The crystal structures of {LnCu5}3+ (Ln = Gd, Dy and Ho) 15-metallacrown-5 complexes and a reevaluation of the isotypic EuIII analogue

Abstract

Three new isotypic heteropolynuclear complexes, namely pentaaquacarbon-atopentakis(glycinehydroxamato)nitratopentacopper(II)lanthanide(III) x-hydrate, [LnCu5(GlyHA)5(CO3)(NO3)(H2O)5]xH2O (GlyHA2 is glycinehydroxamate, N-hydroxyglycinamidate or aminoacetohydroxamate, C2H4N2O22), with lanthanide(III) (LnIII) = 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 GlyHA2 anions, forming a [CuGlyHA]5 metallamacrocyclic core. The LnIII 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 LnIII 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 EuIII-CuII 15-metallacrown-5 complex with glycinehydroxamate of proposed composition [EuCu5(GlyHA)5(OH)(NO3)2-(H2O)4]3.5H2O [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 EuCu5 complex and suggest that the formula is actually [EuCu5(GlyHA)5(CO3)(NO3)(H2O)5]3.5H2O.