Heteroleptic μ-nitrido diiron complex supported by phthalocyanine and octapropylporphyrazine ligands: Formation of oxo species and their reactivity with fluorinated compounds

Article abstract of DOI:10.1142/S1088424617500274

The synthesis and reactivity of N-bridged diiron macrocyclic complexes have been a topic of increasing interest in recent years since the observation of particular catalytic properties of these complexes. Herein, we report a preparation of a novel heteroleptic μ-nitrido diiron complex with unsubstituted phthalocyanine and octapropylporphyrazine macrocycles. This complex reacts with m-chloroperbenzoic acid to form high-valent diiron oxo species showing strong oxidizing properties. The formation and structure of the transient oxo species was investigated by cryospray collision induced dissociation MS/MS technique. Analysis of fragmentation pattern showed that the attachment of oxo moiety occurred at either iron phthalocyanine or at iron porphyrazine site with slight preference for the phthalocyanine iron site. The catalytic properties of the heteroleptic μ-nitrido diiron complex were evaluated in the oxidative transformation of hexafluorobenzene and perfluoro(allylbenzene).

Full text of DOI:10.1142/S1088424617500274

Journal of Porphyrins and Phthalocyanines
J. Porphyrins Phthalocyanines 2017; 21: 1–9
DOI: 10.1142/S1088424617500274
Published at http://www.worldscinet.com/jpp/
Heteroleptic µ-nitrido diiron complex supported by
phthalocyanine and octapropylporphyrazine ligands: Formation
of oxo species and their reactivity with fluorinated compounds
Cédric Colombana, Evgeny V. Kudrika,b and Alexander B. Sorokin*a
a Institut de Recherches sur la Catalyse et l’Environnement de Lyon, IRCELYON, UMR 5256, CNRS-
Universitè Lyon 1, 2 av. Albert Einstein, 69626 Villeurbanne Cedex, France
b Ivanovo State University of Chemistry and Technology 7, av F. Engels; 153000 Ivanovo, Russia
Dedicated to Professor Claudio Ercolani on the occasion of his 80th birthday
Received 22 December 2016
Accepted 12 February 2017
ABSTRACT: The synthesis and reactivity of N-bridged diiron macrocyclic complexes have been a
topic of increasing interest in recent years since the observation of particular catalytic properties of
these complexes. Herein, we report a preparation of a novel heteroleptic µ-nitrido diiron complex with
unsubstituted phthalocyanine and octapropylporphyrazine macrocycles. This complex reacts with m-
chloroperbenzoic acid to form high-valent diiron oxo species showing strong oxidizing properties. The
formation and structure of the transient oxo species was investigated by cryospray collision induced
dissociation MS/MS technique. Analysis of fragmentation pattern showed that the attachment of oxo
moiety occurred at either iron phthalocyanine or at iron porphyrazine site with slight preference for
the phthalocyanine iron site. The catalytic properties of the heteroleptic µ-nitrido diiron complex were
evaluated in the oxidative transformation of hexafluorobenzene and perfluoro(allylbenzene).
KEYWORDS: diiron complexes, phthalocyanine, porphyrazine, µ-nitrido, oxo species, C–F bonds.
complexes was compehensively summarized by Ercolani
INTRODUCTION
and co-workers in 2003 [17]. Among µ-oxo, µ-carbido
Fourty years ago, Summerville and Cohen have
reported the first paper on the preparation of the N-bridged
dimeric iron tetraphenylporphyrin [1]. This complex has
attracted attention of many research groups due to unusual
and µ-nitrido diiron macrocyclic complexes, the proper-
ties of the latter are particularly interesting. Metal sites in
µ-nitrido dimers are strongly connected by the nitrogen
bridge and their Mössbauer spectra show a single dou-
structure and properties [2–6]. The next important step
blet signal indicating that both iron sites are identical,
was the synthesis of µ-nitrido diiron phthalocyanine
complex by Goedken and Ercolani in 1984 [7] followed
by the extensive studies of the structural and spectro-
scopic properties of µ-nitrido diiron homoleptic phthalo-
each in an +3.5 oxidation state. The iron–iron distance in
µ-nitrido dimers is quite short, between 3.25 and 3.36 Å,
indicating a significant p-p interaction between aromatic
macrocycles. Several X-ray structures of µ-nitrido diiron
cyanine [8, 9], porphyrin [10] and tetraazaporphyrin [11,
complexes are available [18]. These formally Fe(III)
12] complexes as well as heteroleptic species [13–16].
Fe(IV) complexes bear one unpaired electron. Since
Further progress in synthesis and spectroscopic charac-
2000 only few papers on the synthesis and characteriza-
terization of single-atom bridged binuclear macrocyclic
tion of µ-nitrido dimers have been published.
