The synthesis of functional derivatives of the [1-CB9H 10]- anion by Brellochs reaction

Article abstract of DOI:10.1016/j.jorganchem.2005.01.052

Reactions of decaborane with various aldehydes in alkaline media were studied. The reactions with HCOH and 2-MeOC₆H₄CHO give the corresponding arachno-carboranes [6-R-arachno-CB₉H ₁₃]^- (R = H, C₆H₄-2-OMe), whereas the reactions with C₆H₅CHO, 4-BrC₆H ₄CHO, 4-MeCONHC₆H₄CHO, and 2-SC ₄H₃CHO result in the nido-carboranes [6-R-nido-CB ₉H₁₁]^- (R = C₆H₅, C ₆H₄-4-Br, C₆H₄-4-NHCOMe, 2-SC ₄H₃). Both the arachno- and nido-carboranes can be easily oxidized with elemental iodine in an alkaline aqueous solution giving the corresponding closo-derivatives [2-R-closo-2-CB₉H₉] ^-. These closo-2-isomers, under heating in solution, undergo rearrangement to more thermodynamically favorable closo-1-isomers [1-R-closo-1-CB₉H₉]^-. The structure of (Bu ₄N)[1-(4-BrC₆H₄)-1-CB₉H ₉] was determined using single crystal X-ray diffraction.

Full text of DOI:10.1016/j.jorganchem.2005.01.052

Journal of Organometallic Chemistry 690 (2005) 2790–2795
www.elsevier.com/locate/jorganchem
The synthesis of functional derivatives of the [1-CB9H10]À anion
by Brellochs reaction q
a,
a
a
Igor B. Sivaev *, Zoya A. Starikova , Pavel V. Petrovskii ,
a
Vladimir I. Bregadze , Stefan Sjoberg
b
¨
a
A.N. Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences, Vavilov Str. 28, 119991, Moscow, Russia
b
Department of Chemistry, Organic Chemistry, Uppsala University, Box 599, SEE-75124, Uppsala, Sweden
Received 12 October 2004; accepted 14 January 2005
Available online 14 March 2005
Abstract
Reactions of decaborane with various aldehydes in alkaline media were studied. The reactions with HCOH and 2-MeOC6H4-
CHO give the corresponding arachno-carboranes [6-R-arachno-CB9H13]À (R = H, C6H4-2-OMe), whereas the reactions with
C6H5CHO, 4-BrC6H4CHO, 4-MeCONHC6H4CHO, and 2-SC4H3CHO result in the nido-carboranes [6-R-nido-CB9H11]À
(R = C6H5, C6H4-4-Br, C6H4-4-NHCOMe, 2-SC4H3). Both the arachno- and nido-carboranes can be easily oxidized with elemental
iodine in an alkaline aqueous solution giving the corresponding closo-derivatives [2-R-closo-2-CB9H9]À. These closo-2-isomers,
under heating in solution, undergo rearrangement to more thermodynamically favorable closo-1-isomers [1-R-closo-1-CB9H9]À.
The structure of (Bu4N)[1-(4-BrC6H4)-1-CB9H9] was determined using single crystal X-ray diffraction.
ꢀ 2005 Elsevier B.V. All rights reserved.
Keywords: 1-carba-closo-decaborate; Derivatives; Synthesis; X-ray structure
1. Introduction
open the way to the synthesis of various functional deriv-
atives that might be able to accumulate selectively in tu-
mor cells, which is one of the important requirements in
BNCT. The second advantage is good solubility of the
[1-CB9H10]À anion in water as the sodium salt [6]; this as-
pect is very important for the delivery of the BNCT
agents to the tumor.
