Tetraazacycloalkanes With Pendant Carboxylates. Copper(II)-Directed Syntheses and Crystal Structure of (Ethyl 1,5,9,13-tetraazabicyclo[11.2.2]heptadecane-7-carboxylate)copper(II) Perchlorate

Abstract

Reaction of copper(II) complexes of the tetraamines H₂N-(CH₂)n-NH-(CH₂)m-NH-(CH₂)n-NH₂ (n, m=5, 6), N,N′- bis (3-aminopropyl)-1,4-diazacyclohexane and ethane-1,2-diamine with formaldehyde and diethyl malonate in methanolic base produces macrocycles where initially new -NH-CH₂-C( COOEt )₂-CH₂-NH-links are built by joining the cis-disposed primary amines in the precursor complexes. Under the basic conditions of the reaction, the macrocyclic product may be isolated not simply with gem ethoxycarbonyl groups, but as the carboxy ethoxycarbonyl, or even with a single carboxy pendant or its ester following ester hydrolysis and/or decarboxylation reactions. All diesters or acid esters can be hydrolysed conveniently to the stable monoacid in aqueous base, producing complexes of macrocyclic tetraamines with a single carboxylate group pendant to the ring at the central carbon of a propyl chain. Physical properties of the copper(II) complexes are reported and compared with analogues where a nitro group is pendant to the ring rather than the carboxylate group. The (ethyl 1,5,9,13-tetraazabicyclo[11.2.2]heptadecane-7-carboxylate)copper(II) perchlorate monohydrate was crystallized in the monoclinic space group P 2₁/c, a 8.968(3), b 8.435(3), c 32.007(11)Ǻ, β 99.18(3)°, Z = 4, and a single-crystal X-ray structure determination refined to R 0.045 for 2631 'observed' reflections. The copper ion exists in a square pyramidal geometry of four nitrogen donors and a perchlorate anion oxygen, with a quite short Cu-O distance (2.30Ǻ). The Cu-N(secondary) and Cu-N(tertiary) distances are 2.037(4), 2.035(4), and 2.082(4), 2.062(4)Ǻ respectively.