Synthesis, structure, and reactivity of C-isopropyl-ortho-carborane organoboron derivatives

Article abstract of DOI:10.1007/s11172-014-0745-x

A reaction of isopropyl-ortho-carborane with n-butyllithium, followed by treatment of the lithium derivative formed with boron trichloride, chlorodimethoxyborane, or chloropinacolatoborane furnished C-boryl-ortho-carboranes 1a-c. Further functionalization

Full text of DOI:10.1007/s11172-014-0745-x

Russian Chemical Bulletin, International Edition, Vol. 63, No. 10, pp. 2343—2350, October, 2014
2343
Synthesis, structure, and reactivity
of Cꢀisopropylꢀorthoꢀcarborane organoboron derivatives*
S. V. Svidlov,a,b Ya. Z. Voloshin,b N. S. Yurgina,a T. V. Potapova,a A. Yu. Belyy,c I. V. Ananyev,b and Yu. N. Bubnova,b
aN. D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences,
47 Leninsky prosp., 119991 Moscow, Russian Federation
bA. N. Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences,
28 ul. Vavilova, 119991 Moscow, Russian Federation.
Fax: +7 (499) 135 5085. Eꢀmail: voloshin@ineos.ac.ru
cHigher Chemical College of the Russian Academy of Sciences,
9 Miusskaya pl., 125047 Moscow, Russian Federation
A reaction of isopropylꢀorthoꢀcarborane with nꢀbutyllithium, followed by treatment of the
lithium derivative formed with boron trichloride, chlorodimethoxyborane, or chloropinacolatoꢀ
borane furnished Cꢀborylꢀorthoꢀcarboranes 1a—c. Further functionalization of 1ꢀCl2Bꢀ2ꢀPriꢀ
1,2ꢀC2B10H10 (1a) with pentafluorophenylmagnesium bromide or pentafluorophenol led to
1ꢀ(C6F5)2Bꢀ2ꢀPriꢀ1,2ꢀC2B10H10 (2) and (1ꢀ(C6F5O)Bꢀ2ꢀPriꢀ1,2ꢀC2B10H10)2O (3), respectively.
A reaction of 1ꢀ(MeO)2Bꢀ2ꢀPriꢀ1,2ꢀC2B10H10 (1b) with the complexes of BH3 with THF and
dimethyl sulfide gave rise to carboranylborane adducts 4a,b. The use of the complex of 1ꢀH2Bꢀ
2ꢀPriꢀ1,2ꢀC2B10H10 with dimethyl sulfide 4b as a hydroboration agent in the reactions with
hexꢀ1ꢀene and phenylacetylene allowed us to obtain dialkylꢀ and di(phenylolefin)ꢀcontaining
Cꢀisopropylꢀorthoꢀcarboranylboranes, respectively. The reaction of Cꢀisopropylꢀorthoꢀcarboꢀ
ranyldimethoxyborane with triallylborane led to the substitution of only one of two MeO groups
with the allyl one, which is explained by the steric effects of bulky carboranyl substituent in the
precursor. Compounds obtained are characterized by Xꢀray diffraction analysis.
Key words: carboranes, carboranylboranes, perfluoroarylboranes, hydroboration.
Derivatives of icosahedral carborane C2B10H12 are of
undoubted interest for modern materials science, enerꢀ
getics, organic catalysis, and medicine, which is explained
by their unusual chemical properties and cageꢀlike naꢀ
ture.1,2 A large amount of boron atoms in their molecules
makes this type of compounds promising agents for boron
neutron capture therapy of cancer.3 Besides, a unique reꢀ
activity of organoboron compounds allows one to use them
as a powerful synthetic instrument in various fields of orꢀ
ganic, organoelement, and pharmaceutical chemistry. At
the same time, the chemistry of boron derivatives with
carboranyl substituents RCB10H10C—BX2 is not yet fully
developed: only several methods for the synthesis of this
class of compounds are elaborated; by now, molecular and
crystal structures are determined only for a limited numꢀ
ber of compounds of a similar type.4 It was found, that the
reactivity of Cꢀboronꢀsubstituted carboranes has a specific
feature to readily cleave the exoꢀB—Ccore bond in their
molecules.
The purpose of the present work is the development of
synthetic strategy for the preparation of Cꢀisopropylꢀorthoꢀ
carborane derivatives, the establishment of their structure
(including involvement of Xꢀray diffraction analysis), as
well as the studies of reactivity of these compounds.
Results and Discussion
Carboranylboranes can be obtained by two principal
methods: (1) the B—C bond formation via the reaction of
haloboranes with carborane lithium derivatives and (2)
interconversions of Cꢀborylcarboranes5 (thermal transꢀ
formations, nucleophilic substitution, etc). CꢀBorylꢀorthoꢀ
carboranes 1a—c were synthesized by the first of these
methods, namely, by lithiation6,7 of isopropylꢀorthoꢀcarbꢀ
orane with butyllithium in diethyl ether with subsequent
treatment of the lithium derivative formed with the correꢀ
sponding chloroboranes (Scheme 1).
