[ { "id": "authors:a5b8v-ekz38", "collection": "authors", "collection_id": "a5b8v-ekz38", "cite_using_url": "https://authors.library.caltech.edu/records/a5b8v-ekz38", "type": "article", "title": "Redox Processes Involving Oxygen: The Surprising Influence of Redox-Inactive Lewis Acids", "author": [ { "family_name": "Lionetti", "given_name": "Davide", "orcid": "0000-0002-4937-886X", "clpid": "Lionetti-Davide" }, { "family_name": "Suseno", "given_name": "Sandy", "clpid": "Suseno-Sandy" }, { "family_name": "Shiau", "given_name": "Angela A.", "orcid": "0000-0003-4395-9847", "clpid": "Shiau-Angela-A" }, { "family_name": "de Ruiter", "given_name": "Graham", "orcid": "0000-0001-6008-286X", "clpid": "de-Ruiter-Graham" }, { "family_name": "Agapie", "given_name": "Theodor", "orcid": "0000-0002-9692-7614", "clpid": "Agapie-T" } ], "abstract": "
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Metalloenzymes with heteromultimetallic active sites perform chemical reactions that control several biogeochemical cycles. Transformations catalyzed by such enzymes include dioxygen generation and reduction, dinitrogen reduction, and carbon dioxide reduction–instrumental transformations for progress in the context of artificial photosynthesis and sustainable fertilizer production. While the roles of the respective metals are of interest in all these enzymatic transformations, they share a common factor in the transfer of one or multiple redox equivalents. In light of this feature, it is surprising to find that incorporation of redox-inactive metals into the active site of such an enzyme is critical to its function. To illustrate, the presence of a redox-inactive Ca2+ center is crucial in the Oxygen Evolving Complex, and yet particularly intriguing given that the transformation catalyzed by this cluster is a redox process involving four electrons. Therefore, the effects of redox inactive metals on redox processes–electron transfer, oxygen- and hydrogen-atom transfer, and O–O bond cleavage and formation reactions–mediated by transition metals have been studied extensively. Significant effects of redox inactive metals have been observed on these redox transformations; linear free energy correlations between Lewis acidity and the redox properties of synthetic model complexes are observed for several reactions. In this Perspective, these effects and their relevance to multielectron processes will be discussed.

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", "doi": "10.1021/jacsau.3c00675", "pmcid": "PMC10900226", "issn": "2691-3704", "publisher": "American Chemical Society", "publication": "JACS Au", "publication_date": "2024-02-26", "series_number": "2", "volume": "4", "issue": "2", "pages": "344-368" }, { "id": "authors:pwcm0-0p211", "collection": "authors", "collection_id": "pwcm0-0p211", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20211209-231160000", "type": "article", "title": "Remote Oxidative Activation of a [Cp*Rh] Monohydride", "author": [ { "family_name": "Boyd", "given_name": "Emily A.", "orcid": "0000-0003-0150-5396", "clpid": "Boyd-Emily-A" }, { "family_name": "Hopkins Leseberg", "given_name": "Julie A.", "orcid": "0000-0001-6895-7333", "clpid": "Hopkins-Leseberg-Julie-A" }, { "family_name": "Cosner", "given_name": "Emma L.", "clpid": "Cosner-Emma-L" }, { "family_name": "Lionetti", "given_name": "Davide", "orcid": "0000-0002-4937-886X", "clpid": "Lionetti-Davide" }, { "family_name": "Henke", "given_name": "Wade C.", "orcid": "0000-0002-4574-8544", "clpid": "Henke-Wade-C" }, { "family_name": "Day", "given_name": "Victor W.", "clpid": "Day-Victor-W" }, { "family_name": "Blakemore", "given_name": "James D.", "orcid": "0000-0003-4172-7460", "clpid": "Blakemore-James-D" } ], "abstract": "Half-sandwich rhodium monohydrides are often proposed as intermediates in catalysis, but little is known regarding the redox-induced reactivity accessible to these