Modification of fullerene C60 by phosphorylated diazo compounds

Article abstract of DOI:10.1023/A:1026096403043

New representatives of phosphorylated methanofullerenes were prepared by the reactions of [60]fullerene with O,O-diethyl α-diazoethyl- and O,O-diethyl α-diazobenzylphosphonates. Electrochemical reduction of the above-mentioned products proceeded stepwise

Full text of DOI:10.1023/A:1026096403043

1750
Russian Chemical Bulletin, International Edition, Vol. 52, No. 8, pp. 1750—1757, August, 2003
Modification of fullerene C60 by phosphorylated diazo compounds
ꢀ
I. P. Romanova, E. I. Musina, A. A. Nafikova, V. V. Zverev, D. G. Yakhvarov, and O. G. Sinyashin
A. E. Arbuzov Institute of Organic and Physical Chemistry, Kazan Research Center of the Russian Academy of Sciences,
8 ul. Akad. Arbuzova, 420088 Kazan, Russian Federation.
Fax: +7 (843 2) 75 2253. Еꢀmail: romanova@iopc.knc.ru
New representatives of phosphorylated methanofullerenes were prepared by the reactions
of [60]fullerene with O,Oꢀdiethyl αꢀdiazoethylꢀ and O,Oꢀdiethyl αꢀdiazobenzylphosphonates.
Electrochemical reduction of the aboveꢀmentioned products proceeded stepwise and reversibly.
Key words: [60]fullerene, O,Oꢀdiethyl αꢀdiazoethylꢀ and O,Oꢀdiethyl αꢀdiazobenzylꢀ
phosphonates, phosphorylated methanofullerenes, electrochemistry, quantumꢀchemical calꢀ
culations.
The modification of fullerenes by diazo compounds is
one of procedures most widely used for fixing various
organic fragments at the carbon skeleton of fullerenes.1 It
is assumed that a combination of hydrophilic phosphoꢀ
rusꢀcontaining groups and hydrophobic fullerene fragꢀ
ments in one molecule can lead to the construction of
new phospholipid substances.2 It should be noted that all
known phosphorylated derivatives of fullerene C60, are
6,6ꢀclosed adducts regardless of the procedure for their
preparation.2—12 In the reaction of C60 with O,Oꢀdimethyl
diazomethylphosphonate,8 an adduct was detected, which
is, most probably, a 5,6ꢀopen adduct (or homofullerene).
However, this adduct was not isolated in individual form.
We studied the reaction of C60 with O,Oꢀdiethyl αꢀdiꢀ
azoethylꢀ (1) and O,Oꢀdiethyl αꢀdiazobenzylphosphoꢀ
nates (2). It was of interest to reveal the influence of the
substituent at the αꢀcarbon atom of phosphonate on the
structures of the resulting adducts.
Several HPLC peaks (C18 reversedꢀphase column)
were observed in the mixture prepared by the reaction of
C60 with αꢀdiazoethylphosphonate 1 in toluene (110 °C,
4—5 h). Based on the retention times, the main peak in
the chromatogram (5.2 min) can be assigned to the
monoadduct and the remaining lowꢀintensity peaks are
attributable to unconsumed [60]fullerene (6.3 min) and
polyadducts (3.8, 4.2, 5.8, and 6.7 min). The unconsumed
fullerene was separated by column chromatography to
give a fraction containing three products, as demonstrated
by HPLC (normalꢀphase column) and NMR spectroꢀ
scopy. The 31P—{1H} NMR spectra (CDCl3) have three
signals (δ 26.00, 20.62, and 20.04) in the region characꢀ
teristic of phosphonates. The 1H and 13C NMR spectra of
this fraction also show three sets of signals for the hydroꢀ
gen atoms of the methyl groups and ethoxy substituents at
the phosphorus atom. The 13C—{1H} NMR spectrum has
three broadened singlets at δ 15.93, 16.14, and 16.96,
three doublets at δ 17.02 (3JP,C = 5.1 Hz), 16.88 (3JP,C
3.3 Hz), and 17.27 (3JP,C = 2.0 Hz) and also at δ 63.63
(2JP,C = 6.0 Hz), 63.46 (2JP,C = 4.6 Hz), and 63.97 (2JP,C
=
=
7.9 Hz). In addition, the spectra have signals at δ 138—148
corresponding to the carbon atoms of the fullerene sphere,
which indicates that the fraction under study consists of a
mixture of three fullereneꢀcontaining adducts. Since we
failed to separate these adducts by column chromatoꢀ
graphy, their mixture was heated in oꢀdichlorobenzene
(oꢀDCB) at 140 °C until only one signal at δ 19.65 perꢀ
sisted in the 31P NMR spectrum (oꢀDCB) and only one
peak was observed in the HPLC chromatogram (normalꢀ
phase column). oꢀDichlorobenzene was removed in vacuo
and the resulting darkꢀbrown powdered compound was
identified by physicochemical methods. The laserꢀdesꢀ
orption mass spectrum of this compound has peaks at
m/z 884, 907, and 923. The first peak corresponds to the
monoadduct of fullerene with diazo compound 1 with a
loss of the dinitrogen molecule and the remaining two
peaks correspond to the sodium and potassium salts of
this monoadduct, respectively. The elemental analysis data
are also indicative of this monoadduct. The 31P NMR
spectrum of this compound (in CDCl3) has a signal at
δ 20.00, whose chemical shift is identical with that of the
most intense signal in the initially isolated mixture of
adducts (δ 20.04). The IR spectrum shows a highꢀintenꢀ
sity band at 526 cm–1 characteristic of [60]fullerene
monoadducts. The UV spectrum has a band at 424 nm
indicative of the formation of the 6,6ꢀclosed monoadduct.
