X-Ray and potentiometric studies on a pentanuclear copper( II ) complex with β-alaninehydroxamic acid

Potentiometric and X-ray studies on the system copper(II)–L-β-alaninehydroxamic acid have shown the formation of a very stable pentanuclear complex [Cu5A4H–4]2+ at pH around 4. In this species all donor atoms of the aminohydroxamic acid are involved in the metal ion co-ordination. Four peripheral metal ions form an almost planar structure and the central metal ion is 0.4 Å above this plane. There are twelve five- and six-membered chelate rings with different conformations. The X-ray structure results support earlier suggestions based on potentiometric and spectroscopic data for the formation of oligomeric structures at relatively low pH.