Zirconium propoxide (70 w% in propanol) or zirconium butoxide (80 w% in butanol) reacts with an excess of acetic acid (8 equivalents) to form the Zr12-acetate cluster, which is a dimer of Zr6. The reaction is performed in dichloromethane (DCM) solvent to obtain higher quality crystals. Both acetic acid and DCM are co-crystallized with the cluster. The balanced chemical equation is shown in Scheme 1. We further washed the crystalline powder with a solution of acetic acid in DCM to remove reaction by-products and other zirconium species. Although the powder can be handled in air, it is recommended for long term storage to keep the clusters in a glovebox or desiccator, since they react slowly with atmospheric water and become partially insoluble. Scheme 1: Balanced chemical equation for the synthesis of Zr12-acetate clusters from zirconium propoxide (or butoxide) and acetic acid. The final product has co-crystallized acetic acid and dichloromethane (the latter is not shown). Also the structures of the other carboxylic acids used here for cluster synthesis are shown.