The crystal structures of {LnCu(5)}(3+) (Ln = Gd, Dy and Ho) 15-metallacrown-5 complexes and a reevaluation of the isotypic Eu(III) analogue.

Three new isotypic heteropolynuclear complexes, namely penta-aqua-carbonato-penta-kis-(glycinehydroxamato)nitrato-penta-copper(II)lanthanide(III) x-hydrate, [LnCu(5)(GlyHA)(5)(CO(3))(NO(3))(H(2)O)(5)]·xH(2)O (GlyHA(2-) is glycine-hydrox-amate, N-hy-droxy-glycinamidate or amino-aceto-hydroxamate, C(2)H(4)N(2)O(2) (2-)), with lanthanide(III) (Ln (III)) = gadolinium (Gd, 1, x = 3.5), dysprosium (Dy, 2, x = 3.28) and holmium (Ho, 3, x = 3.445), within a 15-metallacrown-5 class were obtained on reaction of lanthanide(III) nitrate, copper(II) acetate and sodium glycinehydroxamate. Complexes 1-3 contain five copper(II) ions and five bridging GlyHA(2-) anions, forming a [CuGlyHA](5) metallamacrocyclic core. The Ln (III) ions are coordinated to the metallamacrocycle through five O-donor hydroxamates. The electroneutrality of complexes 1-3 is achieved by a bidentate carbonate anion coordinated to the Ln (III) ion and a monodentate nitrate anion coordinated apically to one of the copper(II) ions of the metallamacrocycle. The lattice parameters of complexes 1-3 are similar to those previously reported for an Eu(III)-Cu(II) 15-metallacrown-5 complex with glycine-hydroxamate of proposed composition [EuCu(5)(GlyHA)(5)(OH)(NO(3))(2)(H(2)O)(4)]·3.5H(2)O [Stemmler et al. (1999 ▸). Inorg. Chem. 38, 2807-2817]. High-quality X-ray data obtained for 1-3 have allowed a re-evaluation of the X-ray data solution proposed earlier for the EuCu(5) complex and suggest that the formula is actually [EuCu(5)(GlyHA)(5)(CO(3))(NO(3))(H(2)O)(5)]·3.5H(2)O.