Oxidation of triphenylantimony with 4-hydroperoxy-2-hydroxy-3,4,6- triisopropylcyclohexa-2,5-dienone or 3,4,6-triisopropyl-1,2-benzoquinone

Article abstract of DOI:10.1007/s11172-007-0282-y

According to the NMR spectroscopic data, the oxidation of triphenylantimony with 4-hydroperoxy-2-hydroxy-3,4,6-triisopropylcyclohexa-2,5-dienone involves three steps. The first step affords the 2,4,10,12-tetraoxa-3,11- distibatricyclo[11.3.1.1^5,9]octadecatetraene derivative. The latter is rearranged into benzodioxastibolone derivatives followed by the rearrangement into 4,6,7-triisopropyl-2,2,2-triphenyl-1,3,2-benzodioxastibol-5-ol. The transformation of the latter depends on the presence of oxygen and the mode of its dosing.

Full text of DOI:10.1007/s11172-007-0282-y

Russian Chemical Bulletin, International Edition, Vol. 56, No. 9, pp. 1813—1820, September, 2007
1813
Oxidation of triphenylantimony with
4ꢀhydroperoxyꢀ2ꢀhydroxyꢀ3,4,6ꢀtriisopropylcyclohexaꢀ2,5ꢀdienone
or 3,4,6ꢀtriisopropylꢀ1,2ꢀbenzoquinone
G. A. Abakumov, N. N. Vavilina, Yu. A. Kurskii,ꢀ L. G. Abakumova, G. K. Fukin,
V. K. Cherkasov, A. S. Shavyrin, and E. V. Baranov
G. A. Razuvaev Institute of Organometallic Chemistry, Russian Academy of Sciences,
49 ul. Tropinina, 603950 Nizhny Novgorod, Russian Federation.
Fax: +7 (831 2) 62 7497. Eꢀmail: kursk@iomc.ras.ru
According to the NMR spectroscopic data, the oxidation of triphenylantimony with
4ꢀhydroperoxyꢀ2ꢀhydroxyꢀ3,4,6ꢀtriisopropylcyclohexaꢀ2,5ꢀdienone involves three steps. The
first step affords the 2,4,10,12ꢀtetraoxaꢀ3,11ꢀdistibatricyclo[11.3.1.15,9]octadecatetraene deꢀ
rivative. The latter is rearranged into benzodioxastibolone derivatives followed by the rearꢀ
rangement into 4,6,7ꢀtriisopropylꢀ2,2,2ꢀtriphenylꢀ1,3,2ꢀbenzodioxastibolꢀ5ꢀol. The transforꢀ
mation of the latter depends on the presence of oxygen and the mode of its dosing.
Key words: organoantimony compounds, hydroperoxides, quinones, catecholates, oxidaꢀ
tion, oxygen, Xꢀray diffraction study, NMR.
Recently, the unique ability of oꢀamidophenolate1 and
catecholate2 derivatives of antimony(V) to reversibly bind
molecular oxygen has been discovered. This process can
proceed only with antimony(V) complexes, which have a
relatively low ligand oxidation potential.2 In this connecꢀ
tion, new antimony catecholate complexes containing
electronꢀdonating substituents in the aromatic ring of
catecholate are of considerable interest. Among these
compounds are, in particular, adducts of triphenylꢀ
antimony(III) (1) with 4ꢀhydroperoxyꢀ2ꢀhydroxyꢀ3,4,6ꢀ
triisopropylcyclohexaꢀ2,5ꢀdienone (2) and 3,4,6ꢀtriꢀ
isopropylꢀ1,2ꢀbenzoquinone (3) synthesized in the present
study.
Various phenyl derivatives of antimony(V) can be preꢀ
pared by the oxidative method,3 to be more precise, by
the reaction of triphenylantimony(III) with hydroperoxide
and compounds containing labile hydrogen (RC(O)H,
RC(O)OH, etc.). The characteristic feature of dienone 2
is that it contains simultaneously the hydroperoxide and
hydroxy groups.
The reaction pathway of dihydroxybenzenes with
triphenylantimony in the presence of tertꢀbutylhydroꢀ
peroxide depends on the structure of phenol.4 For exꢀ
ample, the reaction of pyrocatechol produces antimony(V)
triphenylcatecholate. The reaction of resorcinol gives
3,3,3,11,11,11ꢀhexaphenylꢀ2,4,10,12ꢀtetraoxaꢀ3,11ꢀdiꢀ
stibatricyclo[11.3.1.15,9]octadecaꢀ1,5,6,8,13,15ꢀhexaene,
in which each antimony atom is bound to the oxygen
atoms of two different resorcinol fragments. The reaction
of hydroquinone affords polymeric triphenylantimony(V)
hydroquinolate. Not only hydroperoxides but also quinoꢀ
nes can serve as oxidants. For example, 1 is quantitaꢀ
tively oxidized with oꢀquinones to the corresponding
antimony(V) catecholates.5
The reaction of 1 with 2 (Scheme 1) under considerꢀ
ation is of interest because molecule 2 contains two
fragments, quinone and hydroperoxide, with potenꢀ
tial oxidative activity. The arrangement of the oxygen
atoms in compound 2 allows the formation of cateꢀ
cholate, dimeric, or polymeric derivatives of antiꢀ
mony(V). Apparently, the first step of the reaction inꢀ
volves the insertion of 1 at the peroxide bond of 2 to
form the unstable intermediate HOSbPh3OR. Earlier, it
has been shown3,4 that this intermediate rapidly reacts
with the hydroxy groups that are present in the system
to give the corresponding derivative of antimony and
water.
The reaction of 1 with 2 was monitored by NMR
spectroscopy. In benzene or toluene, the solution turned
turbid at the instant of mixing. Immediately after mixing,
the 1H NMR spectrum in C6D6 shows the signal of water
present as an emulsion (δ 5.4). In CDCl3, the signal of
water is observed at δ 1.8. In both solvents, the signals of
the starting reagents disappeared within 2—3 min after
mixing of compounds 1 and 2 in a ratio of 1 : 1. Taking
into account the structure of the known reaction
product of 1 with resorcinol4 and the NMR spectra of
the reaction mixture, the reaction most probably proꢀ
duces 1,7,9,15,17,18ꢀhexaisopropylꢀ3,3,3,11,11,11ꢀ
hexaphenylꢀ2,4,10,12ꢀtetraoxaꢀ3,11ꢀdistibatriꢀ
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1750—1757, September, 2007.
