Ionic-liquid-promoted decaborane olefin-hydroboration: A new efficient route to 6-R-B10H13 derivatives

Article abstract of DOI:10.1021/ic801000c

Unlike in conventional organic solvents where transition metal catalysts are required, decaborane olefin-hydroboration reactions have been found to proceed in biphasic ionic-liquid/toluene mixtures with a wide variety of olefins, including alkyl, alkenyl, halo, phenyl, ether, ester, pinacolborane, ketone, and alcohol-substituted olefins, and these reactions now provide simple high-yield routes to 6-R-B₁₀H₁₃ derivatives. Best results were observed for reactions with bmimX (1-butyl-3-methylimidazolium, X = Cl ^- or BF₄^-) and bmpyX (1-butyl-4- methylpyridinium, X = Cl^- or BF₄^-). Both the experimental data for these reactions and separate studies of the reactions of B₁₀H₁₃^- salts with olefins indicate a reaction sequence involving (1) the ionic-liquid-promoted formation of the B ₁₀H₁₃^- anion as the essential initial step, (2) the addition of the B₁₀H₁₃^- anion to the olefin to form a 6-R-B₁₀H₁₂^- anion, and finally, (3) protonation of 6-R-B₁₀H₁₂^- to form the final neutral 6-R-B₁₀H₁₃ product. The 6-R-B ₁₀H₁₃ derivatives also undergo ionic-liquid-mediated dehydrogenative alkyne-insertion reactions in biphasic bmimCl/toluene mixtures, and these reactions provide high yield routes to 3-R-1,2-R′₂-1, 2-C₂B₁₀H₉ ortho-carborane derivatives.

Full text of DOI:10.1021/ic801000c

Inorg. Chem. 2008, 47, 9203-9215
Ionic-Liquid-Promoted Decaborane Olefin-Hydroboration: A New Efficient
Route to 6-R-B10H13 Derivatives
Upal Kusari, Patrick J. Carroll, and Larry G. Sneddon*
Department of Chemistry, UniVersity of PennsylVania, Philadelphia, PennsylVania 19104-6323
Received May 31, 2008
Unlike in conventional organic solvents where transition metal catalysts are required, decaborane olefin-hydroboration
reactions have been found to proceed in biphasic ionic-liquid/toluene mixtures with a wide variety of olefins, including
alkyl, alkenyl, halo, phenyl, ether, ester, pinacolborane, ketone, and alcohol-substituted olefins, and these reactions
now provide simple high-yield routes to 6-R-B10H13 derivatives. Best results were observed for reactions with bmimX
(1-butyl-3-methylimidazolium, X ) Cl- or BF4-) and bmpyX (1-butyl-4-methylpyridinium, X ) Cl- or BF4-). Both
the experimental data for these reactions and separate studies of the reactions of B10H13- salts with olefins indicate
-
a reaction sequence involving (1) the ionic-liquid-promoted formation of the B10H13 anion as the essential initial
step, (2) the addition of the B10H13- anion to the olefin to form a 6-R-B10H12- anion, and finally, (3) protonation of
-
6-R-B10H12 to form the final neutral 6-R-B10H13 product. The 6-R-B10H13 derivatives also undergo ionic-liquid-
mediated dehydrogenative alkyne-insertion reactions in biphasic bmimCl/toluene mixtures, and these reactions
provide high yield routes to 3-R-1,2-R′2-1,2-C2B10H9 ortho-carborane derivatives.
Introduction
boron neutron capture therapy). While Gaines4,5 has reported
excellent stoichiometric routes to 6-alkyl-B10H13 derivatives,
these routes require multiple steps and are not suitable to
produce complex functional derivatives. We have previously
shown that platinum-6 and titanium-catalyzed7,8 decaborane
olefin-hydroborations provide high yield routes to 6,9-R2-
B10H12 and 6-R-B10H13 derivatives, respectively. However,
both the platinum- and titanium-catalyzed reactions are slow
(typically less than one turnover per hour) and are also not
useful for most functional olefins. While Wei has reported9
an excellent route to many functional 6-R-B10H13 derivatives
by utilizing the ruthenium-catalyzed metathesis reactions of
6-hexenyl-B10H13 with functional olefins, this sequence still
requires the use of the slow titanium-catalyzed reaction of
decaborane with 1,5-hexadiene to produce the key 6-hexenyl-
B10H13 intermediate. Thus, there is still a need for the
development of improved routes to more complex decabo-
rane-derivatives.
In the preceding paper,1 we demonstrated that decaborane
dehydrogenative alkyne-insertion reactions proceed in ionic
liquids with a wide variety of alkynes to give high yields of
ortho-carborane products without the need of the added
Lewis base catalyst that is required in conventional syntheses
in organic solvents. In this paper, we describe complimentary
studies of ionic-liquid-mediated decaborane olefin-hydrobo-
ration reactions that further illustrate the unique advantages
of ionic liquids for activating polyborane reactions.
Decaborane is the most available polyborane, and its
functionally substituted derivatives are potentially important
in a number of applications2,3 ranging from materials science
(e.g., components in preceramic polymers) to medicine (e.g.,
* To whom correspondence should be addressed. E-mail: lsneddon@
sas.upenn.edu.
(1) Li, Y.; Carroll, P. J.; Sneddon, L. G. Inorg. Chem. 2008, 47, 9193–
9202.
(2) (a) Plesek, J. Chem. ReV. 1992, 92, 269–278. (b) Packirisamy, S. Prog.
Polym. Sci. 1996, 21, 707–773. (c) Wei, X.; Carroll, P. J.; Sneddon,
L. G. Chem. Mater. 2006, 18, 1113–1123. (d) Teixidor, F.; Vinas, C.;
Demonceau, A.; Nunez, R. Pure Appl. Chem. 2003, 75, 1305–1313.
(e) Grimes, R. N. J. Chem. Educ. 2004, 81, 657–672.
(3) (a) Hawthorne, M. F. Angew. Chem., Int. Ed. Engl. 1993, 32, 950–
984. (b) Barth, R. F.; Soloway, A. H.; Fairchild, R. G. Sci. Am. 1990,
100–107. (c) Soloway, A. H.; Tjarks, W.; Barnum, B. A.; Rong, F-G.;
Barth, R. F.; Codogni, I. M.; Wilson, J. G. Chem. ReV. 1998, 98, 1515–
1562.
(4) Gaines, D. F.; Bridges, A. N. Organometallics 1993, 12, 2015–2016.
(5) Bridges, A. N.; Powell, D. R.; Dopke, J. A.; Desper, J. M.; Gaines,
D. F. Inorg. Chem. 1998, 37, 503–509.
(6) Mazighi, K.; Carroll, P. J.; Sneddon, L. G. Inorg. Chem. 1993, 32,
1963–1969.
(7) Pender, M. J.; Wideman, T.; Carroll, P. J.; Sneddon, L. G. J. Am.
Chem. Soc. 1998, 120, 9108–9109.
(8) Pender, M. J.; Carroll, P. J.; Sneddon, L. G. J. Am. Chem. Soc. 2001,
123, 12222–12231.
10.1021/ic801000c CCC: $40.75  2008 American Chemical Society
Inorganic Chemistry, Vol. 47, No. 20, 2008 9203
Published on Web 09/19/2008

Kusari et al.
(D, 99.5%), C6D6 (D, 99.5%), and CD2Cl2 (D, 99.9%) (Cambridge
Isotope) were used as received.
Recent reports that transition metal catalyzed hydrosily-
lation and monoborane-hydroborations of alkynes and alk-
enes can be carried out in ionic liquids10 stimulated our initial
interest11 in the use of ionic liquids as noncoordinating
solvents for the metal-catalyzed reactions of decaborane. We
report in this paper the surprising result that when decaborane
olefin-hydroboration reactions are carried out in ionic liquids,
high yields of 6-R-B10H13 products are obtained eVen in the
absence of any metal catalysts.
Physical Measurements. 1H NMR at 400.1 MHz and 11B NMR
spectra at 128.4 MHz were obtained on a Bruker DMX 400
spectrometer. All 11B NMR chemical shifts are referenced to
external BF3 ·OEt2 (0.00 ppm) with a negative sign indicating an
upfield shift. All 1H chemical shifts were measured relative to
residual protons in the lock solvents and are referenced to Me4Si
(0.00 ppm). High- and low-resolution mass spectra (HRMS and
LRMS) using negative chemical ionization (NCI) techniques were
recorded on a Micromass Autospec Spectrometer. Infrared spectra
were recorded on a Perkin-Elmer Spectrum 100 FT-IR spectrometer
using KBr pellets or NaCl plates and are listed in Table S1,
Supporting Information. Elemental analyses were performed at
Robertson Microlit Laboratories, Madison, NJ. Melting points were
obtained on a standard melting point apparatus and are uncorrected.
