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

Article abstract of DOI:10.1002/anie.202002768

The perfluorinated dihydrophenazine derivative (perfluoro-5,10-bis(perfluorophenyl)-5,10-dihydrophenazine) (“phenazine^F”) can be easily transformed to a stable and weighable radical cation salt by deelectronation (i.e. oxidation) with Ag[Al(OR<

Full text of DOI:10.1002/anie.202002768

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Accepted Article
Title: Innocence is Bliss: Synthesis and Application of a very strong
Perfluorinated Ammoniumyl Radical Cation in Deelectronation
Chemistry.
Authors: Ingo Krossing, Marcel Schorpp, Tim Heizmann, Maximillian
Schmucker, Stephan Rein, and Stefan Weber
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To be cited as: Angew. Chem. Int. Ed. 10.1002/anie.202002768
Angew. Chem. 10.1002/ange.202002768
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Angewandte Chemie International Edition
10.1002/anie.202002768
Innocence is Bliss: Synthesis and Application of a very strong Perfluorinated
Ammoniumyl Radical Cation in Deelectronation Chemistry.
[
a]
[a]
[a]
[b]
[b]
Marcel Schorpp, Tim Heizmann , Maximillian Schmucker , Stephan Rein , Stefan Weber , Ingo
Krossing*[a]
[
a]
Institut für Anorganische und Analytische Chemie and Freiburger Materialforschungszentrum (FMF),
Albert-Ludwigs-Universität Freiburg, Albertstr. 21, 79104 Freiburg, Germany. [b] Institut für Physikalische
Chemie, Albert-Ludwigs-Universität Freiburg, Albertstr. 21, 79104 Freiburg, Germany. *Correspondence to
krossing@uni-freiburg.de.
Abstract: The perfluorinated dihydrophenazine derivative (perfluoro-5,10-bis(perfluorophenyl)-5,10-
F
dihydrophenazine) (“phenazine ”) can be easily transformed to a stable and weighable radical cation salt by
deelectronation with Ag[Al(ORF)
] / Br
mixtures (R = C(CF
F
). As an innocent deelectronator it possesses a
4
2
3
)
3
+
strong and fully reversible half-wave potential vs. Fc /Fc in coordinating MeCN (E°’ = 1.21 V), but also in
III
]+ to
almost non-coordinating oDFB (= 1,2-F
C H
2 6 4
; E°’ = 1.29 V). It allows for the deelectronation of [Fe Cp*
] and [Fe (CN- Bu)Cp*
]2+ in common laboratory solvents and is compatible with good σ-
2
IV
2+
IV
t
[
Fe (CO)Cp*
2
2
donor ligands like L = trispyrazolylmethane to generate novel [M(L)
elemental metals.
x
]n+ complex salts from the respective
[
1]
Oxidation, or better deelectronation, represents one of the most fundamental transformations in synthetic
chemistry. Very useful and extremely strong deelectronating agents like SbF or MF (M = Pd, Pt, …) show
disadvantages, as they require the use of difficult to handle solvents, such as anhydrous HF (aHF), while MF
species are best freshly prepared by reacting the respective metals with F . Both require appropriate facilities
5
6
6
2
as well as trained personnel.[2a,3,2b] Well established and easy to generate and use deelectronating agents are
solvent-free nitrosonium and silver salts of weakly coordinating anions (WCAs). Since high performance
WCAs like [B(C
6
F
5
)
4
]– or [B(C
6
H
3
(CF
3
) )
]– do not withstand high electrochemical potentials or even only
2
4
+
F
−
F
solvent free silver and NO salts, the electrochemically robust [Al(OR )
stable WCAs,[4,5] are of particular relevance herein. However, Ag as primary deelectronator is small and Lewis
4
] (OR = OC(CF ) ), or related redox
3
3
+
acidic, which opens unwanted side reactions like halide abstraction or coordination rather than
+
deelectronation. In addition, the influence of solvation on the formal potential of Ag is large and spans, for
[
4]
example, a range of 0.6 V between CH
