The structure of tetranuclear zirconium pivalate ZR₄O₂ [(CH₃)₃CCO₂]₁₂ according to X-ray diffraction analysis and quantum chemical calculations

The crystal and molecular structure of a polynuclear pivalate complex obtained by the interaction of ZrCl₄ with pivalic acid was determined by X-ray diffraction analysis. The compound C₇₁H₁₂₄O₂₈Zr₄ (compound 1) crystallizes in the monoclinic crystal system. The crystal structure was refined in the nonstandard space group I2. The asymmetric part of the structure includes three Zr atoms, six pivalate ligands, a bridging µ₃-O oxygen atom, as well as disordered crystallization molecules of pivalic acid with an occupancy of 50% and benzene with an occupancy of 50%. The zirconium complex molecule is a tetranuclear cluster that contains three types of Zr atoms that differ in ligand environment. Comparison of the results of quantum chemical calculations of the model reaction ZrCl₄ with acetic acid with the literature data on reactions of ZrCl₄ with aliphatic acids have shown the possibility of the formation of both mononuclear Zr(RCO₂)₄ and polynuclear clusters in this reaction, which is a new route for obtaining polynuclear zirconium clusters. The structure of the clusters formed depends on the steric properties of carboxylate ligands.