Metal-oxo clusters without organic ligands are akin to soluble metal oxides, and are typified by structurally diverse group V/VI polyoxometalates (POMs). Their defining characteristics include rich redox chemistry and accompanying color change, negative charge, acid or base chemistry, and ligation of other heterometal species. Consequently, POMs have been implemented for catalysis, protein crystallization and cleavage, sensing and detection, energy storage, single-molecule magnets, modeling the metal-oxide-water interface, and more. It is far more challenging to isolate metal-oxo clusters outside of groups V/VI without employing organic ligands, but organic ligands hinder function for many of these applications. On the other hand, metal-oxo clusters of different chemistries open new opportunities in the aforementioned disciplines and applications.<br/><br/>We are developing new synthetic strategies to discover ligand-free (or labile ligand) chemistry from across the periodic table; employing both simple water-based chemistries and advanced instrumentation to identify transient reaction intermediates. I will present several examples of these from recent published and unpublished work. Prior, we extended aluminum polycation chemistry into chromium-aluminum polycation chemistry by exerting careful control over pH-eH conditions. More recently, we have extended this chemistry to Al-free, chromium-zinc polycations, representing a new class of molecular metal oxides. Electrospray ionization mass spectrometry and X-ray scattering track the growth of these clusters from monomers to small oligomers to fully-formed Keggin ions; providing new insight into cluster formation mechanisms. Moreover, the clusters are readily uncapped and capped with metal cations, leading to design of magnetic materials. More recent studies on Bi-capped iron Keggin ions has shown further insight into formation mechanisms of the ubiquitous Keggin geometry, as well as the utility of Bi to stabilize, and even promote growth of clusters in highly acidic conditions. These studies likewise were implemented with extensive use of aforementioned techniques. Additionally, we are exploiting inorganic ligands (peroxide) to expand group IV polyoxocation chemistry. Here I will present new Ti, Zr and Hf clusters with peroxide ligands, their use in inorganic nanolithography, and preliminary computational studies in advanced Pourbaix diagram development.  <br/>

Inorganic metal-oxo clusters: Breaking down the metal-ligand wall

256th National Meeting (2018)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.