2
Cl and MeCN. This dependence also prohibits the use of good σ-
2
and π-donating ligands, as they will effectively quench the deelectronation potential of silver(I) by forming
coordinatively saturated complexes. The use of halogens together with weakly coordinated silver salts can
boost their deelectronation potential tremendously. Only recently, we isolated the molecular equivalents of
+
)]+ (X = Cl
(I )
]2+ (n = 2,4,6) complexes.[6] Side
the Ag /X
2
couple as a series of [Ag(X
2
2 2 2
, Br , I ) as well as [Ag
2
2
n
reactions of this class of compounds are yet to be investigated. However, preliminary studies with transition
+
metal carbonyl complexes have shown that they may act as a source for electrophilic X . Nitrosyl salts, with
+
0
[7]
a publishedformal potential vs. Fc /Fc of 1.00 V in CH
2
Cl , often act as irreversible deelectronating agents,
2
if the gaseous reaction byproduct NO can be removed. However, the generated neutral NO is likely to
[
8]
undergo further ligand-substitution, e.g. with transition-metal complexes. Moreover, nitrosyl salts show a
noticeable solvent dependency of their formal potential and are known to form colored charge transfer
complexes with arenes as the first step towards electrophilic substitution, thus lessening their applicability.[9]
1
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Angewandte Chemie International Edition
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Another class of deelectronating agents, and part of the work documented herein, are ammoniumyl radical
cations, first observed over 100 years ago by Wieland et. al.[10] The intense blue color of phenylamine
derivatives in deelectronating media was later assigned by Weitz and Schwechten to the formation of an
ammoniumyl radical cation.[11] When protecting the para positions on the aryl moieties, these radicals can
be isolated and by variation of the substitution pattern on the aryl ring, the formal potentials tuned over a
range of 1.5 V.[12] The most prominent and commercial example is [N(C
][SbCl ], colloquially called
6 4
H Br-4)
3
6
+
“
magic blue” with E°’ = 0.70 V vs Fc /Fc. In addition, the solvent dependency of the formal potential of
ammoniumyl radical cations compared to silver(I) or nitrosonium salts is very small.[4] Furthermore,
ammoniumyl radical cations were shown to generally undergo innocent electron transfer (ET), and can be
used in a wide variety of common laboratory solvents. For these reasons the ammoniumyl radical cations
have found wide application in organic synthesis, catalysis, as mediators in electrochemistry or as doping
agents in polymer sciences.[13] Interestingly, reported uses in organometallic or inorganic chemistry are
comparatively scarce;[14] the most pertinent example being the generation of a variety of fullerene and azo-
fullerene radical cations by Reed and coworkers with magic blue amine derivatives.[15]
Thus, this class of deelectronating agents appeared to offer advantages over the commonly used reagents
described above. We have therefore replaced the poor [SbCl
the much better performing WCA [Al(ORF) ]−. However, it soon became evident that this straightforward and
6
]− WCA in the commercial “magic blue” salt for
4
in good yield accessible ET agent (cf. SI) is not compatible with the use of σ-donor ligands like
dimethylaminopyridine, carbenes (e.g, IPr) or phosphines (see Scheme 1).
Scheme 1. Reactivity of [N(C
6
H
4
Br)
3
][Al(ORF)
] S1 towards σ-donor ligands and degradation of S1. In all cases
4
F
–
the counterion is [Al(OR )
4
] . For the molecular structures of S1, S2, S3 and S4 see SI.