1066ꢀ5285/07/5609ꢀ1813 © 2007 Springer Science+Business Media, Inc.

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Russ.Chem.Bull., Int.Ed., Vol. 56, No. 9, September, 2007
Abakumov et al.
Scheme 1
cyclo[11.3.1.15,9]octadecaꢀ5,7,13,15ꢀtetraeneꢀ6,14ꢀdione
(4) (see Scheme 1).
atom of the complex is in a single plane with the oxygen
atoms and the ring of the catecholate ligand. The obꢀ
served distribution of the C—C, C—O, and Sb—O bond
lengths in 6 is characteristic of SbV catecholate comꢀ
plexes.7,8
In CDCl3 or C6D6, catecholate 6 slowly (during
3—4 weeks) decomposes into SbPh3 (1) and 2ꢀhydroxyꢀ
3,4,6ꢀtriisopropylꢀ1,4ꢀbenzoquinone (7). Therefore,
hydroperoxide 2 is finally decomposed with triphenylꢀ
antimony into hydroxyꢀpꢀquinone 7 and water, comꢀ
pound 7 being the only organic product of this transforꢀ
mation of 2.
The starting hydroperoxide 2 contains the chiral cenꢀ
ter, resulting in the nonequivalence of the methyl fragꢀ
ments of the isopropyl groups in the NMR spectra.6 For
example, the difference in the chemical shifts of the meꢀ
thyl protons of the PriC(4)OOH fragment is 0.39 ppm.
Compound 4 is also chiral, the difference in the chemical
shifts for the protons of the diastereotopic methyl groups
of the PriC(1,9) fragments being larger (0.72 ppm). Comꢀ
pound 4 is completely transformed into 4,6,7ꢀtriisopropylꢀ
2,2,2ꢀtriphenylꢀ1,3,2ꢀbenzodioxastibolꢀ5(6H )ꢀone (5)
within 1 h. The structure of compound 5 was determined
1
1
by H and 13C NMR spectroscopy. The H NMR specꢀ
trum of compound 5 shows a doublet at δ 2.82 assigned to
the HC(6) proton. The difference in the chemical shifts
for the protons of the diastereotopic methyl groups of the
PriC(6) fragment is 0.35 ppm. The transformation 4 → 5
proceeds, apparently, as a result of the migration of the
isopropyl groups from positions 1 and 9 to positions 16
and 8, respectively.
C(20)
C(7)
C(6)
C(5)
C(4)
O(1)
Sb
C(7a)
O(3)
After the completion of the induction period (~8 h in
CDCl3), compound 5 undergoes the rearrangement into
4,6,7ꢀtriisopropylꢀ2,2,2ꢀtriphenylꢀ1,3,2ꢀbenzodioxaꢀ
stibolꢀ5ꢀol (6) (see Scheme 1), which is completed in one
day. The structure of catecholate 6 recrystallized from
methanol was established by Xꢀray diffraction (Fig. 1,
Tables 1 and 2). According to the Xꢀray diffraction study,
the antimony atom in molecule 6 is in a distorted octaꢀ
hedral environment. In addition to two oxygen atoms of
the catecholate ligand and three carbon atoms of the pheꢀ
nyl groups, the antimony atom in the crystal structure of 6
is coordinated by the MeOH molecule. The antimony
C(14)
C(8)
O(2)
C(3a)
O(4)
Fig. 1. Molecular structure of catecholate 6. The hydrogen atoms
only at the hydroxy groups are shown. Displacement ellipsoids
are drawn at the 30% probability level.

Oxidation of triphenylantimony complexes
Russ.Chem.Bull., Int.Ed., Vol. 56, No. 9, September, 2007
1815
Table 1. Selected bond lengths in compounds 6, 12, and 13*
Table 2. Selected bond angles (ω) in compounds 6, 12, and 13*
Bond
d/Å
Bond
d/Å
Angle
ω/deg
6
12
6
Sb—O(3)
Sb—O(1)
O(1)—C(7a)
O(3)—C(3a)
O(2)—C(5)
(C—C)**
2.034(1)
2.026(1)
1.370(2)
1.356(2)
1.403(2)
1.392(2)—
1.417(2)
12
2.106(3)
2.490(3)
1.968(6)
1.334(6)
1.227(5)
1.215(5)
1.483(5)
1.462(4)
1.361(1)
1.629(5)
1.368(7)
1.377(5)
2.139(3)
2.543(3)
1.937(6)
1.299(5)
1.239(5)
1.223(4)
C(57)—C(56) 1.342(6)
C(56)—C(55) 1.372(6)
C(55)—C(54) 1.520(7)
C(54)—C(53) 1.333(6)
13
O(3)—Sb—O(1)
Sb—O(3)—C(3a)
Sb—O(1)—C(7a)
79.39(5)
113.21(10)
113.10(10)
12
175.0(4)
121.2(2)
111.3(2)
125.4(3)
113.7(3)
71.0(1)
68.5(1)
13
166.91(6)
65.8(1)
66.2(1)
128.7(1)
117.1(1)
128.0(1)
112.5(1)
Sb(1)—O(4)—Sb(2)
Sb(1)—O(1)—C(1)
Sb(1)—O(2)—C(6)
Sb(2)—O(6)—C(53)
Sb(2)—O(5)—C(52)
O(1)—Sb(1)—O(2)
O(5)—Sb(2)—O(6)
Sb—O(1)
Sb...O(3)
2.109(2)
2.668(3)
1.324(3)
1.231(3)
1.225(3)
1.351(3)
1.468(3)
1.514(3)
1.346(4)
1.482(3)
1.498(3)
2.113(2)
2.619(3)
1.325(3)
1.232(3)
1.231(3)
O(1)—C(1)
O(2)—C(3)
O(3)—C(6)
C(1)—C(2)
C(2)—C(3)
C(3)—C(4)
C(4)—C(5)
C(5)—C(6)
C(6)—C(1)
Sb—O(4)
Sb(1)—O(1)
Sb(1)...O(2)
Sb(1)—O(4)
O(1)—C(1)
O(2)—C(6)
O(3)—C(3)
C(1)—C(6)
C(6)—C(5)
C(5)—C(4)
C(4)—C(3)
C(3)—C(2)
C(1)—C(2)
Sb(2)—O(6)
Sb(2)...O(5)
Sb(2)—O(4)
O(6)—C(53)
O(5)—C(52)
O(7)—C(55)
O(1)—Sb—O(4)
O(1)—Sb—O(3)
O(4)—Sb—O(6)
Sb—O(1)—C(1)
Sb—O(3)—C(6)
Sb—O(4)—C(16)
Sb—O(6)—C(21)
Sb...O(6)
O(4)—C(16)
O(5)—C(18)
O(6)—C(21)
* For complex 13, the geometric characteristics of one indepenꢀ
dent molecule are given.
