The first carborane triflates: Synthesis and reactivity of 1-trifluoromethanesulfonyImethyl- And 1,2-bis(trifluoromethanesulfonylmethyl)-o- carborane

Article abstract of DOI:10.1039/b417199c

The first carborane Inflates, namely, 1-trifluoromethanesulfonylmethyl-o- carborane (2) and 1,2-bis(trifluoromethanesulfonylmethyl)-o-carborane (7), were obtained in high yields in the reactions of 1-hydroxymethyl-o-carborane (1) or 1,2-bis(hydroxymethyl)-o-carborane (6) with triflic anhydride (Tf₂O) in CH₂Cl₂ in the presence of pyridine. When an excess of pyridine is employed, 1-o-carboranylmethylpyridinium triflate (3), which retains a closo-icosahedral structure, or a pyridinium salt (4) with a zwitterionic nido-dicarbaundecaborate anion are obtained from 1, while the nido compound 8 is formed from 6. The reaction of compound 2 or 7 with excess pyridine also gave 3 or 8, respectively. Compound 2 proved to be a convenient carboranylmethylating agent which reacts with nucleophiles (e.g., potassium phthalimide, PPh ₃ or KCN) to give the corresponding substitution products N-[(o-carboranyl-1-yl)methyl]phthalimide (9), o-carboranylmethylphosphonium salt 10, and 1-cyanomethyl-o-carborane (11). All compounds were characterized by ¹H and ¹¹B NMR spectroscopy. The structures of compounds 4, 7 and 8 were established by X-ray analysis. The Royal Society of Chemistry 2005.

Full text of DOI:10.1039/b417199c

View Article Online / Journal Homepage / Table of Contents for this issue
F U L L P A P E R
The first carborane triflates: synthesis and reactivity of
1-trifluoromethanesulfonylmethyl- and
1,2-bis(trifluoromethanesulfonylmethyl)-o-carborane†
V. N. Kalinin,*a E. G. Rys,a A. A. Tyutyunov,a Z. A. Starikova,a A. A. Korlyukov,a
V. A. Ol’shevskaya,a D. D. Sung,b A. B. Ponomaryov,a P. V. Petrovskiia and E. Hey-Hawkinsc
a A. N. Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences,
28 Vavilova str., Moscow, 119991, Russia. E-mail: vkalin@ineos.ac.ru; Fax: +7095/1356549
b Department of Chemistry, Dong-A University, Pusan, Korea.
E-mail: ddsung@seunghak.donga.ac.kr; Fax: +8251/2007259
c Institut fu¨r Anorganische Chemie der Universita¨t Leipzig, Johannisallee 29, 04103, Leipzig,
Germany. E-mail: hey@rz.uni-leipzig.de; Fax: +0341/9739319
Received 10th November 2004, Accepted 7th January 2005
First published as an Advance Article on the web 28th January 2005
The first carborane triflates, namely, 1-trifluoromethanesulfonylmethyl-o-carborane (2) and
1,2-bis(trifluoromethanesulfonylmethyl)-o-carborane (7), were obtained in high yields in the reactions of
1-hydroxymethyl-o-carborane (1) or 1,2-bis(hydroxymethyl)-o-carborane (6) with triflic anhydride (Tf2O) in CH2Cl2
in the presence of pyridine. When an excess of pyridine is employed, 1-o-carboranylmethylpyridinium triflate (3),
which retains a closo-icosahedral structure, or a pyridinium salt (4) with a zwitterionic nido-dicarbaundecaborate
anion are obtained from 1, while the nido compound 8 is formed from 6. The reaction of compound 2 or 7 with excess
pyridine also gave 3 or 8, respectively. Compound 2 proved to be a convenient carboranylmethylating agent which
reacts with nucleophiles (e.g., potassium phthalimide, PPh3 or KCN) to give the corresponding substitution products
N-[(o-carboranyl-1-yl)methyl]phthalimide (9), o-carboranylmethylphosphonium salt 10, and 1-cyanomethyl-
o-carborane (11). All compounds were characterized by 1H and 11B NMR spectroscopy. The structures of
compounds 4, 7 and 8 were established by X-ray analysis.