The molecular structures of several reaction products suggest that these ligands are deelectronated with
∙
formation of the very sharp σ-ligand-radical cations, which rapidly undergo a series of H/Br abstraction on
the neutral magic blue amine to give a plethora of substitution products, which have been characterized by
∙
scXRD and mass spectrometry (Fig. S4-7; SI). Decomposition by H/Br abstraction has also been reported
before to occur in the solid state upon simple storage of “magic blue” salt, e.g. formation of S2.[16] As all of
the established and commonly used ammoniumyl radical cations always contain C-H and often also C-Br
bonds, comparable reactivities are expected for these radicals.[17] A potent alternative, the perchlorinated
+
∙
trisarylammoniumyl radical cation [N(C
6
Cl ) ] , was only reported as a personal communication; its use in the
5
3
literature is scarce and no preparations for either neutral amine nor the radical cation could be found.[18]
2
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Angewandte Chemie International Edition
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This motivated us to look for more stable alternatives with suitably high formal potential. To hinder the
homolytic cleavage of C–X bonds (X = H, Br), we set out to design amines only employing very strong and
weakly nucleophilic C–F bonds. The precursor for our herein described system, a bis-perfluoroarylamide
NArF
] (Ar = -C
−
F
and C
F on a multigram
[
2
6 5
F ) can be easily prepared from the cheap starting materials LiNH
2
6
6
scale as described by Sundermeyer and coworkers, who used this amide as WCA in electrochemical
applications.[19,20] The weak coordination ability underlines the very poor nucleophilicity of the amide
nitrogen, which explains numerous own and others failed attempts to generate the corresponding
trisarylamine derivative N(ArF)
solvent-free Li[NArF
] 2 above 180 °C to yield a perfluorinated dihydrophenazine derivative 3 by
intermolecular abstraction of two equivalents of LiF (see Eq. 1).[20]
in satisfying yields. Yet, Sundermeyer et al. noticed the decomposition of
3
2
(1)
First own synthesis attempts were carried out in analogy to the method described by Sundermeyer et. al.
Solvent-free 2 was generated by the reaction between HNArF
1 and Li{N(SiMe } (LiHMDS) in toluene. The
2
)
3 2
isolated product was then charged into a Schlenk tube equipped with a cool finger and heated in a vertical
tube oven to 220 °C under dynamic vacuum. When the set temperature was reached, the reaction proceeded
quickly and the brown reaction product could be washed from the cool finger with toluene. NMR
investigations of the obtained crude product, however, have shown equimolar amounts of the amine 1 and
t
target compound 3. Suspected reprotonation by leftover HN(SiMe
3
)
2
in the heat was ruled out by use of BuLi
1
19
as base. Closer analysis of the starting material 2 revealed the presence of 1 as determined by H- F NOESY
NMR experiments. The non-quantitative deprotonation of 1 is presumably attributable to strong
intermolecular [(F
5 6
C )
2
N--H--N(C
6
F )
]– hydrogen-bonding between 1 and 2 explaining the NOESY cross
5
2
correlation between the acidic proton and the ortho-fluorine atom in the single resonance set observed. This
prevents complete deprotonation even in strongly coordinating solvents like acetonitrile or THF. 2 free of
solvent coordination and with only trace amounts (less than 1%) of 1 could be generated by deprotonation
with LiHMDS and switching from non-polar toluene to ortho-difluorobenzene (oDFB). Amine-free 2,
crystallizing as 2∙2 oDFB (molecular structure in SI), was then charged into a Schlenk-tube and submitted to
controlled heating to 200 °C under dynamic vacuum on a hot-stirrer plate with a commercially available
aluminum heating block. Purification by sublimation of the obtained crudes at 170 °C in dynamic vacuum
gave only poor yields of pure 3 as the reaction side products form a highly viscous oil, from which 3 is not
readily liberated. Precipitation of 3 from MeCN solution with H O followed by additional sublimation has
2
resulted in acceptable multi-gram yields of 3 (2.8 g, 38 %; molecular structure of 3 in Fig. 1a).
Compound 3 was examined by cyclovoltammetry experiments (see Fig. 1c and SI) and gave a reversible
+
oxidation wave at 1.21 V against Fc /Fc in MeCN and at 1.29 V in oDFB with external reference to N(C
H Br)
6 4 3
+
(
E
1/2 = 0.70 V, ref. Fc /Fc). Thus, the formal potential of 3 exceeds that of both, silver and nitrosonium salts.
+
Chemical deelectronation of 3 was successful by reaction with the synergistic Ag / ½ X deelectronator pair.