All the above data provide evidence that the compound
synthesized is an individual monoadduct 3 with the
methano[1,2][60]fullerene structure. The NMR spectroꢀ
scopic studies completely confirmed this conclusion.
Theoretically,13 based on the Cs symmetry of the molꢀ
ecule (the symmetry plane is perpendicular to the bond
between two sp3ꢀhybridized carbon atoms), the fullerene
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1660—1667, August, 2003.
1066ꢀ5285/03/5208ꢀ1750 $25.00 © 2003 Plenum Publishing Corporation

Modification of C60 by phosphorylated diazo compounds Russ.Chem.Bull., Int.Ed., Vol. 52, No. 8, August, 2003
1751
sphere in adduct 3 should be characterized by 31 13C NMR
signals (4 signals with an intensity of 1C each and 27 signals
with an intensity of 2C each) for the sp2ꢀhybridized carꢀ
bon atoms and one 13C NMR signal (with an intensity
of 2C) for the sp3ꢀhybridized carbon atoms of the cycloꢀ
propane fragment. The latter signal is generally observed
at δ 60—80 and the signals for the sp2ꢀhybridized carbon
atoms are observed at δ 134—148.10,11
In reality, the fullerene sphere of adduct 3 is characꢀ
terized (Table 1) by 27 13C NMR signals at δ 138—148
(25 signals with an intensity of 2C each and 2 signals with
an intensity of 4 C each), which is attributed to the ranꢀ
dom superposition of the signals, and also by a doublet at
δ 74.41 with JP,C = 2.1 Hz. The presence of the phosphoꢀ
rus atom made it possible to identify signals for some
carbon atoms of the fullerene sphere. Thus, the signals at
δ 147.21 and 147.66 have JP,C = 5.3 and JP,C = 4.2 Hz,
respectively, and these signals, most likely, belong to
the sp2ꢀhybridized carbon atoms directly bound to the
sp3ꢀhybridized carbon atoms of the sphere. The signal for
the exohedral carbon atom of the cyclopropane fragment
(C(61)) is observed at δ 35.90 (JP,C = 180 Hz). In the
protonꢀdecoupled 13C NMR spectrum, two equivalent
ethoxy fragments at the phosphorus atom are characterꢀ
ized by two doublets at δ 63.41 (JP,C = 7 Hz) and 16.80
(JP,C = 5.3 Hz). Since the 13C NMR spectrum of the
starting diazophosphonate 1 (see Table 1) has a signal of
the methyl group at the αꢀcarbon atom as a doublet with
JP,C = 8.3 Hz, the signal of the methyl group at C(61) in
the spectrum of adduct 3 should also be characterized by
a doublet. However, the 13C—{1H} NMR spectrum has a
singlet at δ 15.68 rather than a doublet due, apparently, to
a small constant of spinꢀspin coupling between the carꢀ
bon atom of the methyl group and the phosphorus atom.
1
The H NMR spectrum of adduct 3 (Table 2) conꢀ
firms the equivalence of two ethoxy groups at the phosꢀ
phorus atom and the presence of the methyl substituent at
the C(61) atom.
Therefore, the results of physicochemical studies inꢀ
dicate that O,Oꢀdiethyl αꢀmethyl(methano[1,2][60]fulꢀ
lerenyl)phosphonate (3) is the most thermally stable prodꢀ
uct of the reaction of C60 with diazophosphonate 1. The
reaction proceeds through the formation of two intermeꢀ
diates, which are transformed into adduct 3 upon heating.
According to the data from HPLC and 31P NMR specꢀ
troscopy, the reaction of C60 with diazophosphonate 1 in
oꢀDCB at 140 °C for 3 h afforded the same mixture of
adducts as that prepared by the reaction in toluene at
110 °C. An increase in the temperature of heating to
180 °C (3 h) also led to the formation of adduct 3.
According to the scheme of dipolar cycloaddition of
diazo compounds to C60,14 the reaction under considerꢀ
ation can proceed through the intermediate formation
of fullerenopyrazoline 4 or homofullerenes 5 and 6
(Scheme 1). Taking into account the reaction temperaꢀ
ture (higher than 60 °C), homofullerenes 5 and 6, which
Table 1. 13C NMR spectra (CDCl3, δ, J/Hz) of compounds 1—3 and 7
C atom
1
2
3
7
СH3—C—P
9.06
—
15.68
—
(q, 1JC,H = 132.5,
d, 2JP,C = 8.3)
16.30
(q, 1JC,H = 130.5,
d, 2JP,C = 0.0)
16.80
CH3CH2O
CH3CH2O
16.33
16.83
(q, 1JC,H = 126.9, (q, 1JC,H = 127.2, (q, 1JC,H = 125.5,
(q, 1JC,H = 127.2,
d, 3JP,C = 6.2,
t, 2JC,H = 2.8)
62.45
(t, 1JC,H = 147.4,
d, 2JP,C = 5.5,
q, 2JC,H = 4.2)
21.42
(d, 1JP,C = 136.0)
—
d, 3JP,C = 6.9)
d, 3JP,C = 5.3)
d, 3JP,C = 5.8,
t, 2JC,H = 2.9)
63.10
(t, 1JC,H = 147.5,
d, 2JP,C = 5.6)
63.41
(t, 1JC,H = 149.0,
d, 2JP,C = 6.3)
64.12
(t, 1JC,H = 148.2,
d, 2JP,C = 6.5,
q, 2JC,H = 4.4)
Сα or С(61)
С60
50.77
(d, 1JP,C = 226.1)
35.89
(d, 1JP,C = 180.0)
2С: 74.41 (d, JP,C = 2.11),
138.63, 140.96, 141.10, 141.46,
142.43, 142.51, 143.05, 143.26,
143.29, 143.37, 143.69, 143.98,
144.30, 144.48, 144.86, 144.93,
144.98, 145.04, 145.29, 145.38,
145.45, 145.59, 145.67,
49.02
(d, 1JP,C =179.5)
2
—
2С: 73.65 (d, 2JP,C = 2.18),
138.53, 140.97, 141.01, 141.89,
142.02, 142.11, 142.44, 142.51,
142.97, 143.23, 143.25, 143.41,
143.50, 144.08, 144.41, 144.67,
144.80, 144.96, 145.04, 145.12,
145.13, 145.39, 145.48, 145.53,
145.57, 146.03,
147.21 (d, 3JP,C = 5.2),
147.66 (d, 3JP,C = 4.2)
4C: 142.06, 145.51
146.87 (d, 3JP,C = 5.8),
148.30 (d, 3JP,C = 3.6),
1C: 144.76, 145.26

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Russ.Chem.Bull., Int.Ed., Vol. 52, No. 8, August, 2003
Romanova et al.