Despite these advantages, no attempt has been taken
to use the [closo-1-CB9H10]À anion in the BNCT-related
projects because a high-yield preparative method for its
synthesis has not been found until recently. The synthesis
of this anion was first reported by Knoth [7] as a product
of the thermal disproportionation of the [nido-CB10H13]À
anion (together with [closo-1-CB11H12]À as the second
product), and it can also be obtained in low yield from
the reductive deamination of [6-Me3N-nido-CB9H11]
with sodium metal [7]. Much later, a more convenient
synthesis based on the reaction of [6-Me3N-nido-
The 1-carba-closo-decaborate anion [closo-1-CB9H10]À
has been considered as a potential boron moiety for bor-
on neutron capture therapy (BNCT) for cancer [2]. From
the BNCT point of view, this boron cluster has two evi-
dent advantages over more commonly used and widely
investigated compounds, based on dicarba-closo-dodeca-
boranes C2B10H12 [3,4] and dodecahydro-closo-
dodecaborate anion [B12H12]2À [5]. The first advantage
is that the numerous methods of functionalisation via
the carbon atom that were developed for dicarboranes
will be possible to apply to the [1-CB9H10]À anion. This
q
Preliminary results of this study were reported at XI International
Meeting on Boron Chemistry (IMEBORON-XI) in Moscow, 2002 [1].
*
Corresponding author. Fax: +7 95 1355085.
E-mail address: sivaev@ineos.ac.ru (I.B. Sivaev).
0022-328X/$ - see front matter ꢀ 2005 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2005.01.052

I.B. Sivaev et al. / Journal of Organometallic Chemistry 690 (2005) 2790–2795
2791
CB9H11] with piperidine was proposed [8]. More recently,
two new methods based on the deamination of [1-Me3N-
closo-1-CB9H9] [9] and [1-H3N-closo-1-CB9H9] [10] were
proposed. These findings have made the 1-carba-closo-
decaborate anion more available and by now a number
of its halogen derivatives were prepared [10–12].
aldehydes under the Brellochs reaction conditions.
Unfortunately, the Brellochs original preliminary no-
tice [13] contains no experimental details. However,
during the initial phases of our study, two very useful
communications concerning the first stage of the Brell-
ochs reaction appeared [14,15]. More recently, the
excellent review [16] and several papers [17–19], con-
cerning the synthesis of various arylderivatives of the
1-carba-closo-decaborate anion were published. Unfor-
tunately, most of these papers provide virtually no
information regarding the experiment details.
However, all of these methods suffer from some
experimental drawbacks, the principal of which is the
necessity of using multi-step synthetic procedures which
markedly decrease the yield of the desired product from
10
the very expensive 10B-enriched decaborane B10H14.
The solution of this problem was given by Brellochs
[13] who reported an elegant route for the preparation
of the ten-vertex monocarboranes [1-R-closo-1-CB9H9]À
(R = H, Me, Ph). According to Brellochs, the reaction of
decaborane with aldehydes in alkaline solution results in
[6-R-arachno-6-CB9H13]À, which can be easily oxidized
to [2-R-closo-2-CB9H9]À that under heating undergoes
rearrangement into the more stable [1-R-closo-1-
CB9H9]À isomer.
In our ongoing search for functional derivatives of the
1-carba-closo-decaborate anion applicable for synthesis
BNCT agents, we have studied the Brellochs reaction with
various functional aromatic and heteroaromatic alde-
hydes. Some results of this study are reported in the pres-
ent paper.
To prepare functional derivatives of the 1-carba-
closo-decaborate anion we studied reactions of decabo-
rane with a series of various aldehydes, namely RC(O)H
(R = H, C6H5, C6H4-4-COOH, C6H4-2-OH, C6H4-3-
OH, C6H4-4-OH, C6H4-4-NO2, C6H4-2-OMe, C6H4-4-
NHCOMe, C6H4-4-Br, 2-SC4H3). It was found that
reactions of decaborane with different aldehydes pro-
ceed in somewhat varied ways (Scheme 1). As reported
initially by Brellochs [13] and verified later [14,19], the
reaction with formaldehyde results in [arachno-6-
CB9H14]À. The reaction of decaborane with benzalde-
hyde gives [6-Ph-nido-6-CB9H11]À [15,17] rather than
the arachno product [13]. No carborane products were
obtained with aldehydes containing acidic functions,
such as 2-, 3-, and 4-hydroxybenzaldehydes and
4-carboxybenzaldehyde.