Renewed interest in these complexes has been initi-
ated by our recent observation of the remarkable catalytic
properties of µ-nitrido diiron macrocyclic complexes [19,
20]. Of particular interest is the ability of the µ-nitrido
*Correspondence to: Alexander B. Sorokin, email: alexander.
sorokin@ircelyon.univ-lyon1.fr; fax: +33 472-445-399; tel:
+33 472-445-337
Copyright © 2017 World Scientific Publishing Company

2
C. COLOMBAN ET AL.
complexes to catalyze difficult reactions, such as the oxi-
dation of methane [21–25] and ethane [26], benzene [27],
formation of C–C bonds [28] and oxidative dehalogena-
tion of chlorinated [29] and even fluorinated compounds
[30]. Among single-atom bridged binuclear macrocyclic
complexes, µ-nitrido diiron species are particularly active
in catalysis due to their ability to form high-valent diiron
oxo species [31]. Thus, the catalytic properties have been
associated with transient high-valent oxo species which
are very reactive and can be characterized by spectro-
scopic methods only at very low temperatures [19, 23,
32]. In order to understand the origin of unusual catalytic
activity of µ-nitrido dimers, it is important to character-
ize the active species involved in these reactions and key
reaction intermediates. It should be noted that a very lim-
ited number of high-valent iron oxo species on phthalo-
cyanine platform have been obtained and characterized
[21, 24, 33] compared with their counterparts supported
by porphyrin ligands [34–37].
Both iron sites of the Fe(III)NFe(IV) construction
responsible for the catalytic properties can be supported
by porphyrin, phthalocyanine or porphyrazine ligands
to form homoleptic complexes [17–19]. Another pos-
sible arrangement is a heteroleptic combination of two
iron complexes bearing different macrocyclic ligands
[13, 14] or the same type of macrocyclic ligands but with
different substitution pattern [38]. Properties of the sup-
porting ligands can influence the electronic properties of
the dimers and their oxidation state [39–41]. Taking into
account that the properties of the supporting ligands can
influence the catalytic activity of the iron sites, this might
open new interesting possibilities. Recently, we have pre-
pared heteroleptic phthalocyanine µ-nitrido diiron com-
plexes to probe the differences in chemical properties of
the two iron centers within the same molecule [24]. One
iron site was supported by an electron-deficient phthalo-
cyanine ligand having four or eight alkylsulfonyl groups
whereas the other iron site was coordinated with a much
more electron-rich unsubstituted phthalocyanine. Using
cryospray MS and collision induced dissociation MS/MS
techniques as well as DFT calculations, we have shown
that the oxidizing oxo unit was preferencially formed
at the more electron-rich iron site. In the line with this
finding, the increase of the electron density at iron site
resulted in the significant gain in the catalytic activity
[24]. It would be also interesting to evaluate whether the
nature of the supporting ligand might influence the for-
mation of active species. To this aim we have designed
a heteroleptic µ-nitrido diiron complex with phthalo-
cyanine and octapropylporphyrazine ligands (PcFe(µN)
FePz, Fig. 1)
Fig. 1. Structure of heteroleptic µ-nitrido diiron complex with
phthalocyanine and octaethylporphyrazine ligands, PcFe(µN)
FePz
reactivity represents a major objective for chemists. Thus,
the catalytic properties of PcFe(µN)FePz were evaluated
in the oxidative transformation of hexafluorobenzene and
perfluoro(allylbenzene).
EXPERIMENTAL
Equipment and methods
UV-vis spectra of solutions were recorded on a Perkin–
Elmer Lambda 35 or Agilent 8453 spectrophotometers.
Infrared spectra were obtained using a Bruker Vector 22
1
FTIR spectrometer using KBr pellets. H and 19F NMR
spectra were acquired on a AM 250 Bruker spectrometer.
The reaction products were identified by GC-MS method
(Hewlett Packard 5973/6890 system; electron impact at
70 eV, He carrier gas, 30 m × 0.25 mm HP-INNOWax
capillary column, polyethylene glycol (0.25 µm coating).
To analyze acidic organic products, the reaction mixtures
were treated with 2.0 M solution of (trimethylsilyl)diazo-
methane in diethyl ether to transform carboxylic groups
to the corresponding methyl esters.
The mass spectra of the complexes were recorded on
a MicroTOF Q II, a quadrupole time of flight (Q-TOF)
mass spectrometer (Bruker Daltonics, Bremen), equipped
with a cold spray ionization source with a spray voltage of
5 kV. The temperature of the spray gas was -30°C and that
of the dry gas was -5°C. The solutions of the complexes
(~10-6 M) in acetonitrile in the presence of 1000 equiv.
of m-chloroperbenzoic acid (m-CPBA) were introduced
into the gas flow at 180 µL.h-1. The m-CPBA oxidant was
added to the frozen complex solution in acetonitrile and
the sample was introduced immediately after melting. All
mass spectra were recorded in the positive ion mode.