C(16)—C(17) 1.352(3)
C(17)—C(18) 1.463(3)
C(18)—C(19) 1.514(3)
C(19)—C(20) 1.342(3)
C(20)—C(21) 1.478(3)
C(21)—C(16) 1.492(3)
To confirm the structure of catecholate 6, we perꢀ
formed its acidolysis (Scheme 3). Unexpectedly, the reꢀ
action produced, along with 1,2,4ꢀtrihydroxyꢀ3,5,6ꢀ
triisopropylbenzene (9), isomeric nonaromatic 2ꢀhydroxyꢀ
3,5,6ꢀtriisopropylcyclohexꢀ2ꢀeneꢀ1,4ꢀdione (10), the raꢀ
tio between the products being dependent on the reaction
conditions. In the reaction with HCl in methanol, the
ratio between products 9 and 10 is 2 : 1, whereas the
acidolysis with acetic acid affords predominantly prodꢀ
uct 10.
C(52)—C(53) 1.539(6)
C(52)—C(57) 1.476(7)
* For complex 13, the geometric characteristics of one indepenꢀ
dent molecule are given.
** The catecholate fragment.
The structure of product 7 was established by IR specꢀ
troscopy, H and 13C NMR spectroscopy, and elemental
1
analysis. In addition, hydroxyꢀpꢀquinone 7 was syntheꢀ
sized by the twoꢀstep oxidation of oꢀquinone 3 (Scheme 2).
Scheme 3
Scheme 2
The loss of aromaticity occurs only in the coordinaꢀ
tion sphere of antimony, because product 10 is not generꢀ
ated upon the treatment of compound 9 with HCl/MeOH
or AcOH under an inert atmosphere. Compound 9 is
oxidized to hydroxyꢀpꢀquinone 7 upon the contact with
atmospheric oxygen in an acidic medium. Unlike triol 9,
its isomer 10 is stable to oxidation both in the crystalline
state and in solution. The structure of compound 10 was
determined by oneꢀdimensional and twoꢀdimensional

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Russ.Chem.Bull., Int.Ed., Vol. 56, No. 9, September, 2007
Abakumov et al.
NMR spectroscopy. The presence of intense crossꢀpeaks
in the twoꢀdimensional NOESY spectrum with dipoleꢀ
dipole coupling between the HC(5) and HC(6) protons
is indicative of their spatial proximity. The vicinal
spinꢀspin coupling constants between the protons
H—C(5)—C(6)—H is only 0.9 Hz. Consequently, the
dihedral angle between these protons is close to 90°, which
is possible only if these atoms are in equatorial positions.
Consequently, the isopropyl groups bound to the C(5)
and C(6) atoms of the cyclohexene ring are in axial poꢀ
sitions.
major oxidation product. In both cases, the oxidation is
irreversible.
Scheme 5
In solution, quinone 3 oxidizes triphenylantimony imꢀ
mediately after mixing (Scheme 4). The oxidation affords
4,5,7ꢀtriisopropylꢀ2,2,2ꢀtriphenylꢀ1,3,2ꢀbenzodioxaꢀ
stibole (11) as the only product. Compound 11 proved to
be stable to atmospheric oxygen both in solution and in
the crystalline state.
Scheme 4
i. Deficiency of O2. ii. Excess of O2.
The structures of complexes 12 and 13 were estabꢀ
lished by Xꢀray diffraction. Product 12 is the dinuclear
oxyꢀparaꢀquinoid complex, in which the antimony atoms
are oxygenꢀbridged (Fig. 2, see Tables 1 and 2). Each
antimony atom is in a distorted octahedral environment
and is bound to three types of oxygen atoms, which is
reflected on the Sb—O bond lengths. The rings of the
oxyꢀpꢀquinone ligands and the antimony and oxygen
atoms are approximately in a single plane (the
O(1)Sb(1)Sb(2)O(6) pseudotorsion angle is 171.1(3)°).
The oxyꢀpꢀquinone fragments are in trans positions with
respect to the virtually linear SbOSb triad (Sb—O—Sb,
175.0(4)°). The Sb(1)...O(2) and Sb(2)...O(5) distances
(2.490(3) and 2.543(3) Å, respectively) are substantially
smaller than the sum of the van der Waals radii of these
Unlike compound 11, catecholate 6 is readily oxiꢀ
dized in solution with atmospheric oxygen (Scheme 5).
The slow dosage of oxygen leads to the predominant forꢀ
mation of 1,3ꢀbis[(20´,4´,5´ꢀtriisopropylꢀ3´,6´ꢀdioxoꢀ
cyclohexaꢀ1´,4´ꢀdienꢀ1´ꢀyl)oxy]ꢀ1,1,1,3,3,3ꢀhexaphenylꢀ
1,3ꢀdistiboxane (12). If a solution is rapidly saturated with
oxygen, bis[(2,4,5ꢀtriisopropylꢀ3,6ꢀdioxocyclohexaꢀ1,4ꢀ
dienꢀ1ꢀyl)oxy](triphenyl)stiborane (13) is formed as the
O(1)
C(57)
C(2)
O(5)
C(1)
O(3)
C(52)
Sb(1)
C(56)
O(4)
C(55)
O(2)
C(3)
C(4)
Sb(2)
C(6)
C(54)
C(53)
O(7)
C(5)
O(6)
Fig. 2. Molecular structure of product 12. Displacement ellipsoids are drawn at the 30% probability level.