2
When employing iodine, non-quantitative turnover to the desired radical species was observed, as even after
prolonged reaction times crystallization attempts showed aside from the desired needle shaped deep purple
3
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Angewandte Chemie International Edition
10.1002/anie.202002768
crystals of 4, a thin film of off-white powder in the crystallization ampoule; presumably from continuously
+
formed AgI. When switching to Ag / ½ Br
2
however, quantitative turnover was achieved, with an isolated
as solvent for synthesis, the radical was also
Cl as solvent. In analogy to the described
]− salt can be accessed, when employing Ag[SbF
] in SO solution giving stable
yield of 4 of 97 %. While solvent-free 4 is best isolated from SO
successfully generated and is stable in both oDFB and CH
procedure, the respective [SbF
2
2
2
6
6
2
deeply purple colored solutions. Pure 4 is also stable in MeCN and can be indefinitely stored in the solid state
and does not decompose, when exposed to a dry ambient atmosphere. However, introduction of moisture
to a solution of 4 proceeds with ready color loss. Crystals suitable for single crystal diffraction analysis could
be obtained by layering of an oDFB or CH
2
Cl solution with pentane. For the first solvent combination, a
2
super-structure in the analyzed deep purple crystal was found. A reliable molecular structure of 4 was
gathered from crystals grown in CH
Cl
2 2
as shown in Fig. 1b.
F
F
F
Fig. 1 a) Molecular structure of “phenazine ” 3 and b) molecular structure of [“phenazine ”][Al(OR )
4
] 4. Data
collected at 100 K. Co-crystallized CH
2
Cl
2
omitted for clarity. Thermal displacement ellipsoids set at 50 %
as internal reference and
] (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 SO 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
119HS-W1 (Bruker) cavity using a microwave power of 0.04743 mW (35 dB attenuation, 200 mW source
probability. c) Cyclovoltammogram of 3 (10 mM) in MeCN with FeCp
2
F
[
NBu
4
][Al(OR )
4
2
4
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).
The central nitrogen atoms here are almost perfectly planar coordinated with a bond angle sum of 358.2°
compared to more pyramidal neutral 3 with an angle sum of 342.2°. The isolated crystals of 4 were analyzed
by ESI-mass spectrometry and show mass envelopes for the desired radical at 658.08 m/z (calc. N
C F ;
2 24 18
6
57.98 m/z) as well as little of an iminium cation at 491.17 m/z (calc. N
2 18
C F
13
N ; 490.99 m/z), the latter of
2
4
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Angewandte Chemie International Edition
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which is formed by fragmentation processes as verified by collision induced decomposition experiments CID.
Continuous-wave (cw) electron paramagnetic resonance (EPR) measurements were carried out at X-band
frequency to investigate a sample of 4 in SO at ambient temperature (see Fig. 1d). The EPR spectrum
2
unambiguously shows an organic radical, centered at giso = 2.0031. The EPR spectrum exhibits a well-resolved
pattern with multiple hyperfine lines. The hyperfine pattern could be reproduced by a spectral simulation of
the EPR spectrum in the isotropic limit using the EasySpin simulation package[17] in combination with non-
linear least-squares optimization algorithms and initial parameter sampling. The obtained fit result indicates
two sets of six and two magnetically equivalent hyperfine couplings to I = ½ nuclei. These hyperfine couplings
can be assigned to the coupling between the unpaired electron spin and the fluorine atoms (I = ½). While the
EPR simulation is able to reproduce the experimental data, it is noteworthy that in analogy to NMR spectra
+
of neutral 3 no six magnetically equivalent fluorine atoms can be present in the molecular ion 4 . DFT studies
have shown that the largest coupling should come from 4:2:2 equivalent fluorine atoms. The two very similar
calculated median coupling constants for F2, F3, F6, F7 of 9.7 MHz and F13, F18 of 10.5 MHz (numbering
scheme see Fig. 1b) may therefore be indistinguishable in the experiment. Together with the larger calculated
coupling to the para-fluorine in C
:2 coupling scheme.
F
6 5
moieties (F11, F16) of 15.6 MHz, these calculations support the simulated
6
+
To verify the measured very high formal potentials of 1.21/1.29 V against Fc /Fc, the deelectronation of
model substrates was investigated (see Fig. 3). As such, 4 was reacted with sheeted tin metal in MeCN. The
reaction proceeds via complete loss of the intense purple color after 1h at ambient temperature. NMR
spectra of the dried reaction mixture in oDFB revealed the intact counterion and neutral 3 in a 1:1 ratio;
underlining both stability and purity of employed 4. 119Sn resonances were not detectable, probably due to
the low sample concentration. However, the ratio between MeCN and counterion determined by NMR
F
as product.[21] Yet, the pentasolvate
integration is 6:2, hinting to the already known [Sn(MeCN)
6
][Al(OR )]
2
F
[
Sn(MeCN)
5
][Al(OR )]
2
5 crystallized from oDFB (see Fig. 2 a). To prove the ligand compatibility of 4, it was
) in the deelectronation of elemental tin to yield the
][Al(ORF)
6 with each of the chelating ligands binding
used together with trispyrazolylmethane (CHpz
3
respective biscoordinated complex [Sn(CHpz
3
)
2
]
4 2
2
strongly κ (dSn-N = 2.448(3) Å) and an additional third longer Sn-N contact at 2.715(3) Å (see Fig. 2 b).
