Macrocycle Formation From Copper(II)Directed Condensation of Linear Tetraamines With Formaldehyde Alone and With Added 2-Aminoethanol

Abstract

Reaction of several tetraaminecopper(II) complexes with paraformaldehyde in acetonitrile or dioxan yields oxatetraazacycloalkanecopper(II) complexes, with a new -NH-CH₂-O-CH₂-NH-link completing the cyclization. The complexes are stable in aqueous acid for appreciable lengths of time, but eventually decompose, with the precursor tetraaminecopper(II) the major product. In alcohol with aqueous formaldehyde, the products are not detected. However, aqueous formaldehyde reacts with a methanolic solution of the copper(II) complex of 4,7- diazadecane-1,10-diamine in the presence of added 2-aminoethanol to produce the polycyclic polyamino ether complex (3-oxa-1,6,8,12,15-pentaazatricyclo[13.3.1.1.^8,12]icosane)copper(II) perchlorate. This complex crystallized in the monoclinic space group C2/c, a 32.777(8), b 9.395(2), c 14.914(6)Ǻ, β 111.97(2)°. The structure identifies three -NH-CH₂-NH- links, two as parts of new diazacyclohexane rings, and a single -O-CH₂-NH- link, all arising from condensation of the polyamine and/or the amino alcohol with formaldehyde. The copper ion lies in a plane of three nitrogens [Cu-N 1.976(4), 2.012(4) and 2.020(3)Ǻ] and the ether oxygen [Cu-O 2.008(3)Ǻ].