Experimental Section
General Synthetic Procedures and Materials. Unless otherwise
noted, all reactions and manipulations were performed in dry
glassware under nitrogen or argon atmospheres using the high-
vacuum or inert-atmosphere techniques described by Shriver.12
B10H14 (Callery) was freshly sublimed prior to use. The
[Et3NH+][B10H13-] and [Bu4N+][B10H13-] salts were prepared
according to literature methods.13 The 1-hexene, 1-octene, cis-4-
octene, trans-4-octene, 1,7-octadiene, 2,5-dimethyl-2-hexene, 6-bro-
mo-hexene, cyclohexene, cis-cyclooctene, allylbenzene, allyltrim-
ethylsilane, styrene, allyl propyl ether, allyl benzyl ether, allyl
alcohol, 5-hexen-2-one, norbornylene, 3-hexyne, allylboronic acid
pinacol ester, and acetic acid 5-hexen-1-yl ester were purchased
from Aldrich, TCI America, or Alfa Aesar, dried over CaH2 or
MgSO4 as appropriate, and vacuum transferred prior to use. The
ionic liquids, 1-butyl-3-methylimidazolium chloride [bmimCl],
1-butyl-3-methylimidazolium bromide [bmimBr], 1-butyl-4-meth-
ylpyridinium chloride [bmpyCl], 1-butyl-3-methylimidazolium tet-
rafluoroborate [bmimBF4], 1-butyl-4-methylpyridinium tetrafluo-
roborate [bmpyBF4], 1-butyl-3-methylimidazolium phosphorus
hexafluoride [bmimPF6], 1-ethyl-3-methylimidazolium chloride
[emimCl], 1-butyl-2,3-dimethylimidazolium chloride [bdmimCl],
1-butyl-3-methylimidazolium acetate [bmimOAc], 1-butyl-3-me-
thylimidazolium trifluoromethanesulfonate [bmimOTf], 1-ethyl-2,3-
dimethylimidazolium ethyl sulfate [emimEtSO4], 1,3-dimethylim-
idazolium methyl sulfate [dmimMeSO4], and tetrabutylammonium
methanesulfonate [TBAMeSO3], were from Fluka. 1-Butyl-3-
methylimidazolium iodide [bmimI] was from EMD Chemicals Inc.
Two additional samples of bmimBF4 with different chloride contents
were obtained from (a) Aldrich-Fluka (catalysis grade, assay purity
g98.5%) and (b) Alfa-Aesar (assay purity 98%+). The bis(triph-
enylphosphoranylidene) ammonium chloride [PPNCl], N,N,N′,N′-
tetramethyl-1,8-naphthalenediamine [Proton Sponge], 2,6-dimeth-
ylpyridine, Me4NF, Me4NBF4, Et4NBF4, Bu4NCl, Bu4NPF6,
Bu4NBF4, Bu4NSCN, NaBF4, NH4BF4, NaHSO4, CH3COONa, NaF,
NaCl, and C6H5COOH (Aldrich) were used as received. All ionic
liquids and Bu4NF, tetrabutylammonium fluoride [TBAF] (Aldrich),
were dried by carrying out an azeotropic distillation with toluene,
followed by heating overnight under high-vacuum and storage in
a dry box. Toluene, glyme (ethylene glycol dimethyl ether), and
hexanes were dried by passing them through an activated alumina
column prior to use. HPLC or ACS grade hexanes, toluene, Et2O,
CH2Cl2, NEt3, and silica gel (Fisher) were used as received. CDCl3
Reaction of B10H14 and an Olefin in the Absence of an
Ionic Liquid. A 10 mL, 2-neck round-bottom flask equipped with
a septum and stir bar was charged with 0.122 g (1.0 mmol) of
B10H14, 0.5 g (4.1 mmol) of 1-octene, and ∼2 mL of toluene. The
flask was attached to a water condenser open to argon, and the
body of the flask was then submerged in a 125 °C oil bath equipped
with a magnetic stir plate. After the mixture was stirred vigorously
for ∼8.0 h, 11B NMR analysis of the toluene layer showed only
unreacted B10H14.
General Experimental Procedure for Hydroboration
Reactions. A 25 mL, 2-neck round-bottom flask equipped with a
septum, stir bar, and vacuum adapter was charged in a dry box
with an ionic liquid, inorganic salt, or nitrogen base. The flask was
sealed, taken out of the box and then charged under Ar with the
indicated amounts of B10H14, olefin, and ∼3-4 mL of solvent
(toluene or dichloroethane). Using the vacuum adapter, the flask
was attached to a water condenser open to argon, and the body of
the flask then submerged in a hot oil bath (typically at 85-140 °C,
as indicated) equipped with a magnetic stir plate. The reactions
were vigorously stirred to form an emulsion. The reaction was
monitored by 11B NMR analysis of the toluene layer and stopped
when all starting decaborane had been consumed. The top organic-
layer of the reaction mixture was separated by pipet. The ionic
liquid layer was then extracted multiple times with ether. The
combined organic solutions were vacuum concentrated and then
flash-filtered through a silica gel column.
6-R-B10H13 Syntheses in Ionic Liquids. 6-[CH3(CH2)7]-
B10H13 (1). Reaction of 0.611 g (5.0 mmol) of B10H14 with 2.0 g
(17.8 mmol) of 1-octene in biphasic toluene (∼4 mL)/bmimCl
(0.175 g, 1.0 mmol) at 125 °C for ∼12 h gave, following elution
with a 1:1 hexanes/toluene eluent from a silica gel column, 1.05 g
(4.5 mmol, 90% yield) of 1 as an oily liquid. GC/MS analysis of
the oil showed 1 as the only product. NCI-HRMS (m/e) calcd (M)-
11
for 12C8
B
10
1H30: 236.3278; found 236.3289. Anal. Calcd: C, 40.99;
H, 12.90. Found: C, 41.67; H, 11.15. 11B NMR (128.4 MHz, CDCl3,
ppm): δ 25.5 (s, 1, B6), 9.7 (d, 2, B1,3), 8.0 (d, 1, B9), 0.5 (d, 2,
1
B5,7), -3.4 (d, 2, B8,10), -34.4 (d, 1, B2), -39.3 (d, 1, B4). H
NMR (400.1 MHz, CDCl3, ppm): δ 1.55 (m, 2, CH2), 1.29 (m, 12,
CH2), 0.89 (t, 3, CH3), -1.68 (br, s, 2, BHB), -2.04 (br, s, 2,
BHB).
Reaction of 0.611 g (5.0 mmol) of B10H14 with 2.0 g (17.8 mmol)
of 1-octene in biphasic toluene (∼4 mL)/bmpyBF4 (2.5 g, 10.5
mmol) at 140 °C for ∼11 h gave 1.03 g (4.4 mmol, 88% yield) of
1. As summarized in Table S2, Supporting Information, another 4
cycles of reaction and product isolation following periodic additions
over 57 h of new mixtures of 0.611 g of B10H14, 2.0 g of 1-octene,
(9) Wie, X.; Carroll, P. J.; Sneddon, L. G. Organometallics 2006, 25,
609–621.
(10) Aubin, S.; Le Floch, F.; Carre, D.; Guegan, J. P.; Vaultier, M. ACS
Symp. Ser. 2002, 334.
(11) Kusari, U.; Li, Y.; Bradley, M. G.; Sneddon, L. G. J. Am. Chem. Soc.
2004, 126, 8662–8663.
(12) Shriver, D. F.; Drezdon, M. A. Manipulation of Air SensitiVe
Compounds, 2nd ed.; Wiley: New York, 1986.
(13) Graybill, B. M.; Pitochelli, A. R.; Hawthorne, M. F. Inorg. Chem.
1962, 1, 622–623.
9204 Inorganic Chemistry, Vol. 47, No. 20, 2008

Polyborane Reactions in Ionic Liquids
and 4 mL of toluene to the reaction flask containing the used
bmpyBF4 produced a total of 3.9 g (16.7 mmol, 83.5%) of 1.
The reactions of 0.122 g (1.0 mmol) of B10H14 with 0.5 g (4.5
mmol) of 1-octene at 140 °C for ∼13.3 h in a biphasic mixture of
toluene (∼3 mL) and 0.5 g (2.2 mmol) of either (1) Alfa-Aesar
98%+ (chloride content not reported) bmimBF4 or (2) Fluka
“catalytic grade” (∼10 ppm Cl) bmimBF4, gave comparable yields
of 1, 0.20 g (0.85 mmol, 85% yield) and 0.20 g (0.85 mmol, 85%
yield), respectively.
MHz, CDCl3, ppm): δ 4.07 (t, 2, -OCH2-), 2.05 (s, 3, CH3), 1.65
(m, 2, CH2), 1.55 (m, 2, CH2), 1.39 (m, 6, CH2), -1.68 (br, s, 2,
BHB), -2.02 (br, s, 2, BHB).
Reaction of 0.49 g (4.0 mmol) of B10H14 with 1.5 g (10.5 mmol)
of acetic acid 5-hexen-1-yl ester in biphasic toluene (∼3 mL)/Bu4NF
(0.174 g, 0.67 mmol) at 125 °C for ∼3.3 h gave 0.97 g (3.7 mmol,
92% yield) of 4.
6-[CH3(CH2)2O(CH2)3]-B10H13 (5). Reaction of 0.366 g (3.0
mmol) of B10H14 with 1.5 g (15.0 mmol) of allyl propyl ether in
biphasic toluene (∼3 mL)/bmimCl (0.105 g, 0.6 mmol) at 125 °C
for ∼45 h gave, following toluene elution from a silica gel column,
Reactions carried out with identical amounts of decaborane and
1-octene in the presence of other ionic-liquids, salts, or conditions
are compared in Table S3, Supporting Information.
0.47 g (2.1 mmol, 70% yield) of 5 as an oily liquid. NCI-HRMS
6-[(CH3)3Si(CH2)3]-B10H13 (2). Reaction of 0.49 g (4.0 mmol)
of B10H14 with 1.5 g (13.1 mmol) of allyltrimethylsilane in biphasic
toluene (∼3 mL)/bmimCl (0.14 g, 0.8 mmol) at 125 °C for ∼11 h
gave, following elution with a 1:1 hexanes/toluene eluent from a
silica gel column, 0.84 g (3.6 mmol, 89% yield) of 2 as an oily
11
(m/e) calcd (M)- for 12C6
B
10
1H2616O1: 224.2914; found 224.2910.
