Completing the Redox‐Series of Silicon Trisdioxolene:ortho‐Quinone and Lewis Superacid Make a Powerful Redox Catalyst

Abstract

Quinones are mild oxidants, the redox potentials of which can be increasedb ys upramolecular interactions. Whereas this goal has been achieved by hydrogen bondingo rm olecular encapsulation, aL ewis acid-binding strategyf or redox amplificationo fq uinones is unexplored. Herein,t he redox chemistry of silicon tris(perchloro)dioxolene 1 was studied, whichi st he formal adduct of orthoperchloroquinone Q Cl with the Lewiss uperacid bis(perchlorocatecholato)silane 2.B yi solatingt he anionic monoradical 1C À À ,t he redox-series of ac entury-old class of compounds was completed. Cyclic voltammetry measurements revealed that the redox potentiali n1 was shifted by more than 1V into the anodic direction compared to Q Cl ,r eaching that of "magic blue" or NO + .I ta llowed oxidation of challenging substrates such as aromatic hydrocarbons and couldb ea pplieda sa ne fficient redox catalyst. Remarkably,t his powerful reagent formed in situ by combining the twoc ommercially available precursors SiI 4 and Q Cl .

Interplay and Competition Between Two Different Types of Redox‐Active Ligands in Cobalt Complexes: How to Allocate the Electrons?

“…The cobalt atom is octahedrally coordinated. The four Co−O bond lengths (1.890(2), 1.901(3), 1.920(2) and 1.897(2) Å) clearly argue for the presence of low‐spin Co III [45,46] . An estimation of the metrical oxidation state (MOS) [47] of the two Cl 4 ‐cat units resulted in a MOS of −1.82±0.15 and −1.76±0.12 respectively.…”

“…In a complex, the oxolene-type ligands compete with the bisguanidine/urea azine ligands for the electron density, leading to intriguing electronic properties that are difficult to predict. From cyclic voltammetry measurements, redox potentials (E 1/2 value) for the benzoquinone/semiquinone couples of À 0.33 V for (Cl 4 -bq)/(Cl 4 -sq) in CH 2 Cl 2 [46] (À 0.29 V [47] or À 0.27 V [48] in CH 3 CN) and À 0.92 V in CH 3 CN for (tBu 2 -bq)/(tBu 2 -sq) [41] (À 0.96 V according to an earlier analysis [42] ) were obtained. For the redox couple (Cl 4 -sq)/(Cl 4 -cat), E 1/2 values of À 1.19 V in CH 2 Cl 2 [40] and À 1.06 V [42] in CH 3 CN were reported, and for the redox couple (tBu 2 -sq)/(tBu 2 -cat), an E 1/2 value of À 1.7 V [49] was given.…”

Proton‐Coupled Electron Transfer (PCET) with 1,4‐Bisguanidino‐Benzene Derivatives: Comparative Study and Use in Acid‐Initiated C‐H Activation

“…used 1.3 equivalents of Q Cl in combination with 0.1 equivalents of the special silicon redox catalyst Si(Cat Cl )(SQ Cl ) 2 (see Table 9 ) to obtain >95 % NMR yield, again in CH 2 Cl 2 at 4 °C after 24 h reaction time. [42] Moreover, a photo‐catalytic reaction in CH 3 CN solution at room temperature with 5 mol% DDQ and 50 mol% tert‐butyl nitrite was reported, using dioxygen from air as terminal oxidant. [43] The mixture was irradiated for 24 h by a blue compact fluorescent lamp with λ=450±50 nm light.…”

Bis(catecholato)germane: an effective catalyst for Friedel–Crafts alkylation reaction

“…[11][12][13][14][15][16] A number of Lewis acid catalysts of group 14 elements have been developed. [17][18][19] However, the Lewis acid catalyst of germanium (IV) is limited in the literature. Recently, substituted catecholate ligands have successfully been employed in the synthesis of germanium(IV) compounds.…”