Reaction of the closo-decaborate anion B10H 10 2- with dichloroethane in the presence of hydrogen halides

Article abstract of DOI:10.1134/S0036023607070042

The reactions of the closo-decaborate anion with hydrogen halides and dichloroethane have been studied. Irrespective of the hydrogen halide used (HCl, HBr, HI), chlorination to give mono-, di-, and trihalosubstituted products is the major process. The product ratio depends on the hydrogen halide used and on the synthesis temperature and time. The products have been identified by ¹¹B NMR, IR, and ESI mass spectra. The structure of (Ph ₃(NaphCH₂)P)₂B₁₀H₈Cl ₂ has been studied by X-ray diffraction. The geometry distortion of the closo-decaborate core found in the chlorinated derivatives is retained on further chemical transformations of the compound.

Full text of DOI:10.1134/S0036023607070042

ISSN 0036-0236, Russian Journal of Inorganic Chemistry, 2007, Vol. 52, No. 7, pp. 996–1001. © Pleiades Publishing, Inc., 2007.
Original Russian Text © V.V. Drozdova, K.Yu. Zhizhin, E.A. Malinina, I.N. Polyakova, N.T. Kuznetsov, 2007, published in Zhurnal Neorganicheskoi Khimii, 2007, Vol. 52,
No. 7, pp. 1072–1077.
SYNTHESIS AND PROPERTIES
OF INORGANIC COMPOUNDS
2
10
–
Reaction of the closo-Decaborate Anion B H
10
with Dichloroethane in the Presence of Hydrogen Halides
V. V. Drozdova, K. Yu. Zhizhin, E. A. Malinina, I. N. Polyakova, and N. T. Kuznetsov
Kurnakov Institute of General and Inorganic Chemistry, Russian Academy of Sciences,
Leninskii pr. 31, Moscow, 119991 Russia
Received July 6, 2006
Abstract—The reactions of the closo-decaborate anion with hydrogen halides and dichloroethane have been
studied. Irrespective of the hydrogen halide used (HCl, HBr, HI), chlorination to give mono-, di-, and trihalo-
substituted products is the major process. The product ratio depends on the hydrogen halide used and on the
1
1
synthesis temperature and time. The products have been identified by B NMR, IR, and ESI mass spectra. The
structure of (Ph (NaphCH )P) B H Cl has been studied by X-ray diffraction. The geometry distortion of the
3
2
2
10
8
2
closo-decaborate core found in the chlorinated derivatives is retained on further chemical transformations of the
compound.
DOI: 10.1134/S0036023607070042
The closo-decaborate anion is a pseudoaromatic
system prone to numerous reactions involving replace-
ment of exopolyhedral hydrogen atoms, including chlo-
rination. It is known from published data that halogena-
tion of the closo-decaborate anion with free halogen in
an aqueous solution of the ammonium salt
EXPERIMENTAL
2–
The [B H ] anion was synthesized by a reported
procedure [5] via 1,6-bis(triethylaminedecaborane).
10 10
The hydrogen halides used in the reaction were pre-
pared by known procedures [6]: HCl was obtained by
the reaction of sodium chloride with sulfuric acid; HBr
and HI were obtained by the reaction of an aqueous
solution of the respective hydrohalic acid with phos-
phorus(V) oxide or by the reaction of bromine or iodine
with tetralin.
(
NH ) B H [1] results in mono- and dihalogenated
4 2 10 10
2
–
anions B H
X , where X = Cl, Br, I; n = 1, 2,
n
10
10 – n
which were identified by NMR, IR, and Raman spec-
troscopy. The structure of monohalogenated deriva-
tives
of
the
closo-decaborate
anion
Prior to being supplied to the reactor, the hydrogen
halide gas was passed through two absorption tubes
with phosphorus(V) oxide for complete drying.
[
(C H N) CH ][2-XB H ], where X = Cl, Br, I, was
5
5
2
2
10
9
determined more precisely by X-ray diffraction [2, 3].