The molecular ions (M+) of the oxo and peroxo diiron
species observed in the regular MS experiment cannot be
trapped in the quadrupole region due to the formation of
multimers by p-stacking interactions. To overcome this
problem, a low activation of ions during transmission
The focus of this work was to prepare a heteroleptic
µ-nitrido diiron complex with different ligands having
similar electronic properties in order to explore regiose-
lectivity of the formation of the oxo species by collision
induced dissociation MS/MS approach. Development
of catalysts for challenging reactions showing new
Copyright © 2017 World Scientific Publishing Company
J. Porphyrins Phthalocyanines 2017; 21: 2–9

HETEROLEPTIC µ-NITRIDO DIIRON COMPLEX SUPPORTED BY PHTHALOCYANINE AND OCTAPROPYLPORPHYRAZINE
3
through the ion funnels was applied by In Source
Collision Induced Dissociation (ISCID) at 20 eV, which
enabled us to do MS/MS measurements. This activation
allowed us to mass select the oxo and peroxo diiron spe-
cies in the quadrupole part of the mass spectrometer. The
collision energy applied in the collision cell was about
60 eV and the collision gas was nitrogen.
corresponding homoleptic complexes and the desired
heteroleptic complex can be usually obtained. To limit
the amount of homoleptic by-products and to avoid
tedious purification procedures, the heteroleptic complex
PcFe(µN)FePz was prepared by using FePc/FePz mixture
in a 7.5/1 ratio. These conditions favor the preferential
formation of the targeted heteroleptic complex PcFe(µN)
FePztogetherwiththehomolepticunsubstituted(FePc)2N
poorly soluble in common organic solvents which can
be readily separated by filtration. A pure product was
obtained by column chromatography using basic alumina
applying CH2Cl2 and a 10:1 CH2Cl2:MeOH eluents in a
54% yield. The successful preparation of PcFe(µN)FePz
wasconfirmed by IR, UV-visand ESI-MS techniques.The
ESI-MS spectrum of PcFe(µN)FePz showed a prominent
molecular peak at m/z = 1286.50 corresponding to the
expected value of the molecular ion. When the molecular
ion PcFe(µN)FePz+ was subjected to collision induced
dissociation (CID), FePc (m/z = 568.1) and NFePz
(m/z = 718.4) monomeric units were observed as prin-
cipal fragments indicating that the bridging nitrogen
atom was preferentially bound to more electron-rich iron
octapropylporphyrazine moiety (Fig. 2). Only minor
signals of NFePc (m/z = 582.1) and FePz (m/z = 704.4)
were observed (Fig. 2, inset). This finding indicates that
tandem ESI-MS/MS technique can be used for the deter-
mination of the fine structural features of these binuclear
complexes.
Materials
All chemicals were purchased from Alfa Aesar or
Sigma-Aldrich and were used for the syntheses with-
out further purification. Iron octapropylporphyrazine
was prepared according to published procedure [42].
m-Chloroperbenzoic acid (m-CPBA, 85% peroxide con-
tent) purchased from Sigma-Aldrich was recrystallized
from pentane prior to use. Hydrogen peroxide (35%) was
obtained from Sigma-Aldrich.
Synthesis of heteroleptic µ-nitrido diiron complex
with phthalocyanine and octapropylporphyrazine
ligands, PcFe(µN)FePz. Iron phthalocyanine (300 mg,
0.53 mmol) and iron octapropylporphyrazine (50 mg,
0.07mmol)weredissolvedindeoxygenated1-chloronaph-
thalene (30 mL) and NaN3 (500 mg, 7.7 mmol) was added
to the solution. The reaction mixture was stirred at 180°C
for 2 h. The cold solution was filtered to remove NaN3 left
and homoleptic (FePc)2N. The solid was washed with ben-
zene. Combined organic phases were submitted to column
chromatography with basic alumina and benzene was used
to remove 1-chloronaphthalene. Then, the impurities were
eluted with CH2Cl2. The pure product was eluted with a
10:1 CH2Cl2:MeOH mixture. ESI-MS analysis showed
neither presence of homoleptic (FePc)2N and (FePz)2N
dimers nor FePc and FePz monomers.Yield 52 mg (54%).
ESI-MS: m/z 1286.50 [M]+ (100); calcd. for C72H72N17Fe2:
1286.48. IR (KBr): n, cm-1 920 (Fe=N–Fe). UV-vis
(CH2Cl2): lmax, nm 284, 314, 512 (sh), 608, 660 (sh).
Typical procedure for catalytic reactions with per-
fluorinated aromatic compounds. A 3 mL Teflon
reactor was charged with 2 mL CD3CN containing per-
fluorinated substrate (0.1 M), H2O2 (typically 1.6 M) and
catalyst (0.4 mM). The catalyst:substrate:oxidant ratio
was 1:250:4000. The reaction mixture was stirred at
60°C for 6 h. The products were identified and quantified
by GC-MS and 19F NMR techniques.
The UV-vis spectrum of the heteroleptic PcFe(µN)
FePz complex is compared with those of the monomeric
FePz and homoleptic (FePz)2N in Fig. 3.
Similarly to the heterolytic tetraphenylporphyrin/
tetra-tert-butylphthalocyanine complex (TPP)Fe(µN)
Fe(PctBu4) [16], only one broad Q-band at 608 nm was
observed. The maximum of the PcFe(µN)FePz Q-band
is in between those of the homogeneous (FePz)2N at 584
nm and (FePc)2N 625 nm (in py) [7]. This broad band
results from the combination of Q-bands of both mac-
rocycles [16]. As for Soret region, two bands at 284 and
314 nm were observed. The IR spectrum of PcFe(µN)
FePz exhibits a typical anti-symmetric Fe–N–Fe stretch
vibration at 920 cm-1 which is close to the correspond-
ing Fe–N–Fe vibrations for the homoleptic complexes
FePc2N at 915 cm-1 [17] and FePz2N at 914 cm-1 [42].