Dichloroborane 1a was further functionalized using
pentafluorophenylmagnesium bromide C6F5MgBr and
pentafluorophenol C6F5OH as nucleophiles. The interest
to such perfluorophenylꢀsubstituted boranes is caused by
the fact that this type of compounds (with two or three
* Dedicated to the 60th anniversary of A. N. Nesmeyanov Instiꢀ
tute of Organoelement Compounds of the Russian Academy
of Sciences.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 2343—2350, October, 2014.
1066ꢀ5285/14/6310ꢀ2343 © 2014 Springer Science+Business Media, Inc.

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Svidlov et al.
Scheme 1
The use of pentafluorophenol as a nucleophile in the
reaction with dichloroborane 1a led to oxide 3 (Scheme 3),
the mechanism of the formation of which, apparently, is
similar to that described earlier for the reaction of pentaꢀ
fluorophenol with PCl5.9 Molecular structure of comꢀ
pound 3 was established by Xꢀray analysis.
Scheme 3
X = Cl (a), MeO (b), chloropinacolatoborane (c)
perfluorophenyl groups) are capable of reversible binding
molecular hydrogen in the presence of sterically hindered
Lewis bases.8 At the same time, carborane perfluoroꢀ
phenylboryl derivatives are not yet described in the literaꢀ
ture. The reaction of dichlorocarboranylborane 1a with
two equivalents of C6F5MgBr in diethyl ether led to
di(perfluorophenyl)boryl derivative 2 (Scheme 2). The
11B{1H} NMR spectrum of this compound exhibits signals
for four boron atoms of the cluster fragment at  –10.7,
–6.3, –3.2, and 3.0 and a signal for the boron atom of the
di(perfluorophenyl)boryl fragment at  73.4.
The known10 methods for the synthesis of carboraneꢀ
containing boron hydrides are characterized by low or
moderate yields (7—55%). We suggested and successfully
used a new simple approach to the preparation of this type
of compounds from methyl carboranylboronate. In parꢀ
ticular, we found that the ester groups in (Cꢀisopropylꢀ
orthoꢀcarboranyl)dimethoxyborane 1b can be easily reꢀ
placed with the hydrogen atom as a result of the reacꢀ
tion with derivatives of parent borane, viz., the complexꢀ
es of BH3 with THF and dimethyl sulfide (Scheme 4).
The reaction of borane 4a with the equimolar amount
of 4ꢀ(dimethylamino)pyridine (DMAP) in hexane gave
crystals of complex 4c, whose crystal and molecular
structures were established by Xꢀray diffraction studies
(see below).
Scheme 2
Hydroboration of hexꢀ1ꢀene and phenylacetylene with
the dimethyl sulfide complex of Cꢀisopropylꢀorthoꢀcarboꢀ
ranylborane 4b led to the formation of boranes 5 and 6,
respectively. The 1H NMR spectra of the reaction mixture
show that the addition proceeds regiospecifically (Scheme 5).
Both hydroboration reactions are slow (48 and 72 h).

Synthesis and reactivity of Cꢀborylcarboranes
Russ.Chem.Bull., Int.Ed., Vol. 63, No. 10, October, 2014
2345
Scheme 4
tion state. Carrying out the reaction with excess of trialꢀ
lylborane at reduced pressure (200 Torr) and heating to
90 C leads to trihomoallylboronate and a carboraneꢀconꢀ
taining polymer. It is obvious that these products are
formed by the radical mechanism involving molecular
oxygen in trace amounts as a radical initiator.
Scheme 6
All3B (excess)
L = ТHF (а), Me2S (b)
Scheme 5
Xꢀray diffraction studies of Cꢀisopropylꢀorthoꢀcarboraꢀ
nylboranes. The structures of obtained organoboron comꢀ
pounds 1a, 1b, 2, 3, and 4c (Figs 1—5) were established by
single crystal Xꢀray diffraction studies. Principal geometꢀ
ric parameters of the molecules are close to expected valꢀ
ues and insignificantly depend on the nature of substituꢀ
ents in the boryl fragment (Table 1). In particular, in molꢀ
ecules 1a, 1b, 2, and 3 with the trigonal surrounding of
atom B(1), the B(1)—C(2) bond distance ranges within
1.579(2)—1.611(2) Å. At the same time, in the case of
tetracoordinated boron atom in molecule 4c, the B(13)—C(2)
Table 1. Selected geometric characteristics of molecules 1a, 1b,
2, 3, and 4c
i. Et2O, hexꢀ1ꢀene (2.1 equiv.); ii. Et2O,
(2.1 equiv.).
