New method of metal-induced oxidative phosphorylation of benzene

Article abstract of DOI:10.1007/s11172-015-1095-z

A new approach to phosphorylation of benzene with diethyl phosphite is suggested, which is based on the electrocatalytic oxidation of a mixture of benzene and diethyl phosphite (1 : 1) under mild conditions (room temperature, normal pressure) in the presence of bimetallic catalytic systems Mn^II/Co^IIL (MnSO₄/CoCl₂dmphen or MnCl₂/CoCl₂bipy). This method gives diethyl phenylphosphonate in high yield (up to 90%) and practically 100% conversion of the phosphite.

Full text of DOI:10.1007/s11172-015-1095-z

Russian Chemical Bulletin, International Edition, Vol. 64, No. 8, pp. 1926—1932, August, 2015
1926
New method of metalꢀinduced oxidative phosphorylation of benzene*
M. N. Khrizanforov, S. O. Strekalova, T. V. Gryaznova, V. V. Khrizanforova, and Yu. H. Budnikova
A. E. Arbuzov Institute of Organic and Physical Chemistry, Kazan Scientific Center, Russian Academy of Sciences,
8 ul. Akad. Arbuzova, 420088 Kazan, Russian Federation.
Eꢀmail: khrizanforov@gmail.com
A new approach to phosphorylation of benzene with diethyl phosphite is suggested, which is
based on the electrocatalytic oxidation of a mixture of benzene and diethyl phosphite (1 : 1)
under mild conditions (room temperature, normal pressure) in the presence of bimetallic
catalytic systems MnII/CoIIL (MnSO4/CoCl2dmphen or MnCl2/CoCl2bipy). This method gives
diethyl phenylphosphonate in high yield (up to 90%) and practically 100% conversion of the
phosphite.
Key words: phosphorylation, oxidation, electrosynthesis, catalyst, metal, complex,
C—H functionalization.
Dialkyl arylphosphonates are important intermediates
The synthesis of arylphosphonates by a direct phosꢀ
phorylation of a C—H bond in aromatic substrates reꢀ
mains one of the most important approaches, since it meets
the generally accepted criteria of "green chemistry". In
this connection, a search for the catalytic conditions is
especially promising, since there are only few catalytic
phosphorylation reactions of aromatic compounds. Perꢀ
haps, benzene in this regard is one of the most problematic
objects, since its structure lacks factors facilitating a C—H
substitution, i.e., functional group which activate bonds
or direct functionalization. As a rule, if conditions for
phosphorylation of benzene are selected properly, its deꢀ
rivatives give even higher yields of the target products.17—19
Phosphorylation of benzene by the methods described
above does not give high product yields or conversion. We
suggested that phosphorylation of benzene at room temꢀ
perature in one step would be feasible using advantages of
electrochemical metal complex catalysis.22,23 As the cataꢀ
lytic systems for electrochemical phosphorylation of benꢀ
zene, we have chosen metal complexes and salts (M) in
the oxidation state II, which can undergo electrochemical
oxidation to MIII: PdCl2bipy (bipy stands for 2,2´ꢀbiꢀ
pyridyl), manganese citrate Mn3(C6H5O7)2, Mn3(C6H5O7)2/
CoCl2dmphen (dmphen stands for 1,10ꢀdimethylphenꢀ
anthroline), MnCl2, MnCl2/CoCl2dmphen, MnCl2/
CoCl2bipy, MnSO4, MnSO4/Ni(BF4)2bipy, MnCl2bipy,
Ni(BF4)2dmphen, and CoCl2dmphen. The process was
conducted with the equimolar benzene : dialkyl phosphite
ratio (1 : 1) at room temperature, which earlier have never
given good yields of arylphosphonate (Scheme 1, Table 1).