Table 2. 1H NMR spectra (CDCl3) of compounds 1—3 and 7
Comꢀ
pound
δ, J/Hz
СH3 (3 H)
Ph (5 H)
OCH2CH3 (6 H)
OCH2CH3 (4 H)
3
1
2
1.77 (d, 3JP,H = 9.8)
—
1.26 (t, JH,H = 7.0)
4.03 (dq, 3JPO,CH = 7.0, 3JH,H = 7.0)
3.86, 4.00 (both dq, 3JPO,CH = 10.2,
3JH,H = 7.3)
3
—
6.97 (t, Hp, 3JH,H = 7.3);
7.18 (t, Hm, 3JH,H = 7.7);
7.30 (d, Ho, 3JH,H = 8.1)
—
1.03 (t, JH,H = 7.3)
3
3
7
2.44 (d, 3JP,H = 12.4)
1.55 (t, JH,H = 7.3)
4.47 (dq, 3JPO,CH = 7.7, 3JH,H = 7.3)
4.29 (dq, 3JPO,CH = 7.0, 3JH,H = 7.0)
3
—
7.49—7.55 (m);
7.96 (ddd, Ho, 3JH,H = 7.8,
4JH,H = 2.0, 4JP,H = 1.6)
1.45 (t, JH,H = 7.0)
Scheme 1
Reagents and conditions: i. toluene, 110 °C, 4—5 h or oꢀDCB, 140 °C, 3 h; ii. oꢀDCB, 180 °C, 4 h.
Scheme 2
differ in the arrangement of the phosphonate fragment
above the fiveꢀ or sixꢀmembered rings, are the most probꢀ
able intermediates.
With the aim of preparing thermally less stable adꢀ
ducts 4, 5, and 6, we changed the conditions of the reacꢀ
tion of C60 with diazophosphonate 1. Taking into account
that the dipolar cycloaddition to olefins proceeds more
efficiently in polar solvents, we used oꢀDCB instead of
toluene and the reaction temperature was decreased
to 25 °C. However, according to the HPLC data, the
target adducts were not produced even after stirring of the
reagents for four weeks. An increase in the reaction temꢀ
perature to 50—60 °C also did not afford adducts.
The reaction of C60 with O,Oꢀdiethyl αꢀdiazobenzylꢀ
phosphonate (2) was carried out in a toluene solution
both at room temperature (one month) and at the boiling
point of the solvent (110 °C, 2—3 h) (Scheme 2). The
reaction mixture prepared at 110 °C was chromatographed
on a column of silica gel to give unconsumed fullerene,
polyadducts, and a fraction, which, unlike the fraction
i. toluene, 110 °C, 2—3 h or 25 °C, 1 month.
formed in the reaction of C60 with phosphonate 1, conꢀ
tained (according to the data from HPLC and 31P NMR
spectroscopy) only product 7. This product was also preꢀ

Modification of C60 by phosphorylated diazo compounds Russ.Chem.Bull., Int.Ed., Vol. 52, No. 8, August, 2003
1753
Table 3. Theoretical (δcalc) and experimental (δexp) chemical
shifts of the signals for the carbon atoms in the 13C NMR specꢀ
trum of methanofullerene 7
pared by the reaction of C60 with phosphonate 2 at room
temperature. It should be noted that no polyadducts were
detected by HPLC in the reaction mixture obtained at
room temperature. Dry adduct 7 was prepared as a darkꢀ
brown powder. Its structure was established by 31P, 13C,
1
and H NMR, IR, and UV spectroscopy and mass specꢀ
trometry.