Anal. Calcd: C, 32.41; H, 11.78. Found: C, 33.05; H, 11.71. 11B
NMR (128.4 MHz, CDCl3, ppm): δ 26.4 (s, 1, B6), 8.7 (d, 2, B1,3),
7.0 (d,1, B9), 0.1 (d, 2, B5,7), -5.0 (d, 2, B8,10), -33.8 (d, 1,
B2), -39.7 (d, 1, B4). 1H{11B} NMR (400.1 MHz, CDCl3, ppm):
δ 3.43 (t, 2, CH3), 3.27 (t, 2, CH2), 1.80 (m, 2, CH2), 1.53 (m, 2,
CH2), 1.45 (m, 2, CH2), 0.87 (t, 3, CH3) -1.31 (br, s, 2, BHB),
-2.13 (br, s, 2, BHB).
1
liquid. NCI-HRMS (m/e) calcd (M)- for 12C611B10 H2828Si1: 238.2891;
found 238.2895. Anal. Calcd: C, 30.47; H, 11.93. Found: C, 30.94;
H, 12.10. 11B NMR (128.4 MHz, CDCl3, ppm): δ 25.6 (s, 1, B6),
9.5 (d, 2, B1,3), 8.2 (d,1, B9), 0.4 (d, 2, B5,7), -3.3 (d, 2, B8,10),
6-[C6H5(CH2)O(CH2)3]-B10H13 (6). Reaction of 0.366 g (3.0
mmol) of B10H14 with 0.90 g (6.1 mmol) of allyl benzyl ether in
biphasic toluene (∼4 mL)/bmimCl (0.105 g, 0.6 mmol) at 125 °C
for ∼40 h gave, following toluene elution from a silica gel column
and drying on a high-vacuum line overnight at ∼125 °C, 0.60 g
1
-34.4 (d, 1, B2), -39.2 (d, 1, B4). H{11B}NMR (400.1 MHz,
CDCl3, ppm): δ 1.56 (m, 2, CH2), 1.18 (m, 2, CH2), 0.61 (m, 2,
CH2), 0.07 (s, 9, CH3), -1.68 (br, s, 2, BHB), -2.02 (br, s, 2,
BHB).
Reaction of 0.49 g (4.0 mmol) of B10H14 with 1.5 g (13.1 mmol)
of allyltrimethylsilane in biphasic toluene (∼3 mL)/Bu4NF (0.174
g, 0.67 mmol) at 125 °C for ∼3.3 h gave 0.86 g (3.64 mmol, 91%
yield) of 2.
6-[CH2dCH(CH2)6]-B10H13 (3). Reaction of 0.611 g (5.0 mmol)
of B10H14 with 2.0 g (18.1 mmol) of 1,7-octadiene in biphasic
toluene (∼4 mL)/bmimCl (0.175 g, 1.0 mmol) at 125 °C for ∼12
h gave, following elution with a 3:1 hexanes/toluene eluent from a
(2.2 mmol, 74% yield) of 6 as an oily liquid. NCI-HRMS (m/e)
11
calcd (M - H)- for 12C10
B
10
1H2616O1: 271.2835; found 271.2827.
Anal. Calcd: C, 44.42; H, 9.69. Found: C, 45.10; H, 9.87. 11B NMR
(128.4 MHz, CDCl3, ppm): δ 26.6 (s, 1, B6), 8.7 (d, 2, B1,3), 7.1
(d,1, B9), 0.02 (d, 2, B5,7), -3.6 (d, 2, B8,10), -33.8 (d, 1, B2),
-39.5 (d, 1, B4). 1H{11B} NMR (400.1 MHz, CDCl3, ppm): δ 7.34
(m, 5, C6H5-), 4.34 (s, 2, CH2), 3.55 (t, 2, CH2), 1.85 (m, 2, CH2),
1.56 (m, 2, CH2), -1.50 (br, s, 2, BHB), -2.27 (br, s, 2, BHB).
Reaction of 0.366 g (3.0 mmol) of B10H14 with 1.0 g (6.7 mmol)
of allyl benzyl ether in biphasic toluene (∼4 mL)/Bu4NF (0.13 g,
0.5 mmol) at 125 °C for ∼6.3 h gave 0.63 g (2.3 mmol, 77% yield)
of 6.
silica gel column, 1.03 g (4.4 mmol, 89% yield) of 3 as an oily
11
liquid. NCI-HRMS (m/e) calcd (M)- for 12C8
B
1H28: 234.3122;
10
found 234.3125. Anal. Calcd: C, 41.34; H, 12.14. Found: C, 41.28;
H, 12.07. 11B NMR (128.4 MHz, CDCl3, ppm): δ 25.5 (s, 1, B6),
9.8 (d, 2, B1,3), 8.0 (d,1, B9), -0.5 (d, 2, B5,7), -3.4 (d, 2, B8,10),
1
-34.5 (d, 1, B2), -39.3 (d, 1, B4). H{11B} NMR (400.1 MHz,
6-[HO(CH2)3]-B10H13 (7). Reaction of 0.366 g (3.0 mmol) of
B10H14 with 0.5 g (8.6 mmol) of allyl alcohol in biphasic toluene
(∼3 mL)/bmimCl (0.105 g, 0.6 mmol) at 125 °C for ∼7 h gave,
following CH2Cl2 elution from a silica gel column, 0.325 g (1.8
CDCl3, ppm): δ 5.86 (m, 1, )CH-), 5.05 (m, 2, CH2)), 2.12 (m,
2, CH2), 1.61 (m, 2, CH2), 1.42 (m, 8, CH2), -1.63 (br, s, 2, BHB),
-1.97 (br, s, 2, BHB).
Reaction of 0.611 g (5.0 mmol) of B10H14 with 2.0 g (18.1 mmol)
of 1,7-octadiene in a biphasic mixture of toluene (∼4 mL), Bu4NF
(0.22 g, 0.83 mmol) and bmimOTf (1.0 g, 3.5 mmol) at 125 °C for
∼3.3 h gave 1.05 g (4.5 mmol, 90% yield) of 3. As summarized in
Table S4, Supporting Information, another 4 cycles of reaction and
product isolation following periodic additions over 54 h of new
mixtures of 0.611 g (5.0 mmol) of B10H14, 2.0 g (18.1 mmol) of
1,7-octadiene and 4 mL of toluene to the reaction flask containing
the used Bu4NF/bmimOTf mixture, produced 4.16 g (17.4 mmol,
87.0%) of 3.
6-[CH3C(O)O(CH2)6]-B10H13 (4). Reaction of 0.49 g (4.0 mmol)
of B10H14 with 1.5 g (10.5 mmol) of acetic acid 5-hexen-1-yl ester
in biphasic toluene (∼3 mL)/bmimCl (0.14 g, 0.8 mmol) at 125
°C for ∼12 h gave, following elution with a 2:1 hexanes/toluene
eluent from a silica gel column and drying on a high-vacuum line
mmol, 55% yield) of 7 as an oily liquid. NCI-HRMS (m/e) calcd
11
(M - H)- for 12C3
B
1H2016O1: 181.2366, found 181.2361. Anal.
10
Calcd: C, 19.98; H, 11.18. Found: C, 20.15; H, 11.40. 11B NMR
(128.4 MHz, CDCl3, ppm): δ 25.0 (s, 1, B6), 9.2 (d, 2, B1,3), 7.5
(d,1, B9), -0.1 (d, 2, B5,7), -3.9 (d, 2, B8,10), -35.0 (d, 1, B2),
-39.8 (d, 1, B4). 1H{11B} NMR (400.1 MHz, CDCl3, ppm): δ 3.79
(m, 2, CH2), 1.81 (s, 1, OH), 1.58-1.53 (m, 2, CH2), 1.3 (m, 2,
CH2), -1.67 (br, s, 2, BHB), -2.02 (br, s, 2, BHB).
6-[(CH3)4C2O2B(CH2)3]-B10H13 (8). Reaction of 0.366 g (3.0
mmol) of B10H14 with 1.5 g (8.9 mmol) of allylboronic acid pinacol
ester (2-allyl-4,4,5,5-tetramethyl-1,3,2-dioxaborolane) in biphasic
toluene (∼3 mL)/bmimCl (0.105 g, 0.6 mmol) at 125 °C for ∼9.0
h gave, following elution with a 1:1 hexanes/toluene eluent mixture
from a silica gel column and drying on a high-vacuum line overnight
at ∼125 °C, 0.78 g (2.7 mmol, 90% yield) of 8 as an oil. NCI-
overnight at ∼125 °C, 0.95 g (3.6 mmol, 90% yield) of 4 as an
11
HRMS (m/e) calcd (M - H)- for 12C9
B
1H3116O2: 291.3269;
11
11
oily liquid. NCI-HRMS (m/e) calcd (M)- for 12C8
B
1H2816O2:
10
found 291.3265. Anal. Calcd: C, 37.24; H, 10.76. Found: C, 36.59;
H, 11.14. 11B NMR (128.4 MHz, CDCl3, ppm): δ 33.0 (s, 1,
O-B-O), 25.3 (s, 1, B6), 9.8 (d, 2, B1,3), 8.0 (d,1, B9), 0.5 (d, 2,
B5,7), -3.2 (d, 2, B8,10), -34.4 (d, 1, B2), -39.2 (d, 1, B4).