Oxidation of triphenylantimony complexes
Russ.Chem.Bull., Int.Ed., Vol. 56, No. 9, September, 2007
1817
C(37)
O(4)
C(43)
C(17)
O(1)
Sb
C(16)
C(18)
O(5)
C(2)
C(3)
C(1)
O(6)
C(31)
C(21)
O(2)
C(5)
C(6)
C(19)
O(3)
C(20)
C(4)
Fig. 3. Molecular structure of 13. Displacement ellipsoids are drawn at the 30% probability level.
atoms (3.7 Å). This is evidence of the presence of the
coordination bond between the antimony atoms and the
carbonyl oxygen atoms of the ligands.
To summarize, we synthesized two new triphenylꢀ
antimony catecholates containing three isopropyl groups
in the aromatic ring. Triphenylantimony triisopropylꢀ
catecholate does not react with atmospheric oxygen. The
catecholate ligand containing an additional hydroxy group
is unstable to oxidation, resulting in the irreversible oxiꢀ
dation of this catecholate with molecular oxygen. This is
the difference between this compound and the already
known antimony(V) catecholate derivatives, which reversꢀ
ibly bind molecular oxygen to form endoꢀperoxides.
Unlike complex 12, complex 13 is mononuclear. In
spite of the fact that the coordination number of the antiꢀ
mony atom is formally 7, its configuration can be considꢀ
ered as a distorted trigonalꢀbipyramidal (Fig. 3, see
Tables 1 and 2). The equatorial positions are occupied by
the Ph substituents. The oxyꢀpꢀquinone groups are in
axial positions. The oxyꢀpꢀquinone rings and the antiꢀ
mony and oxygen atoms in complex 13, like those in 12,
are approximately in a single plane. The equatorial
Ph—Sb—Ph angle from the side of the carbonyl oxygen
atoms is substantially larger than the other Ph—Sb—Ph
angles, which confirms the presence of interactions beꢀ
tween the antimony atom and the carbonyl oxygen atoms
of the oxyꢀpꢀquinone ligands. The Sb...O(3) and Sb...O(6)
distances are 2.668(3) and 2.619(3) Å, respectively, and
they are substantially longer than the corresponding disꢀ
tances in complex 12, whereas the Sb—O(1) and Sb—O(4)
bond distances (2.109(2) and 2.113(2) Å, respectively)
are comparable with the corresponding distances in comꢀ
pound 12.
The distribution of the C—C, C—O, and Sb—O bond
lengths in compounds 12 and 13 (see Tables 1 and 2)
differs substantially from that observed in catecholate 6
and is characteristic of quinoid structures. This fact conꢀ
firms the oxyꢀparaꢀquinone structure of the ligands in
complexes 12 and 13. After the hydrolysis of compounds
12 and 13 with an HCl solution in methanol, hydroxyꢀ
pꢀquinone 7 was isolated. The structure of compound 13
was additionally confirmed by its synthesis from
Ph3SbCl2 and 7.
Experimental
Oneꢀdimensional and twoꢀdimensional NMR spectra were
recorded on a Bruker Avance DPXꢀ200 instrument at 200 MHz
for 1H and at 50 MHz for 13C with Me4Si as the internal standard.
The spectra were processed with the use of the XwinNMR 2.1
program. The IR spectra were measured on a Specord Mꢀ80
instrument in Nujol mulls. Xꢀray diffraction data were collected
on an automated Smart APEX diffractometer. All structures
were solved by direct methods and refined by the leastꢀsquares
method based on F2 with anisotropic displacement paramꢀ
hkl
eters for all nonhydrogen atoms. All H atoms in compound 12
were positioned geometrically and refined using a riding model.
In compounds 6 and 13, some H atoms were located in differꢀ
ence Fourier maps and refined isotropically. All calculations
were carried out with the use of the SHELXTL v. 6.10 proꢀ
gram package.9 Absorption corrections were applied using the
SADABS program.10 Principal crystallographic characteristics
and the Xꢀray diffraction data collection and refinement statisꢀ
tics are given in Table 3.
Triphenylantimony (1) was synthesized according to a known
procedure11 and purified by recrystallization from methanol,
m.p. 52—53 °C. 4ꢀHydroperoxyꢀ2ꢀhydroxyꢀ3,4,6ꢀtriisopropylꢀ
cyclohexaꢀ2,5ꢀdienone (2) was synthesized by oxidation of a soꢀ

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Russ.Chem.Bull., Int.Ed., Vol. 56, No. 9, September, 2007
Abakumov et al.
Table 3. Principal crystallographic characteristics and the Xꢀray data collection and refinement
statistics for compounds 6, 12, and 13
Parameter
6
12
13
Molecular formula
Molecular weight
C34H41O4Sb
635.42
C66H72O7Sb2
1220.74
C48H57O6Sb
851.69
Temperature/K
Space group
a/Å
b/Å
c/Å
100(2)
293(2)
P1
100(2)
P2(1)/c
9.2210(8)
10.4354(9)
31.897(3)
90
97.073(2)
90
3046.0(5)
4
P–1
10.6721(6)
11.0913(7)
14.5105(9)
107.195(1)
108.147(1)
99.042(1)
1499.3(26)
1
12.3165(6)
18.529(1)
29.343(2)
93.286(1)
100.856(1)
101.951(1)
6401.8(6)
6
α/deg
β/deg
γ/deg
V/Å3
Z
ρ
calc/g cm–3
1.386
0.941
1312
1.352
0.952
626
1.325
0.694
2664
µ/mm–1
F(000)
θ
max/deg
29.63
26.0
24.50
hkl Ranges
–12 ≤ h ≤ 12
–11 ≤ k ≤ 14
–41 ≤ l ≤ 43
22259/8359
(0.0234)
5
–13 ≤ h ≤ 13
–13 ≤ k ≤ 13
–17 ≤ l ≤ 17
12947/11108
(0.0187)
69
–14 ≤ h ≤ 14
–21 ≤ k ≤ 21
–28 ≤ l ≤ 34
34158/21261
(0.0224)
0
Number of measured/inꢀ
dependent reflections (Rint
Number of constraints
Number of variables
GOOF (F 2)
)
534
1.138
629
1.055
2082
1.072
R1/wR2 (I > 2σ(I ))
0.0335/0.0758
0.0405/0.0785
?