According to the massꢀspectrometric data, comꢀ
pound 7 is the fullerene monoadduct with diazo comꢀ
pound 2 whose formation was accompanied by liberation
of the dinitrogen molecule. The 31P NMR spectrum of 7
has one signal at δ 15 characteristic of phosphonates. The
IR spectrum of 7 contains a band at 1198 cm–1 characterꢀ
istic of the P=O group of the phosphonate fragment and a
band at 526 cm–1 assigned to the fullerene sphere of the
monoadduct. The UV spectrum of adduct 7, like that of
adduct 3, has a band with λmax = 426 cm–1 characteristic
of 6,6ꢀclosed adducts. The 13C NMR spectrum of adꢀ
C atom
δ
δ
C atom
δ
δ
exp
calc
exp
calc
duct 7 (see Table 1) has two doublets at δ 73.68 (2JC,P
=
1C
2С
1C
2С
2.2 Hz) and 49.02 (1JC,P = 178 Hz) belonging to the
sp3ꢀhybridized carbon atoms of the fullerene sphere and
the exocyclic C(61) atom of the cyclopropane fragment,
respectively. These data as well as the results of UV specꢀ
troscopy are indicative of the methanofullerene structure
of adduct 7. In addition, the 13C NMR spectrum of adꢀ
duct 7 has a set of signals at δ from 138 to 148 (28 signals
with an intensity of 2C each and 2 signals with an intenꢀ
sity of 1C each) for the sp2ꢀhybridized carbon atoms of
the fullerene sphere. According to the Cs symmetry of the
molecule, the fullerene sphere of adduct 7 should be charꢀ
acterized by 31 13C signals for the sp2ꢀhybridized carbon
atoms (27 signals with an intensity of 2C each and 4 signals
with an intensity of 1C each). Apparently, the chemical
shifts of two signals with an intensity of 1C each, like
those in the spectrum of adduct 3, have close values to an
extent that these signals overlap. To refine this question,
we carried out quantumꢀchemical calculations of the
chemical shifts of the 13C NMR signals for the carbon
atoms of the fullerene sphere in adduct 7. The results of
these calculations are given in Table 3. The calculations
demonstrated that the signals for the individual sp2ꢀhybridꢀ
ized carbon atoms should be observed at δ 144—145
and ∼142. The experimental chemical shifts of the signals
for the C(27) and C(18) atoms are in good agreement
with the calculated data. It should be noted that the real
spectrum of adduct 7 has only signals with an intensity of
2C each at δ 141—142, which confirms the assumption
that the signals for the C(45) and C(36) atoms overlap.
Two signals in the real spectrum of adduct 7 at δ 148.03
and 146.59 have JC,P of 3.6 and 5.8 Hz, respectively, and,
hence, they can be assigned to the C(3), C(6) and C(9),
C(12) atoms, which are directly bound to the sp3ꢀhybridꢀ
ized carbon atoms of the fullerene sphere. However, it
should be noted that the calculated chemical shifts of the
signals for these carbon atoms differ substantially from
45
36
142.72
142.98
27
18
144.36
145.22
144.76
145.26
142.97
21, 15
24, 30
10, 11
26, 28
42, 48
23, 31
39, 33
19, 17
22, 32
41, 49
40, 50
43, 47
38, 34
5, 4
138.32
138.37
139.26
140.86
140.95
141.05
141.12
141.16
141.91
142.24
142.29
143.36
143.98
144.28
138.53
140.97
141.01
141.89
142.02
142.11
142.44
142.51
143.23
143.25
143.41
143.50
144.08
144.41
57, 58
53, 52
20, 16
25, 29
55, 60
8, 13
54, 51
7, 14
56, 59
44, 46
37, 35
3, 6
144.34
144.44
144.49
144.68
145.22
145.24
145.40
145.56
145.62
145.70
145.75
152.08
153.33
144.67
144.80
144.96
145.04
145.12
145.13
145.39
145.48
145.53
145.57
146.03
146.87a
148.30b
9, 12
a d, 3JP,C = 5.8 Hz.
b d, 3JP,C = 3.6 Hz.
the experimental values. In all other cases, there is a satisꢀ
factory agreement between the calculated and experimenꢀ
tal data, which made it possible to identify the signals in
the experimental 13C NMR spectrum of adduct 7.
The 13C and 1H NMR spectra of adduct 7 (see Tables 1
and 2) also confirm the presence of the phenyl fragment
and two equivalent ethoxy groups at the phosphorus atom.
Therefore, the reaction of C60 with diazophosphoꢀ
nate 2, like the reaction with diazophosphonate 1, afꢀ
forded the 6,6ꢀclosed adduct, viz., O,Oꢀdiethyl αꢀpheꢀ
nyl(methano[1,2][60]fullerenyl)benzylphosphonate (7).
However, it should be emphasized that other homofulleꢀ
renes were not detected in this reaction at all. In addition,
it should be noted that compounds 3 and 7 are thermally
very stable. Thus, after refluxing of these compounds in
oꢀDCB for 20 h, even traces of C60 were not detected by
HPLC and TLC.

1754
Russ.Chem.Bull., Int.Ed., Vol. 52, No. 8, August, 2003
Romanova et al.
lier.15 However, unlike the latter compounds, which unꢀ
dergo the retroꢀBingel reaction in the second step of reꢀ
duction, reduction of methanofullerenes 3 and 7 was unꢀ
expectedly completely reversible. Generally, methanoꢀ
fullerenes undergo opening of the cyclopropane ring,
which takes place in different steps of their electrochemiꢀ
cal reduction depending on the nature of substituents.16,17
One possible explanation of the electrochemical and
thermal stabilities of methanofullerenes 3 and 7 is the
presence of intramolecular interactions between the orꢀ
ganic fragments at the bridging C(61) atom and the
fullerene sphere in the molecules of these compounds.
