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.