The catalytic systems were tested using commercially
available, relatively stable and inexpensive phosphorylting
agent — diethyl phosphite.
in the synthesis of pesticides and biologically active comꢀ
pounds.1—4 There are several traditional methods for the
synthesis of dialkyl arylphosphonates. Among them, phosꢀ
phorylation of aryl halides5—13 is the most frequently used
reaction. There are known separate examples of radical
phosphorylation of aromatic compounds with diethyl
phosphite, for example, naphthalene in the presence of
tertꢀbutyl peroxide,14 a number of arenes in the presence
of oxidants (NH4)2[Ce(NO3)6] (see Ref. 15) or Na2S2O8
and AgNO3,16 MnII/CoII/O2.17 The most successful phosꢀ
phorylation of benzene with Ishii dialkyl phosphite17 has
a number of disadvantages: an elevated temperature of the
reaction and not very high conversion of the substrates to
the monophosphorylation product, which in the case of
benzene is 6% (25 C) and 69% (60 C). Arylphosphoꢀ
nates were obtained18,19 in up to 59% yield by electroꢀ
chemical oxidation of trialkyl phosphites in the presence
of benzene or its derivatives at the 5 : 1 ratio of benzꢀ
ene : diethyl phosphite in acetonitrile in the presence of
a supporting salt NaClO4. An electrochemical oxidative
phosphorylation was suggested20 for benzene nitro derivaꢀ
tives with phosphorus(III) compounds, including diethyl
phosphite. However, this approach cannot be used for unꢀ
substituted benzene, since a key step of the process is
a nucleophilic addition of Hꢀphosphonate to the aromatic
ring (SNArꢀmechanism), followed by the oxidation of the
ꢀHꢀadducts. A method for phosphorylation of benzene
derivatives was also elaborated.21
* Based on the materials of the XXVI International Chugaev
Conference on Coordination Chemistry (October 6—10, 2014,
Kazan).
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1926—1932, August, 2015.
1066ꢀ5285/15/6408ꢀ1926 © 2015 Springer Science+Business Media, Inc.

Phosphorylation of benzene
Russ.Chem.Bull., Int.Ed., Vol. 64, No. 8, August, 2015
1927
Table 1. Electrochemical phosphorylation of benzene with diethyl phosphite (taken in the ratio 1 : 1) in the presence of
various catalystsa
Catalytic
system
Content of catalyst
(mol.%)
MeCN : AcOHb
Yield of PhP(O)(OEt)2
(%)
PdCl2bipy
Mn3(C6H5O7)2
10
10
1 : 0
1 : 2
1 : 1
2 : 1
1 : 2
1 : 1
2 : 1
1 : 2
1 : 1
2 : 1
1 : 2
1 : 1
2 : 1
2 : 1
1 : 2
1 : 1
2 : 1
2 : 1
2 : 1
1 : 0
1 : 0
1 : 0
—
10
22
10
—
15
25
—
Mn3(C6H5O7)2/CoCl2dmphen
MnCl2
10/0.5
1
—
30
10
50
90
90
—
MnCl2/CoCl2dmphen
10/0.5
MnCl2/CoCl2bipy
MnSO4
10/0.5
1
—
Traces
90
30
35
15
15
10
15
MnSO4/CoCl2dmphen
MnSO4/Ni(BF4)2bipy
MnCl2bipy
Ni(BF4)2dmphen
CoCl2dmphen
MnCl2/CoCl2
—
10/0.5
10/10
10
10
0.5
10/1
1 : 0
a Conditions: ~20 C, Q = 2 F per 1 mole of diethyl phosphite, galvanostatic mode.
b Acetic acid was added to increase the solubility of manganese salts.
earlier undescribed pair MnII/MnIII does catalyze the
phosphorylation of benzene under oxidative conditions,
though with not very high yield of diethyl phenylphosphoꢀ
nate (30%, see Table 1). Apart from that, a difficult to
separate mixture of phosphorylation products (mono, di,
tri) is obtained in this case.
Scheme 1
To find out the factors influencing efficiency of electroꢀ
catalytic phosphorylation, we used a CVA method to deꢀ
termined electrochemical parameters for all the catalyst
complexes (Table 2).
The concentration of each component of the catalytic
systems was determined with allowance for its solubility
and activity (manganese compounds are poorly soluble
under these conditions, therefore, they were used in the
maximum attainable concentration).