Characꢀ
teristics
1a
1b
2
3
4c
Upon treatment of isopropylꢀorthoꢀcarboranyldimethꢀ
oxyborane with excess of triallylborane, only one of two
methoxy groups is replaced with the allyl one to give carboꢀ
ranylborane 7 (Scheme 6), whereas the second group reꢀ
mains in place even at 90 C. This result can be explained
by the steric effects of bulky carboranyl substituent, which
in this case are more pronounced than in the reaction with
borane complexes, since the mechanism of the methoxyꢀ
toꢀallyl group exchange assumes a sixꢀmembered transiꢀ
C(1)—C(2)/Å 1.681(2) 1.676(2) 1.702(2) 1.6812(19)1.6893(17)
C(2)—B(1)/Å 1.611(3) 1.605(2) 1.579(3) 1.589(2) 1.649(2)
B(1)—Xa/Å 1.715(3) 1.349(3) 1.577(3) 1.351
1.575(
90
b
 /deg
93
104.7
27.9
116
a X is the atoms of a substituent at atom B(1) for all the structures
except 4c; an average value for two substituents is given, for
structure 4c, the B—N bond distance is given.
b The torsion angle C(1)—C(2)—B(1)—X, choosing the X so that
the angle  has a positive value.

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Russ.Chem.Bull., Int.Ed., Vol. 63, No. 10, October, 2014
Svidlov et al.
bond distance is expectedly considerably longer (1.649(2) Å).
In molecules 1a, 1b, and 3, the plane, which is formed by
substituents at the boron atom B(1), is orthogonal to the
C(1)—C(2) bond in the carborane cage, whereas the corꢀ
responding dihedral angles change from 93 to 116. Conꢀ
versely, in molecule 2 this angle is considerably smaller
(27.9), that is apparently explained by the steric repulsion
between the bulky pentafluorophenyl substituents and
the isopropyl group. The change in the position of substitꢀ
uent BX2C with respect to the C(1)—C(2) bond also leads
to a slight change of this bond length. However, in contrast
to Cꢀarylcarboranes studied earlier,11 the orthogonal arranꢀ
F(8)
F(9)
F(7)
F(10)
C(12)
C(5)
F(1)
F(2)
C(3)
B(1)
F(6)
C(6)
C(4)
F(3)
F(4)
C(1)
F(5)
C(2)
C(4)
Cl(1)
Cl(2)
C(3)
С(5)
B(1)
Fig. 3. General view of molecule 2 in representation of nonꢀ
hydrogen atoms with probability ellipsoids of atomic displaceꢀ
ments (p = 50%). Hydrogen atoms are not shown.
C(1)
C(1A)
Fig. 1. General view of molecule 1a in representation of nonꢀ
hydrogen atoms with probability ellipsoids of atomic displaceꢀ
ments (p = 50%). Hydrogen atoms are not shown.
O(1)
C(7)
C(8)
B(1)
F(2)
F(1)
F(3)
C(6)
F(4)
F(5)
O(2)
O(2)
C(4)
O(1)
C(7)
C(3)
B(1)
Fig. 4. General view of molecule 3 in representation of nonꢀ
hydrogen atoms with probability ellipsoids of atomic displaceꢀ
ments (p = 50%). Hydrogen atoms are not shown.
C(5)
C(1)
C(2)
gement makes this bond to be shorter (1.676(2)—1.689(2) Å)
than in the case of the eclipsed conformation (1.702(2) Å).
This demonstrates an exclusive influence of steric factors
on the structural features of molecule 2.
Analysis of crystal packings carried out using geometꢀ
ric criteria showed the absence of noticeable intermolecuꢀ
lar interactions in all the crystals studied by Xꢀray diffracꢀ
tion analysis (see Figs 1—5), except compound 4c. Its
crystal is characterized by the stackingꢀinteraction between
the pyridine rings, combining molecules into the cenꢀ
Fig. 2. General view of molecule 1b in crystal in representation
of nonhydrogen atoms with probability ellipsoids of atomic disꢀ
placements (p = 50%). Hydrogen atoms are not shown.

Synthesis and reactivity of Cꢀborylcarboranes
Russ.Chem.Bull., Int.Ed., Vol. 63, No. 10, October, 2014
2347
C(5)
recorded on a Bruker ACꢀ200P spectrometer (200 MHz).
IR spectra of solution of compounds in dichloromethane in the
400—4000 cm–1 region were obtained on a Bruker Alpha IR
Fourierꢀtransform spectrometer. Mass spectra were recorded on
a Finnigan MAT DSQII instrument (EI, 70 eV).
C(3)
C(4)
B(3)
B(6)
C(1)
B(5)
All the manipulations were carried out under dry argon using
thoroughly dried solvents.
