The forgotten chemistry of group(IV) metals: A survey on the synthesis, structure, and properties of discrete Zr(IV), Hf(IV), and Ti(IV) oxo clusters

Abstract

• Group IV metal oxo clusters (MOCs) applications in materials and catalysis are rapidly expanding. • Group IV MOCs are prepared in aqueous or organic medium with a variety of ligands. • Ligands influence structure and properties, thus impacting materials syntheses and catalysis. • Ligand-exchanged happens with or without rearrangement of the inorganic core. Group (IV) metal oxo clusters are a diverse class of compounds with rapidly growing applications in catalysis, materials chemistry, electronics and optics. They possess unique structural stability, reactivity and electronic properties; however, their potential remains underexplored due to the gaps in fundamental understanding about their structure, intrinsic features, and nuances in their synthesis that overall would allow for great tunability of their properties. In this context, here we review the chemistry of discrete zirconium, hafnium, and titanium metal oxo clusters reported in the literature in order to provide a critical overview of the structural features, properties and reactivity disclosed to date. While a comprehensive summary of Zr and Hf clusters is presented, only the most recent Ti oxo clusters are discussed in addition to some key compounds that have been revised elsewhere. Envisioning the growing relevance group (IV) metal oxo clusters for the synthesis of nanostructure materials and in catalysis, we also summarize key principles of their surface chemistry, and the photoactivity of Ti oxo clusters, given the paramount importance of these properties for the development of future applications.