2
–
These products are formed upon the reaction of B H
10
1
0
2
–
Chlorination of the [B H ] anion. A solution of
1
0
10
with chlorine, bromine, or iodine or with N-halosuccin-
imide and can be separated from the unreacted starting
anions or highly substituted halo derivatives by ion
exchange chromatography. Halogenation processes of
the closo-decaborate anion have not been adequately
studied; therefore, it is pertinent to carry out further
studies of this process and to search for new halogena-
tion methods under different conditions in order to
avoid the formation of product mixtures with different
degrees of substitution.
tetrabutylammonium decaborate (1.0 g) in dichloroet-
hane (30 mL) was placed into a three-necked flask
equipped with a bubbling device, a reflux condenser, a
thermometer, and a stirrer, and the mixture was heated
to 40–60°ë. Thoroughly dried hydrogen halide was
bubbled continuously through the mixture for 1–5 h.
The yellow reaction mixture was concentrated on a
rotary evaporator until a precipitate formed. The reac-
tion conditions, the reactants, and the products are sum-
marized in Table 1.
Previously, we reported the reaction of the closo-
Synthesis of (Ph (NaphCH )P) B H Cl . The reac-
3
2
2
10
8
2
2
–
dodecaborate anion B H with hydrogen halides in tion mixture (0.8 g) was dissolved in CH CN (25 mL).
1
2
12
3
A solution of (ë H ) (CH C H )PCl (2.0 g in 20 mL of
6
5 3
2
10
7
dichloroethane [4] giving mono- and dichlorinated
products. The present work continues this study and
deals with the reaction of the closo-decaborate anion
H O) was added with stirring to the resulting solution.
2
After 24 h, a white finely crystalline precipitate formed,
which was filtered off and recrystallized from acetoni-
trile to give white crystals.
2
–
B H with hydrogen halides.
1
0
10
9
96

REACTION OF THE closo-DECABORATE ANION
997
2
10
–
Table 1. Main products of the reactions of the B H anion salts with dichloroethane and hydrogen halides
1
0
4
0°C
60°C
Dichloroethane + hydrogen chloride (C H Cl + HCl)
2
4
2
2
2
–
–
2–
2–
2
1
5
h B H Cl
B H Cl , B H Cl
10 9 10 8
1
0
9
2
2
–
2–
3
2–
2–
3
h B H Cl , B H Cl , B H Cl
B H Cl , B H Cl
2
10 8 10 7
1
0
9
10
8
10
7
Dichloroethane + hydrogen bromide (C H Cl + HBr)
2
4
2
2
2
–
–
2–
2–
2–
3
1
5
h B H Cl
B H Cl , B H Cl , B H Cl
2
10 9 10 8 10 7
1
0
9
2
2
–
2–
3
2–
2
2–
3
2–
2
2–
5
2–
2–
h B H Cl , B H Cl , B H Cl
B H Cl , B H Cl , B H Cl Br , B H Cl Br , B H Cl Br , B H Br
1
0
9
10
8
10
7
10
8
10
7
10
7
2
10
7
2
10
6
3
10
5
Dichloroethane + hydrogen iodide (C H Cl + HI)
2
4
2
2
–
2–
2–
3
1
5
h B H Cl
B H Cl , B H Cl
2
10 8 10 7
1
0
9
2
2
–
2–
3
2–
2–
2
2
–
2–
h B H Cl , B H Cl
B H Cl I , B H Cl I , B H Cl I , B H Cl I
2
10 7 2 10 6 3 10 6 2 10 5 3
1
0
8
10
7
Table 2. Elemental analysis data for chlorinated closo-decaborates
B, %
C, %
N, %
H, %
Compound
found/calcd.
found/calcd.
found/calcd.
found/calcd.