Preparation of high-valent diiron oxo complex
and their ESI-MS analysis
RESULTS AND DISCUSSION
Addition of active oxygen donors, e.g. peracids, hydro-
gen peroxide or organic hydroperoxides, to solutions
of µ-nitrido diiron macrocyclic complexes leads to the
formation of short-lived high-valent diiron oxo species
which can be only detected at very low temperatures [19,
43]. These species exhibit very strong oxidizing properties
and are capable of oxidizing the most recalcitrant organic
molecules like methane [21–25], ethane [26], chlorinated
[29, 44] or perfluorinated aromatic compounds [30].
Preparation of heteroleptic complex
The synthesis of µ-nitrido diiron phthalocyanines
is typically carried out by refluxing iron phthalocya-
nine in a high-temperature boiling solvent like xylenes
or 1-chloronaphthalene in the presence of an excess of
NaN3 [1, 8, 17]. If an equimolar mixture of two differ-
ent monomeric complexes is used, a mixture of the two
Copyright © 2017 World Scientific Publishing Company
J. Porphyrins Phthalocyanines 2017; 21: 3–9

4
C. COLOMBAN ET AL.
Fig. 2. CID MS/MS spectrum of the heteroleptic PcFe(µN)FePz complex. Phthalocyanine and octapropylporphyrazine ligands are
shown as red and blue ovals, respectively. Inset: zoom of the fragmentation pattern of PcFe(µN)FePz
Fig. 3. UV-vis spectra of the monomeric FePz (---), homoleptic (FePz)2N (∙∙∙∙) and heteroleptic PcFe(µN)FePz (__) complexes,
0.02 mM in CH2Cl2
Heteroleptic binuclear complexes having two Fe sites in
the different ligand environment can form two isomeric
high-valent diiron oxo species (Fig. 4).
In this mass spectrometry study, m-CPBA was used as a
convenient source of the oxo group.
An acetonitrile solution containing an excess of
m-CPBA was added to the frozen ~1 µM solution of
PcFeNFePz in acetonitrile. After melting of acetonitrile at
-46°C the resulting solution was immediately introduced
into mass spectrometer. The mass spectrum of the reaction
mixture showed the presence of several species (Fig. 5).
Along with a molecular peak of PcFeNFePz at m/z
1286.5, the signal centered at m/z = 1457.4 due to the
formation of peroxo complex was observed. The mech-
anism of the formation of the identified species is pro-
posed in Fig. 6.
We have previously shown that collision induced dis-
sociation MS/MS (CID-MS/MS) technique can be used
for the determination of the iron site where oxo group is
attached via analysis of the fragmentation pattern [24]
as shown in Fig. 4. µ-Nitrido high-valent diiron spe-
cies can be prepared using H2O2 or m-chloroperbenzoic
acid (m-CPBA) as active oxygen donors. In our previous
research we have shown that using of both oxidants in
combination with heteroleptic phthalocyanine complexes
resulted in the formation of the same oxo species [24].
Copyright © 2017 World Scientific Publishing Company
J. Porphyrins Phthalocyanines 2017; 21: 4–9

HETEROLEPTIC µ-NITRIDO DIIRON COMPLEX SUPPORTED BY PHTHALOCYANINE AND OCTAPROPYLPORPHYRAZINE
5
Fig. 4. Formation of two isomeric diiron oxo species at the heteroleptic PcFe(µN)FePz platform and the expected fragmentation
under collision induced dissociation of the molecular peaks
Fig. 5. Mass spectrum of the PcFeNFePz solution in MeCN recorded between 0.7 and 1.9 min after m-CPBA addition. Phthalocyanine
and octapropylporphyrazine ligands are schematically shown as red and blue ovals, respectively. Only one possible isomer of each
species issued from the interaction with m-CPBA is shown
Fig. 6. Formation of peroxo-, oxo- and µ-oxo species of PcFe(µN)FePz in the presence of m-CPBA diiron oxo species detected by
cryospray MS. Only one possible isomer of each species is shown
The peroxo complex (PcFeNFePz)-OOC(O)Ar under-
goes a heterolytic cleavage of the O–O bond to generate
oxo species (PcFeNFePz)=O. Due to the basicity of the
oxo group in µ-nitrido diiron porphyrinoid complexes
[25], this species is protonated and exhibits a molecu-
lar cluster peak centered at m/z = 1303.4. Interestingly,
a two-charged species with m/z = 1295.0 was also
observed. This signal was attributed to the protonated
Copyright © 2017 World Scientific Publishing Company
J. Porphyrins Phthalocyanines 2017; 21: 5–9

6
C. COLOMBAN ET AL.
Fig. 7. Fragmentation pattern of the protonated isomeric diiron oxo species at the heteroleptic PcFe(µN)FePz platform and their
experimental fragmentation pattern under collision induced dissociation of the molecular peaks. Phthalocyanine and octapropylpor-
phyrazine ligands are shown as red and blue ovals, respectively
µ-oxo complex of µ-nitrido diiron dimer formed in the
reaction of the oxo species (PcFeNFePz)=O with the
starting complex PcFeNFePz. Related µ-oxo dimeric
species of monomeric high-valent non-heme [45–47],
porphyrazine [48], phthalocyanine [49–51] and porphy-
rin [52] iron complexes have been previously described.
