Nonspectator Feature of Redox Noninnocent Ligands: CC/CH Functionalization

Abstract

Redox noninnocent ligands, capable of participating in electron transfer processes have gained profound attention toward small molecule activation, catalysis, function of selective metalloenzymes as well as for their fascinating ligand centered reactivity. This article is therefore highlighted the terms “redox noninnocence” and “chemical noninnocence” of the ligands in the context of their chemical ramification at the ligand backbone. Two main types of reactivity by the redox noninnocent ligands have been illustrated here: (i) redox‐induced CC coupling phenomenon via reductive or oxidative pathway and (ii) dioxygen fixation into the ligand backbone to furnish oxygenated or ring cleavage product. Further, potential application of the redox noninnocent ligands in the catalytic transformation by virtue of their multielectron reservoir capability has been briefly introduced.

Metal–ligand synergy driven functionalisation of alkylene linked bis(aldimine) on a diruthenium(ii) platform. Cyclisation versus oxygenation

“…Redox-active ligands play a crucial role in numerous metalloenzymes, 1 such as the conversion of d -galactose to d -galactohexodialdose by galactose oxidase proceeding via the intermediacy of active Cu II –Tyr˙ (Tyr = tyrosine), 1 a the oxidation of R–H → R–OH by cytochrome P450s involving a ferryl-oxo porphyrin π-cation radical intermediate in the catalytic cycle to abstract the hydrogen atom from R–H, 1 b and the uptake of necessary electrons by quinol oxidases for the reduction of O 2 to H 2 O from ubiquinol (2,3-dimethoxy-5-methyl-6-polyprenyl-1,4-benzoquinol). 1 c Multielectron reservoir capability/bistability of redox-active ligand derived metal complexes also enables catalytic performances, 2 activation of small molecules 3 and designing of molecular materials.…”