One-dimensional chain structures of hexanuclear uranium(iv) clusters bridged by formate ligands

Abstract

Three one-dimensional chain structures of uranium(iv) hexanuclear clusters have been synthesized under hydrothermal/solvothermal conditions. Crystallographic studies disclose that the structures of [U6O4(OH)4(HCOO)12(H2O)]·3H2O (1a), [U6O4(OH)4(HCOO)12(HCOOH)(H2O)]·3H2O (1b) and (H6C5N)2[U6O4(OH)4(HCOO)14(H5C5N)] (2) contain a U(iv) hexanulear core [U6(μ3-OH)4(μ3-O)4]12+ which is decorated by terminal HCOO- ligands and water (1a, 1b), HCOOH (1b) or pyridine molecules (2). These hexanuclear U(iv) clusters are further linked into zig-zag 1-D chain structures via bridging HCOO- ligands. UV-vis-NIR spectra, together with bond valence calculations, indicate that all U atoms in three compounds exist as U(iv). Magnetic susceptibility data reveal that compound 2 exhibits paramagnetic characteristics.