B(13)
C(2)
C(10)
1ꢀIsopropylꢀ2ꢀdimethoxyborylꢀ1,2ꢀdicarbaꢀclosoꢀdodecaꢀ
borane (1b). 1ꢀIsopropylꢀorthoꢀcarborane (10.3 g, 0.055 mol) in
diethyl ether (80 mL) was placed into a threeꢀneck flask equipped
with a dropping funnel, a thermometer, a magnetic stirrer, and
a reflux condenser with an argon lock. The solution obtained was
cooled to –78 C, followed by dropwise addition of 1.6 M soluꢀ
tion of butyllithium in hexane (29 mL, 0.055 mol) at such a rate
that to maintain the temperature below –60 C. After addition of
BuLi, the reaction mixture was warmedꢀup to room temperaꢀ
ture, stirred for 1 h, then cooled to –78 C. A solution of chloroꢀ
dimethoxyborane (6 g, 0.055 mol) in diethyl ether (10 mL) was
added to the mixture at such a rate that to maintain the temperaꢀ
ture below –65 C. After addition of borane, the reaction mixꢀ
ture was warmedꢀup to room temperature and stirred for 10 h.
A white precipitate of LiCl was filtered off, the filtrate was conꢀ
centrated in vacuo of a waterꢀjet pump. Fraction distillation of
the oily residue (139—140 C, 2 Torr) gave 1ꢀisopropylꢀ2ꢀ
dimethoxyborylꢀ1,2ꢀdicarbaꢀclosoꢀdodecaborane (1b) (12.5 g,
92%). 1H NMR, : 0.45—3.5 (br.m, 10 H, B—H); 1.29 (d, 6 H,
Me, J = 5.8 Hz); 2.38 (m, 1 H, CH, J = 5.8 Hz); 3.46 (s, 6 H,
OMe). 13C{1H} NMR, : 21.5 (s, Me); 35.2 (s, CH); 53.4
(s, OMe). 11B{1H} NMR, : –13.9 (br.s, B(3), B(6)); –10.7 (br.s,
B(4), B(5), B(8), B(10)); –7.5 (br.s, B(7), B(11)); –3.3 (br.s,
B(12)); –0.8 (br.s, B(9)); 22.8 (br.s, C—B(OMe)2). Found (%):
C, 32.50; H, 9.00. C7H23B11O2. Calculated (%): C, 32.57;
H, 8.98. MS (EI, 70 eV), m/z (Irel (%)): 259 [M]+ (31), 185
[M – B(OMe)2]+ (100). IR (CH2Cl2), /cm–1: 2985, 2950 (C—H),
2580 (B—H), 1108 (B—O).
N(1)
C(6)
B(4)
C(9)
C(8)
B(7)
C(7)
B(10)
C(12)
B(8)
B(9)
B(11)
B(12)
N(2)
C(11)
Fig. 5. General view of molecule 4c in representation of nonꢀ
hydrogen atoms with probability ellipsoids of atomic displaceꢀ
ments (p = 50%). Hydrogen atoms, except those at atom B(13),
are not shown.
2ꢀ(1ꢀIsopropylꢀ1,2ꢀdicarbaꢀclosoꢀdodecaboraneꢀ2ꢀyl)ꢀ
4,4,5,5ꢀtetramethylꢀ1,3,2ꢀdioxaborolane (1c). Chloropinacolaꢀ
toborane (Pin) (8.1 g, 0.05 mol) was added dropwise to a soluꢀ
tion of isopropylꢀoꢀcarboranyllithium (obtained according to the
procedure for the synthesis of 1b) (0.05 mol) in THF (50 mL) at
–100 C. The mixture was warmedꢀup to room temperature and
allowed to stand for 10 h. The solvent was evaporated in vacuo
(10 Torr), diethyl ether was added, a precipitate formed was
filtered off. The filtrate was concentrated to dryness. Lowꢀtemꢀ
perature crystallization from toluene gave compound 1c as
a colorless fine crystals (8.9 g, 58%). 1H NMR, : 0.75—4.20 (br.m,
10 H, B—H); 1.17 (t, 3 H, Me (Pri), J = 5.9 Hz); 1.22 (s, 12 H,
Me (Pin)); 2.34 (sept, 1 H, CH, J = 5.9 Hz). 13C{1H} NMR,
 14.4 (s, Me (Pri)); 24.1 (s, Me (Pin)); 31.4 (s, CH); 86.3
(s, C—O). 11B{1H} NMR, : –10.3 (br.s, B(3), B(4), B(5), B(6),
B(8), B(10)); –8.1 (br.s, B(7), B(11)); –4.9 (br.s, B(12)), –0.9
(br.s, B(9)), 23.4 (br.s, C—BO2). Found (%): C, 42.25; H, 9.42.
C11H29B11O2. Calculated (%): C, 42.31; H, 9.36. MS (EI, 70 eV),
m/z (Irel (%)): 312 [M]+ (40), 185 [M – BPin]+(100). IR
(CH2Cl2), /cm–1: 2977, 2963 (C—H), 2572 (B—H), 1102 (B—O).
