A discrete neutral transition-metal citrate cubane with an M4O4 core; coordinative versatility of the [MII4(citrate)4]8− fragment†
Abstract
The neutral cluster [MnII8(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.