Reversible homolytic activation of water via metal–ligand cooperativity in a T-shaped Ni(ii) complex

Abstract

Ligand based storage of H-atoms enables the reversible homolysis of water by a T-shaped Ni complex.

Generation and Oxidative Reactivity of a Ni(II) Superoxo Complex via Ligand-Based Redox Non-Innocence

“…51,52 Specifically, this functionality in Ph,Tol DHP ( Ph,Tol DHP = 2,5-bis((2-phenylhydrazono)(p-tolyl)methyl)pyrrole) complexes of Ni enables the homolytic cleavage of H 2 O and subsequent oxidative reactivity, but also results in aerobic decomposition via ligand-based C−H oxidation. 53 To avoid this decomposition pathway, tBu,Tol DHP ( tBu,Tol DHP = 2,5-bis((2-t-butylhydrazono)(p-tolyl)methyl)-pyrrole) was targeted as a variant where the less reactive C−H bonds on the t Bu substituent should prevent ligand-based oxidation and subsequently facilitate oxidative reactivity. Herein, we report that this ligand enables the activation of O 2 to superoxide via ligand-based electron transfer, leading to a Ni(II) superoxo complex that can mediate oxidative reactivity including alcohol ■ RESULTS AND DISCUSSION Synthesis and Electronic Structure of a T-Shaped Ni Complex.…”

“…The use of ligand-based redox couples for aerobic oxidative reactivity with synthetic systems is comparatively underexplored. ,− We have been interested in investigating ligands that can store both protons and electrons and have demonstrated this reactivity on dihydrazonopyrrole (DHP) scaffolds. , Specifically, this functionality in Ph,Tol DHP ( Ph,Tol DHP = 2,5-bis­((2-phenylhydrazono)­( p -tolyl)­methyl)-pyrrole) complexes of Ni enables the homolytic cleavage of H 2 O and subsequent oxidative reactivity, but also results in aerobic decomposition via ligand-based C–H oxidation . To avoid this decomposition pathway, t Bu,Tol DHP ( t Bu,Tol DHP = 2,5-bis­((2- t -butylhydrazono)­( p -tolyl)­methyl)-pyrrole) was targeted as a variant where the less reactive C–H bonds on the t Bu substituent should prevent ligand-based oxidation and subsequently facilitate oxidative reactivity.…”

Harnessing the active site triad: merging hemilability, proton responsivity, and ligand-based redox-activity

“…As stated above, systems that incorporate redox-activity, hemilability, and proton responsivity, all in single ligand scaffolds are rare. However, two recent ligand systems that intentionally integrate hemilability, proton responsivity and redox activity [43][44][45] display some exciting chemistry pertinent to the topics of energy storage (from water) and nitrogen management. The first set of systems is based on the diiminopyrrole ligand scaffold 2,5bis(N-cyclohexyl-1-(p-tolyl)methanimine) pyrrolide ( Tol,Cy DIPy).…”

Neocuproine as a Redox-Active Ligand Platform on Iron and Cobalt

“…We have been broadly interested in investigating the storage of redox equivalents on ligands, such as with the previously published dihydrazonopyrrole (DHP) ligand scaffold. ,, We found it likely that neocuproine could serve as a redox-noninnocent ligand but noted that this redox activity had not been systematically explored. We therefore set out to carefully evaluate the redox activity of neocuproine bound to first-row transition metals.…”