As it follows from Table 1, the most efficient catalytic
systems are MnSO4/CoCl2dmphen and MnCl2/CoCl2bipy.
The phosphorylation virtually does not occur in the
absence of the catalysts. It is important to point out that in
these syntheses a 100% conversion of diethyl phosphite is
reached after passing 2 F of electricity. In contrast to the
results published earlier17 (according to which no phosꢀ
phorylation takes place at all in the absence of Mn(OAc)2),
under our conditions the phosphonate can be also obꢀ
tained in the presence of a monoꢀcomponent catalyst (both
MnII and CoII), though in this case the yield of the target
product is considerably lower. It should be noted that the
It should be noted that diethyl phosphite and benzene
under the selected conditions do not form oxidation peaks
on the CVA curves. However, their addition to the soluꢀ
tions of catalyst complexes leads to considerable changes
in the CVA curves. For example, the unsaturated complex
CoCl2bipy undergoes a oneꢀelectron oxidation at the
peak potential of 1.34 V, whereas after the addition of
HP(O)(OEt)2 to its solution (Fig. 1), the CVA curve exꢀ
hibits a new quasiꢀreversible anode peak at a 0.54 V potenꢀ
tial. The further addition of the increasing amounts of
HP(O)(OEt)2 (1 : 1, 1 : 2, 1 : 3, 1 : 6, 1 : 9, 1 : 27) (see Fig. 1)
influences the voltamperogram little. It can be suggested
that the cobalt complex reacts with diethyl phosphite to
form a new complex, which oxidizes at lower potentials.

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Khrizanforov et al.
Table 2. The values of potentials (EP) and currents (i)
for the first peaks of oxidation of complexes and
salts (C = 0.5 mmol L–1) used for phosphorylation of
benzenea
10 A
6
5
7
4
3
2
Complex/metal salt
Ep/V
i/A
NiBF4dmphen
CoCl2dmphen
CoCl2bipy
0.90
1.51
1.34
1.14
1.27
1.34
68
35
35
32
70
19
1
0
MnCl2bipy
MnCl2
b
MnSO4
a Conditions: working electrode glassy carbon, referꢀ
ence electrode Ag/AgCl, ~20 C, supporting salt
Bu4NBF4, MeCN.
b Paste electrode: carbon (0.0009 g)/But3PC12H25BF4
(0.0005 g)/MnSO4 (0.0007 g).
–0.3
0.3
0.9
1.5
2.1 U/V
Fig. 2. CVA curves of complex CoCl2bipy (5•10–4 mol L–1) in
the presence of increasing amounts of HP(O)(OEt)2 and benzꢀ
ene with the ratio CoCl2bipy : HP(O)(OEt)2 : C6H6 = 1 : 0 : 0 (1),
1 : 1 : 1 (2), 1 : 2 : 2 (3), 1 : 3 : 3 (4), 1 : 4 : 4 (5), 1 : 5 : 5 (6), and
1 : 6 : 6 (7) in MeCN; Et4NBF4, reference electrode Ag/AgCl.
Upon addition of benzene to a solution of CoCl2bipy conꢀ
taining HP(O)(OEt)2 (Fig. 2), the anode quasiꢀreversible
peak is slightly shifted, and the oxidation occurs at a 0.70 V
potential. It should be noted that the addition of a mixture
of substrates (HP(O)(OEt)2 and benzene) to the catalyst
CoCl2bipy leads to a catalytic increase in current (see Fig. 2).
Thus, the complex : phosphite : benzene ratio equal to
1 : 6 : 6 gives icat/idif = 2.
Similar changes in the CVA curves are observed in the
case of the catalyst CoCl2dmphen in the presence of the
substrates. In turn, the CVA curves of CoCl2bipy and
CoCl2dmphen upon addition of increasing amounts of
benzene (in the absence of phosphite) remain unchanged.
In the case of Ni(BF4)2dmphen, the changes in the
CVA curves in the presence of HP(O)(OEt)2 are also simꢀ
ilar to those observed for CoCl2bipy (see Fig. 1), in particꢀ
ular, emerges a new quasiꢀreversible anode peak (Ep = 0.5 V),
which changes little as the content of HP(O)(OEt)2 in the
solution increases (Fig. 3).