However, to the best of our knowledge, such a µ-oxo
dimer of a binuclear diiron complex was observed for the
first time. Alternative formulation as µ-hydroxo dimer
of µ-nitrido dimeric complex cannot be excluded since
µ-oxo species can be protonated. The protonation of
µ-oxo iron porphyrin was previously reported [53].
For the sake of simplicity, only one possible isomer of
the high-valent µ-nitrido diiron oxo complex is depicted
in Fig. 6 while two possible isomeric oxo species can be
formed. In order to determine whether the site-specific
formation of the oxo species occurs, i.e. wherther the
chemical nature of the macrocyclic ligand can lead to the
preferencial attachment of oxo ligand at one of the two
possible iron sites, we used CID-MS/MS approach. The
collision induced fragmentation of the parent molecular
ion of the (PcFeNFePz)=O species results in the forma-
tion of mononuclear units containing or not oxo and/or
nitrogen ligands. The analysis of the fragmentation pat-
tern should allow to determine whether the oxo ligand is
attached at phthalocyanine or porphyrazine iron site. To
this aim, the mass-selected oxo species was studied by
CID-MS/MS and results are shown in Fig. 7.
718.4 and 734.4 belong to the iron porphyrazine frag-
ments [PzFe + H]+, [PzFe=N]+ and [PzFe=O(N)]+,
respectively. Similarly to the initial PcFeNFePz complex
(Fig. 2), iron porphyrazine moiety tends to keep the
bridging nitrogen atom. It should be noted that the frag-
ments containing oxo ligand were observed at both phtha-
locyanine and porphyrazine iron platforms: m/z = 584.1
and 600.1 and m/z = 734.4, respectively. The intensity of
signals of [PcFe=O]+ and [PcFe-OH(NH)]+ fragments is
higher than that of [PzFe=O]+ suggesting a slight prefer-
ence of the oxo group binding to iron phthalocyanine site.
Oxidation of perfluorinated aromatic compounds
catalyzed by PcFeNFePz
The catalytic potential of PcFeNFePz was evaluated
in the oxidative transformation of hexafluorobenzene and
perfluoro(allylbenzene).Although m-CPBA is a convenient
active oxygen donor for obtaining oxo species for spectro-
scopic and mechanistic studies, it is not the best choice for
the catalytic experiments, especially when potent oxidiz-
ing species can be formed. m-CPBA itself can be oxidized
along with the substrate, especially in this particular case
since m-CPBA is less deactivated toward an attack of a
strong electrophilic high-valent oxo species than the elec-
tro-deficient perfluorinated aromatic substrates. For this
t
reason, we used conventional H2O2 or BuOOH oxidants.
The reactions were performed at 60°C in CD3CN using
catalyst:substrate:oxidant ratio = 1:250:4000 (Scheme 1).
The abundant signals in the m/z ranges of 569–600
and 703–734 corresponding to iron phthalocyanine
and iron porphyrazine fragments, respectively, were
observed. Iron phthalocyanine fragments with m/z cen-
tered at 569.1, 584.1 and 600.1 are associated with
[PcFe + H]+, [PcFe=O]+ and [PcFe–OH(NH)]+ formula-
tions, respectively. In turn, the signals with m/z 705.4,
t
When BuOOH was used, no conversion of C6F6 was
observed. In contrast, in the presence of H2O2 a 11% con-
version of C6F6 and turnover number of 28 were achieved.
The main product was pentafluorophenol accompanied
by difluoromaleic acid and HF. Each catalyst molecule
transformed 34.5 C–F bonds. This catalytic activity was
Copyright © 2017 World Scientific Publishing Company
J. Porphyrins Phthalocyanines 2017; 21: 6–9

HETEROLEPTIC µ-NITRIDO DIIRON COMPLEX SUPPORTED BY PHTHALOCYANINE AND OCTAPROPYLPORPHYRAZINE
7
Scheme 1. Catalytic transformation of C6F6 by PcFeNFePz–H2O2 system
Scheme 2. Catalytic transformation of perfluoro(allylbenzene) by PcFeNFePz–H2O2 and PcFeNFePz–tBuOOH systems. TONSub
was calculated as molar amount of substate transformed per mole of the catalyst. TONF- was defined as molar amount of F- formed
per mole of the catalyst
slightly lower compared with that of previously obtained
using (FePctBu4)2N catalyst under the same conditions
(29% conversion of C6F6) [30].