5
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Angewandte Chemie International Edition
10.1002/anie.202002768
Fig. 2 Reactivity of the deelectronator 4 towards different substrates with molecular structures of a)
F
F
F
[
Sn(MeCN)
5
[Al(OR )
]
4 2
5, b) [Sn(CHpz
3
)
2
][Al(OR )
]
4 2
6, c) [Fe(CO)Cp*
2
][Al(OR )
]
4 2
7 and d) [Fe(CN-
t
F
Bu)Cp*
2
][Al(OR )
]
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. Some selected spectroscopic data is
included.
III
]+ to the only recently
As upper limit of possible ET reactions, the deelectronation of monocationic [Fe Cp*
2
IV
]2+ was chosen, a compound so far only accessible by deelectronation of the
reported dicationic [Fe Cp*
2
[
3]
decamethylferrocenium ion with SbF
with very slow loss of the intense purple color of 4, only the starting material [FeCp*
of neutral 3 could be identified by scXRD respectively NMR spectroscopy. When switching to SO
medium, the purple color of 4 seems persistent indefinitely. When repeating the reaction between
FeCp* ] and 4 under 3 atm of CO gas in oDFB, a ready color change from deep purple to red-brown
][Al(ORF)
was observed allowing access to the 18 VE dicationic Fe(IV) complex [Fe(CO)Cp* 7 in 63 %
][Al(ORF)
] dication was hitherto only accessible in aHF. 7 was crystallized from
5
in SO
2
solution. While reactions in both CH
2
Cl
2
and oDFB proceeded
][Al(ORF)
] and traces
as reaction
2
4
2
[
2
2
2
]
4 2
2+
[22]
crystalline yield. The [Fe(CO)Cp*
2
concentrated oDFB solution by either vapor diffusion or layering of the reaction mixture with n-pentane.
Structure determination by scXRD experiments has however proven difficult. With both crystallization
methods, 7 crystallized in large cells with underlying super-structure. However, the identification of the
crystals as 7 was unambiguous (molecular structure, see Fig. 2 c). Presence of the assigned cationic species
was verified by IR spectroscopic analysis showing a strong vibrational band of the single coordinated carbonyl
−
1
moiety with a stretching frequency of 2057 cm , which is, as expected due to the better WCA performance
−
1
of our counterion, slightly blue-shifted towards the literature (cf. [Fe(CO)Cp*
2
][X]
2
; X = [AsF
6
] 휈̃ = 2042 cm ,
−
1
−1
6
X = [SbF ] 휈̃ = 2034 cm ) and fits very well to the DFT-calculated IR spectrum ( 휈̃ = 2058 cm
@
BP86/D3(BJ)/def-SV(P)). Furthermore, bulk purity was confirmed by powder diffraction analysis and NMR
6
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Angewandte Chemie International Edition
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1
19
spectra of isolated crystalline material. Internal referencing with solvent oDFB in both H & F-NMR spectra
shows a 2:2 ratio between Cp* and [Al(ORF)
]−, underlining purity of diamagnetic 7.