Introduction
The synthesis of carboranylmethylating agents which allow
the introduction of a carboranylmethyl group into organic
and natural compounds is of major interest in the medicinal
chemistry of carboranes,2 as this generates compounds suitable
for boron neutron capture therapy of tumors.3 A simple solution
of this problem would be the application of 1-halomethyl-
Scheme 1
o-carborane, but the carborane cage does not allow their
The reaction of 1 with Tf2O and an excess of pyridine can give
use in Friedel–Crafts reactions, even with activated aromatic
different compounds, namely 1-o-carboranylmethylpyridinium
hydrocarbons. Thus, prolonged heating of 1-bromomethyl-o-
triflate (3), which retains a closo-icosahedral structure, or the
carborane with sodium iodide in acetone at 170 ◦C results only
pyridinium salt 4 with a zwitterionic nido-dicarbaundecaborate
in partial replacement of bromide by iodide.4 An example of a
anion. The latter is obtained when aqueous pyridine is employed
compound that is more reactive than 1-halomethyl-o-carboranes
(Scheme 2). The introduction of a strongly electron withdrawing
is 1-tosyloxymethyl-o-carborane, which in some cases reacts
substituent into the carborane cage facilitates deboronation
with secondary amines to give carboranylmethylamines,5 while
and formation of the dicarbaundecaborate anion;12 thus, the
attempts to react 1-mesyloxymethyl-o-carborane with triethyl
polyhedral framework in substituted closo-carboranyl triflates
phosphite and sodium diethylphosphide failed.6 With the aim of
will be less stable toward the action of bases.
synthesizing a more efficient carboranylmethylating reagent, we
The unusual course of the reaction of compound 1 with Tf2O
prepared previously unknown carboranylmethyl triflates. We ex-
in the presence of an excess of pyridine is due to the strong
pected that the strong electron-withdrawing effect of the triflate
electron-acceptor effect of the triflate group in 2, which is formed
group [ri (CF3SO3) = +0.847 would enhance the reactivity of
in the early stages of the reaction and immediately reacts with
carboranylmethyl triflates in nucleophilic substitution reactions
excess pyridine with replacement of the triflate group by pyridine
compared to 1-mesyloxymethyl-o-carborane [ri (MeSO3) =
to afford 3. The reaction between the pyridinium salt 3 and
+0.61], and 1-tosyloxymethyl-o-carborane [ri (MeC6H4SO3) =
aqueous pyridine (strong nucleophile) results in deboronation of
+0.54].7 Being a good leaving group, triflate is widely used in
the carborane polyhedron of 3 to produce the nido zwitterionic
organic syntheses in nucleophilic substitution reactions.8–10
salt 4, which is also favored by the strong electron-withdrawing
effect of the pyridinium group. The reaction of 2 with pyridine
Results and discussion
gives 3, which was isolated and in turn reacted with aqueous
pyridine to form 4. This confirms the reaction pathway discussed
above (Scheme 3). Compound 4 was previously obtained as a
mixture with the boron-substituted pyridinium derivatives in the
reaction of 1-bromomethyl-o-carborane with pyridine in boiling
toluene but was only characterized by elemental analyses.13
To confirm the assumption of a decisive role of the electron-
withdrawing effect of the triflate group in the stability of
Hydroxymethyl-o-carborane (1)11 reacts smoothly with Tf2O in
the presence of pyridine (1 : 1 : 1 molar ratio) at −5 to 0 ◦C to
give o-carboranylmethyl triflate (2) (Scheme 1).
† Presented at the 10th International Congress on Neutron Capture
Therapy (Essen), 8–13 September 2002, Germany (ref. 1).
T h i s j o u r n a l i s
T h e R o y a l S o c i e t y o f C h e m i s t r y 2 0 0 5
D a l t o n T r a n s . , 2 0 0 5 , 9 0 3 – 9 0 8
9 0 3
©

View Article Online
Scheme 2
11NMR spectra confirmed the closo-carborane structures of 2,
3, 5, 7, 9, 10 and 11. For all these compounds, changes in the
11B chemical shifts of the ten boron atoms in the corresponding
11B NMR spectra are insignificant compared to the spectrum
17
Scheme 3
of unsubstituted o-C2B10H12 and lie in the range d −1.48 to
12.88 ppm. The 11B NMR spectrum of the zwitterion 4 exhibits
eight signals at d −9.31 to 35.40 ppm corresponding to nine
boron atoms of the nido polyhedron compared to five signals for
the unsubstituted nido-7,8-C2B9H12− anion.17 The spectrum also
contains a dd signal corresponding to B10, which also couples to
the bridging H10 atom of the polyhedron (d −31.31 ppm, JBH
=
135 Hz, JB(l−H) = 41 Hz). The 11B NMR spectrum of 8 also
confirmed the nido structure of the carborane polyhedron and is
Scheme 4
−
similar to the spectrum of the unsubstituted nido-7,8-C2B9H12
anion. Changes in the chemical shifts of the nine boron atoms
1
of the polyhedron are also small.18 The H NMR spectra of
compounds 2, 3, 5, 7, 9 and 11 exhibit singlets for the CH2
1
protons. The H NMR spectrum of compound 3 also exhibits
three groups of pyridinium proton resonances at d 8.07, 8.56
and 8.92 ppm with a relative intensity ratio of 2 : 1 : 2. In the
1H NMR spectra of the nido derivatives 4 and 8 the methylene
protons are magnetically inequivalent and manifest themselves
2
as doublets with JHH = 14 Hz. Apparently, this is due to the
Scheme 5
zwitterionic structure of these compounds. The expected signals
of the pyridinium protons in 4 and 8 also appear as three groups
of resonances with a relative intensity ratio of 2 : 1 : 2.