and in C–C bond formation [19]. It is expected that the
scope of the catalytic applications of these complexes
can be further increased. In this context, the synthesis of
novel µ-nitrido diiron complexes will not only enlarge
the choice and scope of these promising catalysts but
also should provide a deeper insight into properties of
µ-nitrido macrocyclic dimers important for their catalytic
activity. Particular catalytic properties of µ-nitrido diiron
platform can be associated with the formation of high-
valent diiron oxo species having strong oxidizing proper-
ties. In this work, we have prepared and characterized a
novel heteroleptic N-bridged diiron complex with phtha-
locyanine and porphyrazine ligands. We have studied in
detail the formation of the high-valent diiron oxo com-
plexes by cryospray mass spectrometry using m-CPBA
as active oxygen donor. Initially formed isomeric peroxo
complexes (PcFeNFePz)–OOC(O)Ar underwent to a
heterolytic cleavage of O–O bond to form two isomeric
oxo species, O=(Pc)FeNFePz and PcFeNFe(Pz)=O. The
iron site of binding of the oxo group was determined by
CID-MS/MS technique via analysis of the composition
of fragments obtained after bombardment of the molecu-
lar ions of the oxo species. The fragments bearing oxo
ligand were observed at both the monomeric iron phtha-
locyanine and porphyrazine units: m/z = 584.1 and 600.1
and m/z = 734.4, respectively. The intensity of signals
of [PcFe=O]+ and [PcFe-OH(NH)]+ fragments is higher
than that of [PzFe=O]+ suggesting a slight preference
of the oxo group binding to iron phthalocyanine site. In
our previous study [24] we found that heteroleptic com-
plex containing one electron-poor iron phthalocyanine
site and one more electron-rich iron phthalocyanine site
Perfluoro(allylbenzene) combining fluorinated aro-
matic cycle and fluorinated olefinic moiety is a useful sub-
strate to study the selectivity of defluorination reaction.
In contrast to hexafluorobenzene, both PcFeNFePz–H2O2
and PcFeNFePz–tBuOOH catalytic systems were very
efficient in the transformation of perfluoro(allylbenzene).
Importantly, perfluorinated olefinic fragment exhibited
significantly higher activity in the defluorination reaction
(Scheme 2).
The PcFeNFePz–tBuOOH catalytic system was
even more active providing a 97% conversion of
C6F5CF2CF=CF2 compared with a 58% conversion in
the case of the PcFeNFePz–H2O2 system. Heptafluoro-
benzeneacetic and pentafluorobenzoic acids obtained
via the cleavage of the double bond accompanied by
defluorination were the principal products. Interestingly,
the PcFeNFePz–H2O2 system was more selective to the
formation of C6F5CF2COOH (37% yield) whereas the
PcFeNFePz–tBuOOH system provided C6F5COOH with
a 51% yield. Very high turnover numbers in terms of the
number of C–F bonds transformed by one catalyst mol-
ecule were achieved with both oxidants: 538 and 1465
using H2O2 and tBuOOH, respectively.
CONCLUSION
µ-Nitrido diiron macrocyclic complexes find increas-
ing applications in catalysis, in particular, in different
oxidation reactions, in dehalogenation transformations
Copyright © 2017 World Scientific Publishing Company
J. Porphyrins Phthalocyanines 2017; 21: 7–9

8
C. COLOMBAN ET AL.
formed high-valent diiron oxo species with oxo group
bound exclusively at the electron-rich site of the dimer.
In this work we observed comparable affinity of oxo
group to iron phthalocianine and iron porphyrazine units
with only slight preference for the former site. This result
confirms that the properties of the supporting ligand of
µ-nitrido diiron platform are important for the formation
of high-valent diiron oxo catalytic species. The reaction
of (PcFeNFePz)=O species with PcFeNFePz led to the
formation of µ-oxo dimer complex of µ-nitrido dimer
(PcFeNFePz)–O–(PcFeNFePz). Such a tetrairon com-
plex was observed for the first time.
project 6295) and Russian Foundation of Basic Research
(RFBR, project 14-03-91054). C.C. is grateful to Région
Rhône-Alpes for PhD fellowship. We are grateful to Dr.
F. Albrieux for the assistance with mass spectrometry
experiments.
REFERENCES
1. Summerville DA and Cohen IA. J. Am. Chem. Soc.
1976; 98: 1747–1752.
2. Scheidt WR, Summerville DA and Cohen IA. J. Am.
Chem. Soc. 1976; 98: 6623–6628.