The oxidation of the system Ni(BF4)2dmphen in the
presence of HP(O)(OEt)2 and benzene (Fig. 4) occurs at
slightly more positive potential (Ep = 0.75 V), the oxidaꢀ
tion peak has a complicated shape. Under identical conꢀ
ditions, a higher catalytic current efffect is observed as
compared to cobalt catalysts: the icat/idif value reaches 4.1
at the ratio [Ni(BF4)2dmphen] : [HP(O)(OEt)2] : C6H6 =
= 1 : 6 : 6.
The oxidation voltamperogram of complex MnCl2bipy
in the presence of increasing amounts of HP(O)(OEt)2
(Fig. 5) somewhat differs from those for CoCl2bipy and
Ni(BF4)2dmphen described above. A oneꢀelectron oxidaꢀ
5
6
10 A
10 A
7
6
7
4
3
3
2
4
5
2
1
1
0
0
0
0.4
0.8
1.2
1.6 U/V
0
0.4
0.8
1.2
1.6 U/V
Fig. 1. CVA curves of complex CoCl2bipy (5•10–4 mol L–1) in
the presence of increasing amounts of HP(O)(OEt)2 with the
ratio CoCl2bipy : HP(O)(OEt)2 = 1 : 0 (1), 1 : 1 (2), 1 : 2 (3),
1 : 3 (4), 1 : 6 (5), 1 : 9 (6), and 1 : 27 (7) in MeCN; Et4NBF4,
reference electrode Ag/AgCl.
Fig. 3. CVA curves of complex Ni(BF4)2dmphen (5•10–4 mol L–1
)
in the presence of increasing amounts of HP(O)(OEt)2 with the
ratio Ni(BF4)2dmphen : HP(O)(OEt)2 = 1 : 0 (1), 1 : 1 (2), 1 : 2 (3),
1 : 3 (4), 1 : 6 (5), 1 : 9 (6), and 1 : 27 (7) in MeCN; Et4NBF4,
reference electrode Ag/AgCl.

Phosphorylation of benzene
Russ.Chem.Bull., Int.Ed., Vol. 64, No. 8, August, 2015
1929
1
30 A
7
6
10 A
2
5
4
3
2
0
1
0
0
0.4
0.9
1.4
1.9
U/V
Fig. 6. CVA curves of complex MnCl2bipy (5•10–4 mol L–1) in
the presence of HP(O)(OEt)2 (1 : 168) (1), as well as MnCl2bipy
in the presence of HP(O)(OEt)2 and benzene (1 : 168 : 168) (2)
in MeCN; Et4NBF4, reference electrode Ag/AgCl.
–0.3
Fig. 4. CVA curves of complex Ni(BF4)2dmphen (5•10–4 mol L–1
in the presence of increasing amounts of HP(O)(OEt)2 and benzꢀ
ene with the ratio Ni(BF4)2dmphen : HP(O)(OEt)2 : C6H6
0.3
0.9
1.5
U/V
)
=
= 1 : 0 : 0 (1), 1 : 1 : 1 (2), 1 : 2 : 2 (3), 1 : 3 : 3 (4), 1 : 4 : 4 (5),
1 : 5 : 5 (6), and 1 : 6 : 6 (7) in MeCN; Et4NBF4, reference elecꢀ
trode Ag/AgCl.
4
30 A
3
10
10 A
2
9
8
7
1
6
5
0
4
1
2
3
0
–0.3
0.3
0.9
1.5
2.1 U/V
Fig. 7. CVA curves of complex Ni(BF4)2dmphen (5•10–4 mol L–1
)
0
0.4
0.9
1.4
1.9 U/V
(1), Ni(BF4)2dmphen in the presence of HP(O)(OEt)2 (1 : 6)
(2), Ni(BF4)2dmphen in the presence of HP(O)(OEt)2 and benzꢀ
ene (1 : 6 : 6) (3), as well as Ni(BF4)2dmphen in the presence of
MnCl2bipy, HP(O)(OEt)2 and benzene (1 : 1 : 6 : 6) (4) in
MeCN; Et4NBF4, reference electrode Ag/AgCl.
