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. 2020 Jun 8;59(24):9453-9459.
doi: 10.1002/anie.202002768. Epub 2020 Apr 24.

Synthesis and Application of a Perfluorinated Ammoniumyl Radical Cation as a Very Strong Deelectronator

Affiliations

Synthesis and Application of a Perfluorinated Ammoniumyl Radical Cation as a Very Strong Deelectronator

Marcel Schorpp et al. Angew Chem Int Ed Engl. .

Abstract

The perfluorinated dihydrophenazine derivative (perfluoro-5,10-bis(perfluorophenyl)-5,10-dihydrophenazine) ("phenazineF ") can be easily transformed to a stable and weighable radical cation salt by deelectronation (i.e. oxidation) with Ag[Al(ORF )4 ]/ Br2 mixtures (RF =C(CF3 )3 ). As an innocent deelectronator it has a strong and fully reversible half-wave potential versus Fc+ /Fc in the coordinating solvent MeCN (E°'=1.21 V), but also in almost non-coordinating oDFB (=1,2-F2 C6 H4 ; E°'=1.29 V). It allows for the deelectronation of [FeIII Cp*2 ]+ to [FeIV (CO)Cp*2 ]2+ and [FeIV (CN-t Bu)Cp*2 ]2+ in common laboratory solvents and is compatible with good σ-donor ligands, such as L=trispyrazolylmethane, to generate novel [M(L)x ]n+ complex salts from the respective elemental metals.

Keywords: Iron complexes; main-group chemistry; oxidizing agents (deelectronators); radical ions; weakly coordinating anions.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Scheme 1
Scheme 1
Reactivity of [N(C6H4Br)3][Al(ORF)4] (S1) towards σ‐donor ligands and the degradation of S1. In all cases the counterion is [Al(ORF)4]. For the molecular structures of S1, S2, S3, and S4 see Supporting Information.28
Figure 1
Figure 1
a) Molecular structure of “phenazineF” (3) and b) molecular structure of [“phenazineF”][Al(ORF)4] (4). Data collected at 100 K. Co‐crystallized CH2Cl2 omitted for clarity. Thermal displacement ellipsoids set at 50 % probability.28 c) Cyclic voltammogram of 3 (10 mm) in MeCN with Fc+/Fc as internal reference and [NBu4][Al(ORF)4] (100 mm) as conducting salt. The half‐wave potential is independent of the sweep rate. d) X‐band continuous‐wave‐EPR spectrum of 4 in SO2 at ambient temperature (black). The spectrum was recorded at a microwave frequency of 9.7973 GHz on an Elexsys E580 (Bruker Biospin) spectrometer equipped with a 4119HS‐W1 (Bruker) cavity using a microwave power of 0.04743 mW (35 dB attenuation, 200 mW source power), a modulation frequency of 100 kHz and a modulation amplitude of 0.05 mT. The corresponding spectral simulation is shown in gray. Two sets of six and two equivalent fluorine atoms with isotropic hyperfine coupling constants were used for the simulation. The isotropic hyperfine constants were determined as 15.44 and 20.35 MHz, respectively. The Gaussian linewidth was determined to be 0.267 mT (full width at half maximum).
Figure 2
Figure 2
Reactivity of the deelectronator 4 towards different substrates and the molecular structures of a) [Sn(MeCN)5[Al(ORF)4]2 (5), b) [Sn(CHpz3)2][Al(ORF)4]2 (6), c) [Fe(CO)Cp*2][Al(ORF)4]2 (7), and d) [Fe(CN‐tBu)Cp*2][Al(ORF)4]2 (8). Data collected at 100 K. H atoms, counterions and (co‐crystallized) oDFB were omitted for clarity. Thermal displacement ellipsoids set at 50 % probability.28 Some selected spectroscopic data is included.

References

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    1. Here and in the following we use the particle-based view on the classical oxidation=deelectronation and reduction=electronation processes. Thus, an oxidant is a deelectronator and a reductant an electronator. This evolved from our work on the protoelectric potential map (PPM) for keeping with the successful and self-explaining acid–base picture. Thus, the equivalent to a deprotonation reaction is a deelectronation reaction. This is in keeping with earlier textbook suggestions by Bockris and Reddy and follows our concept paper on the PPM (Ref. [1 b]) and the recent Review (Ref. [1 c]);
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