1ꢀIsopropylꢀ2ꢀdipentafluorophenylborylꢀ1,2ꢀdicarbaꢀclosoꢀ
dodecaborane (2). Magnesium turnings (0.42 g, 0.0175 mol) in
diethyl ether (50 mL) were placed into a threeꢀneck flask
equipped with a dropping funnel, a reflux condenser, and a magꢀ
netic stirrer. The mixture was activated with several drops of
dibromoethane, followed by a dropwise addition of bromoꢀ
Fig. 6. Formation of centrosymmetric dimers due to the interꢀ
molecular stackingꢀinteractions in crystal 4c. Hydrogen atoms
are not shown.
trosymmetric dimers (Fig. 6): the distance between the
meanꢀsquare planes passing atoms N(1), C(6), C(7), C(8),
C(9), and C(10) is ~3.51 Å and the aromatic rings are
displaced with respect to each other by ~1.55 Å.
Experimental
Commercial 1.6 M solution of BuLi (in hexane), 1 M soluꢀ
tion of BCl3 (in hexane), C6F5Br, C6F5OH, BH3•SMe2,
4ꢀ(dimethylamino)pyridine, hexꢀ1ꢀene, phenylacetylene (Aldrich)
were used without additional purification. CꢀIsopropylꢀorthoꢀ
carboranyldichloroborane (1a),6 chlorodimethoxyborane,12
chloropinacolatoborane,13 C6F5MgBr,14 BH3•THF,15 and triꢀ
allylborane16 were obtained according to the procedures pubꢀ
lished earlier.
Elemental analyses for carbon and hydrogen were performed
on a Carlo Erba, model 1106 microanalyzer. 1H, 11B, and
13C NMR spectra of solutions of compounds in CDCl3 were

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Svidlov et al.
pentafluorobenzene (2.2 mL, 0.0175 mol) with stirring. The reꢀ
action mixture was refluxed for 1 h. Pentafluorophenylmagneꢀ
sium bromide obtained was added dropwise to a solution of isoꢀ
propyldichloroborylꢀorthoꢀcarborane 1a (2.3 g, 8.75 mmol) in
benzene (30 mL). The solvent was evaporated from the reaction
mixture in vacuo (10 Torr), pentane was added. A precipitate
formed was filtered off and recrystallized from toluene, the yield
was 4.1 g (88%). 1H NMR, : 1.11 (d, 6 H, Me, J = 5.3 Hz); 2.12
(sept, 1 H, CH, J = 5.3 Hz). 13C{1H} NMR,  22.7 (s, Me); 34.8
(s, CH). 11B{1H} NMR,  –10.7 (br.s, B(3), B(4), B(5), B(6),
B(8), B(10)); –6.3 (br.s, B(7), B(11)); –3.2 (br.s, B(12)); 3.0 (br.s,
B(9)); 73.4 (br.s, B(C6F5)2). 19F NMR,  –126.5 (m, orthoꢀF);
–145.9 (m, paraꢀF); –158.3 (m, metaꢀF). Found (%): C, 38.24;
H, 3.18. C17H17B11F10. Calculated (%): C, 38.33; H, 3.22. MS
(EI, 70 eV), m/z (Irel (%)): 530 [M]+ (37), 185 [M – B(C6F5)2]+
(100). IR (CH2Cl2), /cm–1: 2988, 2944, 2918 (C—H); 2610,
2569 (B—H).
Bis(Cꢀisopropylꢀorthoꢀcarboranyl(pentafluorophenoxy)borꢀ
yl)oxide (3). Isopropylꢀorthoꢀcarboranyldichloroborane 1a (0.78 g,
2.9 mmol) was dissolved in dichloromethane (5 mL) in a flask
equipped with a dropping funnel with an argon lock and a magꢀ
netic stirrer, followed by a dropwise addition of a solution of
pentafluorophenol (1.07 g, 5.8 mmol) in dichloromethane
(5 mL) with stirring. Volatile components were evaporated in vacuo
(10 Torr). Hexane (2 mL) was added to the dark brown oil obꢀ
tained. A light yellow precipitate was filtered off and the product
was recrystallized from hexane. The yield was 1.02 g (90%).
1H NMR, : 1.30 (d, 6 H, Me, J = 5.5 Hz); 2.50 (sept, 1 H, CH,
J = 5.5 Hz). 13C{1H} NMR, : 24.4 (s, Me); 35.6 (s, CH). 11B{1H}
NMR, : –11.3 (br.s, B(3), B(4), B(5), B(6), B(8), B(10)); –7.8
(br.s, B(7), B(11)); –4.0 (br.s, B(12)); 0.5 (br.s, B(9)); 23.1 (br.s,
B—O). 19F NMR, : –156.3 (m, 4 F, orthoꢀF); –159.6 (m, 2 F,
paraꢀF); –161.9 (m, 4 F, metaꢀF). Found (%): C, 34.29; H, 4.38.
C22H34B22F10O3. Calculated (%): C, 34.12; H, 4.43. MS (EI,
70 eV), m/z (Irel (%)): 774 [M]+ (100). IR (CH2Cl2), /cm–1: 2944,
2918, 2853 (C—H); 2578 (B—H); 1536, 1520 (C=C); 1015 (B—O).
