THE NON-FORMATION OF MACROCYCLIC TETRAAMIDES BY COORDINATED LIGAND REACTIONS

A recent paper has described the synthesis of macrocyclic tetraamide c omplexes by the reaction of a diamine (ethylenediamine or propylenedia mine) with malonic, succinic or glutaric acids in methanol solution in the presence of a metal(II) salt at room temperature. We present evid ence that macrocycle formation does not occur under these conditions a nd only mixed-ligand complexes are formed. The blue crystalline comple x obtained with malonic acid, 1,3-diaminopropane and copper(II) chlori de is shown by X-ray crystallography to be [Cu(mal)(pn)Cl-2](2-) pnH(2 )(2+) (mal = malonate; pn = 1,3-diaminopropane). The structure compris es discrete [Cu(mal)(pn)Cl-2](2-) anions and pnH(2)(2+) cations. Withi n the anionic complex the geometry at each copper(II) is tetragonal wi th two long axial bonds to the chloride ligands, Cu-Cl(1) = 2.862(2) a nd Cu-Cl(2) = 3.042(2) Angstrom. The malonato ring has a boat conforma tion with Cu-O = 1.966(3) Angstrom and the 1,3-diaminopropane ring a c hair conformation with Cu-N = 1.393(4) Angstrom. A crystallographic mi rror plane bisects the two rings through the copper and chloride ligan ds. (C) 1997 Elsevier Science Ltd.