(
Bu N) (B H Cl)
16.92/16.96
16.02/16.09
60.21/60.28
57.15/57.19
4.34/4.39
4.15/4.17
12.78/12.81
11.95/12.00
4
2
10
9
(Bu N) (B H Cl )
4
2
10
8
2
The elemental analysis for carbon, hydrogen, and Table 3. Maxima of some absorption bands in the IR spectra
of chlorinated closo-decaborates
nitrogen was carried out on a CHNS-3 FA 1108 ana-
lyzer (Carlo Erba). Boron was determined by electro-
thermal atomization atomic absorption spectroscopy on
Perkin-Elmer spectrophotometers (model 2100 with
HGA-700 and model 403 with HGA-72) [7]. Elemental
analysis data are presented in Table 2.
Compound
ν(B–H), cm–1 ν(BBCl), cm–1
(
(
(
Bu N) (B H Cl)
2479
2475
2476
960
962
961
4
2
10
9
Bu N) (B H Cl )
4
2
10
8
2
IR spectra were measured on a Infralum FT-02 spec-
trophotometer (the Lumeks Scientific and Production
Company for Analytical Instrument Making) in the
Ph (NaphCH )P) B H Cl
2
3
2
2
10
8
–
1
range 4000–400 cm . The samples were prepared as
mineral oil mulls. The assignment for most informative
absorption bands observed in the IR spectra of chlori-
nated closo-decaborates is presented in Table 3.
–
anions (CatAn) determined from the spectra by analy-
sis of reaction mixtures are given in Table 5.
X-ray diffraction studies were carried out on an
Enraf-Nonius CAD-4 automated diffractometer
11
The B NMR spectra of acetonitrile solutions of the
studied compounds were recorded on a Bruker AC 200
spectrometer operating at 64.297 MHz with internal
deuterium lock. Boron trifluoride etherate was used as
(
λMoK , graphite monochromator, ω scan mode). The
α
absorption correction was applied by azimuthal scan-
ning. The structure was solved by direct methods. The
structure solution and refinement were carried out
using SHELXS97 and SHELXL97 software [8].
11
the external standard. The B NMR data for chlori-
nated closo-decaborates are presented in Table 4.
Electrospray ionization mass spectra (microspray,
The set of diffraction data I(hkl) at í = 120(2) K
4
500 V) of solutions of the compounds were recorded was obtained by a standard procedure [9] on a Bruker
on a Bruker Esquire 3000 plus mass spectrometer in an AXS SMART 100 diffractometer (λMo, graphite
acetonitrile (50%)–water mixture containing formic monochromator, ω scan mode, θmax = 30°) from a
acid (0.2%). The average analytical concentration of 0.55 × 0.30 × 0.15 mm single crystal. A semiempirical
the samples for ESI MS was (1.00 ± 0.20) mg/mL solu- correction for absorption was applied by the SADABS
tion. The molecular masses of the single-charged program [10].
RUSSIAN JOURNAL OF INORGANIC CHEMISTRY Vol. 52 No. 7 2007

9
98
DROZDOVA et al.
Table 4. 11B NMR data for chlorinated closo-decaborates thesis showed the presence of halogenated derivatives
(
in CH CN)
3
with degrees of substitution of mainly 1, 2 and 3.
The product ratio depends on the hydrogen halide
used and on the synthesis temperature and time. The
use of a heavier hydrogen halide and also an increase in
the temperature and time of the synthesis promote
accumulation of products with higher degrees of substi-
tution.
Compound
The formation of the major chlorination products is
always accompanied by the formation of derivatives
with higher degrees of substitution, including those
with different halides, which are formed when hydro-
gen bromide and hydrogen iodide are used.
For none of the reactions were we able to select con-
ditions under which one chlorinated product would be
formed predominantly, because the yields of products
present in the reaction mixtures in all reactions were
commensurable. However, the products with lower
substitution degrees (1 and 2) can be easily isolated
from the reaction mixture by HPLC in a 3 : 8 acetoni-
trile–dichloroethane system, as their retention times are
shorter than that of the initial unsubstituted anion
(
Bu N) B H Cl
–2.3
7.2
2
1
4
2
1
1
1
1
1
1
d
s
Ba
4
2 10 9
–
BCl
–
–
–
20.7
24.5
28.8
–4.3
d
d
d
d
s
Be
(
Bu N) B H Cl ,
Ba
4
2
10
8
2
(
Ph (NaphCH )P) B H Cl
3 2 2 10 8 2
–
7.8
BCl
–
–
–
21.4
25.1
30.9
d
d
d
Be
(
~7 min) or than those of more halogenated products,
including the products with mixed halogens (>6 min)
Table 7).