0.0467/0.1100
0.0607/0.1158
0.51(3)
0.0422/0.0948
0.0539/0.0994
?
R1/wR2 (based on all reflections)
Absolute structure parameter
Residual electron density
peaks, max/min, e Å–3
0.791/–0.662
1.116/–0.411
1.489/–0.502
lution of 3,4,6ꢀtriisopropylpyrocatechol in hexane with atmoꢀ
spheric oxygen.6 3,4,6ꢀTriisopropylꢀ1,2ꢀbenzoquinone (3) was
prepared according to a procedure described earlier.6
the reaction of 1 with 2 within 1 h after the beginning of the
reaction. 1H NMR (CDCl3), δ: 0.72 and 1.07 (both d, 3 H each,
C(6)(CH3)CHCH3, J = 7.0 Hz); 1.14 and 1.21 (both d, 3 H each,
C(7)(CH3)CHCH3, J = 7.0 Hz); 1.22 and 1.26 (both d,
3 H each, C(4)(CH3)CHCH3, J = 7.0 Hz); 2.12 (sept.d, 1 H,
C(6)HCHMe2, J = 7.0 Hz, J = 2.8 Hz); 2.44 (sept, 1 H,
C(4)CHMe2, J = 7.0 Hz); 2.82 (d, 1 H, HC(6), J = 2.8 Hz);
3.21 (sept, 1 H, C(7)CHMe2, J = 7.0 Hz); 7.42—7.58 and
7.72—7.77 (both m, 9 H, 6 H, Sb(C6H5)3). 13C NMR DEPT
(CDCl3), δ: 17.0, 20.26, 20.41, 20.9, and 21.4 (all CH3); 24.0,
31.5, and 32.8 (all CHMe2); 58.6 (C(6)H); 117.1; 129.0, 129.4,
137.7 (C(3a), C(4), C(7), C(7a)); 129.6 (oꢀCH Ph); 131.8
(pꢀCH Ph); 135.2 (mꢀCH Ph); 136.4 (CSb Ph); 200.1 (C(5)=O).
The assignment of the signals for the protons of the isopropyl
groups was made based on the 1Hꢀ{1H} NMR spectroscopic data.
4,6,7ꢀTriisopropylꢀ2,2,2ꢀtriphenylꢀ1,3,2ꢀbenzodioxastibolꢀ
5ꢀol (6). A solution of hydroperoxide 2 (0.27 g, 1 mmol) in
toluene (20 mL) was slowly added to a solution of SbPh3
(0.35 g, 1 mmol) in toluene (20 mL) at ~20 °C in vacuo
(10–3 Torr). The colorless components turned brightꢀyellow
upon mixing. The reaction mixture was kept at 20 °C for 1 h,
during which the color of the solution changed to brightꢀorange.
Then toluene together with water that was liberated in the course
of the reaction were removed in vacuo, and the orangeꢀyellow
oily precipitate was dissolved in hexane and kept in an evacuated
tube at 15 °C for 10—15 h. Paleꢀorange crystals of catecholate 6,
Reaction of Ph3Sb (1) with hydroperoxide 2. Hydroperoxide
2 (0.0135 g, 0.05 mmol) and Ph3Sb (1) (0.0175 g, 0.05 mmol)
were placed in an NMR tube. Then CDCl3 or C6D6 (0.5 mL)
was frozen under vacuum into the NMR tube, and the tube was
sealed and kept at 77 K. The progress of the reaction was moniꢀ
tored by NMR spectroscopy. Before the measurements, the
NMR tube was heated to ~20 °C, and the solution was stirred.
1,7,9,15,17,18ꢀHexaisopropylꢀ3,3,3,11,11,11ꢀhexaphenylꢀ
2,4,10,12ꢀtetraoxaꢀ3,11ꢀdistibatricyclo[11.3.1.15,9]octadecaꢀ
5,7,13,15ꢀtetraeneꢀ6,14ꢀdione (4) was identified in an NMR
tube within the first 5—10 min after the beginning of the reacꢀ
1
tion of 1 with 2. H NMR (CDCl3), δ: 0.12 and 0.84 (both d,
6 H each, (CH3)CHCH3 at C(1) and C(9), J = 6.8 Hz); 0.90 (d,
6 H, CHCH3, J = 6.8 Hz); 0.99—1.41 (three d, 6 H each,
CHCH3); 2.06 (sept, 2 H, CHMe2 at C(1) and C(9), J = 6.8 Hz);
2.74 and 2.78 (both sept, 2 H each, CHMe2 at C(7), C(15), and
C(17), C(18)); 6.49 (s, 2 H, C(8)CH, C(16)CH); 7.42—7.58
and 7.72—7.77 (both m, 18 H, 12 H, Sb(C6H5)3). The assignꢀ
ment of the signals for the protons of the isopropyl groups at
1
C(1) and C(9) was made based on the Hꢀ{1H} NMR spectroꢀ
scopic data.