The structures of compounds 4, 7 and 8 were established by X-
ray analysis (Fig. 1) and selected geometrical data (bond lengths
and torsion angles) are given in Table 1.
the carborane cage in 2, we synthesized 1-mesyloxymethyl-
o-carborane (5)6 under conditions identical to those for the
synthesis of 4 (Scheme 4). In contrast to 3, the carborane 5
is not transformed into the corresponding nido analogue under
the action of aqueous pyridine nor is a pyridinium salt formed.
The pattern established during the synthesis of the triflate
2 clearly manifests itself in the synthesis of bis-triflates. Thus,
1,2-bis(hydroxymethyl)-o-carborane (6)11 smoothly reacts with
Tf2O in the presence of pyridine (1 : 2 : 2 molar ratio) to give the
bis-triflate 7 in good yield (Scheme 5).
In contrast to 2, the reaction of compound 7, which contains
two electron-withdrawing OSO2CF3 groups, with an excess
of pyridine in anhydrous CH2Cl2 at 20 ◦C afforded the nido
compound 8 (Scheme 6). The latter is also obtained directly
from 6, Tf2O and an excess of pyridine.
The reactivity of the triflate group in 2 is typical for
triflates in substitution reactions. The carboranylmethyl triflate
2 smoothly reacts with potassium phthalimide or PPh3 to
give N-[(o-carboranyl-1-yl)methyl]phthalimide (9)14 or the o-
carboranylmethylphosphonium salt 10, respectively (Scheme 7).
Another example of nucleophilic substitution of the triflate
group is the synthesis of 1-cyanomethyl-o-carborane (11)15,16 by
the Pd-catalyzed reaction of 2 with KCN in acetonitrile. No
replacement of the triflate group in 2 by the CN group occurs in
the uncatalyzed reaction.
The triflate substituents in 7 and pyridine rings in 8 have
different orientations relative to the carborane cage. The dis-
similarity in the conformations of the S1–O1–C13–C1–C2–
C15–O4–S2 and CH2Py moieties can be seen from the values
of the corresponding torsion angles in 7 (C1–C2–C15–O4
105.6(2), C2–C1–C13–O1 92.9(2), C1–C13–O1–S1 125.4(1),
C2–C15–O4–S2 165.2(1), C15–C2–C1–C13 0.4(2)◦) and 8 (C8–
C7–C6–N1 146.9(2), C7–C8–C6ꢀ–N1ꢀ 76.7(3), C7–C6–N1–C5
92.1(3), C8–C6ꢀ–N1ꢀ–C5ꢀ 116.4(2), C6–C7–C8–C6ꢀ 10.2(3)◦).
The geometric parameters of the carborane cage in the molecules
of 4 and 8 are very similar.
The most important difference in the geometry of the
carborane cage of 7 and those of 4 and 8 is the shortening of the
˚
C7–C8 bond in 4 and 8 (1.562(2) and 1.592(3) A, respectively)
˚
in comparison to the C1–C2 bond in 7 (1.682(2) A). This can be
regarded as a characteristic feature of a nido carborane cage.
Conclusion
We have synthesized and characterized the first carborane
triflates. The high reactivity of these compounds toward
nucleophilic reagents provides the possibility of performing
The carborane triflates and their derivatives obtained in this
work were characterized by 1H and 11B NMR spectroscopy. The
Scheme 6
9 0 4
D a l t o n T r a n s . , 2 0 0 5 , 9 0 3 – 9 0 8

View Article Online
Scheme 7
Fig. 1 X-Ray structures of compounds 4, 7 and 8.
Table 1 Selected geometrical data (bond lengths and torsion angles) in 4, 7 and 8
4
7
8
C7–C8
C7–C6
1.562(2)
1.512(2)
C1–C2
C2–C15
C1–C13
O1–S1
O4–S2
C1–B4
C1–B6
C2–B3
C2–B11
1.682(2)
1.512(2)
1.511(2)
1.554(1)
1.560(1)
1.697(2)
1.729(2)
1.725(2)
1.712(2)
C7–C8
C7–C6
C8–C6ꢀ
C6–N1
C6ꢀ–N1ꢀ
C7–B11
C8–B9
1.592(3)
1.518(3)
1.514(3)
1.491(3)
1.504(3)
1.619(3)
1.623(3)
C6–N1
1.496(2)
C7–B11
C8–B9
1.617(2)
1.620(2)
C8–C7–C6–N1
C7–C6–N1–C5
90.6(1)
C1–C2–C15–O4
C2–C1–C13–O1
C2–C15–O4–S2
C1–C13–O1–S1
C15–C2–C1–C13
105.6(2)
92.9(2)
165.2(1)
125.4(1)
0.4(2)
C7–C8–C6ꢀ–N1ꢀ
C8–C7–C6–N1
C7–C6–N1–C5
C8–C6ꢀ–N1ꢀ–C5ꢀ
C6–C7–C8–C6ꢀ
76.7(3)
146.9(2)
92.1(3)
116.4(2)
10.2(3)
117.3(1)
previously impracticable transformations leading to various
functional derivatives of carboranes in a simple and selective
manner. Further research in this area is currently in progress.
