Copper(II) and nickel(II) complexes of N,N′,N″,Nâ�—-tetrakis(2-aminoethyl)-1,4,7,11-tetra-azacyclotetradecane (taei), -1,4,8,12-tetra-azacyclopentadecane (taep), and -1,5,9,13-tetra-azacyclohexadecane (taeh). Crystal structures of [Cu2(taep)][ClO4]4, [Cu2(taeh)][ClO4]4, and [Cu2(N3)(taeh)][ClO4]3

Abstract

New octaamine dinucleating ligands, N,N′,N″,N‴-tetrakis(2-aminoethyl)-1,4,7,11-tetra-azacyclo-tetradecane (taei), -1,4,8,12-tetra-azacyclopentadecane (taep), and -1,5,9,13-tetra-azacyclohexadecane (taeh) and their complexes with Cu^II and Ni^II were synthesized. Of the 19 complexes isolated, the structures of [Cu₂(taep)][ClO₄]₄, [Cu₂(taeh)][ClO₄]₄, and [Cu₂(N₃)(taeh)][ClO₄]₃ were determined by X-ray crystal analysis. In all these complexes each copper is co-ordinated by two ring nitrogens and two pendant amino nitrogens, and the two CuN₄ co-ordination sets face each other. In the azido complex the N₃^– is bonded to both coppers in an end-to-end fashion. The dinuclear complexes [Cu₂L][ClO₄]₄(L = taei or taep) further incorporate various anions between the two coppers to form [Cu₂X(L)][ClO₄]₃. However, only the azido complex was obtained with taeh. The results are discussed in terms of the ring-size effect.