266.3020, found 266.3026. Anal. Calcd: C, 36.34; H, 10.67. Found:
C, 35.43; H, 10.83. 11B NMR (128.4 MHz, CDCl3, ppm): δ 25.3
(s, 1, B6), 9.8 (d, 2, B1,3), 8.1 (d,1, B9), 0.4 (d, 2, B5,7), -3.4 (d,
2, B8,10), -34.5 (d, 1, B2), -39.3 (d, 1, B4). 1H{11B} NMR (400.1
Inorganic Chemistry, Vol. 47, No. 20, 2008 9205

Kusari et al.
1H{11B} NMR (400.1 MHz, CDCl3, ppm): δ 1.67 (m, 2, CH2),
1.43 (m, 2, CH2), 1.25 (s, 12, CH3), 0.86 (m, 2, CH2), -1.68 (br,
s, 2, BHB), -2.03 (br, s, 2, BHB).
Calcd: C, 42.45; H, 9.80. Found: C, 42.77; H, 10.14. 11B NMR
(128.4 MHz, CDCl3, ppm): δ 24.5 (s, 1, B6), 9.6 (d, 2, B1,3), 7.7
(d, 1, B9), 0.3 (d, 2, B5,7), -3.5 (d, 2, B8,10), -34.5 (d, 1, B2),
-39.3 (d, 1, B4). 1H{11B} NMR (400.1 MHz, CDCl3, ppm): δ 7.29
(m, 5, C6H5), 3.02 (t, 2, CH2), 1.43 (m, 2, CH2), -1.80 (br, s, 2,
BHB), -2.15 (br, s, 2, BHB).
6-((exo)-Bicyclo-[2,2,1]-hept-2-yl)-B10H13 (9). Reaction of 0.366
g (3.0 mmol) of B10H14 with 1.0 g (10.6 mmol) of norbornylene in
biphasic toluene (∼3 mL)/bmimCl (0.105 g, 0.6 mmol) at 125 °C
for ∼10.3 h gave, following elution with a 1:3 hexanes/toluene
eluent from a silica gel column, 0.55 g (2.55 mmol, 85% yield) of
6-[C6H5(CH2)3]-B10H13 (14). Reaction of 0.366 g (3.0 mmol)
of B10H14 with 0.75 g (6.3 mmol) of allylbenzene in biphasic toluene
(∼3 mL)/bmpyBF4 (1.5 g, 6.3 mmol) at 140 °C for ∼13 h gave,
following elution with a 1:1 hexanes/toluene eluent from a silica
gel column and drying on a high-vacuum line overnight at ∼125
9 as an oily liquid. NCI-HRMS (m/e) calcd (M - H)- for
11
12C7
B
1H24: 217.2730; found 217.2726. Anal. Calcd: C, 38.86;
10
H, 11.18. Found: C, 38.30; H, 11.46. 11B NMR (128.4 MHz, CDCl3,
ppm): δ 27.0 (s, 1, B6), 9.1 (d, 2, B1,3), 7.5 (d,1, B9), 0.1 (d, 2,
B5,7), -4.6 (d, 2, B8,10), -35.0 (d, 1, B2), -39.7 (d, 1, B4).
1H{11B} NMR (400.1 MHz, CDCl3, ppm): δ 2.33 (m, 2, CH), 1.61
(m, 4, CH), 1.44 (m, 2, CH), 1.28 (m, 2, CH), 0.92 (m, 1, CH),
-1.62 (br, s, 2, BHB), -2.03 (br, s, 2, BHB).
°C, 0.62 g (2.6 mmol, 86% yield) of 14 as an oily liquid. NCI-
11
HRMS (m/e) calcd (M)- for 12C9
B
1H24: 242.2809; found
10
242.2803. Anal. Calcd: C, 44.97; H, 10.06. Found: C, 45.16; H,
10.52. 11B NMR (128.4 MHz, C6D6, ppm): δ 25.4 (s, 1, B6), 10.7
(d, 2, B1,3), 8.4 (d,1, B9), 0.1 (d, 2, B5,7), -2.7 (d, 2, B8,10),
1
-33.4 (d, 1, B2), -38.0 (d, 1, B4). H{11B} NMR (400.1 MHz,
6-[CH3(CH2)5]-B10H13 (10). Reaction of 0.366 g (3.0 mmol) of
B10H14 with 2.0 g (23.8 mmol) of 1-hexene in biphasic toluene
(∼4 mL)/Bu4NF (0.13 g, 0.5 mmol) at 125 °C for ∼14 h gave,
following elution with a 3:1 hexanes/toluene eluent from a silica
C6D6, ppm): δ 7.13 (m, 5, C6H5), 2.42 (t, 2, CH2), 1.68 (m, 2,
CH2), 1.06 (m, 2, CH2), -2.30 (br, s, 2, BHB), -2.67 (br, s, 2,
BHB).
6-[CH3C(O)(CH2)4]-B10H13 (15). Reaction of 0.366 g (3.0 mmol)
of B10H14 with 1.0 g (10.2 mmol) of 5-hexen-2-one in biphasic
toluene (∼3 mL)/bmpyBF4 (1.5 g, 6.3 mmol) at ∼140 °C for ∼7.3
h gave, following toluene elution from a silica gel column, 0.463
gel column, 0.50 g (2.4 mmol, 80% yield) of 10 as an oily liquid.
11
NCI-HRMS (m/e) calcd (M)- for 12C6
B
1H26: 208.2965; found
10
208.2966. Anal. Calcd: C, 34.92; H, 12.70. Found: C, 34.86; H,
13.16. 11B{11H} NMR (128.4 MHz, CDCl3, ppm): δ 25.5 (s, 1,
B6), 9.7 (d, 2, B1,3), 7.9 (d,1, B9), 0.4 (d, 2, B5,7), -3.4 (d, 2,
B8,10), -34.5 (d, 1, B2), -39.4 (d, 1, B4). 1H{11B} NMR (400.1
MHz, CDCl3, ppm): δ 1.54 (m, 2, CH2), 1.35 (m, 8, CH2), 0.90 (t,
3, CH3), -1.68 (br, s, 2, BHB), -2.03 (br, s, 2, BHB).
6-[2,5-(CH3)2-Hex-3-yl]-B10H13 (11). Reaction of 0.367 g (3.0
mmol) of B10H14 with 1.5 g (13.4 mmol) of 2,5-dimethyl-2-hexene
in biphasic toluene (∼3 mL)/bmpyBF4 (1.5 g, 6.3 mmol) at 140
°C for ∼13 h gave, following elution with a 3:1 hexanes/toluene
eluent from a silica gel column, 0.60 g (2.6 mmol, 85% yield) of
g (2.1 mmol, 70% yield) of 15 as an oily liquid. NCI-HRMS (m/e)
11
calcd (M)- for 12C6
B
10
1H2416O1: 222.2757; found 222.2756. Anal.
Calcd: C, 32.7; H, 10.98. Found: C, 33.10; H,11.10. 11B NMR
(128.4 MHz, CDCl3, ppm): δ 25.1 (s, 1, B6), 9.8 (d, 2, B1,3), 8.4
(d, 1, B9), 0.5 (d, 2, B5,7), -3.3 (d, 2, B8,10), -34.4 (d, 1, B2),
-39.0 (d, 1, B4). 1H{11B} NMR (400.1 MHz, CDCl3, ppm): δ 2.46
(t, 2, CH2-CO), 2.14 (s, 3, CH3), 1.59 (m, 4, CH2), 1.38 (m, 2,
CH2), -1.65 (br, s, 2, BHB), -1.95 (br, s, 2, BHB).
6-[C8H15]-B10H13 (16). Reaction of 0.366 g (3.0 mmol) of B10H14
with 0.75 g (6.8 mmol) of cis-cyclooctene in biphasic toluene (∼3
mL)/bmpyBF4 (1.5 g, 6.3 mmol) at ∼140 °C for ∼4.0 h gave,
following elution with a 3:1 hexanes/toluene eluent from a silica
gel column and drying on a high-vacuum line overnight at ∼125
11 as an light yellow oily liquid. GC/MS analysis showed 11 as
11
the only product. NCI-HRMS (m/e) calcd (M)- for 12C8
B
1H30,
10
236.3278, found 236.3280. Anal. Calcd: C, 40.99; H, 12.90. Found:
C, 41.20; H, 12.95. 11B NMR (128.4 MHz, C6D6, ppm): δ 26.3 (s,
1, B6), 10.6 (d, 2, B1,3), 7.9 (d, 1, B9), 1.1 (d, 2, B5,7), -3.0 (d,
2, B8,10), -34.1 (d, 1, B2), -38.6 (d, 1, B4). 1H{11B} NMR (400.1
MHz, C6D6, ppm): δ 2.2 (m, 1, CH), 1.72 (m, 1, CH), 1.43 (m, 3,
CHCH3), 1.08 (d, 12, CH3), -1.79 (br, s, 2, BHB), -2.25 (br, s, 2,
BHB).
6-[Br(CH2)6]-B10H13 (12). Reaction of 0.366 g (3.0 mmol) of
B10H14 with 1.5 g (9.2 mmol) of 6-bromo-1-hexene in biphasic
toluene (∼3 mL)/bmpyBF4 (1.5 g, 6.3 mmol) at 140 °C for ∼13 h
gave, following elution with a 1:1 hexanes/toluene eluent from a
silica gel column and drying on a high-vacuum line overnight at
°C, 0.62 g (2.7 mmol, 89% yield) of 16 as an oily liquid. NCI-
11
HRMS (m/e) calcd (M)- for 12C8
B
1H28: 233.3043; found
10
233.3033. Anal. Calcd: C, 41.34; H, 12.14. Found: C, 41.31; H,
12.33. 11B NMR (128.4 MHz, CDCl3, ppm): δ 28.0 (s, 1, B6), 9.6
(d, 2, B1,3), 7.9 (d,1, B9), 0.5 (d, 2, B5,7), -4.0 (d, 2, B8,10),
1
-34.8 (d, 1, B2), -39.3 (d, 1, B4). H{11B} NMR (400.1 MHz,
CDCl3, ppm): δ 1.90 (m, 1, CH), 1.74 (m, 4, CH2), 1.55 (m, 10,
CH2), -1.66 (br, s, 2, BHB), -2.04 (br, s, 2, BHB).
