Three Different Modes of Association between Metal Cations in Heterometallic Uranyl–CoIII and Uranyl–MnII Species

Abstract

Three heterometallic complexes including uranyl and either CoIII or MnII cations were crystallized under hydrothermal conditions. Complexes [Co(bipy)3]2[UO2(NO3)4]2[(UO2)2(NO3)4(OH)2] (1) and [UO2(NO3)2Co(bipy)2(OH)2]·NO3·H2O (2) (bipy = 2,2′‐bipyridine) were obtained from the same solution. UO22+ and CoIII are part of separate anions and cations, respectively, in complex 1, the uranyl ion being present in both a mononuclear dianion with two chelating and two monodentate nitrates in cis positions, and in a dinuclear, bis‐hydroxo‐bridged dianion. In contrast, both metal cations are part of a monocationic heterometallic bis‐hydroxo‐bridged complex in 2, UO22+ retaining two nitrate and CoIII two bipy ligands. This is the third example only of a hydroxo‐bridged heterometallic uranyl complex, and the first to involve CoIII. The complex [(UO2)6Mn(O)4(OH)6(H2O)4]·5H2O (3), synthesized in the absence of any added ligand, crystallizes as a three‐dimensional framework in which anionic uranyl oxyhydroxide layers with the α‐U3O8‐type polyhedral arrangement are connected to one another by Mn(H2O)42+ cations axially bound to two uranyl oxo atoms. These very simple systems thus display a large range of possible intermetallic associations, that involving bis‐oxo‐bonding to uranyl enabling formation of a framework through pillaring of sheets.