Fig. 5. CVA curves of complex MnCl2bipy (5•10–4 mol L–1) in
the presence of increasing amounts of HP(O)(OEt)2 with the
ratio MnCl2bipy : HP(O)(OEt)2 = 1 : 0 (1), 1 : 1, 1 : 2, 1 : 3 (2),
1 : 6 (3), 1 : 24 (4), 1 : 48 (5), 1 : 72 (6), 1 : 96 (7), 1 : 120 (8),
1 : 144 (9), and 1 : 168 (10) in MeCN; Et4NBF4, reference elecꢀ
trode Ag/AgCl.
Table 3. The increase in current of the first peaks of oxidation of catalytic systems used for
phosphorylation of benzene at ~20 C
System
Ratio
icat/idif
CoCl2bipy—HP(O)(OEt)2—С6H6
CoCl2dmphen—HP(O)(OEt)2—С6H6
MnCl2bipy—HP(O)(OEt)2—С6H6
Ni(BF4)2dmphen—HP(O)(OEt)2—С6H6
CoCl2dmphen—MnCl2bipy—HP(O)(OEt)2—С6H6
CoCl2bipy—MnCl2bipy—HP(O)(OEt)2—С6H6
Ni(BF4)2dmphen—MnCl2bipy—HP(O)(OEt)2—С6H6
1 : 6 : 6
1 : 6 : 6
1 : 6 : 6
2.07
2.97
2.13
4.10
3.17
2.73
6.13
1 : 6 : 6
0.05 : 1 : 6 : 6
0.05 : 1 : 6 : 6
0.05 : 1 : 6 : 6

1930
Russ.Chem.Bull., Int.Ed., Vol. 64, No. 8, August, 2015
Khrizanforov et al.
upon increase in the content of the phosphonate in the
solution to reach icat/idif = 21 at the ratio of 1 : 168. The
large amounts of diethyl phosphite lead to a quasiꢀreversꢀ
ibility, as in the case of oxidation of CoCl2bipy and other
complexes. However, the addition of benzene to the soluꢀ
tion of a mixture of complex MnCl2bipy and phosphite
does not lead to the increase in the catalytic current effect
(Fig. 6), in contrast to complexes Ni(BF4)2dmphen,
CoCl2dmphen, and CoCl2bipy.
10 A
4
3
2
1
It is probable that the changes in the redox properties
of metal complexes observed in the presence of diethyl
phosphite are due to the strong coordinating properties of
the latter24,25 and the formation of metal phosphonates,
which undergo oxidation at smaller potential than the
starting complexes. Preparative electrolysis does proceed
at potentials corresponding to the oxidation of phosphoꢀ
nate complexes. The current increasing of complexes obꢀ
served upon addition of benzene indicates a rapid regenerꢀ
ation of the catalyst active form in such threeꢀ and fourꢀ
component systems. To compare catalytic efficiencies of
the systems containing cobalt, nickel, and manganese (or
in their absence), we have chosen identical conditions
(Table 3, Figs 7 and 8). The high icat/idif values (see Table 3)
for complex Ni(BF4)2dmphen in both presence and
absence of manganese indicate its higher catalytic activity
in the phosphorylation reaction as compared to other sysꢀ
tems. This explains the formation of polyphosphorylation
0
–0.3
0.3
0.9
1.5
2.1 U/V
Fig. 8. CVA curves of complex CoCl2bipy (5•10–4 mol L–1) (1),
CoCl2bipy in the presence of HP(O)(OEt)2 (1 : 6) (2), CoCl2bipy
in the presence of HP(O)(OEt)2 and benzene (1 : 6 : 6) (3), as
well as CoCl2bipy in the presence of MnCl2bipy, HP(O)(OEt)2
and benzene (1 : 1 : 6 : 6) (4) in MeCN; Et4NBF4, reference elecꢀ
trode Ag/AgCl.
tion of MnCl2bipy is irreversible at a 1.14 V potential.
