Synthesis, structure characterization and thermal properties of [Zr6(μ3-O)4(μ3-OH)4(OOCCH2tBu)9(μ2-OH)3]2

Oxo/hydoxo zirconium(IV) complex of the general formula [Zr6(μ3-O)4(μ3-OH)4(OOCCH2tBu)9(μ2-OH)3]2 has been isolated, when Zr(OiPr)4 reacted with a 2-fold excess of 3,3-dimethylbutyric acid. Single crystal X-ray diffraction data, collected at 103 and 153 K, showed that the studied compound crystallizes in hexagonal system (P63/m (no. 176)). Structure consists of dimers composed of [Zr6(μ3-O)4(μ3-OH)4(OOCCH2tBu)9] sub-units, linked by six μ2-OH bridges. Infrared spectroscopic studies proved the presence of hydroxo groups in the structure of studied clusters and formation of different types of oxo/hydroxo bridges. The application of variable temperature infrared spectroscopy and differential scanning calorimetry revealed that the structure of this complex undergoes the phase transitions at 143–183 and 203–293 K. Comparison of spectral and crystallographic data suggests that these phase transitions might be related to changes in the strength of Zr–O bonds of μ2-OH bridges linking complex sub-units, and change in symmetry of the crystal lattice (from hexagonal to trigonal). Analysis of thermogravimetric data showed that decomposition of [Zr6(μ3-O)4(μ3-OH)4(OOCCH2tBu)9(μ2-OH)3]2 proceeds with complete conversion to ZrO2 (monoclinic form) between 603 and 803 K.

Graphical abstract[Zr6(μ3-O4)(μ3-OH)4(OOCCH2tBu)9(μ2-OH)3]2 has been isolated, when Zr(OiPr)4 reacted with an 2-fold excess of 3,3-dimethylbutyric acid. Analysis of single crystal X-ray diffraction data showed that this complex crystallizes in hexagonal system (P63/m (no. 176)). Results of variable temperature IR spectroscopy and DSC studies revealed phase transitions at 143–183 and 203–293 K. Thermal analysis showed that its decomposition proceeds with complete conversion to ZrO2 between 603 and 803 K.Figure optionsDownload full-size imageDownload as PowerPoint slide