MFeS Clusters as Models for Complex Multimetallic Systems

Citation

Scott, Anna Gustavus (2023) MFeS Clusters as Models for Complex Multimetallic Systems. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/v161-td03. https://resolver.caltech.edu/CaltechTHESIS:06112023-231330051

Abstract

The impressive chemistry of the FeMco-factor of nitrogenase is still under intense study with many remaining mechanistic questions about the important transformation of N₂ to NH₃, including the role of the synthetically interesting carbide ligand and the complex structure of the octanuclear active site cluster. This thesis describes efforts to incorporate bridging carbon based ligands into synthetic MFeS clusters, which remains a significant synthetic challenge in inorganic chemistry. The subsequent characterization and reactivity studies of such clusters provide insight into how cluster structural properties, including ligand identity, metal identity, and cluster composition and geometry affect cluster electronic properties and reactivity.

Chapter II describes the synthesis of an unprecedented WFe₃S₃(µ₃-carbyne) cluster and comparisons with a WFe₃S₃(µ₃-S) cluster provide insight into the role of the bridging carbide in FeMco. The generality of the developed method for synthesis of MFe₃S₃(µ₃-carbyne) clusters is also demonstrated. Characterization of the various carbyne clusters are discussed. Cleavage of the C-Si bond of MFe₃S₃(µ₃-CSiMe₃) clusters towards bridging methylidyne clusters is also demonstrated.

Chapter III discusses the synthesis of novel octanuclear (CH_n) bridged Mo₂Fe₆S₆ clusters and describes the reactivity of these bridges in the context of organometallic and nitrogenase chemistry.

Chapter IV describes spectroscopic data of an extensive family of MFeS cubane clusters that is currently lacking in the literature and provides important structure property benchmarking information for synthetic and biological FeS clusters.

Chapter V describes the synthesis of well-defined high nuclearity Fe₁₃ clusters resulting from studies of WFeS clusters. These clusters exhibit high spin states and undergo well-defined reactivity with small molecules and thus provide an unprecedented atomically resolved study of reactivities of high-nuclearity transition metal clusters.

Thesis Files