Interactions of this type should, most likely, influence the
spectroscopic characteristics of the adducts. In this conꢀ
nection, we compared the chemical shifts of the signals for
I/mA
2.5 mA
1
2
–E/V
1
the carbon and hydrogen atoms in the H and 13C NMR
Fig. 1. Cyclic voltammogram of adduct 7.
spectra of methanofullerenes 3 and 7, phosphonates 1
and 2, and O,Oꢀdiethyl benzylphosphonate 8.
To reveal the influence of the phosphonate fragment
on the electronic structure of the fullerene sphere in
methanofullerenes 3 and 7, we studied electrochemical
reduction of these compounds by cyclic voltammetry.
Four oneꢀelectron reversible reduction peaks were obꢀ
served in the cyclic voltammograms of methanofullerenes
3 and 7 (Fig. 1, an example for adduct 7). Each peak
corresponds to the transfer of one electron to the fullerene
sphere giving rise finally to the tetraanion. Compared to
the positions of the peaks of unmodified C60, all reducꢀ
tion peaks of adducts 3 and 7 were observed in the higher
cathodic region (Table 4). The electron affinities (EA) of
adducts 3 and 7 calculated from the experimental potenꢀ
tials of the first reduction peaks are in good agreement
with the corresponding values calculated by the PM3 and
DFT methods. The potentials of the reduction peaks of
adducts 3 and 7 are consistent with the results of elecꢀ
trochemical reduction of tetraethyl and tetraisopropyl
(methano[1,2][60]fullerenyl)diphosphonates reported earꢀ
The signals for the hydrogen atoms of the ethoxy groups
at the phosphorus atom and the signals of the Me or Ph
groups in the H NMR spectra of methanofullerenes 3
1
and 7 are observed at lower field compared to the signals
for the corresponding hydrogen atoms in the spectra of
phosphonates 1 and 2 (see Table 2). However, the 13C
NMR signals for the carbon atoms of the EtO groups in
methanofullerenes 3 and 7 (see Table 1) differ only slightly
from the signals of these groups in the spectra of phosꢀ
phonates 1 and 2. At the same time, the signal for the
carbon atom of the Me group in the spectrum of phosꢀ
phonate 3 is substantially shifted downfield relative to the
signal of this group in the spectrum of phosphonate 1. The
signals for the carbon atoms of the phenyl ring in the
spectrum of methanofullerene 7 are shifted to a different
extent compared to the positions of the corresponding
signals in the spectrum of phosphonate 2 (Table 5). The
largest shift is observed for the signal of the Co atom, the
signal being shifted compared to the corresponding sigꢀ
nals in the 13C NMR spectra of both phosphonate 2 and
phosphonate 8. Noteworthy are the large constants of
spinꢀspin coupling of this carbon atom with the orthoꢀ and
paraꢀprotons.
Table 4. Potentials (Epred) and peak currents (Ipred) in cyclic
voltammograms,a the experimental electron affinities (EAexp
)
for C60 and compounds 3 and 7, and the corresponding electron
affinities calculated (EAcalc) by the PM3 and DFT methods
However, taking into account the difference in the
environment about the groups of atoms under considerꢀ
ation in methanofullerenes 3 and 7 and phosphonates 1
and 2, we additionally carried out quantumꢀchemical calꢀ
culations of the chemical shifts of the 13C NMR signals
for the carbon atoms of the phenyl ring in methanoꢀ
fullerene 7 (see Table 5). To estimate the contribution
of the fullerene core to the shielding of the carbon
atoms, we examined the cyclopropane derivative
C3H4(Ph)P(O)(OMe)2 (9). A comparison of the chemiꢀ
cal shifts of the signals for the carbon atoms of the phenyl
ring in methanofullerene 7 and compound 9 demonstrated
that the fullerene sphere substantially shields the Cipso
atom and deshields the orthoꢀCo atom. The mutual effect
Comꢀ
pound
Epred/V
EA/eV
(Ipred/µA)
b
EAexp
EAcalc
PM3 DFT
С60
3
–0.83
(4.2)
–0.91
(9.2)
–0.93
(9.2)
–1.24
–1.70
(3.9)
–1.81
(9.0)
–2.16
(4.6)
–2.25
(10.7)
–2.30
(11.7)
2.65 2.65 2.65
2.57 2.54 2.53
2.55 2.51 2.51
(3.8)
–1.30
(8.3)
7
–1.32
(7.3)
–1.84
(8.3)
a In a 3 : 1 oꢀdichlorobenzene—acetonitrile mixture at 25 °C.
b Calculated from Ep
.
1,red

Modification of C60 by phosphorylated diazo compounds Russ.Chem.Bull., Int.Ed., Vol. 52, No. 8, August, 2003
Table 5. Parameters of the 13C NMR spectra of the phenyl fragments in compounds 2 and 7—9
1755
Atom
δ, nJ
, nJ C— H)/Hz
31
13
13
(
1
(
P— C)
2
7
8
9
(experiment)
(experiment)
(calculation)
Experiment
Calculation*
134.88
Со
Сm
Сp
122.8 (d, 1JC,H = 160.9,
d, 3JP,C = 4.2,
d, 3JC,H = 5.5)
134.4 (d, 1JC,H = 162.0,
d, 4JP,C = 3.4,
128.7 (d, 1JC,H = 158.8,
d,3JP,C = 6.7, d, 3JC,H = 5.7,
t, 3J = 6.0)
127.2 (d, 1JC,H = 159.7,
d, 4JP,C = 3.0, dd, 2JC,H = 3.3,
2JC,H = 3.3)
125.6 (d, 1JC,H = 159.7, d,
5JP,C = 3.8, t, 3JC,H = 6.0)
130.8 (d, 2JP,C = 9.1, d,
2JC,H = 6.2, d, 2JC,H = 5.7)
132.75
t, 3JC,H = 7.6)
129.4 (d, 1JC,H = 160.9,
d, 4JP,C = 2.8, dd, 2JC,H = 3.5,
2JC,H = 3.4)
127.8 (d, 1JC,H = 160.9,
d, 3JP,C = 2.2,
127.71
127.52
d, 3JC,H = 7.3)
125.3 (d, 1JC,H = 158.1,
t, 2JC,H = 6.9)
128.6 (d, 1JC,H = 163.5,
128.61
136.00
126.66
142.41
d, 5JP,C = 2.9, t, 3JC,H = 7.3)
132.8 (t, 3JC,H = 7.6,
2JP,C = 0)
Сipso 126.9 (d, 2JP,C = 8.3,
t, 2JC,H = 1.3)
* Calculated by the GIAO—DFT/PBE/TZ2P method with the exchangeꢀcorrelation potential.