The PcFeNFePz complex in combination with H2O2
was active in oxidative transformation of hexafluoro-
benzene and perfluoro(allylbenzene). Perfluorinated ole-
finic fragment exhibited significantly higher activity in
the defluorination reaction than perfluorinated aromatic
moiety. Perfluorinated aromatic acids were obtained with
moderate yields. Using perfluoro(allylbenzene), we have
obtained the oxidative transformation of perfluorinated
substrate by PcFeNFePz–tBuOOH system for the first
time. Moreover, PcFeNFePz–tBuOOH system was even
more efficient than PcFeNFePz–H2O2 system providing a
97% conversion of C6F5CF2CF=CF2. Very high turnover
numbers defined as the number of C–F bonds transformed
by one catalyst molecule were achieved with H2O2 and
tBuOOH: 538 and 1465, respectively. It should be pointed
out that transformation of C–F bonds involving oxida-
tion pathways is a very difficult and rare reaction. Only
a few papers describing the stoichiometric defluorina-
tion of 2-fluorophenolate with a bis(µ-oxo)dicopper(III)
complex [54] and intramolecular C–F bond oxygenation
of the complexes during formation of their oxo species
[55, 56] have been published. The important feature of
µ-nitrido diiron macrocyclic complexes is that they are
capable of performing efficient catalytic oxidation of a
variety of fluorinated aromatic and olefinic compounds
with different fluorination degree and substitution pat-
tern using industrially relevant H2O2 and tBuOOH oxidant
[30]. Taking into account the constantly increasing large-
scale production and application of fluorinated organic
compounds (for example, ~40% of agrochemicals and
~20% of pharmaceuticals currently used are fluorinated
molecules) and their exceptional stability in the environ-
ment, these compounds are considered as emerging pol-
lutants. The development of practical methods for elimi-
nation of these contaminants of increasing concern is of
great importance. We believe that further development of
the catalytic systems based on µ-nitrido diiron macrocy-
clic complexes and industrially relevant peroxide oxidants
might provide a solution to this environmental problem.
3. Kadish KM, Bottomley LA, Brace JG and Wino-
grad N. J. Am. Chem. Soc. 1980; 102: 4341–4344.
4. Tatsumi K and Hoffmann R. J. Am. Chem. Soc.
1981; 103: 3328–3341.
5. Schick GA and Bocian DF. J. Am. Chem. Soc. 1983;
105: 1830–1838.
6. Bocian DF, Findsen EW, Hofmann JA, Schick GA,
English DR, Hendrickson DN and Suslick KS.
Inorg. Chem. 1984; 23: 800–807.
7. Goedken VL and Ercolani C. J. Chem. Soc. Chem.
Commun. 1984: 378–379.
8. Bottomley LA, Gorce J-N, Goedken VL and Ercol-
ani C. Inorg. Chem. 1985; 24: 3733–3737.
9. Kennedy BJ, Murray KS, Homborg H and Kalz W.
Inorg. Chem. Acta 1987; 134: 19–21.
10. Li M, Shang M, Ehlinger N, Schulz CE and Scheidt
WR. Inorg. Chem. 2000; 39: 580–583.
11. Stuzhin PA, Latos-Grazynski L and Jezierski A.
Trans. Met. Chem. 1989; 14: 341–346.
12. Stuzhin PA, Hamdush M and Homborg H. Mendeleev
Commun. 1997; 7: 196–198.
13. Ercolani C, Hewage S, Heucher R and Rossi G.
Inorg. Chem. 1993; 32: 2975–2977.
14. Ercolani C, Jubb J, Pennesi G, Russo U and Tri-
giante G. Inorg. Chem. 1995; 34: 2535–2541.
15. Donzello MP, Ercolani C, Kadish KM, Ou Z and
Russo U. Inorg. Chem. 1998; 37: 3682–3688.
16. Zanotti G, Mattioli G, Notarantonio S, Paoletti AM,
Rossi G, Bonapasta AA and Pennesi G. Macrohet-
erocycles 2011; 4: 161–163.
17. Floris B, Donzello MP and Ercolani C. In The Por-
phyrin Handbook, Vol. 18, Kadish KM, Smith KM
and Guilard R. (Eds.) Elsevier Science: San Diego,
2003; pp. 1–62.
18. İşci Ü, Dumoulin F, Sorokin AB and Ahsen V. Turk.
J. Chem. 2014; 38: 923–949.
19. Afanasiev P and Sorokin AB. Acc. Chem. Res.
2016; 49: 583–593.
20. Sorokin AB. Chem. Rev. 2013; 113: 8152–8191.
21. Sorokin AB, Kudrik EV and Bouchu D. Chem.
Commun. 2008; 2562–2564.
Acknowledgements
22. Sorokin AB, Kudrik EV, Alvarez LX, Afanasiev
P, Millet JMM and Bouchu D. Catal. Today 2010;
157: 149–154.
This research was supported by Agence National de
Recherche (ANR, France, grants nos. ANR-08-BLANC-
0183-01 and ANR-16-CE29-0018-01), by CNRS (PICS
Copyright © 2017 World Scientific Publishing Company
J. Porphyrins Phthalocyanines 2017; 21: 8–9

HETEROLEPTIC µ-NITRIDO DIIRON COMPLEX SUPPORTED BY PHTHALOCYANINE AND OCTAPROPYLPORPHYRAZINE
9
23. Kudrik EV, Afanasiev P, Alvarez LX, Dubourdeaux
P, Clémancey M, Latour J-M, Blondin G, Bouchu D,
Albrieux F, Nefedov SE and SorokinAB. Nat. Chem.
2012; 4: 1024–1029.
24. İşci Ü, Faponle AS, Afanasiev P, Albrieux F, Briois
V, Ahsen V, Dumoulin F, Sorokin AB and de Visser
SP. Chem. Sci. 2015; 6: 5063–5075.