(128.38 MHz) were recorded with a Bruker AMX-400 spec-
trometer. BF3·Et2O was used as external standard for 11B
NMR, 85% H3PO4 for 31P NMR. The residual proton signals
of the deuterated solvents were used as internal references
1
for H NMR spectra. 1-Hydroxymethyl-o-carborane (1),11 1,2-
Experimental
bis(hydroxymethyl)-o-carborane (6)11 and [PdCl2(PPh3)2 were
19
General remarks
synthesized by literature methods.
All experiments were carried out under dry argon. 1H
(400.13 MHz), 31P (161.9 MHz) and 11B NMR spectra
1-Trifluoromethanesulfonylmethyl-o-carborane (2). A solu-
tion of Tf2O (4.23 g, 15 mmol) in CH2Cl2 (5 mL) was added
D a l t o n T r a n s . , 2 0 0 5 , 9 0 3 – 9 0 8
9 0 5

View Article Online
dropwise to a mixture of carborane 1 (2.4 g, 13.8 mmol) and
pyridine (1.1 g, 14 mmol) in CH2Cl2 (10 mL) at 0–3 ◦C. The
mixture was stirred for 3 h at 20 ◦C and then water (20 mL)
was added. The organic layer was separated, washed with water,
and dried over Na2SO4. After removal of the solvent the oil-like
residue was dissolved in hexane and the solution was cooled to
(0.4 mL, 5 mmol) in CH2Cl2 (10 mL) at 20 ◦C. A suspension
formed after 0.5 h. After stirring for 6 h at 20 C the reaction
mixture was filtered. The precipitate was washed with 10% HCl
(5 mL) and water and then recrystallized from MeCN to give
0.2 g (88.1%) of 4, mp 229–230 ◦C. Analytical and spectroscopic
date are identical to those given above.
◦
4
◦C. The resulting colourless crystals were filtered off. Yield:
1-Mesyloxymethyl-o-carborane (5). A solution of mesyl
chloride (1.1 g, 10 mmol) in CH2Cl2 (5 mL) was added to a
mixture of carborane 1 (1.7 g, 10 mmol) and pyridine (3.5 mL,
43 mmol) in CH2Cl2 (10 mL), at 0 to 3 ◦C. The reaction
mixture was stirred for 5 h at 20 ◦C. Then water (10 mL)
was added and the mixture was stirred for an additional 4 h
at 20 ◦C. The organic layer was separated, successively washed
with 10% HCl (20 mL) and water, and dried over Na2SO4. The
mixture was then filtered and the solvent removed. The residue
was recrystallized from CH2Cl2–hexane to give 1.85 g (55.9%) of
5, mp 61–62 ◦C. Analytical and spectroscopic date are identical
to those published in ref. 6.
3.8 g (89.9%); mp 25–26 ◦C. 1H NMR (CDCl3, d/ppm): d 4.79
(s, 2 H, CH2), 3.80 (s, 1 H, CH carborane), 3.3–1.4 (m, 10 H,
BH). 11B NMR (CDCl3, d/ppm): d −1.58 (d, JBH = 159 Hz,
1 B), −3.41 (d, JBH = 161 Hz, 1 B), −8.69 (d, JBH = 164 Hz,
2 B), −11.67 (d, JBH = 159 Hz, 2 B), −12.84 (d, JBH = 161 Hz,
4 B). Calc. for C4H13B10F3O3S (306.30): C 15.70, H 4.28, B 35.31,
F 18.60. Found: C 16.06, H 4.46, B 35.51, F 18.30%.
[(o-Carboran-1-yl)methyl]pyridinium trifluoromethanesulfo-
nate (3). A solution of Tf2O (3.4 g, 12 mmol) in CH2Cl2 (5 mL)
was added to a mixture of carborane 1 (1.7 g, 10 mmol) and
pyridine (3.5 mL, 43 mmol) in CH2Cl2 (10 mL) at 0–3 ◦C. The
mixture was stirred for 4 h at 20 ◦C. The solvent was removed to
dryness in vacuo. The residue was dissolved in CH2Cl2 (20 mL),
and the solution thus obtained was washed with 10% HCl (2 ×
20 mL) and then with water. The organic layer was separated
and dried over Na2SO4. The solvent was removed in vacuo, and
crystallization from CH2Cl2 gave 3 g (77.9%) of 3, mp 166–
1,2-Bis(trifluoromethanesulfonylmethyl)-o-carborane (7).
