(7-methyl-7-nitro-1,5,9,13-tetraaza-bicyclo[11.2.2]heptadecane)copper(II) Perchlorate Hydrate

Abstract

Reaction of (bis(3-aminopropyl) piperazine )copper(11) ion with nitroethane and formaldehyde in basic methanol results in the ready formation of (7-methyl-7-nitro-1,5,9,13- tetraazabicyclo [11.2.2] heptadecane )copper(11) ion in high yield. The perchlorate salt of the macrocyclic complex crystallizes in the orthorhombic space group Pbca, a 19.144(8), b 17.499(5), c 14.635(5) Å, Z=8, with the copper ion in a square-pyramidal environment of four nitrogen donors and a water molecule. The Cu-secondary N and Cu-tertiary N distances are 2.044(8), 2.056(8) and 2.053(8), 2.072(8) Å respectively, with the Cu-O distance 2.259(8)Å. Reduction of the complex with Zn/ HCl yields the 7-methyl-1,5,9,13-tetraazabicyclo [l1.2.2]heptadecane-7-amine analogue, characterized as copper(II) and cobalt(III) complexes. The cobalt(III) complex contains the latter macrocycle as a quinquedentate ligand with the pendant primary amine coordinated trans to a chloride ion, identified as the only isomer by chromatography, and characterized by electronic and n.m.r. spectroscopy. Consequences of 'reinforcement' of the macrocycle by the extra ethane bridge are discussed.