Table 5. Data of the ESI mass spectra of some halogenated
closo-decaborates for the (CatAn) species
–
(
Compound
Exp.
Calcd.
The molecular masses of the single-charged anions
obtained in all syntheses were estimated from ESI mass
(
(
(
(
(
(
(
(
(
(
(
Bu N) B H Cl
394.93
429.53
464.45
508.30
588.13
544.25
755.92
554.48
590.22
681.02
715.89
395.10
429.37
463.33
508.44
587.34
542.89
755.14
555.44
589.89
681.34
715.79
4
2
10
9
spectra (Table 5). As a rule, these spectra of closo-
Bu N) B H Cl
borate anions exhibit signals for single-charged
4
2
10
8
2
–
(
CatAn) species. The results indicate, in all cases, the for-
Bu N) B H Cl
4
2
10
7
3
–
–
mation of (ë H ) N[B H Cl] , (ë H ) N[B H Cl ] , and
4
9 4
10
9
4
9 4
10
8
2
Bu N) B H Cl Br
4
2
10
7
2
–
(
ë H ) N[B H Cl ] anions.
4 9 4 10 7 3
Bu N) B H Cl Br
2
4
2
10
7
2
1
1
The B NMR spectra (Table 4) of mono- and diha-
Bu N) B H Cl Br
4
2
10
6
3
logenated products are the spectra of “classical” mono-
Bu N) B H Br
5
and disubstituted closo-decaborate anions. The
4
2
10
5
1
1
B NMR spectrum of the monochlorinated derivative
exhibits five signals, one from the apical boron atoms at
3.3 ppm, one from the boron atoms bound to substitu-
ents at –7.2 ppm, and three signals at –20.7, –24.5, and
28.8 ppm due to the equatorial boron atoms. The
Bu N) B H Cl I
4
2
10
7
2
Bu N) B H Cl I
4
2
10
6
3
–
Bu N) B H Cl I
2 2
4
2
10
6
–
Bu N) B H Cl I
3 2
4
2
10
5
1
1
B NMR spectrum of the compound (Bu N) B H Cl
4
2
10
8
2
shows five signals, one from the apical boron atoms
−4.3 ppm), one from the boron atoms bound to substit-
uents (–7.8 ppm), and three signals at –21.4, –25.0, and
31.0 ppm due to the equatorial boron atoms. In both
spectra without B–H decoupling, the signals for all
boron atoms that are not bound to the substituents are
split into symmetrical doublets.
(
The crystal data, X-ray experiment details, and
structure refinement data for
Ph (NaphCH )P) B H ël are presented in Table 6,
and the structures of the anions present in the com-
pound are shown in the figure.
–
(
3
2
2
10
8
2
The IR spectra of the halogenated closo-decaborate
–
1
(
Table 3), apart from the bands at 2570–2580 cm typi-
RESULTS AND DISCUSSION
cal of B–H stretches, contain the bands of the B–B–Cl
–
1
It was found that the reactions of the closo-decabo- bending modes at about 960 cm .
