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 is determined by X-ray diffraction analysis. The compound C₇₁H₁₂₄O₂₈Zr₄ crystallizes in a monoclinic crystal system. The crystal structure is refined in the nonstandard space group I2. The asymmetric part of the structure includes three Zr atoms, six pivalate ligands, and 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 the ligand environment. A comparison of the results of the quantum chemical calculations of the model reaction of ZrCl₄ with acetic acid with the published data on reactions of ZrCl₄ with aliphatic acids shows 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.