1ꢀIsopropylꢀ2ꢀ(tetrahydrofuranboryl)ꢀ1,2ꢀdicarbaꢀclosoꢀdoꢀ
decaborane (4a). Isopropyldimethoxyborylꢀorthoꢀcarborane 1b
(0.97 g, 4 mmol) was dissolved in THF (50 mL) in a threeꢀneck
flask equipped with a reflux condenser, a dropping funnel, and
a magnetic stirrer, followed by a dropwise addition of 1.85 M soluꢀ
tion of BH3 in THF (2.1 mL) and stirring of the reaction mixture
for 2 h. Then, the solvent was evaporated in vacuo (10 Torr) and
the solid residue obtained was recrystallized from pentane. The
yield of a white finely crystalline product was 1.1 g (96%).
1H NMR, : 0.75—4.1 (br.m, 12 H, B—H); 1.1 (d, 6 H, Me,
J = 5.0 Hz); 2.18 (m, 4 H, CH2); 2.42 (sept, 1 H, CH, J = 5.0 Hz);
4.25 (t, 4 H, CH2O, J = 5.0 Hz). 13C{1H} NMR, : 24.4 (s, Me);
25.3 (s, CH2); 31.9 (s, CH); 79.5 (s, C—O). 11B{1H} NMR,
: –10.92 (br.s, B(3), B(4), B(5), B(6), B(8), B(10)); –9.4 (br.s,
B(7), B(11)); –4.2 (br.s, B(9), B(12)); 2.88 (br.s, BH2). Found (%):
C, 39.91; H, 9.98. C9H27B11O. Calculated (%): C, 40.00;
H, 10.07. MS (EI, 70 eV), m/z (Irel (%)): 199 [M – THF]+ (100).
IR (CH2Cl2), /cm–1: 2984, 2952, 2944, 2896 (C—H); 2576
(B—H), 2448 (B—H (BH2)).
ether (10 mL) was added to the reaction mixture at room temꢀ
perature and it was stirred for 1 h and then concentrated in vacuo.
The residue was dried in vacuo (1—2 Torr) to obtain the target
compound 4b (7.16 g, 96%) as a clear oily liquid, sensitive to
1
atmospheric oxygen and moisture. H NMR, : 0.8—3.6 (br.m,
12 H, B—H,); 1.15 (d, 6 H, CMe, J = 6.9 Hz); 2.33 (s, 6 H,
SMe); 2.48 (sept, 1 H, C—H, J = 6.9 Hz). 13C{1H} NMR,
: 24.5 (s, CMe); 32.1 (s, CH); 25.1 (s, SMe). 11B{1H} NMR,
: –10.4, –9.4, –4.14 (all br.s, B—H + BH2). Found (%): C, 32.21;
H, 9.58. C7H25B11S. Calculated (%): C, 32.31; H, 9.68. MS (EI,
70 eV), m/z (Irel (%)): 260 [M]+ (100). IR (CH2Cl2), /cm–1
:
2977, 2943, 2932, 2878 (C—H); 2573 (B—H); 2409 (B—H
(BH2)).
1ꢀIsopropylꢀ2ꢀ[4ꢀ(dimethylamino)pyridineboryl]ꢀ1,2ꢀdicarbaꢀ
closoꢀdodecaborane (4c). 4ꢀ(Dimethylamino)pyridine (1 equiv.)
was added to borane 4a (0.8 g, 3 mmol) in hexane (50 mL). The
reaction mixture was refluxed for 2 h. Lowꢀtemperature crystalꢀ
lization gave 4c as a colorless crystalline compound. The yield
1
was 0.7 g (81%). H NMR, : 0.70—3.70 (br.m, 12 H, B—H);
1.15 (d, 6 H, CMe, J = 6.9 Hz); 2.71 (sept, 1 H, CH (Pri),
J = 6.9 Hz); 3.14 (s, 6 H, NMe); 6.55 (d, 2 H, C—Harom
,
J = 7.5 Hz); 7.90 (d, 2 H, C—Harom, J = 7.5 Hz). 13C{1H} NMR,
: 24.5 (s, CMe); 31.6 (s, CH (Pri)); 39.7 (s, NMe); 106.5
(s, metaꢀC); 147 (s, orthoꢀC); 155.6 (s, paraꢀC). 11B{1H} NMR,
: –10.0, –8.4, –5.3, –3.8 (all br.s, B—H + BH2). Found (%):
C, 45.11; H, 9.19. C12H29B11N2. Calculated (%): C, 45.00;
H, 9.13. MS (EI, 70 eV), m/z (Irel (%)): 320 [M]+ (100).