Thereactionwith2-methoxybenzaldehyderesultsinthe
arachno product [6-(2-MeOC6H4)-arachno-6-CB9H13]À.
The formation of the arachno product is unique in the ser-
iesof arylaldehydesinvestigated. Thereasonforthisexcep-
tion is not clear, but one possible explanation is the
stabilization of the arachno form via formation of an intra-
molecular hydrogen bond between the oxygen atom and
the endo-hydrogen atom at position C(6) (five-member
2. Results and discussion
The Brellochs reaction is especially attractive for the
synthesis of functional derivatives of the [1-CB9H10]À
anion because of the commercial availability of alde-
hydes containing various functionalities. Here, we have
studied reactions of decaborane with various functional
-
H
H
B(OH)3
H
R
H
H
1.
4-O2NC6H4
OH-
O
H
2.H+
H
O
H
2-
-
arachno-[6-R-6-CB9H13
]
H
H
OH
H
H
H
H
R
OH-
H2O
R = H, 2-C6H4OMe
H
H
OH-
-
H
R
H
H
arachno-[6-B10H13OH]2
-
B10H14
O
OH-
R
H
-
nido-[6-R-6-CB9H11
]
R = 2-, 3-, 4-C6H4OH,
4-C6H4COOH
R = C6H5, 4-C6H4Br,
4-C6H4NHCOMe,
2-SC4H3
Scheme 1.

2792
I.B. Sivaev et al. / Journal of Organometallic Chemistry 690 (2005) 2790–2795
cycle), or the terminal hydrogen atoms at positions B(5)
and B(7) of the carborane cage (six-member cycle). The
1H NMR spectrum of [6-(2-MeOC6H4)-arachno-6-
CB9H13]À in methanol-d4 contains two sets of signals from
the 2-methoxyphenyl substituent, which may correspond
to existence of a mixture of hydrogen-bonded and non-
bonded forms or (less probably) a mixture of two different
hydrogen-bonded forms. The 11B NMR spectrum of [6-(2-
MeOC6H4)-arachno-6-CB9H13]À demonstrates only the
set of signals corresponding to the arachno structure.
Unfortunately our attempts to grow crystals of this com-
pound appropriate for X-ray study were unsuccessful.
In the case of 4-nitrobenzaldehyde, the reaction
results in the complete destruction of the boron cage,
giving boric acid after acidification of the reaction mix-
ture. The reactions with 4-bromobenzaldehyde, 4-ace-
tamidobenzaldehyde and 2-thiophenecarboxaldehyde,
as in the case of unsubstituted benzaldehyde, gave the
corresponding nido derivatives [6-R-nido-6-CB9H11]À.
Both the arachno- and the nido-derivatives can be eas-
ily oxidized with elemental iodine in an alkaline aqueous
solution to give the corresponding closo-derivatives
[2-R-closo-2-CB9H9]À. These closo-2-isomers, under
heating in solution, undergo rearrangement to more
thermodynamically favorable closo-1-isomers [1-R-
closo-1-CB9H9]À (Scheme 2).
In the case of the acetamido derivative [2-(4-Me-
CONHC6H4)-closo-2-CB9H9]À, the isomerization is
accompanied by hydrolysis giving amine [1-(4-
H2NC6H4)-closo-1-CB9H9]À as a product. The synthesis
of the last derivative as well as its further derivatization
has been described recently in the literature [18] based
on our outlined procedure [1a].
The crystal structure of (Bu4N)[1-(4-BrC6H4)-1-
CB9H9] was determined by method of single crystal
X-ray diffraction. The molecular structure of the
[1-(4-BrC6H4)-1-CB9H9]À anion is presented in Fig. 1
and the selected structural parameters are presented in
Table 1.
All the steps of the described synthetic pathway pro-
ceed with reasonably high yields opening a convenient
route for the synthesis of functional derivatives of the
[closo-1-CB9H10]À anion, which can be used for the
development of BNCT agents, the construction of new
materials.