rate anion with dichloroethane in the presence of
For the dichloro-substituted closo-decaborate anion
hydrogen halides give chloro-substituted derivatives isolated by HPLC, white prismatic single crystals of the
with different degrees of substitution. Analysis of the compound (Ph (NaphCH )P) B H Cl were obtained
3
2
2
10
8
2
11
B NMR spectra of the products (Table 4) and ESI (figure). The X-ray reflections were collected from a
mass spectra (Table 5) carried out at all stages of syn- 0.15 × 0.25 × 0.65 mm single crystal. The C, P, and Cl
RUSSIAN JOURNAL OF INORGANIC CHEMISTRY Vol. 52 No. 7 2007

REACTION OF THE closo-DECABORATE ANION
999
atoms were refined in the anisotropic approximation Table 6. Selected crystal data, X-ray experiment details,
and refinement data for (Ph (NaphCH )P) B H Cl
2
and B atoms, in the isotropic approximation. The occu-
pancy of the chlorine positions was first refined inde-
pendently. Since the sum of position occupancies (µ) of
Cl(1) and Cl(2) atoms is equal to unity, the µCl(2) value
was included in the final refinement and the occupancy
of the Cl(1) position was taken to be 1 – µCl(2). All
H atoms were refined by the riding model in idealized
3
2
2
10
8
Compound
Space group
(Ph (NaphCH )P) B H Cl
3
2
2
10
8
2
C2/c
a, Å
b, Å
24.229(4)
11.816(2)
22.223(2)
122.191(11)
5384.4(1.5)
1.226
positions with isotropic thermal parameters U (H) = c, Å
j
1
.2U (or 1.2U ) of the corresponding non-hydrogen
eq iso
β, deg
V, Å3
ρcalcd, g/cm3
atom.
The structure of the compound is built of the
2
2
–
+
Ph (NaphCH )P cations and B H Cl anions. The
3
2
10
8
Z
4
anions are located on a twofold axis passing through the
midpoints of the B(3)–B(7) and B(5)–B(9) edges. The
Cl atom is disordered over two positions (Cl(2) and
Cl(1)) bound to B(2) and B(1), respectively. The occu-
pancy ratio for the positions is Cl(2) : Cl(1) = 0.8 : 0.2.
The total occupancy of the Cl atom positions is equal to
µ(Mo), mm–1
θmax, deg
1.92
90
Number of independent
reflections (N)
5107
1980
Number of reflections with
I > 2σ(I) (Nobs
2
2
–
unity, which corresponds to the polyhedral B H Cl
1
0
8
)
anion.
R1, wR2 for Nobs
R1, wR2 for N
GOOF
0.081, 0.224
0.221, 0.305
1.021
The great thermal parameters for boron atoms attest
to probable overlap of the polyhedra with similar
geometry. Presumably, the insignificant differences
between the geometries of the decaborate polyhedra
2
2
–
arise in different B H Cl anions under the influence
10
8
Table 7. HPLC data for the initial and some synthesized
halogen derivatives of the closo-decaborate anion (elution
with CH CN : CH Cl = 3 : 8)
of Cl atoms. Taking into account the Cl positions in the
structure, four isomers are possible in which substitu-
ents can be located both at the vertices and in the belt of
the closo-decaborate core. The content of the major
3
2
2
Anion
Compound
Bu N) (B H )
Retention time, min
2
,7-isomer is four times greater than the content of the
other possible 1,10-, 1,2-, and 1,7-isomers. Determina-
tion of the exact structure of the isomers in the crystal
from X-ray diffraction data is impossible.