4,6,7ꢀTriisopropylꢀ2,2,2ꢀtriphenylꢀ1,3,2ꢀbenzodioxastibolꢀ
5(6H )ꢀone (5) was identified in an NMR tube in the course of

Oxidation of triphenylantimony complexes
Russ.Chem.Bull., Int.Ed., Vol. 56, No. 9, September, 2007
1819
which was stable only in the absence of traces of oxygen, were
obtained in a yield of 0.41 g (70%). Found (%): C, 65.53; H, 6.37;
Sb, 19.56. C33H37O3Sb. Calculated (%): C, 65.69; H, 6.18;
Sb, 20.18. IR, ν/cm–1: 3630 (OH hindered); 1160 (C(Ar)O);
with vigorous shaking until the reaction mixture became colorꢀ
less. All operations were carried out in vacuo. White crystals of
reduced product 9 gradually precipitated from an aqueous
methanolic solution. After 0.5 h, triol 9 was filtered off, washed
three times with water, and dried in vacuo. The yield of comꢀ
pound 9 was 0.21 g (80%), m.p. 104—106 °C (from hexane).
Found (%): C, 71.58; H, 9.62. C15H24O3. Calculated (%):
C, 71.43; H, 9.52. IR, ν/cm–1: 3630 (OH free); 3450, 3425
(OH intermolecular interactions). 1H NMR (CDCl3), δ:
1.32—1.42 (three d, 6 H each, CH(CH3)2); 3.35 (sept, 1 H, J =
7.0 Hz, CHMe2); 3.30—3.56 (br.m, 2 H, 2 CHMe2); 4.44, 4.53,
and 5.3 (all s, 1 H each, OH).
1
690, 730 (Ph); 450, 460 (SbC). H NMR (CDCl3), δ: 1.37 (d,
6 H, CHMe2, J = 7.0 Hz); 1.43 and 1.44 (both d, 6 H each,
CHMe2, J = 7.0 Hz); 3.38 (sept, 1 H, CHMe2, J = 7.0 Hz); 3.4
and 3.39 (both br.m, 1 H each, CHMe2); 4.2 (s, 1 H, OH); 7.5
(m, 9 H, Ph3Sb); 7.8 (m, 6 H, Ph3Sb). An analogous NMR
spectrum was recorded in a tube in the course of the reaction
of 1 with 2 within 1 day after the beginning of the reaction.
13C NMR DEPT (CDCl3), δ: 21.4, 22.1 (CHMe2); 25.9,
27.4 (br) and 28.3 (CHMe2); 129.1 (mꢀCH); 131.0 (pꢀCH);
135.2 (oꢀCH); 138.2 (CSb). The signals for the carbon atoms of
the catecholate ligand were not detected because of their strong
broadening. The results of the Xꢀray diffraction study are preꢀ
sented in Tables 1 and 2. The oxygen atom of the coordiꢀ
nated MeOH molecule is disordered over two positions; the
Sb...O(H)Me distances are 2.600(3) and 2.902(3) Å.
2ꢀHydroxyꢀ4,4ꢀdimethoxyꢀ3,5,6ꢀtriisopropylcycloxehaꢀ2,5ꢀ
dienꢀ1ꢀone (8). Sodium hydroxide (0.1 g) and PbO2 (1 g) were
added to a solution of quinone 3 (0.50 g, 2.1 mmol) in methanol
(30 mL). The reaction mixture was magnetically stirred for 1 h.
The redꢀbrown color of oꢀquinone disappeared, and the solution
turned orange. The liquid phase was separated from the inorꢀ
ganic solid phase and acidified with dilute AcOH. The pale
compound that precipitated was filtered off, washed with an
aqueous methanolic solution, dried in air, and recrystallized
from hexane. White crystals of compound 8 were obtained in a
yield of 0.41 g (65%), m.p. 142 °C. Found (%): C, 68.72; H, 9.46.
C17H28O4. Calculated (%): C, 68.89; H, 9.52. IR, ν/cm–1: 3325
(OH intermolecular interactions); 1650 (C=O); 1050 (OMe).
1H NMR (CDCl3), δ: 1.25—1.34 (three d, 6 H each, CH(CH3)2);
2.72 (sept, 1 H, CHMe2, J = 7.0 Hz); 3.05—3.25 (both sept,
1 H each, CHMe2); 3.11 (s, 6 H, OMe); 6.84 (s, 1 H, OH).
13C NMR (CDCl3), δ: 19.8, 20.7, and 21.3 (all CHMe2); 25.6,
26.6, and 28.9 (all CHMe2); 51.9 (OMe); 102.3 (C(OMe)2);
128.1 (C(3)); 143.2, 146.1 (C(2), C(6)) 160.8 (C(5));
182.0 (C=O).
2ꢀHydroxyꢀ3,5,6ꢀtriisopropylꢀ1,4ꢀbenzoquinone (7). Comꢀ
pound 8 (0.30 g, 1 mmol) was dissolved in glacial acetic acid
(15 mL). Then concentrated HNO3 (0.5 mL) was added. The
solution immediately turned red, and then the color of the soluꢀ
tion gradually changed to paleꢀorange. After 30 min, the reacꢀ
tion solution was diluted with an equal amount of water, and the
product was twice extracted with diethyl ether. The ethereal
extract was washed with water and dried over CaCl2. Then diꢀ
ethyl ether was removed. Brightꢀorange crystals of compound 7
were obtained in a yield of 0.24 g (96%), m.p. 45—46 °C.
Found (%): C, 72.13; H, 9.06. C15H22O3. Calculated (%):
C, 71.97; H, 8.86. IR, ν/cm–1: 3380 (OH); 1650, 1640 (C=O);
1270 (C=CO). 1H NMR (CDCl3), δ: 1.22, 1.27, and 1.28 (all d,
6 H each, CH(CH3)2, J = 7.0 Hz); 3.15—3.35 (all sept, 1 H each,
CHMe2, J = 7.0 Hz); 7.12 (s, OH). 13C NMR (CDCl3), δ: 19.9,
20.8, and 21.3 (all CHMe2); 24.3, 27.7, and 27.9 (all CHMe2);
124.9 (C(3)); 143.8, 149.7, 151.7 (C); 184.4 and 187.5
(both C=O).
2ꢀHydroxyꢀ3,5,6ꢀtriisopropylcyclohexꢀ2ꢀeneꢀ1,4ꢀdione (10).