of the addends is transferred predominantly through the
bonds. At the same time, according to the results of calꢀ
culations, the oxygen atom of the phosphoryl group in the
thermodynamically most stable conformation of methanoꢀ
fullerene 7 (Fig. 2) can approach the C(3)—C(4) bond to
a distance of 2.99 Å and the hydrogen atom of the phenyl
ring at Co can approach the C(11)—C(12) bond to a disꢀ
tance of 2.89 Å. The distance between the Co atom and
the C(11)—C(12) bond is 3.20 Å. As a result, the P=O
dipole can shift the electron density from the C(3)—C(4)
bond thus shortening it to 1.3877 Å, while the
C(11)—C(12) bond is elongated to 1.3897 Å. Therefore,
the spectroscopic characteristics and calculated data for
adduct 7 demonstrate that the intramolecular interacꢀ
tions between the organic fragments and the fullerene
sphere in molecule 7 are quite possible, and it is not
inconceivable that these interactions make a contribution
to thermal stability of methanofullerenes 7 and 3 and also
stabilize the anions generated in the course of electroꢀ
chemical reduction of these adducts. We did not exclude
the contributions of other factors as well. The question
about stability of the exocyclic cyclopropane fragments in
organofullerenes will be discussed for a broader spectrum
of methanofullerenes in the future.
To summarize, we prepared new thermally stable phosꢀ
phorylated methanofullerenes whose electrochemical reꢀ
duction proceeds reversibly.
Experimental
The IR spectra were measured on a Вruker Vectorꢀ22 Fouꢀ
rier spectrometer in KBr pellets for fullerene derivatives and in
Nujol mulls for phosphorylated hydrazones and diazo comꢀ
pounds. The 31P, 1H, and 13C NMR spectra were recorded
on a Bruker WMꢀ250 instrument at ν 250 MHz (1H) and
0
101.2 MHz (31P) and on a Bruker MSLꢀ400 instrument at ν
0
400.13 MHz (1H), 100.62 MHz (13C), and 161.92 MHz (31P) in
CDCl3.. The chemical shifts δ were calculated with respect to
CDCl3, Me4Si, and 85% H3PO4. The UV spectra were recorded
on a Specord UVꢀVIS instrument. The mass spectra were obꢀ
tained on a MALDI TOF MS instrument (Dynamo) with the
use of a pꢀnitroaniline matrix. The HPLC analysis was carried
out on a Gilson chromatograph (UV detector; normalꢀphase
and C18 reversedꢀphase columns (Partisilꢀ5 ODSꢀ3); toluꢀ
ene—MeCN, 1 : 1 (v/v) as the eluent, 2 mL min–1; UVꢀVIS
Detector Holochrome detector; λ 328 nm). Elemental analysis
for the phosphorus content of the fullerene adducts was carried
out by pyrolysis of weighed samples in a quartz tube under a
stream of oxygen according to a known procedure.18
Cyclic voltammetry (CV) studies were carried out with the
use of a stationary disk glassyꢀcarbon electrode as a working
electrode with a working surface area of 3.14 mm2. Cyclic
voltammograms (CV curves) were measured with the use of a
PIꢀ50ꢀ1 potentiostat equipped with a PRꢀ8 programmator and
an electrochemical cell according to a threeꢀelectrode scheme.
The CV curves were recorded with the use of a twoꢀcoordinate
recorder at a potential scan rate of 50 mV s–1 using a 3 : 1
oꢀDCB—MeCN mixture with Bu4NBF4 (0.1 mol L–1) as the
background electrolyte. An Ag/0.01 M AgNO3 system in MeCN
Fig. 2. Most thermodynamically stable conformation of
methanofullerene 7.

1756
Russ.Chem.Bull., Int.Ed., Vol. 52, No. 8, August, 2003
Romanova et al.
served as the reference electrode and a 1ꢀmm diameter platinum
wire was used as the auxiliary electrode. The measurements
were carried out in a temperatureꢀcontrolled (25 °C) cell under
an argon atmosphere. The concentrations of solutions of
fullerene and adducts were 1•10–3 and 2—10–3 mol L–1, respecꢀ
at 0 °C. The reaction mixture was stirred at 0 °C for 2 h and then
at ∼20 °C for 12 h. The solvent was removed in vacuo, the
residue was treated with diethyl ether (20 mL), and the precipiꢀ
tate that formed was filtered off. The large crystals, which preꢀ
cipitated from the filtrate upon cooling, were filtered off.
