Oxo-Bridged Zr Dimers as Well-defined Models of Oxygen Vacancies on ZrO2

While ZrO₂ is known to have a large effect on the activity and selectivity of the Cu/ZrO₂ catalyst for methanol synthesis, its role in this process is poorly understood. Surface defects such as oxygen vacancies could play a role in the strong metal-support interaction (SMSI) between Cu and ZrO₂. However, due to the complexity of the surfaces, the exact molecular nature of this interaction is not at present known. Here, we make well-defined models of both reduced and coordinatively unsaturated surface oxygen vacancies on ZrO₂ using the molecular precursor Cp₂ZrCl]₂(μ²-O) ( 1 ). Complex 1 can be reduced to form a complex ( 2 ) containing one Zr(III) center and a bridging hydride ligand (according to EPR and IR spectroscopy) derived from C?H activation of either thf or the Cp ring. Complex 2 reacts with CO₂ to largely produce CO, suggesting that surface defects with similar structures probably do not play a role in the industrial catalyst. Halide abstraction from complex 1 results in the Lewis acidic species 3 , which has similar Lewis acid properties to acidic defects on the ZrO₂ surface. Similarities of both of these model species to real surface oxygen vacancies and their role in the catalytic reaction are discussed.