Upon addition of phosphonate HP(O)(OEt)2 to the soluꢀ
tion of complex MnCl2bipy, a shift of this peak to the less
anodic potentials (0.99 V) is observed, with its slow growth
Scheme 2

Phosphorylation of benzene
Russ.Chem.Bull., Int.Ed., Vol. 64, No. 8, August, 2015
1931
Scheme 3
L = bpy, dmphen
carried out in a thermostated (25 C) electrochemical cell
(1—5 mL) under inert atmosphere (N2).
products of benzene in the process of electrosynthesis with
the nickel complex.
Before recording CVA curves and between measurements,
the solution was vigorously stirred on a magnetic stirrer under
inert atmosphere, which was passed first through a drying system
and then through a BIꢀGAScleaner system (Modern Laboratory
Equipment, Novosibirsk) for purification from the trace amounts
of oxygen.
Preparative electrosynthesis. Preparative electrolysis was carꢀ
ried out using a source of direct current B5ꢀ49 in a 40ꢀmL threeꢀ
electrode cell. The working electrode potential was measured
using a V7ꢀ27 DC voltmeter relative to the reference electrode
Ag/AgCl (0.01 mol L–1) in acetonitrile. The surface of the workꢀ
ing platinum Uꢀshaped electrode was 48.00 cm2. A ceramic plate
with 900ꢀnm pores was used as a diaphragm. During preparative
synthesis, the electrolyte was continuously stirred with a magꢀ
netic stirrer under a constant current of an inert gas, which
was passed through the purification system from oxygen and
other gases.
A generalized scheme for the catalytic cycle can be
suggested (Scheme 2).
A catalytic scheme involving a monoꢀcomponent cataꢀ
lyst simplifies (Scheme 3).
In conclusion, a suggested method for the electrosynꢀ
thesis of diethyl phenylphosphonate proceeds under mild
conditions (room temperature, normal pressure) and with
1 : 1 ratio of reagents gives the product in high yield (up
to 90%) and 100% conversion in the presence of bimetalꢀ
lic catalytic systems MnSO4/CoCl2dmphen or MnCl2/
CoCl2bipy. The mechanism of the process requires further
studies, but we suppose that the first step of the cycle is
probably the formation of the metal (or metals) phosphoꢀ
nate undergoing oxidation at low anodic potentials with
elimination of the phosphonate radical, which reacts with
benzene.
NMR spectra were recorded on a Bruker Avanceꢀ400 multiꢀ
nuclear spectrometer (400.1 (1H) and 162.0 MHz (31Р)) relative
to a reference, the signal of the deuterated solvent (1H NMR) or
phosphoric acid (31Р NMR).
Experimental
Mass spectrometric studies (ESIꢀMS analysis) were carried
out on an AmazonX instrument (Bruker Daltonik GmbH, Gerꢀ
many), electrospray ionization. Nitrogen was used as a drying
gas in the source with temperature 220 C. The source potential
was 4.5 kV. Solutions of the samples were diluted with acetoꢀ
nitrile to the concentration of ~10–3 mg mL–1. The samples
were injected using an autosampler of the Agilent 1260 Infinity
liquid chromatograph (Agilent Technologies, USA).
Cyclic voltammetry. Cyclic voltamgrams were recorded using
a BASi Epsilon E2P potentiometer (USA). The instrument is
composed of a measurement unit and a DellOptiplex 320 perꢀ
sonal computer with the EpsilonꢀECꢀUSBꢀV200 program. Tetraꢀ
ethylammonium and tetrabutylammonium tetrafluoroborates
were used as supporting electrolytes. A stationary glassy carbon
disk (surface area 6 mm2) served as a working electrode, a referꢀ
ence electrode was Ag/AgCl (0.01 mol L–1), platinum wire served
as an auxiliary electrode. CVA curves were recorded at the rates
of potential linear sweep of 100 mV s–1. The measurements were
Reagents and objects of studies. Acetonitrile (Acros Organꢀ
ics, extra purity grade) was used as a solvent in the syntheses,
which before use was thrice distilled, first distillation was carried

1932
Russ.Chem.Bull., Int.Ed., Vol. 64, No. 8, August, 2015
Khrizanforov et al.
out over potassium permanganate, second distillation over phosꢀ
phorus pentoxide, and third over calcium hydride under argon.