Compound 6 (0.30 g, 0.5 mmol) was dissolved in glacial acetic
acid (15 mL) in vacuo. The paleꢀyellow solution was kept at
room temperature for 15 min. Then acetic acid was removed
in vacuo, and hexane was added to the solid residue. Triꢀ
phenylantimony diacetate insoluble in hexane was separated,
and the hexane solution was cooled to –15 °C. After 12 h, pale
crystals of compound 10 were isolated in a yield of 0.08 g (63%),
m.p. 98—100 °C. Found (%): C, 71.65; H, 9.44. C15H24O3.
Calculated (%): C, 71.43; H, 9.52. IR, ν/cm–1: 3250 (OH);
1690, 1670 (C=O); 1630 (C=C). 1H NMR (CDCl3), δ: 0.88 and
0.90 (both d, 3 H each, C(5)(Me)CHCH3, J = 6.7 Hz); 0.90 and
0.93 (both d, 3 H each, C(6)(Me)CHCH3, J = 6.7 Hz); 1.22 (d,
6 H, C(3)CH(CH3)2, J = 7.1 Hz); 1.79 (oct, 1 H, HC(6)CHMe2,
J = 6.8 Hz); 1.92 (oct, 1 H, HC(5)CHMe2, J = 6.7 Hz); 2.55
(dd, 1 H, (6)CH, J = 7.4 Hz, J = 0.9 Hz); 2.67 (dd, 1 H, (5)CH,
J = 6.5 Hz, J = 0.9 Hz); 3.19 (sept, 1 H, C(3)CHMe2, J =
7.1 Hz); 7.09 (br.s, 1 H, C(2)OH). 13C NMR (CDCl3), δ: 19.3,
19.9 (C(3)(Me)CHCH3); 20.4, 20.6, 21.0, 21.2 (MeCHCH3 at
C(5), C(6)); 25.0 (C(3)CHMe2); 33.4 (C(6)CHMe2); 33.7
(C(5)CHMe2); 54.5 (C(5)H); 58.2 (C(6)H); 131.3 (C(3)); 153.8
(C(2)OH); 198.2 (C(1)=O); 200.6 (C(4)=O). The assignment
1
of the signals in the H and 13C NMR spectra was made based
on the data from twoꢀdimensional NMR spectroscopy (protonꢀ
proton (COSY), protonꢀcarbon (CHCORR), and protonꢀproꢀ
ton dipole (NOESY) scalar coupling correlations.
4,5,7ꢀTriisopropylꢀ2,2,2ꢀtriphenylꢀ1,3,2ꢀbenzodioxastibole
(11). A solution of quinone 3 (0.23 g, 1 mmol) in hexane (20 mL)
was added to a solution of Ph3Sb (0.35 g, 1 mmol) in hexane
(30 mL). The darkꢀred color of the quinone immediately disapꢀ
peared, and the reaction mixture turned yellowꢀorange. After
cooling, yellowꢀorange crystals precipitated. The yield of
catecholate 11 was 0.43 g (74%), m.p. 137—139 °C. Found (%):
C, 68.14; H, 6.34; Sb, 20.20. C33H37O2Sb. Calculated (%):
C, 67.47; H, 6.34; Sb, 20.73. IR, ν/cm–1: 690, 740 (Ph); 460,
1
495 (Sb—C). H NMR (CDCl3), δ: 1.23, 1.32, and 1.44 (all d,
6 H each, CH(CH3)2); 3.18, 3.3, and 3.34 (all sept, 1 H each,
CHMe2); 6.51 (s, 1 H, (6)CH); 7.36—7.56, 7.75—7.87 (m, 15 H,
Sb(C6H5)3). 13C NMR DEPT (CDCl3), δ: 21.3, 22.5, 24.5
(CH(CH3)2); 27.3, 29.22, 29.24 (CHMe2); 111.1 ((6)CH); 126.9,
129.2, 134.5, 142.5, 145.1 (C(1)—C(5)); 129.0 (mꢀCH); 131.0
(pꢀCH); 135.3 (oꢀCH); 138.2 (CSb).
1,3ꢀBis[(2´,4´,5´ꢀtriisopropylꢀ3´,6´ꢀdioxocyclohexaꢀ1´,4´ꢀ
dienꢀ1´ꢀyl)oxy]ꢀ1,1,1,3,3,3ꢀhexaphenylꢀ1,3ꢀdistiboxane (12).
A solution of catecholate 6 (0.22 g, 0.5 mmol) in hexane (30 mL)
was kept at room temperature for 3 days in an evacuated tube
connected to a rubber pipe fastened with a clamp. Darkꢀred
crystals of the oxidation product were formed on the bottom and
walls at the interface with the hexane solution. The oxidation
1,2,4ꢀTrihydroxyꢀ3,5,6ꢀtriisopropylbenzene (9). Comꢀ
pound 7 (0.252 g, 1 mmol) was dissolved in MeOH (20 mL)
containing NaOH (0.1 g). The solution turned darkꢀviolet. Then
an aqueous Na2S2O4 solution was added to the reaction solution

1820
Russ.Chem.Bull., Int.Ed., Vol. 56, No. 9, September, 2007
Abakumov et al.
occurs due to the presence of oxygen that slowly diffuses through
the rubber pipe. Crystals of compound 12 were separated in air
and washed three times with cold toluene. The yield was 0.09 g
(39%). In the solid state, the product is stable in air. Found (%):
C, 66.12; H, 6.42; Sb, 19.65. C66H72O7Sb2⋅C6H14. Calcuꢀ
lated (%): C, 65.18; H, 6.63; Sb, 18.63. IR, ν/cm–1: 1625, 1580
(C=O, C=C); 1270 (C=C—O); 690, 760 (Ph); 470, 445 (Sb—C).
1H NMR (CDCl3), δ: 0.93, 1.12, and 1.13 (all d, 12 H each,
2 CH(CH3)2); 2.90 (sept, 2 H, 2 CHMe2); 3.02—3.29 (both m,
2 H each, 2 CHMe2); 7.09—7.24 and 7.64—7.69 (both m, 18 H,
12 H, 2 Sb(C6H5)3). According to the Xꢀray diffraction study
(see Fig. 2, Tables 1 and 2), the Ph groups occupying the axial
positions adopt a nearly eclipsed conformation. In the quinoid
ligands of complex 12, the electron density is delocalized over
the C(1)C(2)C(3) and C(55)C(56)C(57) fragments containꢀ
ing both formally single and double bonds. The C(2)—C(3)
(1.368(7) Å) and C(55)—C(56) (1.372(6) Å) bonds are similar
in length to the C(1)=C(2) (1.377(5) Å) and C(56)=C(57)
(1.342(6) Å) double bonds.
