This thesis presents a number of largely independent forays into developing an understanding of the unique chemistry of transition metal clusters. The first chapter of this thesis represents an initial foray into mapping the chemical reactivity of transition metal clusters - a monumental task that will doubtless continue for some time. The small slice undertaken in this work investigates the reactivity with CO of a series of the smallest possible metal clusters; 4d (Nb - Ag) homonuclear metal trimers. In Chapter 2, two known transition metal clusters were studied using CASSCF (MCSCF) and MRCI methods, only to find that DFT methods provided more accurate Ionisation Potentials (IPs). Thus Chapter 3 was devoted to optimising a density functional to predict IPs. As clusters get larger, the number of possible structures grows rapidly too large for human intuition to handle, thus Chapter 4 is devoted to the use of an automated stochastic algorithm, “Kick”, for structure elucidation. Chapter 5 improves on this algorithm, by permitting chemically sensible molecular fragments to be defined and used. Chapter 6 then comes full circle and uses the new Kick algorithm to investigate the reaction of CO with a series of mono-substituted niobium tetramers (i.e. Nb₃X). / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1350246 / Thesis (Ph.D.) - University of Adelaide, School of Chemistry and Physics, 2009

Thesis (Ph.D.)--Pennsylvania State University, 2001. / Includes bibliographical references.

Thesis (Ph. D.)--State University of New York at Binghamton, Department of Chemistry, 2007. / Includes bibliographical references.

Thesis (Ph. D.)--University of Washington, 2004. / Vita. Includes bibliographical references (leaves 100-106).

Thesis (Ph. D.)--University of Washington, 2006. / Vita. Includes bibliographical references (p. 107-114).

Thesis (Ph. D.)--Chemistry and Biochemistry, Georgia Institute of Technology, 2007. / Dickson, Robert, Committee Chair ; Barry, Bridgette, Committee Member ; Fahrni, Christoph, Committee Member ; Fernandez, Facundo, Committee Member ; Srinivasarao, Mohan, Committee Member.

Hexanuclear transition metal clusters are a distinct class of chemical compounds that have some very interesting chemical and physical properties. Of recent interest in this field has been the [Re₆(μ₃-Se)₈]²⁺ cluster core. This Lewis acidic cluster core contains six substitutable coordination sites, and site differentiation can be accessed through protecting group ligands. The Lewis acidity has been shown to activate unsaturated cluster-bound ligands, and the expanded atom-like structure and high symmetry of the cluster core has potential use in synthesizing some fascinating and novel hybrid materials. Little work has been performed in establishing the scope of these chemical transformations. The work herein describes the efforts and successes of such work. Chapter 1 provides the essential background required for understanding the [Re₆(μ₃-Se)₈]²⁺ cluster core's synthesis, properties, and currently known research directions and successes. This chapter first introduces hexanuclear clusters in a general format, then focuses on the established catalytic and material capabilities that have been determined using this specific cluster core. Chapter 2 discusses the synthesis, characterization, and hydrogen-bonded assemblies formed from [Re₆(μ₃-Se)₈]²⁺ cluster-isonicotinic acid cluster complexes. These complexes have potential uses as hybrid inorganic/organic linkers for the generation of luminescent Lewis acidic metal-organic frameworks (MOFs). Prospective applications of such materials include catalysis, separations, and gas storage. Chapter 3 focuses on the novel chemistry of [Re₆(μ₃-Se)₈]²⁺ cluster-activated CH₃CN with N-based nucleophiles to form acetamidines. These ligands are of interest due to their use in medicinal chemistry, CO₂/CS₂ sequestration, and the formation of synthetically-relevant species. Quantitative yields are obtained and single-crystal XRD analyses reveal specific stereochemical outcomes. Trifluoroacetic acid (TFA) in a cluster-amidine CH₃CN solution removes the ligand as the acetamidinium TFA salt, and the starting cluster solvate is reproduced making a recyclable catalyst. Chapter 4 expands on a project similar to that of chapter 3, except that O-based nucleophiles are utilized for specific cluster isomers. The newly formed ligands, imino esters, are of interest in organic synthesis as valuable starting materials for the generation of β-lactams and heterocycles. ³¹P NMR and single–crystal XRD reveal Z stereochemistry is preferred in the cis isomer, but conflicting results for the hexasubstituted isomer leave stereochemical analyses unresolved. Chapter 5 attempts to incorporate the chemistry established in chapters 2-4 to provide some fresh and interesting research outlooks possible with the [Re₆(μ₃-Se)₈]²⁺ cluster core. Incorporation of the cluster into MOFs is discussed, and the possibility of post-synthetic modifications for metal sequestration, catalysis, and sensing is explained. Appendix A provides all the NMR data obtained for synthesized materials with peak picks and integrations provided. Appendix B entails all crystallographic information for structures determined after syntheses. Appendix C provide high-resolution mass spectra.

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