1556
DROZDOVA et al.
The
11B
NMR
spectrum
of
2,7–
Table 7. Basic crystallographic data and experimental and
refinement details for [NMe2(CH2Cl)]2B10H8 (I) and 3-CH3-
2,8-[NMe2(CH2Cl)]2B10H6 (II)
[NMe2(CH2Cl)]2B10H8 (Table 5) shows four singlets at
–7.40 ppm (B(1), B(2), B(7), B(10)), –24.20 ppm
(B(3), B(6)), –30.55 ppm (B(5), B(8)), and –34.18
(B4), B(9)) with the integrated intensity ratio 2 : 1 : 1 : 1.
In the absence of broadband decoupling from protons,
the signal at –7.40 ppm is an asymmetric doublet and
the upfield signals are symmetric doublets.
Characteristic
Space group
I
II
P212121
10.686(4)
12.037(3)
13.218(3)
P21/n
7.422(1)
19.820(3)
12.139(2)
104.232(4)
1730.9(4)
1.350
a, Å
b, Å
The IR spectrum (Table 3) shows two strong bands
of C–Cl bond stretches at 832 and 860 cm–1. The
boron–hydrogen stretching vibrations are observed at
2516 cm–1, which is about 40 cm–1 higher than in the
salt of the initial anion. Such an increase in frequency
can be evidence of a noticeable effect of the substitu-
ents on the electron density distribution in the closo-
decaborate anion.
c, Å
β, deg
V, Å3
ρ(calcd), g/cm3
1700.2(8)
1.185
4
Z
4
µ(Mo), mm–1
0.364
25
0.517
The change in the electron density distribution in the
closo-decaborate anion induced by the introduction of
two electron-releasing substituents also manifests itself
in electronic absorption spectra (Table 4). The presence
of two electron-releasing substituents is responsible for
the emergence of the absorption band at 240 nm. The
unsubstituted closo-decaborate anion does not absorb
above 200 nm.
θ
max, deg
25
Number of unique re-
flections
2113
3031
Number of reflections
679
1268
with I > 2σ(I) (Nobs
)
R1
0.0725
0.1902
0.1229
0.3151
wR2 for Nobs
As a whole, the zwitterionic structure and the
arrangement of the substituents in the closo-decaborate
anion account for the extremely low polarity of the
compound obtained, which is indicated by its short
retention time on chromatographing (the retention
index is 0.3).
S
0.969
0.982
dimethylformamide and phosphorus(V) oxychloride
yields three products, whose compositions and struc-
tures have been determined by IR spectroscopy, 11B
NMR, and X-ray crystallography.
The major product is neutral disubstituted 2,7-
bis(N,N-dimethyl-N-chloromethylammonium)octahy-
dro-closo-decaborane (compound I). Its structure was
determined by X-ray crystallography. The molecular
structure of 2,7-[NMe2(CH2Cl)]2B10H8 is shown in Fig. 3.
The substituents are in the 2- and 7-positions of the
polyhedral anion. In the substituent at the B(7) atom,
the chlorine atom is disordered over two equally occu-
pied positions (Cl(2) and Cl(3) at the C(4) and C(6)
atoms). Figure 3 shows only one position of the disor-
dered Cl atom.
In the polyhedron, the B–B bonds involving the api-
cal vertices (1.604–1.718 Å) are shortened as compared
to the bonds between the equatorial vertices
(1.750−1.882 Å). The difference between two types of
bonds involving equatorial vertices is not observed
within the error of determination (0.016–0.020 Å). The
lengths of the exopolyhedral B–N bonds are 1.601 (15) Å
for N(1)–B(2) and 1.590(14) Å for N(2)–B(7). The
C−Cl bond lengths in the exopolyhedral substituents
are as follows: Cl(1)–C(1), 1.772(11) Å; Cl(2)–C(4),
1.673(12) Å; Cl(3)–C(6), 1.804(13) Å. The chlorine
atoms in both substituents are at a maximum possible
distance from the polyhedron (the corresponding tor-
sion angles Cl–C–N–Bipso are close to 180°).
Assignment of the 11B NMR and IR spectra (Tables 5
and 3, respectively) of the second fraction product
allowed us to conclude that this product is neutral 2,6-
bis(N,N-dimethyl-N-chloromethylammonium)octahy-
dro-closo-decaborane. The 11B NMR spectrum of 2,6-
[NMe2(CH2Cl)]2B10H8 shows four singlets at –7.57 ppm
(B(1), B(2), B(6), B(10)), –23.78 ppm (B(3), B(7)),
−27.51 ppm (B(5), B(8)), and –34.06 ppm (B(4), B(9))
with the integrated intensity ratio 2 : 1 : 1 : 1. In the
absence of broadband decoupling from protons, the sig-
nal at –7.57ppm is an asymmetric doublet and the
upfield signals are symmetric doublets. This spectrum
is virtually identical to the spectrum of the 2,7-isomer,
which can be observed only in the case of its 2,6-ana-
logue. The IR spectrum is similar to the spectrum of the
2,7-isomer. The electronic absorption spectrum of the
2,6-isomer (Table 4), like the spectrum of the 2,7-iso-
mer, shows a broadened band at 280 nm.
The arrangement of the substituents in the 2- and
6-positions causes a higher polarity of the compound as
compared to the 2,7-substituted product. This is indi-
cated by a longer retention time for the 2,6-isomer: the
retention index is 0.8.
The third product is tetrasubstituted neutral 3-
methyl-2,8-bis(N,N-dimethyl-N-(chloromethyl)ammo-
nium)-7-chlorohydro-closo-decaborane
(compo-
RUSSIAN JOURNAL OF INORGANIC CHEMISTRY Vol. 51 No. 10 2006