3. Experimental
1H, 13C, and 11B NMR spectra were collected using
Varian Unity 400 and Bruker AMX 400 spectrometers.
Chemical shifts were referenced to SiMe4 = 0.00 ppm for
1H and 13C and to Et2O Æ BF3 = 0.0 ppm for 11B. Ele-
mental analyses were performed in the Laboratory of
Microanalysis of the Institute of Organoelement Com-
pounds (Moscow).
3.1. Synthesis of Cs[6-(2-CH3OC6H4)-arachno-6-
CB9H13]
1.22 g (10.0 mmol) decaborane(14) was dissolved in
60 ml of 10% aqueous solution of sodium hydroxide at
0 ꢁC. 4.08 g (30.0 mmol) 2-methoxybenzaldehyde fol-
lowed by 50 ml of ethanol were added and stirred for
3 h. EtOH was removed in vacuo and the residue was
extracted three times with Et2O (3 · 50 ml). The organic
layer was concentrated to 20 ml in vacuo at room tem-
perature and treated with solution of 3.0 g (20.0 mmol)
CsF in 5 ml of methanol. The precipitate formed was fil-
tered, washed with 20 ml of Et2O and dried over P2O5,
1
giving 1.92 g (53%) of the product. H NMR (metha-
nol-d4 ppm): minor isomer À7.33 (1H, dd), 7.23 (1H,
dt), 6.93 (1H, d), 6.92 (1H, t) 3.82 (3H, s); major isomer
À7.06 (1H, dd), 6.99 (1H, dt), 6.74 (1H, d), 6.73 (1H, t),
-
H
H
H
R
H
H
-
R
-
R
-
I2
arachno-[6-R-6-CB9H13
]
heating
OH-
OH-
-
H
R
H
H
[2-R-CB9H9]-
[1-R-CB9H9]-
-
nido-[6-R-6-CB9H11
]
Scheme 2.

I.B. Sivaev et al. / Journal of Organometallic Chemistry 690 (2005) 2790–2795
2793
J = 140 Hz). Anal. Calc. for C8H20B9CsO: C, 26.51; H,
5.56; B, 26.84. Found: C, 26.32; H, 5.67; B, 27.02%.
3.2. Synthesis of (Me4N)[6-(4-CH3CONHC6H4)-
nido-6-CB9H11]
0.61 g (5.0 mmol) decaborane(14) was dissolved in
30 ml of 10% aqueous solution of sodium hydroxide at
0 ꢁC. 2.40 g (15.0 mmol) 4-acetylamidobenzaldehyde
followed by 40 ml of ethanol were added and stirred
for 4 h. The EtOH was removed in vacuo and the resi-
due was extracted three times with Et2O (3 · 50 ml).
The organic phase was concentrated almost to dryness
in vacuo at room temperature, diluted with 5 ml of
water and treated with solution of 1.5 g (10.0 mmol)
Me4NBr in 5 ml of water. The precipitate formed was
filtered, washed with cold water (2 · 10 ml) and diethyl
ether (20 ml), and dried over P2O5, giving 1.05 g (64%)
of the product. 1H NMR (methanol-d4 ppm): 7.29
(2H, d, J = 8.6 Hz), 7.24 (2H, d, J = 8.6 Hz), 3.11
(12H, s, Me4N+), 2.1 (3H, s), À3.42 (2H, br s). 13C
NMR (methanol-d4 ppm): 171.3, 148.9, 136.0, 129.0,
120.6, 55.9 (Me4N+), 23.7. 11B NMR (methanol-d4
ppm): 1.1 (2B, d, J = 134 Hz), À2.3 (1B, d, J =
131 Hz), À4.9 (2B, d, J = 128 Hz), À12.2 (2B, d,
J = 146 Hz), À25.9 (1B, d, J = 146 Hz), À38.1 (1B, d,
J = 140 Hz). Anal. Calc. for C13H31B9N2O: C, 47.50;
H, 9.51; N, 8.52; B, 29.60. Found: C, 47.13; H, 9.68;
N, 8.79; B, 29.56%.