2ꢀDi(nꢀhexyl)borylꢀ1ꢀisopropylꢀ1,2ꢀdicarbaꢀclosoꢀdodecaꢀ
borane (5). Hexꢀ1ꢀene (1.2 mL, 0.010 mol) in diethyl ether (5 mL)
was added dropwise to a solution of 1ꢀisopropylꢀ2ꢀ(dimethylsulꢀ
fideboryl)ꢀ1,2ꢀdicarbaꢀclosoꢀdodecaborane (4b) (5 mL, 0.004 mol)
in diethyl ether (10 mL) at 0 C and the mixture was stirred for
48 h at room temperature. Then, the reaction mixture was conꢀ
centrated in vacuo (10 Torr). Fraction distillation of an oily resiꢀ
due (130—132 C, 0.5 Torr) gave 2ꢀdi(nꢀhexyl)borylꢀ1ꢀisoproꢀ
pylꢀ1,2ꢀdicarbaꢀclosoꢀdodecaborane (5) (1.3 g, 94%) as a colorꢀ
less liquid. 1H NMR, : 0.70—3.70 (br.m, 42 H, nꢀC6H13
+
+ B—H + Me(Pri)); 2.22 (sept, 1 H, C—H, J = 6.9 Hz). 13C{1H}
NMR, : 14.1, 15.8, 21.8, 22.6, 24.8, 34.9, 38.1 (all s). 11B{1H}
NMR, : –11.4, –8.3, –4.5, –1.50 (all br.s, B—H); 69.2 (br.s,
B(nꢀC6H13)2). Found (%): C, 55.81; H, 11.91. C17H43B11. Calꢀ
culated (%): C, 55.72; H, 11.83. MS (EI, 70 eV), m/z (Irel (%)):
366 [M]+ (100). IR (CH2Cl2), /cm–1: 2981, 2975, 2944, 2956
(C—H); 2576 (B—H).
1ꢀIsopropylꢀ2ꢀdi(phenylethylenyl)borylꢀ1,2ꢀdicarbaꢀclosoꢀ
dodecaborane (6). Phenylacetylene (1.0 g, 0.010 mol) was added
dropwise to a solution of 1ꢀisopropylꢀ2ꢀ(dimethylsulfideboryl)ꢀ
1,2ꢀdicarbaꢀclosoꢀdodecaborane (4b) (1.1 g, 4 mmol) in diethyl
ether (10 mL) at 0 C and the mixture was stirred for 72 h (reacꢀ
1
tion progress was monitored by H NMR spectroscopy). The
reaction mixture was concentrated to dryness. The target prodꢀ
uct 6 (1.43 g, 94%) was obtained by crystallization from hexane
(30 mL) as a light yellow crystalline compound, extremely sensitive
1
to atmospheric oxygen and moisture. H NMR, : 0.80—3.50
(br.m, 10 H, B—H); 1.11 (d, 6 H, Me, J = 6.9 Hz); 2.19 (sept, 1 H,
CH, J = 6.9 Hz); 7.15 (d, 2 H, BCH, J = 17.7 Hz); 7.5 (d, 2 H,
CHPh, J = 17.7 Hz); 7.39—7.50, 7.60—7.68 (both m, Ph).
13C{1H} NMR, : 24.7 (s, Me); 34.8 (s, CH); 128.5, 129.1,
130.8 (all s, Ph); 132.1 (br.s, BCH=); 136.9 (s, ipsoꢀC, Ph);
156.8 (s, PhCH=). 11B{1H} NMR, : –11.2, –8.3, –4.2, –0.9
(all br.s, B—H); 59.4 (br.s, B(HC=CHPh)2). Found (%):
1ꢀIsopropylꢀ2ꢀ(dimethylsulfideboryl)ꢀ1,2ꢀdicarbaꢀclosoꢀdodeꢀ
caborane (4b). 1ꢀIsopropylꢀ2ꢀdimethoxyborylꢀ1,2ꢀdicarbaꢀclosoꢀ
dodecaborane (1b) (7.3 g, 0.028 mol) was dissolved in diethyl
ether (50 mL) in a threeꢀneck flask equipped with a magnetic
stirrer, a thermometer, and a dropping funnel and cooled to
0 C. A solution of BH3•SMe2 (5 mL, 0.053 mol) in diethyl

Synthesis and reactivity of Cꢀborylcarboranes
Russ.Chem.Bull., Int.Ed., Vol. 63, No. 10, October, 2014
2349
Table 2. Principal crystallographic and refinement parameters for compounds 1a, 1b, 2, 3, and 4c
Parameter
1a
1b
2
3
4c
Molecular formula
Molecular weight
T/K
C5H17B11Cl2
267.00
120
C7H23B11O2
258.16
120
C17H17B11F10
530.22
120
C22H34B22F10O3
774.31
100
C12H29B11N2
320.28
100
Crystal system
Space group
Z
Orthorhombic
Pnma
Monoclinic
P21
Monoclinic
P21/n
Monoclinic
C2/c
Tricl–inic
P1
4
2
4
4
2
a/Å
b/Å
c/Å
/deg
/deg
/deg
12.7950(9)
14.1447(10)
7.7724(5)
90.00
90.00
90.00
1406.66(17)
1.261
6.9154(7)
13.1723(13)
8.3087(8)
90.00
95.860(2)
90.00
9.6555(9)
13.1802(13)
17.6533(17)
90.00
93.641(2)
90.00
2242.0(4)
1.571
1.42
18.7905(13)
8.7596(6)
22.3636(14)
90.00
97.8193(16)
90.00
3646.8(4)
1.410
1.13
9.6043(9)
10.4412(10)
10.9318(10)
107.689(2)
109.329(2)
96.875(2)
955.50(16)
1.113
3
V/Å
752.90(13)
1.139
dcalc/g cm–3
/cm–1
4.26
0.62
0.56
F(000)
544
272
1056
1560
340
2max/deg
58
57
58
58
58
Reflections collected
Number of independent reflections
Number of reflections with I > 2(I)
Number of refined
parameters
11199
2031
1513
145
5212
2085
1998
225
24281
5951
4150
385
10150
4791
3489
300
11305
5046
3511
278
R1/wR2
GOF
0.0313/0.0873
1.014
0.0320/0.0862
1.048
0.0518/0.1331
1.003
0.0402/0.1111
1.029
0.0499/0.1451
1.028
Residual electron density
–0.210/0.308
–0.184/0.238
–0.244/0.421
–0.224/0.374
–0.207/0.294
–3

min/max/e Å
C, 62.55; H, 7.81. C21H31B11. Calculated (%): C, 62.68; H, 7.77.