6-R-B10H13 Syntheses in the Presence of Chloride or
Acetate Anions. The reactions of separate samples of 0.244 g (2.0
mmol) of B10H14 with 1.0 g (8.9 mmol) of 1-octene in toluene (∼3
mL) at 125 °C in the presence of (1) Bu4NCl (0.11 g, 0.4 mmol,
10.3 h) and (2) bmpyCl (0.074 g, 0.6 mmol, 12 h) gave 0.41 (1.7
mmol, 88% yield) and 0.42 g (1.8 mmol, 89% yield), respectively,
of 1. In a similar manner, the reactions of (1) 0.366 g (3.0 mmol)
of B10H14 with 1.5 g (13.1 mmol) of 1-octene in biphasic toluene
(∼3 mL)/PPNCl (3.44 g, 0.6 mmol) at 125 °C for ∼17.3 h gave
0.36 g (1.53 mmol, 51% yield) of 1; (2) 0.244 g (2.0 mmol) of
B10H14 with 1.0 g (8.9 mmol) of 1-octene in a biphasic mixture of
toluene (∼4 mL), NaOAc (0.033 g, 0.4 mmol), and bmimPF6 (1.0
g, 3.5 mmol) at 125 °C for ∼10.0 h gave 0.38 g (1.6 mmol, 80%
yield) of 1; and (3) 0.244 g (2.0 mmol) of B10H14 with 1.0 g (8.9
mmol) of 1-octene in a biphasic mixture of toluene (∼4 mL),
bmimOAc (0.08 g, 0.4 mmol), and bmimOTf (1.0 g, 3.5 mmol) at
125 °C for ∼18 h gave 0.38 g (1.6 mmol, 80% yield) of 1.
∼125 °C, 0.73 g (2.6 mmol, 85% yield) of 12 as an oily liquid.
11
B
1H2581Br1: 285.1992;
10
NCI-HRMS (m/e) calcd (M - H)- for 12C6
found 285.1998. Anal. Calcd: C, 25.26; H, 8.83. Found: C, 25.72;
H, 8.94. 11B NMR (128.4 MHz, CDCl3, ppm): δ 25.3 (s, 1, B6),
9.8 (d, 2, B1,3), 8.1 (d,1, B9), 0.5 (d, 2, B5,7), -3.3 (d, 2, B8,10),
1
-34.5 (d, 1, B2), -39.2 (d, 1, B4). H{11B} NMR (400.1 MHz,
CDCl3, ppm): δ 3.42 (t, 2, CH2-Br), 1.88 (m, 2, CH2), 1.59 (m, 2,
CH2), 1.43 (m, 6, CH2), -1.68 (br, s, 2, BHB), -2.02 (br, s, 2,
BHB).
6-[C6H5(CH2)2]-B10H13 (13). Reaction of 0.366 g (3.0 mmol)
of B10H14 with 0.70 g (6.7 mmol) of inhibitor-free styrene in
biphasic toluene (∼4 mL)/bmpyBF4 (2.0 g, 8.4 mmol) at 140 °C
for ∼17 h gave, following toluene elution from a silica gel column
and drying on a high-vacuum line overnight at ∼125 °C, 0.51 g
(2.3 mmol, 75% yield) of 13 as an oily liquid. NCI-HRMS (m/e)
11
calcd (M - H)- for 12C8
B
10
1H22: 227.2573; found 227.2570. Anal.
9206 Inorganic Chemistry, Vol. 47, No. 20, 2008

Polyborane Reactions in Ionic Liquids
Reaction of B10H14 with 1-Octene in bmimCl in the
Presence of Acids. The reaction at 125 °C of separate samples of
0.122 g (1.0 mmol) of B10H14 with ∼0.5 g (4.5 mmol) of 1-octene
in biphasic toluene (∼3 mL)/bmimCl (0.035 g, 0.2 mmol) contain-
ing: (1) 0.024 g (0.2 mmol) (22.3 h) of NaHSO4, pKa ) 1.92, and
(2) 0.025 g (0.2 mmol) (12.3 h) of C6H5COOH, pKa ) 4.2, gave
0.19 (0.82 mmol, 82% yield) and 0.20 g (0.86 mmol, 86% yield),
respectively, of 1. Likewise, heating 0.122 g (1.0 mmol) of B10H14
and ∼0.5 g (4.5 mmol) of 1-octene in biphasic toluene (∼3 mL)/
bmimCl (0.035 g, 0.2 mmol) for 8 h at 125 °C while bubbling
anhydrous HCl through the biphasic mixture, resulted in no reaction.
6-R-B10H13 Syntheses via B10H13- Salts. These reactions were
carried out in the manner described in the general procedure except
that once the organic (toluene or DCE) layer was separated by pipet,
it was cooled at 0 °C and then acidified by the dropwise addition
of ∼0.5 mL of concentrated H2SO4. The organic layer was separated
by pipet from the aqueous layer, and following multiple extractions
of the aqueous layer using ether, the combined organic solutions
were vacuum concentrated and then flash filtered through a silica
gel column using a 1:1 hexanes/toluene eluent.
toluene were heated at 90 °C for 1.3 h with either (1) ∼0.5 mL
(4.5 mmol) of 1-octene or (2) ∼0.4 mL (5 mmol) of 3-hexyne and
that there was complete conversion of the [Et3NH+][6-[CH3(CH2)7]-
B10H12-] to 6-[CH3(CH2)7]-B10H13 with loss of Et3N.
-
Reaction of [Bu4N+][6-[CH3(CH2)7]-B10H12
]
(1-) with
B10H14. Reaction of 0.24 g (0.5 mmol) of 1- with 0.036 g (0.3
mmol) of B10H14 in ∼3 mL of DCE for ∼0.3 h, showed by 11B
NMR analysis, the complete consumption of the B10H14 to produce
a mixture containing 6-[CH3(CH2)7]-B10H13, 6-[CH3(CH2)7]-
-
B10H12-, and B10H13
.
3-R-1,2-Et2-1,2-C2B10H9 Syntheses. 3-[CH3(CH2)7]-1,2-(C2H5)2-
1,2-C2B10H9 (17). A 25 mL, 2-neck round-bottom flask equipped
with a septum, stir bar, and vacuum adapter was charged under an
inert atmosphere with 0.35 g (2.0 mmol) of bmimCl, 0.47 g (2.0
mmol) of 1, 1.0 g (12.2 mmol) of 3-hexyne, and ∼3 mL of toluene.
The flask was attached to a water condenser open to argon, and
the body of the flask was then submerged into a 100 °C oil bath
equipped with a magnetic stir plate. After the mixture was stirred
vigorously for ∼4 h, 11B NMR analysis of the toluene layer showed
the absence of any unreacted 6-R-B10H13 and the formation of 17.
The reaction was then stopped, and the top organic layer of the
reaction mixture was separated by pipet; then the ionic-liquid layer
extracted several times with ether. The combined toluene and ether
solutions were vacuum concentrated and then flash filtered on a
silica gel column with toluene eluent to afford, after drying under
highvacuumovernight,0.58g(1.8mmol,92%yield)of3-[CH3(CH2)7]-
1,2-(C2H5)2-C2B10H9 (17) as a dark-yellow oil. GC/MS analysis of
the oil showed 17 as the only product. NCI-HRMS (m/e) calcd
From [Et3NH+][B10H13-]. 11B NMR analyses showed that
heating at 90 °C separate solutions of 0.447 g (2.0 mmol) of
[Et3NH+][B10H13-] in 4 mL of DCE with (1) ∼1.0 mL (8.9 mmol)
of 1-octene (2.3 h) and (2) 1.0 g (8.9 mmol) of 2,5-dimethyl-2-
hexene (3 h) produced (1) mixtures of 6-[CH3(CH2)7]-B10H13 1 and
-
its conjugate anion 6-[CH3(CH2)7]-B10H12 and (2) mixtures of
6-[2,5-(CH3)2-hex-3-yl]-B10H13 11 and it conjugate anion 6-[2,5-
(CH3)2-hex-3-yl]-B10H12-, respectively. Following acidification and
purification, 0.40 g (1.7 mmol, 85% yield) of 1 and 0.30 g (1.3
mmol, 65% yield) of 11 were obtained.
From [Bu4N+][B10H13-]. Reaction of 0.73 g (2.0 mmol) of
[Bu4N+][B10H13-] with ∼1.0 mL (8.9 mmol) of 1-octene in ∼4
mL of DCE at 90 °C for 2.3 h yielded a solution containing only
the 6-[CH3(CH2)7]-B10H12- anion. Acidification and separation gave
0.40 g (1.7 mmol, 85% yield) of 1.