species. Herein, the bis(diphenylphosphino)ferrocene (dppf) ligand has been used to explore the reactivity that can be induced when a [Cp*Rh] monohydride undergoes remote (dppf-centered) oxidation by 1e\u207b. Chemical and electrochemical studies show that one-electron redox chemistry is accessible to Cp*Rh(dppf), including a unique quasi-reversible Rh^(II/I) process at \u22120.96 V vs. ferrocenium/ferrocene (Fc^(+/0)). This redox manifold was confirmed by isolation of an uncommon Rh^(II) species, [Cp*Rh(dppf)]\u207a, that was characterized by electron paramagnetic resonance (EPR) spectroscopy. Protonation of Cp*Rh(dppf) with anilinium triflate yielded an isolable and inert monohydride, [Cp*Rh(dppf)H]+, and this species was found to undergo a quasireversible electrochemical oxidation at +0.41 V vs. Fc^(+/0) that corresponds to iron-centered oxidation in the dppf backbone. Thermochemical analysis predicts that this dppf-centered oxidation drives a dramatic increase in acidity of the Rh\u2212H moiety by 23 pK_a units, a reactivity pattern confirmed by in situ \u00b9H NMR studies. Taken together, these results show that remote oxidation can effectively induce M\u2212H activation and suggest that ligand-centered redox activity could be an attractive feature for the design of new systems relying on hydride intermediates.", "doi": "10.1002/chem.202104389", "pmcid": "PMC8891045", "issn": "0947-6539", "publisher": "Wiley", "publication": "Chemistry - A European Journal", "publication_date": "2022-03-01", "series_number": "13", "volume": "28", "issue": "13", "pages": "Art. No. e202104389" }, { "id": "authors:p3g6h-zy515", "collection": "authors", "collection_id": "p3g6h-zy515", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190207-142044105", "type": "article", "title": "Effects of Lewis Acidic Metal Ions (M) on Oxygen-Atom Transfer Reactivity of Heterometallic Mn\u2083MO\u2084 Cubane and Fe\u2083MO(OH) and Mn\u2083MO(OH) Clusters", "author": [ { "family_name": "Lionetti", "given_name": "Davide", "orcid": "0000-0002-4937-886X", "clpid": "Lionetti-Davide" }, { "family_name": "Suseno", "given_name": "Sandy", "clpid": "Suseno-Sandy" }, { "family_name": "Tsui", "given_name": "Emily Y.", "orcid": "0000-0001-6419-3954", "clpid": "Tsui-Emily-Y" }, { "family_name": "Lu", "given_name": "Luo", "clpid": "Lu-Luo" }, { "family_name": "Stich", "given_name": "Troy A.", "orcid": "0000-0003-0710-1456", "clpid": "Stich-Ttoy-A" }, { "family_name": "Carsch", "given_name": "Kurtis M.", "orcid": "0000-0003-4432-7518", "clpid": "Carsch-Kurtis-M" }, { "family_name": "Nielsen", "given_name": "Robert J.", "orcid": "0000-0002-7962-0186", "clpid": "Nielsen-Robert-J" }, { "family_name": "Goddard", "given_name": "William A., III", "orcid": "0000-0003-0097-5716", "clpid": "Goddard-W-A-III" }, { "family_name": "Britt", "given_name": "R. David", "orcid": "0000-0003-0889-8436", "clpid": "Britt-R-David" }, { "family_name": "Agapie", "given_name": "Theodor", "orcid": "0000-0002-9692-7614", "clpid": "Agapie-T" } ], "abstract": "The modulation of the reactivity of metal oxo species by redox inactive metals has attracted much interest due to the observation of redox inactive metal effects on processes involving electron transfer both in nature (the oxygen-evolving complex of Photosystem II) and in heterogeneous catalysis (mixed-metal oxides). Studies of small-molecule models of these systems have revealed numerous instances of effects of redox inactive metals on electron- and group-transfer reactivity. However, the heterometallic species directly involved in these transformations have rarely been structurally characterized and are often generated in situ. We have previously reported the preparation and structural characterization of multiple series of heterometallic clusters based on Mn\u2083 and Fe\u2083 cores and described the effects of Lewis acidity of the heterometal incorporated in these complexes on cluster