Nucleophilic addition versus electron transfer in carbonylmetallate salts. Donor-acceptor interactions in the precursor ion pairs

Abstract

The isostructural pentacarbonylmetallate anions M(CO)ϪϪ 5 ] is identified as the critical precursor for both electron transfer and nucleophilic coupling. Based on these observations, it is proposed that the rates and mechanisms of these interionic reactions are controlled by donor-acceptor bonding in the transition states, which in turn is directly related to the charge-transfer interactions extant in the ion-pair intermediate. ©

Organic Photoredox Catalysis

“…Moreover, their corresponding neutral quinolinyl radicals (such as NMQ• ) generated upon single electron reduction are sufficiently reducing so as to be turned over by relatively weak oxidants, including O 2 . Unfortunately, quinoliniums display a propensity towards addition of nucleophiles at the 2- and 4- positions in the ground state cations, − as well as radical reactions of quinolinyl radicals at the same positions (Scheme ). ,, Both pathways lead to partial dearomatization of the chromophore, which can severely limit their application as photoredox catalysts.…”

“…Additionally, Acr-Me + possesses a quantum yield of fluorescence equal to 1.0 and an extremely long lifetime of fluorescence at 31 ns . Despite these promising properties, Acr-Me + has found limited use as a photoredox catalyst because of its susceptibility to nucleophile addition at the 9-position in the ground state cation (Scheme ), as well as radical reactions of the acridinyl radical Acr-Me• , both reactivity modes generating dihydroacridines 70.1 . The 9-phenyl substituted Ph-Acr-Me + showed no evidence of radical–radical reactivity at the 9-position in one study .…”

σ-Arsolido complexes

“…Fc/Fe + in MeCN 6 ) towards electrophiles with which they are treated is a documented feature of their chemistry. 7 Märkl has shown arsoles themselves to be reducible species ( e.g. , PhAsC 4 Ph 2 H 2 E = −1.77 V vs .…”

Recent progress in organophotoredox reaction

“…59 In 2004, Fukuzumi and team developed a new photocatalyst, 9-mesityl-10-methylacridinium ion, which shows remarkable photo-reactivity in numerous transformations. 60,61 The key to success is attributed to the ability of this salt to access a charge-transfer state through an electron transfer between the mesityl (donor) and the acridinium (acceptor) groups. 62 In fact, due to the orthogonality of the donor and the acceptor moieties, photoinduced electron transfer from the mesitylene to the singlet excited state of the acridinium gives rise to the formation of the Acr˙-Mes˙ + state.…”