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Remote Oxidative Activation of a [Cp*Rh] Monohydride **
Author(s) -
Boyd Emily A.,
Hopkins Leseberg Julie A.,
Cosner Emma L.,
Lionetti Davide,
Henke Wade C.,
Day Victor W.,
Blakemore James D.
Publication year - 2022
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.202104389
Subject(s) - ferrocene , chemistry , reactivity (psychology) , redox , electron paramagnetic resonance , rhodium , photochemistry , ligand (biochemistry) , trifluoromethanesulfonate , moiety , medicinal chemistry , protonation , hydride , oxidative addition , catalysis , electrochemistry , stereochemistry , inorganic chemistry , organic chemistry , metal , medicine , ion , biochemistry , physics , alternative medicine , receptor , electrode , pathology , nuclear magnetic resonance
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 Rh II/I process at −0.96 V vs. ferrocenium/ferrocene (Fc +/0 ). This redox manifold was confirmed by isolation of an uncommon Rh II 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 p K a 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.