40. Isci Ü, Dumoulin F, Ahsen V and Sorokin AB.
J. Porphyrins Phthalocyanines 2010; 14: 324–334.
41. Kudrik EV, Afanasiev P, Bouchu D and SorokinAB.
J. Porphyrins Phthalocyanines 2011; 15: 583–591.
42. Colomban C, Kudrik EV, Tyurin DV, Albrieux F,
Nefedov SE, Afanasiev P and Sorokin AB. Dalton
Trans. 2015; 44: 2240–2251.
25. Quesne MG, Senthilnathan D, Singh D, Kumar D,
Maldivi P, Sorokin AB and de Visser SP. ACS Catal.
2016; 6: 2230–2243.
26. Alvarez LX and Sorokin AB. J. Organomet. Chem.
2015; 793: 139–144.
43. Afanasiev P, Kudrik EV, Millet JMM, Bouchu D
and Sorokin AB. Dalton Trans. 2011; 40: 701–710.
44. Colomban C, Kudrik EV, Afanasiev P and Sorokin
AB. Catal. Today 2014; 235: 14–19.
45. Kundu S, Thompson JVK, Shen LQ, Mills MR,
Bominaar EL, Ryabov AD and Collins TJ. Chem.
Eur. J. 2015; 21: 1803–1810.
27. Kudrik EV and Sorokin AB. Chem Eur. J. 2008; 14:
7123–7126.
28. Alvarez LX, Kudrik EV and Sorokin AB. Chem.
Eur. J. 2011; 17: 9298–9301.
46. Ghosh M, Singh KK, Panda C, Weitz A, Hendrich
MP, Collins TJ, Dhar BB and Sen Gupta S. J. Am.
Chem. Soc. 2014; 136: 9524–9527.
47. Lyakin OV, ZimaAM, Samsoneneko DG, Bryliakov
KP and Talsi EP. ACS Catal. 2015; 5: 2702–2707.
48. Yusubov MS, Celik C, Geraskina MR, Yoshimura
A, Zhdankin VV and Nemykin VN. Tetrahedron
Lett. 2014; 55: 5687–5690.
49. Neu HM, Zhdankin VV and Nemykin VN. Tetrahe-
dron Lett. 2010; 51: 6545–6548.
50. Pergrale C and Sorokin AB. C. R. Chim. 2000; 3:
803–810.
51. Zalomaeva OV, Ivanchikova ID, Kholdeeva OA and
Sorokin AB. New J. Chem. 2009; 33: 1031–1037.
52. Sil D and Rath SP. Dalton Trans. 2015; 44:
16195–16211.
53. Sainna MA, Sil D, Sahoo D, Martin B, Rath SP,
Comba P and de Visser S. Inorg. Chem. 2015; 54:
1919–1930.
54. Serran-Plana J, Garcia-Bosch I, Miyake R, Costas
M and Company A. Angew. Chem. Int. Ed. 2014;
53: 9608–9612.
55. de Ruiter G, Thompson NB, Takase MK and Agapie
T. J. Am. Chem. Soc. 2016; 138: 1486–1489.
56. Sahu S, Zhang B, Pollock CJ, Dürr M, Davies CG,
Confer AM, Ivanovic-Burmazovic I, Siegler MA,
Jameson GNL, Krebs K and Goldberg DP. J. Am.
Chem. Soc. 2016; 138: 12791–12802.
29. Afanasiev P, Bouchu D, Kudrik EV, Millet JMM
and Sorokin AB. Dalton Trans. 2009: 9828–9836.
30. Colomban C, Kudrik EV, Afanasiev P and Sorokin
AB. J. Am. Chem. Soc. 2014; 136: 11321–11330.
31. Colomban C, Kudrik EV, Briois V, Shwarbrick JC,
Sorokin AB and Afanasiev P. Inorg. Chem. 2014;
53: 11517–11530.
32. Isci Ü, Afanasiev P, Millet JMM, Kudrik EV, Ahsen
V and SorokinAB. Dalton Trans. 2009; 7410–7420.
33. Afanasiev P, Kudrik EV, Albrieux F, Briois V, Koif-
man OI and Sorokin AB. Chem. Commun. 2012;
48: 6088–6090.
34. Groves JT. In Cytochrome P450: Structure, Mecha-
nism and Biochemistry, 3rd ed., Ortiz de Montellano
PR. (Ed.) Kluwer Academic/Plenum Publishers:
New York, 2005; Chap. 1, pp. 1–44.
35. Cong Z, Kinemuchi H, Kurahashi T and Fujii H.
Inorg. Chem. 2014; 53: 10632–10641.
36. CostasM.Coord.Chem.Rev.2011;255:2912–2932.
37. Jung C, de Vries S and Schünemann. Arch. Bio-
chem. Biophys. 2011; 507: 44–55.
38. İşci Ü. J. Porphyrins Phthalocyanines 2013; 17:
1022–1026.
39. Kudrik EV, Afanasiev P, Bouchu D, Millet JMM
and Sorokin AB. J. Porphyrins Phthalocyanines
2008; 12: 1078–1089.
Copyright © 2017 World Scientific Publishing Company
J. Porphyrins Phthalocyanines 2017; 21: 9–9