A
solution of Tf2O (6.71 g, 24 mmol) in CH2Cl2 (5 mL) was added
dropwise to a mixture of carborane 6 (2.04 g, 10 mmol) and
pyridine (1.7 g, 21 mmol) in CH2Cl2 (15 mL) at 0 to 3 ◦C. The
mixture was stirred for 2 h at 20 ◦C and then water (15 mL) was
added. The organic layer was separated, washed with water and
dried over Na2SO4. The solvent was removed in vacuo and the
residue wa◦s recrystallized from hexane to give 4.0 g (85%) of 7,
mp 66–67 C. 1H NMR (CDCl3, d/ppm): d 4.94 (s, 4 H, CH2),
3.3–1.4 (m, 10 H, BH). 11B NMR (CDCl3, d/ppm): d −1.48 (d,
JBH = 153 Hz, 2 B), −9.60 (d, JBH = 155 Hz, 4 B), −10.32 (d,
JBH = 170 Hz, 3 B), −11.87 (d, JBH = 174 Hz, 1 B). Calc. for
C6H14B10F6O6S2 (468.38): C 15.39, H 3.01, B 23.08, F 24.34.
Found: C 15.54, H 3.25, B 22.49, F 24.04%.
◦
1
3
167 C. H NMR (CDCl3, d/ppm): d 8.92 (d, JHH = 5.6 Hz,
3
2 H-ortho, C5H5N), 8.56 (t, JHH = 7.6 Hz, 1 H-para, C5H5N),
8.07 (dd, 3JHH = 5.6 Hz, 3JHH = 7.6 Hz, 2 H-meta, C5H5N), 5.58
(s, 2 H, CH2), 4.72 (s, 1 H, CH carborane), 3.3–1.4 (m, 10 H,
BH). 11B NMR (CDCl3, d/ppm): d −2.30 (d, JBH = 159 Hz,
1 B), −3.39 (d, JBH = 144 Hz, 1 B), −8.38 (d, JBH = 150 Hz, 2 B),
−12.42 (d, JBH = 130 Hz, 6 B). Calc. for C9H18B10F3NO3S
(385.11): C 27.89, H 4.69, B 28.43. Found: C 27.59, H 4.84,
B 28.14%.
nido-7,8-[Bis(N -pyridinium)methyl]-7,8-dicarbaundecabor-
anyl trifluoromethanesulfonate (8). A solution of Tf2O (6.71 g,
24 mmol) in CH2Cl2 (5 mL) was added dropwise to a mixture
of carborane 6 (2.04 g, 10 mmol) and pyridine (8 mL, 99 mmol)
in CH2Cl2 (15 mL) at 0 to 3 ◦C. The mixture was stirred for
2 h at 20 ◦C. The white precipitate that formed was filtered off,
washed with water and recrystallize◦d from ethanol/water (2:1)
to give 8 (3.5 g, 74%), mp 232–233 C. 1H NMR ([D6]acetone,
nido-7-[(N-Pyridinium)methyl]-7,8-dicarbaundecaborate (4).
A solution of Tf2O (6.8 g, 24 mmol) in CH2Cl2 (5 mL) was
added to a mixture of carborane 1 (3.5 g, 20 mmol) and pyridine
(7 mL, 86 mmol) in CH2Cl2 (15 mL) at 0–3 ◦C. The reaction
◦
mixture was stirred for 6 h at 20 C. Then water (10 mL) was
added and the mixture was stirred for an additional 2 h. The
precipitate formed was filtered off and successively washed with
10% HCl (20 mL) and water. Recrystallization from MeCN gave
4 (3.6 g, 79.3%), mp 231–232 ◦C. Compound 4 was reported in
1973 but was not fully characterized.13 H NMR ([D6]acetone,
3
d/ppm): d 9.09 (d, JHH = 6.0 Hz, 2 H-ortho, C5H5N), 8.76 (t,
3
3JHH = 8.0 Hz, 1 H-para, C5H5N), 8.28 (dd, JHH = 6.0 Hz,
2
3JHH = 8.0 Hz, 2 H-meta, C5H5N), 5.48 (d, JHH = 14.0 Hz,
3
d/ppm): d 9.05 (d, JHH = 6.0 Hz, 2 H-ortho, C5H5N), 8.76 (t,
2 H, CH2), 5.10 (d, 2JHH = 14.0 Hz, 2 H, CH2), −2.5 (br s, 1 H,
Hl nido carborane). 11B NMR ([D6]acetone, d/ppm): d −8.60
(d, JBH = 136 Hz, 2 B), −11.16 (d, JBH = 160 Hz, 1 B), −15.42
(d, JBH = 140 Hz, 2 B), −18.87 (d, JBH = 154 Hz, 2 B), −31.28
3
3JHH = 8.0 Hz, 1 H-para, C5H5N), 8.31 (dd, JHH = 6.0 Hz,
2
3JHH = 8.0 Hz, 2 H-meta, C5H5N), 4.87 (d, JHH = 14.0 Hz,
2
1 H, CH2), 4.77 (d, JHH = 14.0 Hz, 1 H, CH2), 2.84 (s, 1H,
CH carborane), −3.10 (br s, 1 H, Hl nido carborane). 11B NMR
([D6]acetone, d/ppm): d −9.31 (d, JBH = 123 Hz, 1 B), −10.18
(d, JBH = 126 Hz, 1 B), −12.84 (d, JBH = 146 Hz, 1 B), −14.11
(d, JBH = 167 Hz, 1 B), −18.86 (d, JBH = 112 Hz, 2 B), −19.68
(dd, JBH = 140 Hz, JB(l−H) = 40 Hz, 1 B), −34.68 (d, JBH
=
142 Hz, 1 B). Calc. for C15H24B9F3N2O3S (466.71): C 38.60, H
5.18, B 20.85, F 12.21, N 6.00. Found: C 38.45, H 5.17, B 21.08,
F 11.37, N 5.92%.