Via In Situ Generation of [Et3NH+][B10H13-] or [PSH+]-
[B10H13-]. Separate reactions at 90 °C of mixtures of 0.366 g (3.0
mmol) of B10H14, toluene (∼3 mL) and Et3N (0.12 g, 1.2 mmol)
with (1) 1.5 g (13.1 mmol) of 1-octene (6 h), (2) 1.5 g (13.1 mmol)
of allyltrimethylsilane (5 h), (3) 1.0 g (7.0 mmol) of acetic acid
5-hexen-1-yl ester (6 h), and (4) 1.0 g (8.9 mmol) of 2,5-dimethyl-
2-hexene (8 h) gave (1) 0.63 g (2.7 mmol, 89% yield) of
6-[CH3(CH2)7]-B10H13 (1), (2) 0.56 g (2.4 mmol, 80% yield) of
6-[(CH3)3Si(CH2)3]-B10H13 (2), (3) 0.51 g (1.92 mmol, 64% yield)
of 6-[CH3C(O)O(CH2)6]-B10H13 (4), and (4) 0.47 g (2.0 mmol, 67%
yield) of 6-[2,5-(CH3)2-hex-3-yl]-B10H13 (11), respectively.
Reaction of 0.366 g (3.0 mmol) of B10H14 with 1.5 g (13.1 mmol)
of 1-octene and (0.26 g, 1.2 mmol) of Proton Sponge in toluene (∼3
mL) at 90 °C for ∼6 h gave 0.60 g (2.6 mmol, 85% yield) of 1.
(M)- for
C
B
1H36: 314.3747; found 314.3764. Anal. Calcd:
12
11
14 10
C, 53.80; H, 11.61. Found: C, 54.16; H, 12.24. 11B NMR (128.4
MHz, C6D6, ppm): δ -0.21 (s, 1, B3), -4.2 (d, 2), -9.7 (s, 2),
1
-11.0 (d, 3), -12.7 (d, 1), -14.4 (d, 1). H{11B} NMR (400.1
MHz, C6D6, ppm): δ 1.56 (m, 2, CH2), 1.50 (m, 4, CH2), 1.36 (m,
2, CH2), 1.27 (m, 10, CH2), 0.88 (m, 3, CH3), 0.63 (t, 6, CH3).
3-[(CH3)3Si(CH2)3]-1,2-(C2H5)2-1,2-C2B10H9 (18). Reaction of
0.473 g (2.0 mmol) of 2 with 1.0 g (12.2 mmol) of 3-hexyne in
biphasic toluene (∼3 mL)/bmimCl (0.35 g, 2.0 mmol) at 100 °C
for ∼4 h gave, following toluene elution from a silica gel column,
0.58 g (1.82 mmol, 91% yield) of 18 as an oily liquid. NCI-HRMS
11
(m/e) calcd (M)- for 12C12
B
10
1H3428Si1: 316.3360; found 316.3364.
Anal. Calcd: C, 45.81; H, 10.89. Found: C, 45.77; H, 11.35. 11B
NMR (128.4 MHz, C6D6, ppm): δ -0.7 (s, 1, B3), -4.7 (d, 2),
1
-10.1 (s, 2), -11.5 (d, 3), -12.4 (d, 1), -14.2 (d, 1). H{11B}
NMR (400.1 MHz, C6D6, ppm): δ 1.69 (m, 2, CH2), 1.57 (m, 2,
CH2), 0.94 (m, 4, CH2), 0.79 (t, 6, CH3), 0.63 (t, 2, CH2), 0.03 (s,
9, CH3).
3-[CH2dCH(CH2)6]-1,2-(C2H5)2-1,2-C2B10H9 (19). Reaction of
0.465 g (2.0 mmol) 3 with 1.0 g (12.2 mmol) of 3-hexyne in
biphasic toluene (∼3 mL)/bmimCl (0.35 g, 2.0 mmol) at 100 °C
for ∼4 h gave, following toluene elution from a silica gel column,
0.57 g (1.82 mmol, 91% yield) of 19 as an oily liquid. NCI-HRMS
Reaction of 6-[CH3(CH2)7]-B10H13 (1) with 1-Octene in
bmimCl/toluene. 11B NMR analysis of the reaction solution showed
that no reaction took place when a mixture of 0.23 g (1.0 mmol)
of 1 and 0.5 g (4.5 mmol) of 1-octene was heated in biphasic toluene
(∼3 mL)/bmimCl (0.035 g, 0.02 mmol) at 125 °C for 8 h.
(m/e) calcd (M)- for
C
B
1H34: 312.3591; found 312.3587.
12
11
14 10
Anal. Calcd: C, 54.15; H, 11.04. Found: C, 54.39; H, 11.25. 11B
NMR (128.4 MHz, CDCl3, ppm): δ -0.8 (s, 1, B3), -5.4 (d, 2),
1
Reactions of [Bu4N+][6-[CH3(CH2)7]-B10H12-] and [Et3NH+]-
[6-[CH3(CH2)7]-B10H12-] with 1-Octene and 3-Hexyne. 11B NMR
analysis showed that no reactions had occurred after heating at 90
°C for 1.3 h separate samples of 0.24 g (0.5 mmol) of [Bu4N+][6-
[CH3(CH2)7]-B10H12-] in ∼3 mL of toluene with either (1) ∼0.5
mL (4.5 mmol) of 1-octene or (2) ∼0.4 mL (5 mmol) of 3-hexyne.
Likewise, 11B NMR analysis showed that there was no reaction
with either the olefin or alkyne when separate samples of 0.24 g
(0.5 mmol) of [Et3NH+][6-[CH3(CH2)7]-B10H12-] in ∼3 mL of
-10.6 (s, 2), -12.1 (d, 3), -12.9 (d, 1), -14.8 (d, 1). H{11B}
NMR (400.1 MHz, CDCl3, ppm): δ5.83 (m, 1, dCH-), 5.0 (m,
2, CH2d), 2.05 (m, 2, CH2), 1.43 (m, 2, CH2), 1.32 (m, 8, CH2),
1.32 (m, 4, CH2), 0.89 (m, 6, CH3).
3-[CH3C(O)O(CH2)6]-1,2-(C2H5)2-1,2-C2B10H9 (20). Reaction
of 0.53 g (2.0 mmol) of 4 with 1.0 g (12.2 mmol) of 3-hexyne in
biphasic toluene (∼3 mL)/bmimCl (0.35 g, 2.0 mmol) at 100 °C
for ∼4 h gave, following toluene elution from a silica gel column,
0.62 g (1.8 mmol, 90% yield) of 20 as an oily liquid. NCI-HRMS
Inorganic Chemistry, Vol. 47, No. 20, 2008 9207

Kusari et al.
11
(m/e) calcd (M)- for 12C14
B
10
1H3416O2: 344.3489; found 344.3478.
-5.7 (d, 2), -11.0 (s, 2), -12.3 (d, 3), -13.1 (d, 1), -14.8 (d, 1).
1H{11B} NMR (400.1 MHz, CDCl3, ppm): δ 2.29 (m, 2, CH2),
1.52 (m, 4, CH2), 1.20 (m, 4, CH2), 1.13 (q, 4, CH2), 1.00 (m, 6,
CH3), 0.84 (m, 1, CH).
Anal. Calcd: C, 49.09; H, 10.00. Found: C, 50.22; H, 9.57. 11B
NMR (128.4 MHz, C6D6, ppm): δ -0.7 (s, 1, B3), -4.6 (d, 2),
-10.1 (s, 2), -11.4 (d, 3), -12.5 (d, 1), -14.1 (d, 1). H{11B}
1
NMR (400.1 MHz, C6D6, ppm): δ 3.95 (t, 2, -OCH2-), 1.73 (s,
3, CH3), 1.69 (m, 4, CH2), 1.45 (m, 6, CH2), 1.25 (m, 4, CH2),
0.78 (m, 6, CH3).
3-[2,5-(CH3)2-hex-3-yl]-1,2-(C2H5)2-1,2-C2B10H9 (26). Reaction
of 0.47 g (2.0 mmol) of 11 with 1.0 g (12.2 mmol) of 3-hexyne in
biphasic toluene (∼3 mL)/bmimCl (0.35 g, 2.0 mmol) at 100 °C
for ∼4 h gave, following toluene elution from a silica gel column,
3-[CH3(CH2)2O(CH2)3]-1,2-(C2H5)2-1,2-C2B10H9 (21). Reaction
of 0.445 g (2.0 mmol) of 5 with 1.0 g (12.2 mmol) of 3-hexyne in
biphasic toluene (∼3 mL)/bmimCl (0.35 g, 2.0 mmol) at 100 °C
for ∼4 h gave, following toluene elution from a silica gel column,
0.58 g (1.82 mmol, 91% yield) of 26 as an oily liquid. NCI-HRMS
11
(m/e) calcd (M - H)- for 12C14
B
10
1H36: 314.3748; found 314.3755.
Anal. Calcd: C, 53.80; H, 11.61. Found: C, 54.22; H, 11.48. 11B
0.54 g (1.78 mmol, 89% yield) of 21 as an oily liquid. NCI-HRMS
NMR (128.4 MHz, C6D6, ppm): δ 1.3 (s, 1, B3), -4.1 (d, 2), -10.1
11
(m/e) calcd (M)- for 12C12
B
10
1H3216O1: 302.3384; found 302.3385.
1
(s, 2), -11.4 (d, 3), -12.4 (d, 1), -14.0 (d, 1). H{11B} NMR
Anal. Calcd: C, 47.96; H, 10.73. Found: C, 49.02; H, 9.11. 11B
(400.1 MHz, C6D6, ppm): δ 2.26 (m, 1, CH), 1.54 (m, 1, CH),
1.33 (m, 5, CH2), 1.10 (m, 10, CH2), 0.87 (m, 8, CH3, CH2), 0.60
(m, 2, CH2).