MS (EI, 70 eV), m/z (Irel (%)): 402 [M]+ (100). IR (CH2Cl2),
/cm–1: 3050 (C—Harom); 2975, 2953 (C—H); 2573 (B—H);
1560 (C=C).
approximation on F2hkl. In crystal of 1a, molecules are located
on the crystallographic plane m, which leads to the overlap of
the Pri and BCl2 groups. The superposition of these group is
also retained in the case of noncentrosymmetric group Pna21,
that indicates the independence of the static disordering from
the crystal symmetry. Apparently, the disordering is explained
by the absence of strong nonvalent interactions for these substitꢀ
uents, capable of discrimination of these functional groups when
forming the crystal. Positions of hydrogen atoms at boron atoms
of the carboranyl group were localized from the difference
Fourierꢀsyntheses of electron density and refined in isoꢀ
tropic approximation, other hydrogen atoms were placed in
geometrically calculated positions. Principal crystallographic
data and parameters of refinement are given in Table 2. All
the calculations were carried out using the SHELXTL PLUS
software.17
2ꢀAllylmethoxyborylꢀ1ꢀisopropylꢀ1,2ꢀdicarbaꢀclosoꢀdodecaboꢀ
rane (7). 1ꢀIsopropylꢀ2ꢀdimethoxyborylꢀ1,2ꢀdicarbaꢀclosoꢀdodeꢀ
caborane (1b) (0.8 g, 3 mmol) and triallylborane (0.84 mL, 5
mmol) were placed in a twoꢀneck flask equipped with a magnetꢀ
ic stirrer and a reflux condenser with an argon lock. The reaction
mixture was stirred for 2 h, volatile components were
evaporated in vacuo (10 Torr) to obtain the target product (0.86 g,
1
98%) as a clear oily liquid. H NMR, : 0.8—3.5 (br.m, 10 H,
B—H); 1.13 (d, 6 H, Me, J = 6.9 Hz); 2.15 (d, 2 H, CH2, J = 7.4 Hz);
2.28 (sept, 1 H, CH, J = 6.9 Hz); 3.91 (s, 3 H, OMe); 5.04—5.87
(m, 2 H, CH2); 5.77 (ddt, 1 H, =CH, Jtrans = 17.3 Hz, Jcis = 9.8 Hz,
J = 7.4 Hz). 13C{1H} NMR (50.32 MHz), : 24.4 (s, Me); 33.1
(br.s, CH2); 34.3 (s, CH); 55.5 (s, Me); 117.9 (s, CH=CH2);
130.4 (s, CH=CH2). 11B{1H} NMR, : –11.4, –8.4, –4.4, –0.9
(all br.s, B—H); 43.3 (br.s, B(OMe)All). Found (%): C, 40.15;
H, 9.47. C9H25B11O. Calculated (%): C, 40.30; H, 9.40. MS
The full Xꢀray diffraction data are available from the
Cambridge Structural Database (CCDC 1010870—1010874,
www.ccdc.ac.uk).
(EI, 70 eV), m/z (Irel (%)): 269 [M]+ (100). IR (CH2Cl2), /cm–1
:
References
2981, 2944 (C—H); 2575 (B—H).
Xꢀray diffraction studies of compounds 1a, 1b, and 2 were
performed on a SMART 1000 CCD diffractometer (graphite
monochromator, MoꢀK radiation, ꢀscan technique). The
structures 3 and 4c were solved using an APEX II CCD diffracꢀ
tometer (graphite monochromator, MoꢀK radiation, ꢀscan
technique). All the structure were solved by direct method and
refined by the least squares method in anisotropic fullꢀmatrix
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Received July 4, 2014;
in revised form August 20, 2014