(d, JBH = 177 Hz, 1 B), −31.31 (dd, JBH = 135 Hz, JB(l−H)
=
41 Hz, 1 B), −35.40 (d, JBH = 142 Hz, 1 B). Calc. for C8H18B9N
(225.53): C 42.25, H 7.98, B 43.61, N 6.16. Found: C 42.11, H
8.08, B 43.68, N 6.19%.
Reaction of 7 with pyridine. Pyridine (0.2 g, 2.5 mmol) was
added to a stirred solution of 7 (0.2 g, 0.43 mmol) in CH2Cl2
(5 mL) at 20 ◦C. Over 5 min a suspension formed. After stirring
for 12 h at 20 ◦C the reaction mixture was filtered. The solid was
washed with CH2Cl2 (5 mL) and recrystallized from ethanol–
water to give 0.16 g (80%) of 8, mp 231–232 ◦C. Analytical and
spectroscopic date are identical to those given above.
Reaction of 2 with pyridine. Pyridine (1.29 g, 16.31 mmol)
was added to a solution of 2 (1.00 g, 3.26 mmol) in CH2Cl2
(8 mL) with stirring. The reaction mixture was stirred for 1 h
at 20 ◦C. The solvent was removed to dryness in vacuo. The
residue was dissolved in CH2Cl2 (10 mL) and the solution thus
obtained was washed with 10% HCl (2 × 5 mL) and then
with water. The organic layer was separated and dried over
Na2SO4. The solvent was removed in vacuo. The residue was
recrystallized from CH2Cl2 to give 0.88 g (70%) of 3, mp 166–
167 ◦C. Analytical and spectroscopic date are identical to those
given above.
N-[(o-Carboran-1-yl)methyl]phthalimide (9). Phthalimide
(0.48 g, 3.3 mmol) and K2CO3 (0.46 g, 3.3 mmol) were added
to a solution of carborane 2 (1.0 g, 3.3 mmol) in THF (30 mL),
and the mixture was refluxed with stirring for 30 h. The
solvent was removed in vacuo and the residue was purified by
chromatography on SiO2 (15 × 3 cm column) with heptane–
ethyl acetate as eluent. The yield of compound 9 was 0.49 g
(50%), mp 203–205 ◦C. Analytical and spectroscopic date are
identical to those published in ref. 12.
Reaction of 3 with pyridine and H2O. Water (1 mL) was
added to a stirred mixture of 3 (0.39 g, 1 mmol) and pyridine
9 0 6
D a l t o n T r a n s . , 2 0 0 5 , 9 0 3 – 9 0 8

View Article Online
Table 2 Crystal data and structure refinement for 4, 7 and 8
Compound
4
7
8
Formula
Mr
C8H18B9N
225.52
C6H14B10F6O6S2
468.39
[C14H24B9N2][CF3SO3]
466.71
Crystal colour, habit
Crystal size/mm
Crystal system
Space group
Cell constants:
Colorless prism
0.45 × 0.35 × 0.25
Monoclinic
P21/c
Colorless needle
0.35 × 0.30 × 0.30
Monoclinic
P21/c
Colorless plate
0.30 × 0.30 × 0.10
Orthorhombic
Pna21
˚
a/A
7.984(4)
10.740(5)
15.354(7)
93.345(9)
1314.3(10)
4 (1)
1.140
110
u and x
56
0.55
6.821(1)
26.485(5)
10.634(2)
97.37(3)
1905.2(7)
4 (1)
1.633
153
h/2h
52
19.400(3)
8.899(1)
12.640(2)
90
2182.3(5)
4 (1)
1.420
110
u and x
58
1.96
˚
b/A
˚
c/A
b/◦
3
˚
V/A
Z (Zꢀ)
Dc/g cm−3
T/K
Scan mode
◦
2hmax
/
l(Mo-Ka)/cm−1
3.59
T
max, Tmin
0.928, 0.290
12170
—
6818
0.983, 0.667
16511
Reflections collected
Independent reflections (Rint
)
3145 (0.0347)
2359
—
235
0.0560
0.1325
0.0333, 1.2332
472
3709 (0.0462)
3290
—
5764 (0.0411)
4434
0.05(7)
394
0.0486
0.1139
0.0605, —
960
Observed reflections (I > 2r(I))
Absolute structure parameter
Parameters
327
R1 (on F for obs. refls.)a
wR2 (on F2 for all refls.)b
Weighting scheme, a, b
F(000)
0.0408
0.1158
0.0733, 0.8047
936
GOOF
Largest diff. peak, hole/e A
1.010
1.050
0.998
0.684, −0.245
−3
˚
0.355, −0.052
0.396, −0.428
ꢀ
ꢀ
ꢀ
ꢀ
a R1 = ꢁFo| − |Fcꢁ/ Fo for observed reflections. b wR2 = { [w(F2 − F2c)2/ [w(F2o)2]} for all reflections.