reduction potential. To determine the effects of Lewis acidity of redox inactive metals on group transfer reactivity in structurally well-defined complexes, we studied [Mn\u2083MO_\u2084, [Mn\u2083MO(OH)], and [Fe\u2083MO(OH)] clusters in oxygen atom transfer (OAT) reactions with phosphine substrates. The qualitative rate of OAT correlates with the Lewis acidity of the redox inactive metal, confirming that Lewis acidic metal centers can affect the chemical reactivity of metal oxo species by modulating cluster electronics.", "doi": "10.1021/acs.inorgchem.8b02701", "pmcid": "PMC6574207", "issn": "0020-1669", "publisher": "American Chemical Society", "publication": "Inorganic Chemistry", "publication_date": "2019-02-18", "series_number": "4", "volume": "58", "issue": "4", "pages": "2336-2345" }, { "id": "authors:tmmea-ka390", "collection": "authors", "collection_id": "tmmea-ka390", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20151109-102021262", "type": "article", "title": "Nitric Oxide Activation by Distal Redox Modulation in Tetranuclear Iron Nitrosyl Complexes", "author": [ { "family_name": "De Ruiter", "given_name": "Graham", "orcid": "0000-0001-6008-286X", "clpid": "De-Ruiter-Graham" }, { "family_name": "Thompson", "given_name": "Niklas B.", "orcid": "0000-0003-2745-4945", "clpid": "Thompson-Niklas-B" }, { "family_name": "Lionetti", "given_name": "Davide", "orcid": "0000-0002-4937-886X", "clpid": "Lionetti-Davide" }, { "family_name": "Agapie", "given_name": "Theodor", "orcid": "0000-0002-9692-7614", "clpid": "Agapie-T" } ], "abstract": "A series of tetranuclear iron complexes displaying a site-differentiated metal center was synthesized. Three of the metal centers are coordinated to our previously reported ligand, based on a 1,3,5-triarylbenzene motif with nitrogen and oxygen donors. The fourth (apical) iron center is coordinatively unsaturated and appended to the trinuclear core through three bridging pyrazolates and an interstitial \u03bc_4-oxide moiety. Electrochemical studies of complex [LFe_3(PhPz)3OFe][OTf]_2 revealed three reversible redox events assigned to the Fe^(II)_4/Fe^(II)_3Fe^(III) (\u22121.733 V), Fe^(II)_3Fe^(III)/Fe^(II)_2Fe^(III)_2 (\u22120.727 V), and Fe^(II)_2Fe^(III)_2/Fe^(II)Fe^(III)_3 (0.018 V) redox couples. Combined M\u00f6ssbauer and crystallographic studies indicate that the change in oxidation state is exclusively localized at the triiron core, without changing the oxidation state of the apical metal center. This phenomenon is assigned to differences in the coordination environment of the two metal sites and provides a strategy for storing electron and hole equivalents without affecting the oxidation state of the coordinatively unsaturated metal. The presence of a ligand-binding site allowed the effect of redox modulation on nitric oxide activation by an Fe^(II) metal center to be studied. Treatment of the clusters with nitric oxide resulted in binding of NO to the apical iron center, generating a {FeNO}^7 moiety. As with the NO-free precursors, the three reversible redox events are localized at the iron centers distal from the NO ligand. Altering the redox state of the triiron core resulted in significant change in the NO stretching frequency, by as much as 100 cm^(\u20131). The increased activation of NO is attributed to structural changes within the clusters, in particular, those related to the interaction of the metal centers with the interstitial atom. The differences in NO activation were further shown to lead to differential reactivity, with NO disproportionation and N_2O formation performed by the more electron-rich cluster.", "doi": "10.1021/jacs.5b07397", "pmcid": "PMC4871614", "issn": "0002-7863", "publisher": "American Chemical Society", "publication": "Journal of the American Chemical Society", "publication_date": "2015-11-11", "series_number": "44", "volume": "137", "issue": "44", "pages": "14094-14106" } ]