First Hexanuclear U(IV) and Th(IV) Formate Complexes - Structure and Stability Range in Aqueous Solution

The actinide(IV) hexanuclear M₆(mu₃-O(H))₈(HCOO)₁₂(LT)₆ complexes were prepared (LT = H₂O or CH₃OH). HCOO- acts as a bridging ligand, which prevents formation of polynuclear hydrolysis species of U(IV) hydrous oxide colloids at least until pH 3.25, and stabilizes the nano-sized clusters in solution. The charge of the hexamer is balanced by the O/OH ratio of the mu3-bridges.