title: A discrete neutral transition-metal citrate cubane with an M₄O₄ core; coordinative versatility of the [M(II)₄(citrate)₄]⁸⁻ fragment.
abstract: The neutral cluster [Mn(II)8(citrate)4(H2O)18] is formed by the [M4(citrate)4](8-) fragment, with an Mn4O4 cubane core, which bonds four peripheral aquomanganese units--two [Mn(H2O)4](2+) and two [Mn(H2O)5](2+)--through a total of six metal-ligand bonds, giving a discrete neutral compound. The compound presents a unique coordination mode in which the citrate cubane acts as a chelate to each of the two peripheral [Mn(H2O)4](2+) (tetra-aquo) units. A detailed analysis of the central and peripheral geometries is given in terms of the tetrahedral distortions of key structural features. A reversible dehydration-rehydration process has been observed in a polycrystalline sample of the complex, whose structure lacks pores or channels.
authors.affiliation: Dpto. de Química Inorgánica and I.C.M.A., Universidad de Zaragoza - C.S.I.C., Pedro Cerbuna 12, E-50009 Zaragoza, Spain. falvello@unizar.es.
authors.forename: Larry R
authors.initials: LR
authors.lastname: Falvello
authors.forename: Elena
authors.initials: E
authors.lastname: Forcén-Vázquez
authors.forename: Fernando
authors.initials: F
authors.lastname: Palacio
authors.forename: Sergio
authors.initials: S
authors.lastname: Sanz
authors.forename: Milagros
authors.initials: M
authors.lastname: Tomás