3-[Br(CH2)6]-1,2-(C2H5)2-1,2-C2B10H9 (27). Reaction of 0.57 g
(2.0 mmol) of 12 with 1.0 g (12.2 mmol) of 3-hexyne in biphasic
toluene (∼3 mL)/bmimCl (0.35 g, 2.0 mmol) at 100 °C for ∼4 h
gave, following toluene elution from a silica gel column, 0.65 g
NMR (128.4 MHz, CDCl3, ppm): δ -0.7 (s, 1, B3), -4.5 (d, 2),
1
-10.2 (s, 2), -11.5 (d, 3), -12.6 (d, 1), -14.4 (d, 1). H{11B}
NMR (400.1 MHz, CDCl3, ppm): δ 3.41 (t, 2, -O-CH2), 3.34 (t,
2, -O-CH2), 1.85 (m, 2, CH2), 1.58 (m, 2, CH2), 1.43 (m, 6, CH2),
0.90 (t, 9, CH3).
3-[C6H5(CH2)O(CH2)3]-1,2-(C2H5)2-1,2-C2B10H9 (22). Reaction
of 0.54 g (2.0 mmol) of 6 with 1.0 g (12.2 mmol) of 3-hexyne in
biphasic toluene (∼3 mL)/bmimCl (0.35 g, 2.0 mmol) at 100 °C
for ∼4 h gave, following toluene elution from a silica gel column,
(1.78 mmol, 89% yield) of 27 as an oily liquid. NCI-HRMS (m/e)
11
calcd (M - Br)- for 12C12
B
10
1H3181Br1: 285.3356; found 285.3362.
Anal. Calcd: C, 39.66; H, 8.60. Found: C, 40.37; H, 9.18. 11B NMR
0.635 g (1.8 mmol, 90% yield) of 22 as an oily liquid. NCI-HRMS
11
(m/e) calcd (M)- for 12C16
B
10
1H3216O1: 350.3384; found 350.3379.
(128.4 MHz, CDCl3, ppm): δ -1.0 (s, 1, B3), -5.3 (d, 2), -10.5
Anal. Calcd: C, 55.14; H, 9.25. Found: C, 56.02; H, 9.62. 11B NMR
1
(s, 2), -12.1 (d, 3), -12.8 (d, 1), -14.7 (d, 1). H {11B} NMR
(128.4 MHz, CDCl3, ppm): δ -1.2 (s, 1, B3), -5.4 (d, 2), -10.6
(400.1 MHz, CDCl3, ppm): δ 3.55 (t, 2, CH2-Br), 2.23 (m, 2, CH2),
1.79 (m, 2, CH2), 1.44 (m, 6, CH2), 1.15 (q, 4, CH2), 0.90 (m, 6,
CH3).
1
(s, 2), -12.2 (d, 3), -12.9 (d, 1), -14.7 (d, 1). H{11B} NMR
(400.1 MHz, CDCl3, ppm): δ 7.36 (m, 5, C6H5-), 4.52 (s, 2, CH2),
3.50 (t, 2, CH2), 2.33 (m, 2, CH2), 1.74 (m, 2, CH2), 1.14 (q, 4,
CH2), 0.95 (m, 6, CH3).
3-[HO(CH2)3]-1,2-(C2H5)2-1,2-C2B10H9 (23). Reaction of 0.36 g
(2.0 mmol) of 7 with 1.0 g (12.2 mmol) of 3-hexyne in biphasic
toluene (∼3 mL)/bmimCl (0.35 g, 2.0 mmol) at 100 °C for ∼4 h
gave, following toluene elution from a silica gel column, 0.43 g
3-[C6H5(CH2)2]-1,2-(C2H5)2-1,2-C2B10H9 (28). Reaction of 0.45 g
(2.0 mmol) of 13 with 1.0 g (12.2 mmol) of 3-hexyne in biphasic
toluene (∼3 mL)/bmimCl (0.35 g, 2.0 mmol) at 100 °C for ∼4 h
gave, following toluene elution from a silica gel column, 0.55 g
(1.78 mmol, 89% yield) of 28 as an oily liquid. NCI-HRMS (m/e)
calcd (M)- for
C
B
1H28: 306.3122; found 306.3126. Anal.
12
11
14 10
(1.64 mmol, 82% yield) of 23 as an oily liquid. NCI-HRMS (m/e)
Calcd: C, 55.23; H, 9.27. Found: C, 55.45; H, 9.24. 11B NMR (128.4
11
calcd (M - C4H10)- for 12C9
B
1H2616O1: 202.2131; found
10
MHz, C6D6, ppm): δ -1.5 (s, 1, B3), -5.4 (d, 2), -10.8 (s, 2),
202.2138. Anal. Calcd: C, 41.83; H, 10.14. Found: C, 42.42; H,
11.86. 11B NMR (128.4 MHz, CDCl3, ppm): δ -0.9 (s, 1, B3),
-5.5 (d, 2), -10.7 (s, 2), -12.2 (d, 3), -13.0 (d, 1), -14.8 (d, 1).
1H{11B} NMR (400.1 MHz, CDCl3, ppm): δ 3.65 (t, 2, CH), 1.8
(s, 1, OH), 1.59 (m, 2, CH), 1.29 (m, 2, CH), 1.15 (q, 4, CH), 0.89
(t, 6, CH).
1
-12.1 (d, 3), -12.9 (d, 1), -14.7 (d, 1). H{11B} NMR (400.1
MHz, CDCl3, ppm): δ 6.98 (m, 5, C6H5), 2.30 (m, 2, CH2), 1.35
(m, 2, CH2), 1.21 (q, 4, CH2), 0.99 (m, 6, CH3).
3-[C6H5(CH2)3]-1,2-(C2H5)2-1,2-C2B10H9 (29). Reaction of 0.481
g (2.0 mmol) of 14 with 1.0 g (12.2 mmol) of 3-hexyne in biphasic
toluene (∼3 mL)/bmimCl (0.35 g, 2.0 mmol) at 100 °C for ∼4 h
gave, following toluene elution from a silica gel column, 0.59 g
(1.82 mmol, 91% yield) of 29 as an oily liquid. NCI-HRMS (m/e)
3-[(CH3)4C2O2B(CH2)3]-1,2-(C2H5)2-1,2-C2B10H9 (24). Reaction
of 0.58 g (2.0 mmol) of 8 with 1.0 g (12.2 mmol) of 3-hexyne in
biphasic toluene (∼3 mL)/bmimCl (0.35 g, 2.0 mmol) at 100 °C
for ∼4 h gave, following toluene elution from a silica gel column,
calcd (M)- for
C
B
1H30: 320.3278; found 320.3287. Anal.
12
11
15 10
0.68 g (1.82 mmol, 91% yield) of 24 as an oily liquid. NCI-HRMS
Calcd: C, 56.56; H, 9.49. Found: C, 57.03; H, 9.45. 11B NMR (128.4
11
(m/e) calcd (M)- for 12C15
B
11
1H3716O2: 370.3817; found 370.3825.
MHz, C6D6, ppm): δ -0.6 (s, 1, B3), -4.5 (d, 2), -10.0 (s, 2),
Anal. Calcd: C, 48.91; H, 10.12. Found: C, 49.10; H, 10.40. 11B
NMR (128.4 MHz, CDCl3, ppm): δ 33.5 (s, O-B-O), -0.9 (s, 1,
B3), -5.3 (d, 2), -10.5 (s, 2), -12.1 (d, 3), -12.8 (d, 1), -14.7
1
-11.4 (d, 3), -12.4 (d, 1), -14.1 (d, 1). H{11B} NMR (400.1
MHz, C6D6, ppm): δ 7.06 (m, 5, C6H5), 2.53 (t, 2, CH2), 1.64 (m,
2, CH2), 0.99 (m, 4, CH2), 0.88 (m, 2, CH2), 0.65 (m, 6, CH3).
3-[CH3C(O)(CH2)4]-1,2-(C2H5)2-1,2-C2B10H9 (30). Reaction of
0.44 g (2.0 mmol) of 15 with 1.0 g (12.2 mmol) of 3-hexyne in
biphasic toluene (∼3 mL)/bmimCl (0.35 g, 2.0 mmol) at 100 °C
for ∼4 h gave, following toluene elution from a silica gel column,
1
(d, 1). H{11B} NMR (400.1 MHz, CDCl3, ppm): δ 2.11 (m, 2,
CH2), 1.54 (m, 2, CH2), 1.25 (s, 12, CH3), 1.14 (q, 4, CH2), 1.02
(m, 2, CH2), 0.91 (m, 6, CH2).
3-[(exo)-Bicyclo-[2,2,1]-hept-2-yl]-1,2-(C2H5)2-1,2-C2B10H9 (25). Re-
action of 0.43 g (2.0 mmol) of 9 and 1.0 g (12.2 mmol) of 3-hexyne
in biphasic toluene (∼3 mL)/bmimCl (0.35 g, 2.0 mmol) at 100
°C for ∼4 h gave, following toluene elution from a silica gel
column, 0.54 g (1.8 mmol, 90% yield) of 25 as an oily liquid. NCI-
0.54 g (1.78 mmol, 89% yield) of 30 as an oily liquid. NCI-HRMS
11
(m/e) calcd (M)- for 12C12
B
10
1H3016O1: 300.3227; found 300.3231.