Fig. 1. Molecular structure of the [1-(4-BrC6H4)-1-CB9H9]À anion.
3.3. Synthesis of (Et4N)[1-(4-NH2C6H4)-closo-1-CB9 H9]
1.22 g (10.0 mmol) decaborane(14) was dissolved in
60 ml of 10% aqueous solution of sodium hydroxide
at 0 ꢁC. 4.80 g (29.5 mmol) 4-acetylamidobenzaldehyde
followed by 70 ml of ethanol were added and stirred
for 4 h. The EtOH was removed in vacuo and the res-
idue was extracted three times with Et2O (3 · 50 ml).
The diethyl ether was pumped off, the residue was dis-
solved in a solution of 2.4 g sodium hydroxide in 50 ml
of water and treated dropwise at room temperature
with solution of 5.08 g (20.0 mmol) iodine in 150 ml
of methanol and stirred for additional 1 h. To the ob-
tained solution of [2-(4-MeCONHC6H4)-closo-2-
CB9H9] (11B NMR (acetone-d6 ppm): 2.4 (1B, d, J =
155 Hz,), À2.1 (1B, d, J = 164 Hz), À20.3 (1B, d,
J = 140 Hz), À24.8 (2B, d, J = 152 Hz), À27.5 (4B, d,
J = 136 Hz)) 10 g sodium hydroxide was added and
heated under reflux for 20 h under N2 atmosphere.
The solution was cooled to room temperature and neu-
tralized by the addition of 1 M hydrochloric acid. The
reaction mixture was evaporated to dryness, the residue
was dissolved in 100 ml of water and treated with solu-
tion of 3.30 g (20.0 mmol) Et4NCl in 10 ml of water.
The precipitate formed was filtered, washed with cold
water (2 · 10 ml) and diethyl ether (50 ml), and dried
Table 1
Bond lengths (A) for the [1-(4-BrC6H4)-1-CB9H9] anion
À
˚
C(1)–B(2)
C(1)–B(3)
C(1)–B(4)
C(1)–B(5)
B(2)–B(3)
B(2)–B(5)
B(3)–B(4)
B(4)–B(5)
B(2)–B(6)
B(2)–B(9)
B(3)–B(6)
B(3)–B(7)
B(4)–B(7)
B(4)–B(8)
B(5)–B(8)
B(5)–B(9)
1.612(3)
1.607(3)
1.605(3)
1.600(3)
1.824(4)
1.838(4)
1.833(3)
1.841(4)
1.797(3)
1.802(3)
1.796(3)
1.818(3)
1.809(3)
1.819(3)
1.804(3)
1.818(4)
B(6)–B(7)
B(6)–B(9)
B(7)–B(8)
B(8)–B(9)
B(6)–B(10)
B(7)–B(10)
B(8)–B(10)
B(9)–B(10)
C(1)–C(2)
C(2)–C(3)
C(2)–C(7)
C(3)–C(4)
C(6)–C(7)
C(4)–C(5)
C(5)–C(6)
C(5)–Br
1.833(4)
1.826(3)
1.837(3)
1.832(3)
1.683(3)
1.697(4)
1.703(4)
1.691(3)
1.494(3)
1.393(3)
1.383(3)
1.388(3)
1.394(3)
1.389(3)
1.372(3)
1.908(2)
3.78 (3H, s); 4.61 (1H, s), À0.24 (1H, s). 13C NMR
(methanol-d4 ppm): 158.3, 134.6, 130.6, 129.6, 129.0,
128.9, 126.4, 121.4. 121.1, 111.2, 110.5, 62.2, 56.1,
55.7. 11B NMR (methanol-d4 ppm): À1.8 (1B, d,
J = 125 Hz), À9.0 (3B, d, J = 143 Hz), À23.5 (1B, t,
J = 107 Hz), À28.5 (2B, d, J = 125 Hz), À39.2 (2B, d,

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I.B. Sivaev et al. / Journal of Organometallic Chemistry 690 (2005) 2790–2795
1
in vacuo, giving 2.65 g (78%) of the product. H NMR
(acetone-d6 ppm): 7.81 (2H, d, J = 8.5 Hz), 7.63 (2H, d,
J = 8.5 Hz), 4.62 (2H, s), 3.44 (8H, q, Et4N+), 1.36
(12H, t, Et4N+). 11B NMR (acetonel-d6 ppm): 30.2
(1B, d, J = 150 Hz), À14.9 (4B, d, J = 150 Hz), À23.0
(4B, d, J = 138 Hz).
