Copper(II) complexes of mono- and di-nucleating hexaamines†

Abstract

The potentially hexadentate polyamines N,N,N′,N′-tetrakis(2-aminoethyl)ethane-1,2-diamine (L¹) and the octamethylated analogue N,N,N′,N′-tetrakis(2-dimethylaminoethyl)ethane-1,2-diamine (L²) have been complexed with copper(II) and the crystal structures of their complexes determined. A trigonal-bipyramidal co-ordination geometry for [Cu(HL¹)][ClO₄]₃ was found where one aminoethyl arm is not co-ordinated. By contrast, a dinuclear structure of formula [(H₂O)Cu(L²)Cu(OH)]³⁺ was determined for the N-methylated analogue, where the hexaamine acts as a bridging ligand between the two square-pyramidal metal centres. Electronic and EPR spectroscopy are both consistent with these structures being maintained in solution.