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Remote Oxidative Activation of a [Cp*Rh] Monohydride.


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- . Chemical and electrochemical studies show that one-electron redox chemistry is accessible to Cp*Rh(dppf), including a unique quasi-reversible RhII/I process at -0.96 V vs. ferrocenium/ferrocene (Fc+/0 ). This redox manifold was confirmed by isolation of an uncommon RhII species, [Cp*Rh(dppf)]+ , 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-H moiety by 23 pKa units, a reactivity pattern confirmed by in situ 1 H NMR studies. Taken together, these results show that remote oxidation can effectively induce M-H activation and suggest that ligand-centered redox activity could be an attractive feature for the design of new systems relying on hydride intermediates.

SUBMITTER: Boyd EA 

PROVIDER: S-EPMC8891045 | biostudies-literature | 2022 Mar

REPOSITORIES: biostudies-literature

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Remote Oxidative Activation of a [Cp*Rh] Monohydride.

Boyd Emily A EA   Hopkins Leseberg Julie A JA   Cosner Emma L EL   Lionetti Davide D   Henke Wade C WC   Day Victor W VW   Blakemore James D JD  

Chemistry (Weinheim an der Bergstrasse, Germany) 20220203 13


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<sup>-</sup> . Chemical and electrochemical studies show that one-electron redox chemistry is accessible to Cp*Rh(dppf), including a u  ...[more]

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