Methyltriskaidecazirconates, Molecular Forms of Zirconia

Repeated methanolysis of [Zr3O](OPrn)10 followed by extraction and crystallization from toluene yields material that is X-ray crystallographically indistinguishable from the compound previously formulated as [Zr13O8](OMe)36. Elemental analysis and 1H solution NMR spectroscopy strongly suggest that this material is a mixture of methyltriskaidecazirconates (MTZ) [Zr13O8](OMe)x(OH)36-x, xav ~ 20, that readily cocrystallize from hydrocarbon solution. These species have the metal-oxygen framework structure reported for [Zr13O8](OMe)36, where the 13 zirconium and 32 bridging oxygen atoms comprise a fragment of the fluorite structure adopted by ZrO2 at elevated temperatures. Ethanolysis of [Zr3O](OPrn)10 yields its ethyl analogue, [Zr3O](OEt)10. Both trizirconates display temperature-dependent 1H solution NMR spectra that are interpreted mechanistically in terms of rearrangement mechanisms involving trigonal twists at the octahedral zirconium centers.