4
t
A related dicationic Fe(IV) complex was synthesized, when excess of tert-Butylisonitrile ( BuNC) instead of CO
t
2+
F
]− salt in the form of deep red
allowed for isolation of unprecedented [Fe(CN- Bu)Cp*
2
] 8 as the [Al(OR )
4
5
−
crystals in 77 % crystalline yield (see Fig. 2 d). The central iron is distorted η -coordinated by the Cp* moieties
with an average Fe-C distance of 2.1674(4) Å (dFe-C = 2.142(4) – 2.194(4) Å). The two Cp* rings are tilted by
t
2
9° against each other forcing the methyl groups opposite of coordinated BuNC out of the ring plane by up
t
to 15°. The BuNC ligand is coordinated to iron at dFe1-C1 = 1.874(4) Å. This lies between reported Fe-(CN-R)
(
II)
[23]
t
bond lengths of divalent [Fe Cp(CO)
2
(CN-Me)][BF
4
] (dFe-C = 1.900(9) Å ) and zero-valent Fe(CO)
n
(CN- Bu)
m
[
24]
[25]
[26]
(
dFe-C = 1.89 {n =4, m = 1} , 1.865(2) {n =3, m = 2} , 1.813(7) to 1.837(7) {n = 0, m = 5} Å) and is by 0.09 Å
[
22]
longer than in the related [Fe(CO)Cp*
][AsF ]
2 6 2
(cf. dFe-C = 1.785(9) Å) . Its C≡N stretching frequency is slightly
blue-shifted to 2176 cm (cf. free BuNC at 2136 cm−1[27]) and in good agreement to its DFT-calculated
−
1
t
−
1
frequency at 휈̃ = 2195 cm (@ BP86/D3(BJ)/def-SV(P)). Bulk purity was proven by powder diffraction analysis
and NMR spectra of isolated crystalline material and revealed with both methods a contamination of the
sample with less than 20% of the starting material [FeCp*
2
][Al(ORF)
4
]. This appears to be due to the instability
t
of the isonitrile ligand in the presence of 4. Thus, part of the employed deelectronator reacts with BuNC to
give a series of undefined degradation products resulting in partial re-isolation of starting material.
In conclusion, we prepared and isolated the radical cation salt of the perfluorinated dihydrophenazine
F
F
derivative [“phenazine ”][Al(OR )
4
] 4 as a stable, weighable and very strong deelectronating agent with broad
F”
solvent compatibility. The intermediate yields of parent neutral “phenazine 3 are attributable to the nature
of the synthesis, but are counterbalanced by the ready and cheap availability of the starting materials as well
as its easy isolation. The during the ET reactions regenerated neutral 3 shows negligible nucleophilicity and
does not interact with the deelectronated substrates, allowing for new synthesis pathways in the generation
of highly reactive cationic species. The promising synthetic scope of this reagent was shown by successful
2+
t
]2+ 8 in oDFB
deelectronation to organometallic tetravalent iron in [Fe(CO)Cp*
solution. Thus, even removal of an electron from an already cationic and evidently very stable species like
FeCp*
]+ proceeds facile. Future investigations will focus on the applicability of this reagent to other main-
2
] 7 and [Fe(CN- Bu)Cp*
2
[
2
group and transition metal species to get access to hitherto inaccessible or only in aHF accessible reactive
cations.
Conflicts of interest
The authors declare no conflict of interest.
Acknowledgements
This work was supported by the Albert-Ludwigs-Universität Freiburg, the Deutsche Forschungsgemeinschaft
DFG in the Normalverfahren and the Carl-Zeiss-Stiftung. We thank Dr. H. Scherer and F. Bitgül for performing
NMR measurements, Dr. T. Ludwig & Dr. M. Daub for measuring pXRD, Dr. D. Kratzert for help with scXRD
measurements, and the Magres Core Facility for EPR and NMR instrument support.
Supporting Information
†
Electronic supplementary information (ESI) available: Experimental details, procedures, weights, 1D- and
2
D-NMR spectra, IR spectra and powder diffraction patterns of the reactions are deposited. Details to the
7
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quantum chemical calculations are given together with crystallographic details. CCDC 1985536, 1985539-
985548. For ESI and crystallographic data in CIF or other electronic format see DOI: …
1
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1] a) Here and in the following we use the particle based view on the classical oxidation = deelectronation
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successful and self-explaining acid-base picture. Thus, the equivalent to a deprotonation reaction is a
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[
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Entry for the Table of Contents
Innocent but very strong: Synthesis and application of a novel perfluorinated phenazine ammoniumyl radical
cation is presented. This novel very strong deelectronator shows broad solvent compatibility, was used
together with good sigma donor ligands, and allows access to tetravalent dicationic iron complexes in
common laboratory solvents.
Keywords: oxidation, weakly coordinating anions, radical ions, main-group chemistry, transition-metal
chemistry
9
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