2–
10
(
(
7.1
5.3
3.3
2.7
B H
4
2
10 10
1
0
Bu N) (B H Cl)
4
2
10
9
The averaged decaborate polyhedron determined by
the refinement has an irregular shape. The ranges of
equivalent bonds are very broad: Ç –Ç 1.45–1.74(2) Å,
(Bu N) (B H Cl )
4 2 10 8 2
(
Bu N) (B H Cl )
4 2 10 7 3
‡
e
Ç –Ç 1.75–2 and 1.60–1.82(2) Å in one belt and bet-
e
e
ween the belts, respectively. The greatest anomalies are
observed in the bonds involving the B(3) atom, which
has the greatest thermal parameter: the B(2)−B(3) bond
is virtually cleaved and amounts to 2.01(2) Å; the
B(1)−B(3) and B(3)–B(7) bonds are shortened to
The geometry distortion of the closo-decaborate
anion in an acid medium has been reported. In particu-
lar, the structure of [(CH CN) ]Cu B H obtained
3
4
2
10 10
in the Cu B H –CH CN–CF COOH system was
2
10 10
3
3
determined. According to X-ray diffraction, the
closo-decaborate anion has a similar geometry distor-
tion, one B–B bond being almost cleaved and two such
1
.45(2) to 1.60(2) Å, respectively. In addition, the poly-
hedron is substantially flattened along the symmetri-
cally bound edges, B(2)–B(3) and B(8)–B(7) (the
B(1)B(2)B(3)/B(2)B(3)B(6) dihedral angle is 164.6°), bonds being shortened. Hence, a distortion of the
and the average deviation of the equatorial B(2), B(3), geometry of the closo-decaborate anion in a highly
B(4), and B(5) atoms from the root-mean-square plane acidic medium appears regular.
reaches 0.041 Å. The B(2)–Cl(2) and B(1)–Cl(1) bond
Thus, the reactions of the closo-decaborate anion
B H10 with dichloroethane and hydrogen halides yield
10
lengths are normal (1.846(9) and 1.86(2) Å, respec-
tively).
2
–
The structures of the closo-decaborate anions in halogenated derivatives in which chlorine atoms from
Ph (NaphCH )P) B H Cl determined by X-ray dif- dichloroethane are mainly present as substituents. The
(
3
2
2
10
8
2
fraction at 120(2) K and at room temperature (293 K) mechanism of reactions resulting in these products is as
are identical to within experimental error. yet unknown; however, the role of hydrogen halide
RUSSIAN JOURNAL OF INORGANIC CHEMISTRY Vol. 52 No. 7 2007

1
000
DROZDOVA et al.
B(1)
B(5)
2
,7-isomer
B(4)
B(3)
B(2)
B(8)
B(9)
B(7)
B(6)
1
,2-isomer
B(10)
1
,7-isomer
1
,10-isomer
Structures of the anions present in the (Ph (NaphCH )P) B H Cl single crystal.
3
2
2
10
8
2
molecules is evident. Performing analogous reactions dichloroethane follows a similar mechanism (hydrogen
at room temperature demonstrated that chlorination of halide initiation).
the closo-decaborate anion does not take place but the
–
11
Apparently, the reaction also involves opening of
the boron cluster anion. As noted above, the geometry
anion is protonated to give B H , which is confirmed
10
11
by B NMR. This fact suggests that hydrogen halides of the closo-decaborate anion is distorted in highly
are the protonating agents initiating halogenation, acidic media, and the products can be isolated only in
which proceeds via the protonated anion. Acid-cata- the presence of acids [11]. The closo-decaborate core in
lyzed nucleophilic substitution of the closo-decaborate the compounds synthesized in this study has a similar
anion has been reported [12]; therefore, one may sug- unusual geometry, which is retained upon further
gest that halogenation of the closo-decaborate anion by chemical transformations.
RUSSIAN JOURNAL OF INORGANIC CHEMISTRY Vol. 52 No. 7 2007

REACTION OF THE closo-DECABORATE ANION
1001
ACKNOWLEDGMENTS
6. Handbuch der präparativen anorganischen Chemie, Ed.
by G. Brauer (Ferdinand Enke, Stuttgart, 1975−1981;
Mir, Moscow, 1985).
This work was supported by the Council for Grants
of the President of the Russian Federation, (grant nos.
MK-4987.2006.3 and NSh-4895.2006.3). The authors
are grateful to the Russian Foundation for Basic
Research (project no. 05-03-32885).
7
. L. I. Ochertyanova, K. Yu. Zhizhin, V. N. Mustyatsa,
et al., Neorg. Mater. 40 (1), 188 (2004).
8. G. M. Sheldrick, SHELXS97 and SHELXL97. Program
for the Solution ind Refinement of Crystal Structures,
Univ. of Göttingen, 1997.
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