{"id":{"repo_id":"mit","oai_identifier":"oai:dspace.mit.edu:1721.1/154186"},"canonical_url":"https://search.dev.ndltd.org/etd/mit/oai:dspace.mit.edu:1721.1/154186","repository":{"repo_id":"mit","name":"MIT","base_url":"https://dspace.mit.edu/oai/request"},"display":{"title":"Metallocluster Site-Differentiation and Subsite Specific Heterometal Substitution","abstract":"The deployment of metalloclusters in applications such as catalysis and materials synthesis requires robust methods for site-differentiation: the conversion of clusters with symmetric ligand spheres to those with unsymmetrical ligand spheres. However, imparting precise patterns of site-differentiation is challenging because, compared with mononuclear complexes, the ligands bound to clusters exert limited spatial and electronic influence on one another. In Chapter 2, we described a method that used sterically encumbering ligands to bind to only a subset of a cluster’s coordination sites. Specifically, we showed that homoleptic, phosphine-ligated Fe–S clusters undergo ligand substitution with N-heterocyclic carbenes to give heteroleptic clusters in which the resultant clusters’ site-differentiation patterns are encoded by the steric profile of the incoming N-heterocyclic carbene. This method afforded access to every site-differentiation pattern for cuboidal [Fe₄S₄] clusters and was extended to other cluster types in Chapter 3, particularly in the stereoselective synthesis of site-differentiated Chevrel-type [Fe₆S₈] clusters. In Chapter 4, we further utilized the 3:1 site-differentiation of cuboidal [M₄S₄] (M = Fe or Co) clusters to perform subsite specific metal atom substitution at each cluster. Specifically, we showed that the unique metal sites of homometallic clusters of the form [M₄S₄(IMes)₃Cl]+ can be selectively excised by addition of 2 equiv TlTp. Reconstitution with M′Cl2 (M′ = Co, Fe, for M = Fe, Co, respectively) yielded the heterometallic clusters [CoFe₃S₄(IMes)₃Cl]+ and [FeCo₃S₄(IMes)₃Cl]+. The reduced clusters, [M′M₃S₄(IMes)₃Cl], as well as the CO-bound clusters, [M′M₃S₄(IMes)₃(CO)], were also prepared, and a comparative analysis of the properties of all three series of clusters was undertaken. Low-valent electronic configurations are accessed in all four clusters, [Fe₄S₄(IMes)₃(CO)], [CoFe₃S₄(IMes)₃(CO)], [Co₄S₄(IMes)₃(CO)], and [FeCo₃S₄(IMes)₃(CO)], and this studied further reveals how heterometal substitution modulates the degree of C–O bond weakening.","abstract_html":"The deployment of metalloclusters in applications such as catalysis and materials synthesis requires robust methods for site-differentiation: the conversion of clusters with symmetric ligand spheres to those with unsymmetrical ligand spheres. However, imparting precise patterns of site-differentiation is challenging because, compared with mononuclear complexes, the ligands bound to clusters exert limited spatial and electronic influence on one another. In Chapter 2, we described a method that used sterically encumbering ligands to bind to only a subset of a cluster’s coordination sites. Specifically, we showed that homoleptic, phosphine-ligated Fe–S clusters undergo ligand substitution with N-heterocyclic carbenes to give heteroleptic clusters in which the resultant clusters’ site-differentiation patterns are encoded by the steric profile of the incoming N-heterocyclic carbene. This method afforded access to every site-differentiation pattern for cuboidal [Fe₄S₄] clusters and was extended to other cluster types in Chapter 3, particularly in the stereoselective synthesis of site-differentiated Chevrel-type [Fe₆S₈] clusters. In Chapter 4, we further utilized the 3:1 site-differentiation of cuboidal [M₄S₄] (M = Fe or Co) clusters to perform subsite specific metal atom substitution at each cluster. Specifically, we showed that the unique metal sites of homometallic clusters of the form [M₄S₄(IMes)₃Cl]+ can be selectively excised by addition of 2 equiv TlTp. Reconstitution with M′Cl2 (M′ = Co, Fe, for M = Fe, Co, respectively) yielded the heterometallic clusters [CoFe₃S₄(IMes)₃Cl]+ and [FeCo₃S₄(IMes)₃Cl]+. The reduced clusters, [M′M₃S₄(IMes)₃Cl], as well as the CO-bound clusters, [M′M₃S₄(IMes)₃(CO)], were also prepared, and a comparative analysis of the properties of all three series of clusters was undertaken. Low-valent electronic configurations are accessed in all four clusters, [Fe₄S₄(IMes)₃(CO)], [CoFe₃S₄(IMes)₃(CO)], [Co₄S₄(IMes)₃(CO)], and [FeCo₃S₄(IMes)₃(CO)], and this studied further reveals how heterometal substitution modulates the degree of C–O bond weakening.","abstract_has_math":false,"creators":["Bostelaar, Trever M."],"institution":"Massachusetts Institute of Technology","degree_name":"Doctoral","degree_level":null,"degree_discipline":null,"degree_department":"Massachusetts Institute of Technology. Department of Chemistry","school":null,"contributors":[],"advisors":["Suess, Daniel L. M."],"committee_chairs":[],"committee_members":[],"year":2023,"date_issued":"2023-09","date_published":"2023-09","updated_at":"2026-07-22T22:20:44Z","subjects":[],"languages":[],"rights":["In Copyright - Educational Use Permitted","Copyright MIT"],"rights_urls":["http://rightsstatements.org/page/InC-EDU/1.0/"],"identifier_entries":[]},"links":{"outbound_url":"https://hdl.handle.net/1721.1/154186","outbound_label":"Handle","outbound_source":"dc:identifier.uri"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor.advisor","label":"Advisor","values":["Suess, Daniel L. M."]