0.5
o
[(o-Carboran-1-yl)methyl]triphenylphosphonium trifluoro-
methanesulfonate (10). A mixture of carborane 2 (0.4 g,
1.3 mmol) and PPh3 (0.42 g, 1.6 mmol) in MeCN (7 mL) was
refluxed under argon for 9 h. The solvent was evaporated to
dryness and diethyl ether (15 mL) was added affording a white
solid, which was filtered off, washed with diethyl ether (10 mL)
and dried in vacuo. Yield 0.6 g (81%); mp 277–278 ◦C. 1H
NMR ([D6]acetone, d/ppm): d 8.42–7.82 (m, 15 H, Ph), 5.25
compounds 4, 7 and 8 suitable for X-ray studies were obtained
by crystallization from CH3CN (4), hexane (7) and aqueous
ethanol (8).
Single-crystal X-ray diffraction experiments for 4 and 8
were carried out with a Bruker SMART 1000 CCD area
detector,20 using graphite monoc◦hromated Mo-Ka radiation
˚
(k = 0.71073 A, x-scans with a 0.3 step in x and 10 s per frame
exposure) at 110 K. The X-ray experiment for 7 was carried
out with a rebuild Syntex P21 four-circle diffractometer, using
graphite monochromated Mo-Ka radiation at 153 K.21 The
absorption correction for 4 and 8 was applied semi-empirically
from equivalent reflections.22
2
(d, JHP = 14.8 Hz, 2 H, CH2), 5.07 (s, 1 H, CH carborane),
3.0–1.3 (m, 10 H, BH). 11B NMR ([D6]acetone, d/ppm): d −2.28
(d, JBH = 160 Hz, 1 B), −3.78 (d, JBH = 150 Hz, 1 B), −7.92
(d, JBH = 154 Hz, 2 B), −12.86 (d, JBH = 140 Hz, 6 B). 31P
NMR ([D6]acetone, d/ppm): d 22.8. Calc. for C22H28B10F3O3PS
(568.61): C 46.47, H 4.96, B 19.01, F 10.02, P 5.45. Found: C
46.98, H 5.26, B 18.83, F 9.98, P 5.33%.
The structures were solved by direct methods and refined by
the full-matrix least-squares techniques against F2. All hydrogen
atoms of the carborane frames were located in the difference
Fourier syntheses and refined in isotropic approximation (in 4,
7 and 8); the positions of the hydrogen atoms of the CH2 groups
and Py were calculated and included in the refinement by using
the riding model approximation with the Uiso(H) = 1.2Ueq(C)
for the methine and Uiso(H) = 1.5Ueq(C) for methyl groups,
where Ueq(C) is the equivalent isotropic temperature factor of
the carbon atom bonded to the corresponding H atom.
All calculations were performed on an IBM PC/AT using the
SHELXTL software.23
1-Cyanomethyl-o-carborane (11). Carborane
2 (1.53 g,
5 mmol) and MeCN (7 mL) were added to KCN (0.65 g,
10 mmol) and [PdCl2(PPh3)2] (0.1 g, 0.14 mmol) and stirred
at 60 ◦C under argon for 1 h. The mixture was poured into water
(20 mL) and extracted with ethyl acetate. The organic layer was
washed with water, dried over Na2SO4 and then the solvent
was evaporated. The residue was subjected to chromatography
on SiO2 (15 × 1.5 cm column) with heptane–ethyl acetate as
eluent affording 0.86 g (95%) of carborane 11; mp 110–111 ◦C
◦
CCDC reference numbers 227517 (4), 227518 (7) and 227519
(8).
See http://www.rsc.org/suppdata/dt/b4/b417199c/ for cry-
stallographic data in CIF or other electronic format.