2ꢀ[2ꢀ(Diethoxyphosphoryl)ꢀ1ꢀphenylmethylidene]ꢀ1ꢀ(pꢀtoluꢀ
enesulfonyl)hydrazinium hydrochloride was prepared in a yield of
5.34 g (65%), m.p. 94—96 °C. IR (Nujol mulls), ν/cm–1: 2776
(NH+), 1244 (P=O). 31P NMR (THF), δ: 8.62, 7.78. The reꢀ
sulting phosphonate was treated with a solution of Na2CO3 (2.5 g,
0.02 mol) in water (50 mL). The reaction mixture was stirred at
∼20 °C for 2 days until the precipitate was completely dissolved
and an orange oil formed. The reaction mixture was extracted
with Et2O (3×20 mL) until the aqueous layer turned colorless.
The combined organic fractions were dried over Na2SO4, the
solvent was removed in vacuo, and the residue was cooled
to –70 °C. The crystals of compound 2 that formed were rapidly
filtered off and washed with cold diethyl ether. Attempts to
prepare an analytically pure sample of compound 2 by column
chromatography (hexane—Et2O, 6 : 1, as the eluent) failed. The
tively. The experimental electron affinities (EAexp) were calꢀ
red
culated by the approximation formula Ep
= 1.0•EAexp +
red
+ constEAexp = 3.48 + Ep for the Ag/0/01 M AgNO3 system
in MeCN.
The theoretical electron affinities were estimated by the PM3
method from the LUMO energies and by the DFT method as
the differences between the total energies of the molecules and
the corresponding radical anions and were scaled against C60
.
The chemical shifts of the carbon atoms in the 13C NMR spectra
and the thermodynamically stable conformation of adduct 7
were calculated by the GIAO method. The wavefunctions and
geometric parameters were calculated by the density functional
theory (DFT/PBE/TZ2P method) with the exchangeꢀcorꢀ
relation potential19 and a threeꢀcomponent basis using the
PRIRODA 2.10 program.20,21 The shielding constants (σ ) were
m
inverted into the theoretical chemical shifts with respect to Me4Si
yield was 1.8 g (59%), m.p. 22—24 °C. IR (Nujol mulls), ν/cm–1
:
(δ ) according to the equation δ = δ(C60) + σ(C60) – σ .
2080 (N=N), 1256 (P=O). 31P NMR (C6D6), δ: 17.98.
m
m
m
Anhydrous toluene was prepared by prolonged heating
O,OꢀDiethyl αꢀmethyl(methano[1,2][60]fullerenyl)phosꢀ
phonate (3). A mixture of C60 (0.119 g, 0.16 mmol) and O,Oꢀdiꢀ
ethyl αꢀdiazoethylphosphonate (1) (0.037 g, 0.19 mmol) was
heated in refluxing toluene (50 mL) for 4 h. The conversion of
C60 was monitored by HPLC. The solvent was removed in vacuo
and the residue was chromatographed on a column of silica gel.
Unconsumed C60 (toluene as the eluent) was obtained in a yield
of 0.009 g and a mixture of adducts 3 (20 : 1 toluene—Et2O
mixture as the eluent; HPLC, normalꢀphase column, the retenꢀ
tion time was 3.7 min), 5 (2.8), and 6 (2.4) was isolated in a yield
over sodium followed by distillation over LiAlH4. Anhydrous
oꢀdichlorobenzene was prepared by distillation over P2O5.
[60]Fullerene was synthesized at the G. A. Razuvaev Institute of
Organometallic Chemistry of the Russian Academy of Sciences
(Nizhny Novgorod).
The starting phosphonates 1 and 2 were synthesized accordꢀ
ing to procedures analogous to the methods developed for
the synthesis of known diazoorganylphosphonates.22,23 Model
O,Oꢀdiethyl benzylphosphonate 8 was prepared according to a
procedure described earlier.24
of 0.047 g. 31P NMR, δ, (I): 26.00 (0.74), 20.62 (2.45), 20.04
3
O,OꢀDiethyl αꢀdiazoethylphosphonate (1). O,Oꢀdiethyl
acetylphosphonate (5.3 g, 0.029 mol) was rapidly added to
pꢀtoluenesulfonhydrazide (4.82 g, 0.026 mol) dissolved in anꢀ
hydrous methanol (100 mL). The reaction mixture was stirred
for one day, the solvent was removed in vacuo, and the residue
was recrystallized from diethyl ether. The crystals were filtered
off and washed with diethyl ether. N´ꢀ[1ꢀ(Diethoxyphosꢀ
phoryl)ethylidene]ꢀpꢀtoluenesulfonhydrazide was prepared in a
(1.00). 1H NMR (CDCl3), δ: CH3CH2O — 1.36 (t, JH,H
=
3
3
6.8 Hz), 1.43 (t, JH,H = 7.2 Hz), 1.57 (t, JH,H = 6.8 Hz);
CH3C — 2.35 (d, JP,H = 0.5 Hz), 2.44 (d, JP,H = 12.2 Hz),
2
2
2
3
3.33 (d, JP,H = 12.7 Hz); CH3CH2O — 4.16 (dq, JPO,CH
=
=
3
3
3
3.9 Hz, JH,H = 7.2 Hz), 4.41 (dq, JPO,CH = 2.4 Hz, JH,H
6.8 Hz), 4.47 (dq, 3JPO,CH = 6.9 Hz, 3JH,H = 6.8 Hz).
A mixture of adducts 3, 5, and 6 was heated in oꢀDCB
(5 mL) at 140 °C for 4 h. The solvent was removed in vacuo.