0 ꢁC. 2.8 ml (3.36 g, 30.0 mmol) 2-thiophene carboxal-
dehyde followed by 60 ml of ethanol were added and
stirred for 5 h. The EtOH was removed in vacuo and
the residue was extracted three times with Et2O
(3 · 50 ml). The diethyl ether was pumped off, the resi-
due containing Na[6-(2-C4H3S)-nido-6-CB9H11] (11B
NMR (D2O, ppm): 1.6 (2B, d, J = 135 Hz), À0.8 (1B,
d, J = 146 Hz), À4.2 (2B, d, J = 137 Hz), À10.8 (2B, d,
J = 137 Hz), À22.9 (1B, d, J = 148 Hz), À36.8 (1B, d,
J = 144 Hz)) was dissolved in solution of 2.4 g sodium
hydroxide in 50 ml of water and treated dropwise at
room temperature with solution of 5.08 g (20.0 mmol)
iodine in 150 ml of methanol. The reaction mixture
was stirred overnight and concentrated in vacuo to
50 ml. The solution containing Na[2-(2-C4H3S)-closo-
2-CB9H9] (11B NMR (D2O, ppm): À0.8 (1B, d), À3.2
(1B, d), À21.6 (1B, d), À25.8 (4B, d), À28.4 (2B, d))
was heated under reflux for 24 h, cooled to room tem-
perature, neutralized with 1 M HCl, concentrated to
15 ml and treated with solution of 2.10 g (15.0 mmol)
of [Et3NH]Cl in 10 ml of water. The precipitate formed
was filtered, washed with Et2O and dried in vacuo, giv-
3.4. Synthesis of (Bu4N)[2-(4-BrC6H4)-closo-2-CB9H9]
0.61 g (5.0 mmol) decaborane(14) was dissolved in
30 ml of 10% aqueous solution of sodium hydroxide
at 0 ꢁC. 2.80 g (15.0 mmol) 4-bromobenzaldehyde fol-
lowed by 20 ml of ethanol were added and stirred for
3 h. The EtOH was removed in vacuo and the residue
was extracted three times with Et2O (3 · 50 ml). The
diethyl ether was pumped off, the residue containing
Na[6-(4-BrC6H4)-nido-6-CB9H11] (11B NMR (metha-
nol-d4 ppm): À0.3 (2B, d, J = 133 Hz,), À3.5 (1B, d, J =
159 Hz), À6.5 (2B, d, J = 133 Hz), À14.0 (2B, d,
J = 137 Hz), À28.1 (1B, d, J = 148 Hz), À39.7 (1B, d,
J = 144 Hz)) was dissolved in a solution of 1.2 g so-
dium hydroxide in 25 ml of water and treated dropwise
at room temperature with solution of 2.54 g
(10.0 mmol) iodine in 75 ml of methanol. The reaction
mixture was stirred overnight, concentrated in vacuo
and treated with solution of 8.05 g (25.0 mmol)
Bu4NBr in 20 ml of water. The precipitate formed
was filtered, washed with water and recrystallized from
methanol, giving 2.17 g (84%) of the product.1H NMR
(acetone-d6 ppm): 7.15 (2H, d, J = 8.6 Hz), 6.81 (2H, d,
J = 8.6 Hz), 3.45 (8H, m, Bu4N+), 1.83 (8H, m,
Bu4N+), 1.44 (8H, m, Bu4N+), 0.98 (12H, t, Bu4N+).