(heptane) (cf. mp 109–110 C (heptane)15). Compound 11 was
previously prepared and characterized by IR15 and NMR (1H
and 13C)16 spectroscopy (in CDCl3). 1H NMR ([D6]acetone,
d/ppm): d 4.36 (s, 2 H, CH2), 5.37 (s, 1 H, CH carborane), 3.7–
1.74 (m, 10 H, BH). 11B NMR ([D6]acetone, d/ppm):d −1.56
(d, JBH = 149 Hz, 1 B), −4.60 (d, JBH = 150 Hz, 1 B), −8.30
(d, JBH = 151 Hz, 2 B), −10.28 (d, JBH = 180 Hz, 2 B), −11.16
(d, JBH = 168 Hz, 2 B), −11.81 (d, JBH = 168 Hz, 2 B).
Acknowledgements
This work was supported by the Deutsche Forschungsgemein-
schaft (DFG 436 Rus 113/598/0–1(R)), General Chemistry and
Material Science Division of RAS (Project No 591-07) and
Russian Foundation for Basic Research (Grant No 03-03-32214
and No 01-03-04000).
X-Ray crystallographic study of 4, 7 and 8
Crystallographic data, data collection procedures and refine-
ment parameters are listed in Table 2. Single crystals of
D a l t o n T r a n s . , 2 0 0 5 , 9 0 3 – 9 0 8
9 0 7

View Article Online
12 M. A. Fox and K. Wade, J. Organomet. Chem., 1999, 573, 279.
13 L. I. Zakharkin and V. S. Kozlova, Zh. Obshch. Khim., 1973, 43,
1097.
14 J. G. Wilson, A. K. M. Anisuzzaman, F. Alam and A. H. Soloway,
Inorg. Chem., 1992, 31, 1955.
15 L. I. Zakharkin, A. B. Grebennikov and A. I. L’vov, Izv. Akad. Nauk,
Ser. Khim., 1970, 106.
16 A. A. Semioshkin, S. G. Inyushin, V. A. Artemov, P. V. Petrovskii and
V. I. Bregadze, Izv. Akad. Nauk, Ser. Khim., 1998, 1825.
17 F. Teixidor, C. Vinas and R. W. Rudolph, Inorg. Chem., 1986, 25,
3339.
References
1 E. G. Rys, E. Hey-Hawkins, D. D. Sung, Z. A. Starikova, A. A.
Korlyukov and V. N. Kalinin, Research and Development in Neutron
Capture Therapy, Monduzzi Editore S.p.A., Bologna, Italy, 2002,
p. 63.
2 J. F. Valliant, K. J. Guenther, A. S. King, P. Morel, P. Schaffer, O. O.
Sogbein and K. A. Stephenson, Coord. Chem. Rev., 2002, 232, 173.
3 M. F. Hawthorne and A. Maderna, Chem. Rev., 1999, 99, 3421.
4 L. I. Zakharkin, V. A. Brattsev and Yu. A. Chapovskii, Zh. Obshch.
Khim., 1965, 35, 2160.
5 A. V. Kazantsev, V. V. Butyaikin, I. E. Gaas, E. A. Otrashchekov and
M. M. Aksartov, Zh. Org. Khim., 2000, 36, 1007.
6 A. A. Semioshkin, S. G. Inyushin, L. V. Ermanson, P. V. Petrovskii,
P. Lemmen and V. I. Bregadze, Izv. Akad. Nauk, Ser. Khim., 1998,
2041.
7 P. J. Stang, M. Hanack and L. R. Subramanian, Synthesis, 1982, 85.
8 Y. Wu, P. J. Carroll and W. Quintana, Polyhedron, 1998, 17, 3391.
9 L. Barazhenok, V. G. Nenajdenko and E. S. Balenkova, Tetrahedron,
2000, 56, 3007.
18 M. F. Hawthorne, D. C. Young, P. M. Carrett, D. A. Owen, S. G.
Schwerin, F. N. Tebbe and P. A. Wegner, J. Am. Chem. Soc., 1968,
90, 862.
19 J. R. Blackburn, R. Nordberg, F. Stevie, R. G. Albridge and M. M.
Jones, Inorg. Chem., 1970, 9, 2374.
20 SMART V5.051 and SAINT V5.00, Area Detector Control and
Integration Software, Bruker AXS Inc., Madison, WI-53719, 1998.
21 P3 and XDISK, Release 4.1, Siemens AXS, Madison, WI, 1989.
22 G. M. Sheldrick, SADABS, Bruker AXS Inc., Madison, WI-53719,
1997.
10 K. Ritter, Synthesis, 1993, 735.
11 L. I. Zakharkin, V. A. Brattsev and V. I. Stanko, Zh. Obshch. Khim.,
1966, 36, 886.
23 G. M. Sheldrick, SHELXTL, v. 5.10. Structure Determination
Software Suite, Bruker AXS, Madison, WI, 1998.
9 0 8
D a l t o n T r a n s . , 2 0 0 5 , 9 0 3 – 9 0 8