Diethyl phenylphosphonate was obtained according to the
procedure described earlier.26 Benzene was purified by ordinary
distillation over sodium. The purified solvents were stored under
inert atmosphere in Schlenk systems.
Tetraethylammonium tetrafluoroborate was obtained by mixꢀ
ing a 30—35% aqueous solution of tetraethylammonium hydrꢀ
oxide and HBF4 until neutrality shown by indicator. A white
crystalline precipitate was formed in the course of the reaction,
which was filtered and dried. A resulting powdered salt was reꢀ
crystallized from ethanol and dried 2—3 days in a drying oven
in vacuo at 55 C.
Synthesis of metal complexes (general procedure). A correꢀ
sponding ligand (1.83•10–2 mol in ethanol (30—50 mL) was
slowly added to a solution of metal salt MX2 (1.83•10–2 mol) in
the same solvent (100 mL) with stirring. The reaction mixture
was stirred at constant temperature (25 C) for 3—24 h until
a crystalline precipitate was formed. the precipitate was filtered
under argon and washed with iceꢀcold ethanol. The complex
was dried in a drying oven in vacuo for 2—3 days at 25—55 C.
Physicochemical characteristics of the synthesized complexes
CoCl2dmphen,27 CoCl2bipy,28 NiBr2dmphen, and NiBr2bipy
(see Ref. 29) agree with the literature data.
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Electrocatalytic phosphorylation of benzene (general proceꢀ
dure). Diethyl phosphite (1.2•10–3 mol), benzene (1.2•10–3 mol),
and a metal complex MX2L (0.12•10–3 mol) in MeCN (40 mL)
were placed into a electrochemical cell. Electrolysis was carried
out in an electrochemical cell with divided anode and cathode
compartments at 23 C under dry argon in galvanostatic mode
with 0.7 V potential on working electrode. The amount of passed
electricity was 2 F per 1 mol of phosphite. After the electrolysis
was complete, the reaction mixture was washed with saturated
aqueous ammonium chloride (3×50 mL) and extracted with
chloroform (3×70 mL). After separation, the organic layer was
dried with magnesium sulfate, the solvent was evaporated, the
residue was purified by passing through a chromatographic
column with silica gel (eluent ethyl acetate—hexane). Physicoꢀ
chemical and spectral characteristics of the product (diꢀ
ethyl phenylphosphonate) agree with the literature data.30
When Ni(BF4)2dmphen was used as a catalyst, the phosphorylaꢀ
tion products were benzene polyphosphonates isolated as
19. E. V. Nikitin, A. S. Romakhin, O. V. Parakin, G. V. Roꢀ
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fosfora [Preparative Phosphorus Chemistry], UrORAN, Perm´,
1992, 69 (in Russian).
a mixture: [M + H]+• = 894.22 (C30H60O18P6); [M + H]+•
=
= 758.91 (C26H51O15P5); [M + H]+• = 622.74 (C22H42O12P4);
[M + H]+• = 486.60 (C18H33O9P3); [M + H]+• = 350.53
(C14H24O6P2).
27. M. J. Hynes, P. F. Brannick, Inorg. Chim. Acta, 1979, 33, 11.
28. G. Muller, J. Sales, J. Vinaixa, J. Org. Chem., 1984, 273, 255.
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Yakhvarov, V. I. Morozov, N. K. Gusarova, B. A. Trofimov,
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[Izv. Akad. Nauk, Ser. Khim., 2005, 919].
This work was financially supported by the Russian
Science Foundation (Grant 14ꢀ23ꢀ00016).
30. M. C. Kohler, J. G. Sokol, Jr., R. A. Stockland, Tetrahedron
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Received December 15, 2014;
in revised form April 17, 2015