Grants of the President of the Russian Federation (Proꢀ
gram for State Support of Leading Scientific Schools of
the Russian Federation, Grants NShꢀ1649.2003.3 and
8017.2006.3).
References
1. V. K. Cherkasov, G. A. Abakumov, E. V. Grunova, A. I.
Poddel´sky, G. K. Fukin, E. V. Baranov, Yu. A. Kurskii, and
L. G. Abakumova, Chem. Eur. J., 2006, 12, 3916.
2. G. A. Abakumov, V. K. Cherkasov, E. V. Grunova, A. I.
Poddel´skii, L. G. Abakumova, Yu. A. Kurskii, G. K. Fukin,
and E. V. Baranov, Dokl. Akad. Nauk, 2005, 405, 199 [Dokl.
Chem., 2005, 405, 222 (Engl. Transl.)].
3. G. A. Razuvaev, T. G. Brilkina, E. V. Krasilnikova, T. I.
Zinovieva, and A. I. Filimonov, J. Organometal. Chem., 1972,
40, 151.
4. V. A. Dodonov, A. Yu. Fedorov, R. I. Usyatinskii, S. N.
Zaburdyaeva, and A. V. Gushchin, Izv. Akad. Nauk, Ser.
Khim., 1995, 748 [Russ. Chem. Bull., 1995, 44, 730 (Engl.
Transl.)].
5. V. K. Cherkasov, E. V. Grunova, A. I. Poddel`sky, G. K.
Fukin, Yu. A. Kurskii, L. G. Abakumova, and G. A.
Abakumov, J. Organometall. Chem., 2005, 690, 1273.
6. G. A. Abakumov, N. N. Vavilina, Yu. A. Kurskii, V. I.
Nevodchikov, V. K. Cherkasov, and A. S. Shavyrin, Izv.
Akad. Nauk, Ser. Khim., 2003, 1751 [Russ. Chem. Bull., Int.
Ed., 2003, 52, 1847].
7. G. K. Fukin, L. N. Zakharov, G. A. Domrachev, A. Yu.
Fedorov, S. N. Zaburdyaeva, and V. A. Dodonov, Izv. Akad.
Nauk, Ser. Khim., 1999, 1744 [Russ. Chem. Bull., 1999, 48,
1722 (Engl. Transl.)]
8. M. Hall and D. B. Sowerby, J. Am. Chem. Soc., 1980,
102, 628.
9. G. M. Sheldrick, SHELXTL v. 6. 12, Structure Determinaꢀ
tion Software Suite, Bruker AXS, Madison, Wisconsin,
USA, 2000.
10. G. M. Sheldrick, SADABS v. 2.01, Bruker/Siemens Area
Detector Absorption Correction Program, Bruker AXS,
Madison, Wisconsin, USA, 1998.
Bis[(2,4,5ꢀtriisopropylꢀ3,6ꢀdioxocyclohexaꢀ1,4ꢀdienꢀ1ꢀ
yl)oxy](triphenyl)stiborane (13). A. A solution of catecholate 6 in
toluene was kept in air. The color of the solution rapidly changed
from yellow to brightꢀred. After 10 h, brightꢀred crystals of 13
were isolated from the solution.
B. A solution of compound 7 (0.251 g, 1 mmol) in toluene
(10 mL) was added to a solution of Ph3SbCl2 (0.212 g, 0.5 mmol)
and Et3N (0.14 mL, 1 mmol) in toluene (15 mL) in vacuo.
A white precipitate of Et3N•HCl immediately formed, and the
solution turned brightꢀred. The reaction mixture was kept at
~20 °C for 3 h. Then Et3N•HCl was filtered off, and toluene
was replaced with hexane. After cooling, brightꢀred crystals of
13 precipitated in a yield of 0.32 g (75%). Found (%): C, 67.63;
H, 6.72; Sb, 13.54. C48H57O6Sb. Calculated (%): C, 67.69;
H, 6.75; Sb, 14.29. IR (Nujol mulls), ν/cm–1: 1635, 1625, 1580
(C=O, C=C); 1260 (C=CO); 730, 690 (Ph); 465, 450 (SbC).
1H NMR (CDCl3), δ: 1.06, 1.09, and 1.22 (all d, 12 H each,
2 CH(CH3)2); 3.03, 3.19, and 3.3 (all sept, 2 H each, 2 CHMe2);
7.27—7.39, 7.48—7.58 (m, 15 H, Sb(C6H5)3). 13C NMR DEPT
(CDCl3), δ: 19.8, 20.5, 21.5 (CH(CH3)2); 23.8—28.5 (CHMe2);
126.4 (C(2)); 141.1, 143.3, 151.1, 155.1 (CSb, C(1), C(4), C(5));
128.6 (mꢀCH); 129.8 (pꢀCH); 133.2 (oꢀCH); 187.2 and 188.0
(both C=O). According to the Xꢀray diffraction study of the
crystals of 13, there are three independent molecules havꢀ
ing similar geometric parameters per asymmetric unit. The
geometric characteristics of only one molecule are given in
Tables 1 and 2.
11. K. A. Kocheshkov, A. P. Skoldinov, and N. N. Zemlyanskii,
Metody elementoorganicheskoi khimii. Sur´ma. Vismut
[Methods of Heteroorganic Chemistry. Antimony. Bismuth],
Nauka, Moscow, 1976, 484 pp. (in Russian).
This study was financially supported by the Russian
Foundation for Basic Research (Project Nos 04ꢀ03ꢀ32409,
06ꢀ03ꢀ32728ꢀa, and 04ꢀ03ꢀ32413) and the Council on
Received November 1, 2006;
in revised form January 26, 2007