11B NMR (acetone-d6 ppm): 2.1 (1B, d, J = 153 Hz),
À2.8 (1B, d, J = 168 Hz), À20.8 (1B, d, J = 143
Hz), À25.6 (2B, d, J = 153 Hz), À28.2 (2B, d,
J = 125 Hz), À29.0 (2B, d, J = 128 Hz).
1
ing 2.15 g (76%) of the product. H NMR (acetone-d6
ppm): 7.38 (1H, dd, J = 3.6, 1.2 Hz), 7.21 (1H, dd,
J = 5.2, 1.2 Hz), 7.00 (1H, dd, J = 5.2, 3.6 Hz), 3.37
(6H, q, J = 7.2 Hz, Et3NH+), 1.38 (9H, t, J = 7.2 Hz,
Et3NH+). 13C NMR (acetone-d6 ppm): 148.6, 127.0,
125.9, 123.0, 47.7 (Et3NH+), 9.2 (Et3NH+). 11B NMR
(acetone-d6 ppm): 30.5 (1B, d, J = 146 Hz), À14.8 (4B,
d, J = 150 Hz), À24.0 (4B, d, J = 140 Hz). Anal. Calc.
for C11H27B9NS: C, 43.65; H, 8.99; N, 4.63; B, 32.14.
Found: C, 43.37; H, 9.08; N, 4.99; B, 31.86%.
3.7. Crystal structure determination of (Bu4N)-
[1-(4-BrC6H4)-1-CB9H9]
Crystal
C23H49B9BrN (M = 516.83), monoclinic, space group
data:
(Bu4N)[1-(4-BrC6H4)-1-CB9H9],
3.5. Synthesis of (Bu4N)[1-(4-BrC6H4)-closo-1-CB9H9]
P21/c (No. 14), a = 15.400(2), b = 10.912(1), c = 19.
3
˚
˚
1.55 g (3.0 mmol) (Bu4N)[2-(4-BrC6H4)-closo-2-
CB9H9] in 200 ml of ethanol was heated under reflux
for 16 h. The reaction mixture was cooled to room tem-
perature and concentrated to dryness in vacuo, giving
047(2) A, b = 110.086(3)ꢁ, V = 3006.0(6) A , Z = 4,
dcalc = 1.142 g cmÀ3
, , F(000) = 1096,
l = 1.380 mmÀ1
crystal colourless size 0.30 · 0.45 · 0.55 mm.
Single-crystal X-ray diffraction experiment was car-
ried out with a Bruker SMART 1000 CCD area detec-
tor, using graphite monochromated Mo Ka radiation
1
1.48 g (95%) of the product. H NMR (dmso-d6 ppm):
7.73 (2H, d, J = 8.2 Hz), 7.56 (2H, d, J = 8.2 Hz), 3.15
(8H, m, Bu4N+), 1.54 (8H, m, Bu4N+), 1.30 (8H, m,
Bu4N+), 0.93 (12H, t, Bu4N+). 11B NMR (dmso-d6
ppm): 30.1 (1B, d, J = 140 Hz), À14.5 (4B, d,
J = 148 Hz), À22.6 (4B, d, J = 140 Hz). Anal. Calc. for
C23H49B9BrN: C, 53.45; H, 9.56; N, 2.71; B, 18.82.
Found: C, 53.18; H, 9.78; N, 3.01; B, 19.02%.
˚
(k = 0.71073 A, x-scans with a 0.3ꢁ step in x and 10 s
per frame exposure, 2h < 58ꢁ) at 120 K. The low temper-
ature of the crystals was maintained with a Cryostream
(Oxford Cryosystems) open-flow N2 gas cryostat.
