Synthesis of (heterometallic) oxo clusters, from early transition metals, by precision hydrolysis

Zirconium and hafnium oxo clusters are building blocks for MOFs, 3D-printing and polymers composites. However, their synthesis is often a matter of trial and error, and new structures are hard to design retrosynthetically. Here, we use our recent insight in the formation mechanism of Zr6O4(OH)4(OOCR)12 oxo clusters to redesign their synthesis with higher reaction rates, more economical precursors, more sustainable solvents and higher atom economy, all at room temperature at gram scale. We add exactly 1.33 equivalents of water for the precision hydrolysis of the metals towards Zr6-carboxylate or Hf6-carboxylate oxo clusters (carboxylate = acetate, oleate and 2-methylbutanoate). Furthermore, we use precision hydrolysis to synthesize the elusive bimetallic Zr/Hf oxo clusters, and to expand rational oxo cluster synthesis to the group 5, accessing the new Nb8O12(OEt)8(OBz)8 and Ta8O12(OEt)8(OBz)8 clusters (OBz = benzoate). Precision hydrolysis allows for a rational design and an economic production of oxo clusters on a multigram scale and we expect it to become the workhorse for cluster synthesis.