},{"key":"dc:contributor.department","label":"Department","values":["Massachusetts Institute of Technology. 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However, imparting precise patterns of site-differentiation is challenging because, compared with mononuclear complexes, the ligands bound to clusters exert limited spatial and electronic influence on one another. In Chapter 2, we described a method that used sterically encumbering ligands to bind to only a subset of a cluster’s coordination sites. Specifically, we showed that homoleptic, phosphine-ligated Fe–S clusters undergo ligand substitution with N-heterocyclic carbenes to give heteroleptic clusters in which the resultant clusters’ site-differentiation patterns are encoded by the steric profile of the incoming N-heterocyclic carbene. This method afforded access to every site-differentiation pattern for cuboidal [Fe₄S₄] clusters and was extended to other cluster types in Chapter 3, particularly in the stereoselective synthesis of site-differentiated Chevrel-type [Fe₆S₈] clusters. In Chapter 4, we further utilized the 3:1 site-differentiation of cuboidal [M₄S₄] (M = Fe or Co) clusters to perform subsite specific metal atom substitution at each cluster. Specifically, we showed that the unique metal sites of homometallic clusters of the form [M₄S₄(IMes)₃Cl]+ can be selectively excised by addition of 2 equiv TlTp. Reconstitution with M′Cl2 (M′ = Co, Fe, for M = Fe, Co, respectively) yielded the heterometallic clusters [CoFe₃S₄(IMes)₃Cl]+ and [FeCo₃S₄(IMes)₃Cl]+. The reduced clusters, [M′M₃S₄(IMes)₃Cl], as well as the CO-bound clusters, [M′M₃S₄(IMes)₃(CO)], were also prepared, and a comparative analysis of the properties of all three series of clusters was undertaken. Low-valent electronic configurations are accessed in all four clusters, [Fe₄S₄(IMes)₃(CO)], [CoFe₃S₄(IMes)₃(CO)], [Co₄S₄(IMes)₃(CO)], and [FeCo₃S₄(IMes)₃(CO)], and this studied further reveals how heterometal substitution modulates the degree of C–O bond weakening."]},{"key":"dc:description.degree","label":"Dc Description Degree","values":["Ph.D."]},{"key":"dc:title","label":"Title","values":["Metallocluster Site-Differentiation and Subsite Specific Heterometal Substitution"]}]}],"canonical_facts":{"dc:contributor.advisor":["Suess, Daniel L. M."],"dc:contributor.department":["Massachusetts Institute of Technology. Department of Chemistry"],"dc:creator":["Bostelaar, Trever M."],"dc:date.accessioned":["2024-04-17T21:09:52Z"],"dc:date.available":["2024-04-17T21:09:52Z"],"dc:date.issued":["2023-09"],"dc:description.abstract":["The deployment of metalloclusters in applications such as catalysis and materials synthesis requires robust methods for site-differentiation: the conversion of clusters with symmetric ligand spheres to those with unsymmetrical ligand spheres. However, imparting precise patterns of site-differentiation is challenging because, compared with mononuclear complexes, the ligands bound to clusters exert limited spatial and electronic influence on one another. In Chapter 2, we described a method that used sterically encumbering ligands to bind to only a subset of a cluster’s coordination sites. Specifically, we showed that homoleptic, phosphine-ligated Fe–S clusters undergo ligand substitution with N-heterocyclic carbenes to give heteroleptic clusters in which the resultant clusters’ site-differentiation patterns are encoded by the steric profile of the incoming N-heterocyclic carbene. This method afforded access to every site-differentiation pattern for cuboidal [Fe₄S₄] clusters and was extended to other cluster types in Chapter 3, particularly in the stereoselective synthesis of site-differentiated Chevrel-type [Fe₆S₈] clusters. In Chapter 4, we further utilized the 3:1 site-differentiation of cuboidal [M₄S₄] (M = Fe or Co) clusters to perform subsite specific metal atom substitution at each cluster. Specifically, we showed that the unique metal sites of homometallic clusters of the form [M₄S₄(IMes)₃Cl]+ can be selectively excised by addition of 2 equiv TlTp. Reconstitution with M′Cl2 (M′ = Co, Fe, for M = Fe, Co, respectively) yielded the heterometallic clusters [CoFe₃S₄(IMes)₃Cl]+ and [FeCo₃S₄(IMes)₃Cl]+. The reduced clusters, [M′M₃S₄(IMes)₃Cl], as well as the CO-bound clusters, [M′M₃S₄(IMes)₃(CO)], were also prepared, and a comparative analysis of the properties of all three series of clusters was undertaken. Low-valent electronic configurations are accessed in all four clusters, [Fe₄S₄(IMes)₃(CO)], [CoFe₃S₄(IMes)₃(CO)], [Co₄S₄(IMes)₃(CO)], and [FeCo₃S₄(IMes)₃(CO)], and this studied further reveals how heterometal substitution modulates the degree of C–O bond weakening."],"dc:description.degree":["Ph.D."],"dc:identifier.uri":["https://hdl.handle.net/1721.1/154186"],"dc:publisher":["Massachusetts Institute of Technology"],"dc:rights":["In Copyright - Educational Use Permitted","Copyright MIT"],"dc:rights.uri":["http://rightsstatements.org/page/InC-EDU/1.0/"],"dc:title":["Metallocluster Site-Differentiation and Subsite Specific Heterometal Substitution"],"dc:type":["Thesis"],"thesis:degree_name":["Doctoral","Doctor of Philosophy"]},"updated_at":"2026-07-22T22:20:44Z"}