Reflection intensities were integrated using SAINT soft-
ware [20] and semi-empirical method SADABS [21]. A
total of 47,870 reflections were measured, 7881
(Rint = 0.0503) independent reflections were used in fur-
ther calculations and refinement. The structures were
solved by direct method and refined by the full-matrix
least-squares method against F2 in anisotropic for
3.6. Synthesis of (Et3NH)[1-(2-C4H3S)-closo-1-CB9H9]
1.22 g (10.0 mmol) decaborane(14) was dissolved in
60 ml of 10% aqueous solution of sodium hydroxide at

I.B. Sivaev et al. / Journal of Organometallic Chemistry 690 (2005) 2790–2795
2795
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950.
[3] C. Morin, Tetrahedron 50 (1994) 12521.
nonhydrogen atoms approximation. The hydrogen
atoms of the carbadodecaborate anion were located
from the difference Fourier syntheses and refined in iso-
tropic approximation. The positions of hydrogen atoms
for phenyl ring and the Bu4N+ cation were calculated
from the geometrical point of view and were included
in the final refinement using a rigid motion model. The
final refinements were converged to R1 = 0.0443 (from
4461 unique reflections with I > 2r s(I)) and wR2 =
0.0943 (from all 7881 unique reflections); the number
of the refined parameters is 343. All calculations were
performed on an IBM PC/AT using the SHELXTL
software [22].
[4] J.F. Valliant, K.J. Guenther, A.S. King, P. Morel, P. Schaffer,
O.O. Sogbein, K.A. Stephenson, Coord. Chem. Rev. 232 (2002)
173.
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(b) I.B. Sivaev, V.I. Bregadze, S. Sjo¨berg, Collect. Czech. Chem.
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Z. Xie, Inorg. Chem. 39 (2000) 3582.
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(1994) 1907.
Crystallographic data for (Bu4N)[1-(4-BrC6H4)-1-
CB9H9] have been deposited with the Cambridge Crystal-
lographic Data Centre, CCDC-252434. Copies of this
information may be obtained free of charge from: The
Director, CCDC, 12 Union Road, Cambridge, CB2
1EZ, UK (Fax: +44 1223 336033; e-mail: deposit@ccdc.
cam.ac.uk or www: http://www.ccdc.cam. ac.uk).
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Solntsev, S.H. Strauss, Inorg. Chem. 35 (1996) 7882;
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Solntsev, S.H. Strauss, Inorg. Chim. Acta 289 (1999) 76.
[13] B. Brellochs, in: K. Wade, M.G. Davidson, A.K. Hughes, T.B.
Marder (Eds.), Contemporary Boron Chemistry, Royal Chemical
Society, Cambridge, 2000, p. 212.
[14] T. Jelinek, B. Stibr, J. Holub, M. Bakardjiev, D. Hnyk,
D.L. Ormsby, C.A. Kilner, M. Thornton-Pett, H.-J. Schanz,
B. Wrackmeyer, J.D. Kennedy, Chem. Commun. (2001)
1756.
Acknowledgments
This work was supported in parts by the Carl Trygger
Foundation for Scientific Research, the Swedish Cancer
Foundation, Russian Foundation for Basic Research
(05-03-32429, 03-03-32214), and Division of Chemistry
and Material Science of Russian Academy of Sciences
(05-07). I.B.S. gratefully acknowledges Russian Foun-
dation for Basic Research for the EUROBORON-3
travel Grant (04-03-427973).
[15] T. Jelinek, C.A. Kilner, M. Thornton-Pett, J.D. Kennedy, Chem.
Commun. (2001) 1790.
[16] A. Franken, C.A. Kilner, M. Thornton-Pett, J.D. Kennedy,
Collect. Czech. Chem. Commun. 67 (2002) 896.
[17] A. Franken, C.A. Kilner, M. Thornton-Pett, J.D. Kennedy,
Inorg. Chem. Commun. 5 (2002) 581.
[18] A. Franken, C.A. Kilner, J.D. Kennedy, Inorg. Chem. Commun.
6 (2003) 1104.
[19] B. Brellochs, J. Backovsky, B. Stibr, T. Jelinek, J. Holub, M.
Bakardijev, D. Hnyk, M. Hofmann, I. Cisarova, B. Wrackmeyer,
Eur. J. Inorg. Chem. (2004) 3605.
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