Adduct 3 was obtained in a yield of 0.053 g (42%). HPLC
(normalꢀphase column); the retention time was 3.7 min.
Found (%): C, 88.97; H, 1.43; P, 3.45 C66H13O3P. Calcuꢀ
lated (%): C, 89.59; H, 1.47; P, 3.51. MALDIꢀTOF MS (pꢀnitroꢀ
aniline as the matrix), m/z: 884 [M]+, 907 [M + Na]+, 923
[M + K]+. UV, λmax/nm: 260, 329, 424, 492, 683. IR (KBr),
ν/cm–1: 526 (fullerene sphere), 1252 (P=O), 1016, 1044
(P—O—C), 2855, 2925 (C—H). 31P NMR (CDCl3), δ: 20.00.
O,OꢀDiethyl αꢀphenyl(methano[1,2][60]fullerenyl)phosꢀ
phonate (7). A mixture of C60 (0.123 g, 0.17 mmol) and
phosphonate 2 (0.046 g, 0.18 mmol) was heated in boiling toluꢀ
ene (50 mL) for 3 h. The conversion of C60 was monitored by
HPLC. The solvent was removed in vacuo and the residue was
chromatographed on a column of silica gel. Unconsumed C60
(toluene as the eluent) was obtained in a yield of 0.0018 g and
adduct 7 (a 95 : 5 toluene—MeCN mixture as the eluent) was
prepared in a yield of 0.114 g (72%). Found (%): C, 89.42;
H, 1.49; P, 3.35. C71H15O3P. Calculated (%): C, 90.06; H, 1.58;
P, 3.28. MALDIꢀTOF MS (pꢀnitroaniline as the matrix), m/z:
946 [M]+, 969 [M + Na]+, 985 [M + K]+. UV, λmax/nm: 260,
yield of 5.19 g (58%), m.p. 100 °C. IR (Nujol mulls), ν/cm–1
:
2976 (NH), 1228 (P=O). 31P NMR (CDCl3), δ: 7.69, 9.92.
The resulting phosphonate was treated with Na2CO3 (2.0 g,
0.019 mol) in water (30 mL). The reaction mixture was stirred
for 12 h and extracted for 3 days with portions of Et2O (20 mL),
which were separated and changed for new portions every 4 h.
To achieve complete decoloration, the aqueous layer was treated
with CH2Cl2. The combined organic fractions were dried over
MgSO4, the solvent was distilled off, and the residue was disꢀ
tilled in vacuo. Phosphonate 1 was prepared in a yield of 0.9 g
(25%), b.p. 49 °C (0.1 Torr). IR (Nujol mulls), ν/cm–1: 2082
(N=N), 1254 (P=O). 31P NMR (CDCl3), δ: 22.65. Purification
of phosphonate 1 by column chromatography on SiO2 (hexꢀ
ane—Et2O, 3 : 1, as the eluent) led to partial decomposition of
the product due to which satisfactory data of elemental analysis
for this compound were not obtained.
O,OꢀDiethyl αꢀdiazobenzylphosphonate (2). Concentrated
HCl (1 mL) and O,Oꢀdiethyl benzoylphosphonate (5.14 g,
0.02 mol) in THF (5 mL) were added with vigorous stirring to
pꢀtoluenesulfonhydrazide (3.95 g, 0.02 mol) in THF (20 mL)

Modification of C60 by phosphorylated diazo compounds Russ.Chem.Bull., Int.Ed., Vol. 52, No. 8, August, 2003
1757
326, 426, 496, 692. IR (KBr), ν/cm–1: 527, 1187 (P=O), 1399.
31P NMR (CDCl3), δ: 15.42.
10. I. A. Nuretdinov, V. P. Gubskaya, L. Sh. Berezhnaya, A. V.
Il´yasov, and N. M. Azancheev, Izv. Akad. Nauk, Ser. Khim.,
2000, 2046 [Russ. Chem. Bull., Int. Ed., 2000, 49, 2048].
11. I. A. Nuretdinov, V. P. Gubskaya, N. I. Shishikina, G. M.
Fazleeva, L. Sh. Berezhnaya, I. P. Karaseva, F. G.
Sibgatullina, and V. V. Zverev, Izv. Akad. Nauk, Ser. Khim.,
2002, 317 [Russ. Chem. Bull., Int. Ed., 2002, 51, 318].
12. F. Cheng, Y. Murata, and K. Komatsu, Org. Lett., 2002,
4, 2541.
13. V. I. Kovalenko, in Struktura i dinamika molekulyarnykh
sistem [Stuctures and Dynamics of Molecular Systems], Ch. 2,
Izdꢀvo MarGTU, IoshkarꢀOla, 1997, 91 (in Russian).
14. H. Irngartinger and T. Escher, Tetrahedron, 1999, 55, 10753.
15. V. V. Yanilkin, N. V. Nastapova, V. P. Gubskaya, V. I.
Morozov, L. Sh. Berezhnaya, and I. A. Nuretdinov, Izv.
Akad. Nauk, Ser. Khim., 2002, 70 [Russ. Chem. Bull., Int.
Ed., 2002, 51, 72].
We thank V. P. Gubskaya for performing HPLC analyꢀ
sis, valuable advice, and helpful discussion.
This study was financially supported by the Russian
Foundation for Basic Research (Project No. 02ꢀ03ꢀ32932)
and the Ministry of Industry, Science, and Technology of
the Russian Federation (State Agreement No. 4/2003
within the framework of the State Agreement No.
41.002.1.1.405).
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Received March 28, 2003;
in revised form May 19, 2003