Anal. Calcd: C, 48.29; H, 10.13. Found: C, 50.02; H, 9.17. 11B
HRMS (m/e) calcd (M)- for
C
B
1H30: 296.3278; found
12
11
NMR (128.4 MHz, CDCl3, ppm): δ -1.0 (s, 1, B3), -5.4 (d, 2),
13 10
1
-10.7 (s, 2), -12.2 (d, 3), -13.0 (d, 1), -14.8 (d, 1). H{11B}
296.3278. Anal. Calcd: C, 53.02; H, 10.27. Found: C, 53.65; H,
10.16. 11B NMR (128.4 MHz, CDCl3, ppm): δ -0.9 (s, 1, B3),
NMR (400.1 MHz, CDCl3, ppm): δ 2.35 (m, 2, CH2-CO), 2.23 (s,
9208 Inorganic Chemistry, Vol. 47, No. 20, 2008

Polyborane Reactions in Ionic Liquids
matrix least-squares based on F2 using SHELXL-97.16 All reflec-
tions were used during refinement (F2 values that were experimen-
tally negative were replaced by F2 ) 0). Non-hydrogen atoms were
refined anisotropically; chain hydrogen atoms were refined using a
“riding” model. Cage hydrogen atoms were refined isotropically,
and chain hydrogen atoms were included as constant contributions
to the structure factors and were not refined. Disordered structures
of the substituent with different orientations were observed for 15
and were resolved accordingly. For 15, four independent molecules
of the asymmetric unit adopt different conformations with the
C1-C2 single bond assuming different orientations.
Table 1. Crystallographic Data Collection and Structural Refinement
Information for 6-[(CH3)3Si(CH2)3]-B10H13 (2) and
6-[CH3C(O)(CH2)4]-B10H13 (15)
2
15
empirical formula
fw
C6B10H28Si
236.47
C6B10H24
220.35
O
cryst class
space group
Z
orthorhombic
Pbca (No. 61)
8
monoclinic
P21/c (No. 14)
16
a, Å
b, Å
c, Å
12.4576(9)
11.0223(8)
24.028(2)
17.146(2)
13.4183(11)
25.820(2)
96.949(2)
5896.7(9)
0.50
ꢀ, deg
V, Å3
3299.3(4)
1.12
µ, cm-1
cryst size, mm
Dcalcd, g/cm3
F(000)
Results
0.32 × 0.10 × 0.04
0.42 × 0.25 × 0.18
0.952
1024
0.993
1888
Syntheses of 6-R-B10H13 via the Ionic-Liquid or Salt
Mediated Reactions of Olefins with B10H14. As summarized
in Table 2, decaborane, B10H14, was found to hydroborate a
variety of olefins in biphasic mixtures of toluene and an ionic
liquid, including, 1-butyl-3-methylimidazolium chloride
(bmimCl), and 1-butyl-4-methylpyridinium tetrafluoroborate
(bmpyBF4), or toluene and an inorganic salt, such as,
anhydrous tetrabutylammonium fluoride (Bu4NF), to give the
corresponding 6-R-B10H13 products, 1-15, in isolated yields
ranging from 55 to 92%.
radiation
2θ angle, deg
temp, K
hkl collected
Mo KR (λ ) 0.71069 Å) Mo KR (λ ) 0.71069 Å)
5.22-50.02
143
5.18-50.02
143
-13 e h e 14
-11 e k e 13
-23 e l e 28
12 587
-19 e h e 20
-13 e k e 15
-30 e l e 30
30 288
reflns measured
unique reflns
2899 (Rint ) 0.0473)
2503
10 348 (Rint ) 0.0357)
6809
observed reflns, (F > 4σ)
reflns used in refinement
params
2899
10 348
267
826
Ra indices (F > 4σ)
R1 ) 0.0483
wR1 ) 0.1180
R1 ) 0.0575
wR2 ) 0.1254
1.149
R1 ) 0.0655
wR1 ) 0.1692
R1 ) 0.1026
wR2 ) 0.1993
1.074
Ra indices (all data)
GOFb
final difference peaks, e/Å3 +0.200, -0.293
+0.298, -0.191
2 2
a R1 ) |Fo| - |Fc|/|Fo|; wR2 ) {w(Fo - Fc )2/w(Fo )2}1/2 b GOF )
.
2
2
2
{w(Fo - Fc )2/(n - p)}1/2 where n ) no. of reflections; p ) no. of
parameters refined.
3, CH3), 2.14 (m, 4, CH2), 1.45 (m, 2, CH2), 1.15 (q, 4, CH2), 0.88
(m, 6, CH3).
3-[C8H15]-1,2-(C2H5)2-1,2-C2B10H9 (31). Reaction of 0.465 g
(2.0 mmol) of 16 with 1.0 g (12.2 mmol) of 3-hexyne in biphasic
toluene (∼3 mL)/bmimCl (0.35 g, 2.0 mmol) at 100 °C for ∼4 h
gave, following toluene elution from a silica gel column, 0.57 g
(1.8 mmol, 90% yield) of 31 as an oily liquid. NCI-HRMS (m/e)
The biphasic reaction mixture, with the ionic-liquid layer
at the bottom and the olefin-toluene layer at the top, was
heated with vigorous stirring to form an emulsion. Reactions
at 125-140 °C, using an excess of the olefin, were typically
complete in ∼12-40 h depending on the olefin. No reaction
was observed when decaborane was heated in an olefin/
toluene solution at 125 °C without an ionic liquid.
12
11
calcd (M)- for
C
B
14 10
1H34: 312.3591; found 312.3605. Anal.
Calcd: C, 54.15; H, 11.04. Found: C, 55.02; H, 10.89. 11B NMR
(128.4 MHz, CDCl3, ppm): δ 1.5 (s, 1, B3), -5.6 (d, 2), -11.0 (s,
2), -12.3 (d, 3), -12.8 (d, 1), -14.7 (d, 1). 1H{11B} NMR (400.1
MHz, CDCl3, ppm): δ 2.22 (m, 1, CH), 1.80 (m, 4, CH2), 1.55 (m,
10, CH2), 1.19 (m, 4, CH2), 0.97 (m, 6, CH3).
As shown in Figure 1 for a reaction with 1-octene in
toluene/bmimBF4, 11B NMR spectra obtained when the
B10H14 was initially added to the biphasic mixture showed
the presence of B10H14 in both the bmpyBF4 and toluene
layers. After heating for 30 min, the toluene layer showed a
characteristic color change to light yellow. As shown in
Figure 2, the 11B NMR spectra of the toluene layer showed
6-R-B10H13 resonances after just 2.3 h. Reactions were
determined to be complete (∼12 h for the reaction with
1-octene in bmimCl at 125 °C; and ∼20.3 h at 125 °C, or
∼12 h at 140 °C, for reactions with 1-octene in bmpyBF4)
when the 11B NMR spectra of the toluene layer showed the
complete consumption of B10H14. The toluene layer was
separated by pipet, and then the ionic-liquid layer was
extracted multiple times with Et2O. The toluene and ether
solutions were combined, vacuum concentrated, and then
flash filtered through a silica gel column using a hexanes/
toluene eluent. Removal of the solvent and excess olefin in
Crystallographic Data for 2 and 15. Single crystals were grown
from a 1:1 toluene/hexanes solution of 2 (Upenn no. 3280) and
from a toluene solution of 15 (Upenn no. 3281) at room temperature.
Collection and Reduction of the Data. X-ray intensity data
(Table 1) were collected on a Rigaku Mercury CCD area detector
employing graphite-monochromated Mo KR radiation. Oscillation
images were processed to produce a listing of unaveraged F2 and
σ(F2) values, which were then passed to the CrystalStructure
program package14 for further processing and structure solution
on a Dell Pentium III computer. The intensity data were corrected
for Lorentz and polarization effects and for absorption.
Solution and Refinement of the Structures. The structures were
solved by direct methods (SIR97).15 Refinements were by full-
(14) Crystal Structure, Crystal Structure Analysis Package; Rigaku Cor-
poration: The Woodlands, TX, 2002.
(15) For SIR97, see: Altomare, A.; Burla, M. C.; Camalli, M.; Cascarano,
G.; Giacovazzo, C.; Moliterni, A.; Polidori, G.; Spagna, R. J. Appl.
Crystallogr. 1999, 32, 115–119.
(16) Sheldrick, G. M. SHELXL-97, Program for the Refinement of Crystal
Structures; University of Go¨ttingen: Go¨ttingen, Germany, 1997.
Inorganic Chemistry, Vol. 47, No. 20, 2008 9209

Kusari et al.
Table 2. Summary of 6-R-B10H13 Syntheses
vacuo afforded final yields of ∼89% of 1 for both the
bmimCl and bmpyBF4 reactions.
As typical of decaborane derivatives, compounds 1-15
were stable under inert atmosphere, slowly hydrolyzing upon
standing in air over days. All compounds were soluble in
common organic solvents like benzene, toluene, methylene
chloride and ethyl acetate, with the exception of compounds
5, 6, 7, 13, and 15, which were only partially soluble in
hexanes, toluene, and benzene. The 11B NMR spectra of
1-15 showed the peaks characteristic of 6-R-B10H13 deriva-
tives,4,5,7-9 and their 1H NMR spectra showed the resonances
expected for their attached substituents and the terminal B-H
cage hydrogens, along with two broad upfield resonances
arising from the two sets of intensity-two bridging hydrogens.
While it is possible, as is usually observed in most uncata-
lyzed monoborane olefin-hydroborations,17 that a Markovni-
kov addition product was produced in minor amounts,
1
analysis of the 6-R-B10H13 products by H NMR and GC/
MS confirmed almost exclusive anti-Markovnikov addition.
The crystallographically determined structures of 6-[(CH3)3-
Si(CH2)3]-B10H13 (2), and 6-[CH3C(O)(CH2)4]-B10H13 (15),
shown in Figures 3 and 4, likewise confirm anti-Markovnikov
addition. The distances and angles observed in these struc-
tures are all in the expected ranges.
As shown in Table S3, Supporting Information, for
reactions with 1-octene, the B10H14 olefin-hydroboration
reaction was found to proceed in a number of ionic liquids,
Figure 1. 11B{1H} NMR spectra showing decaborane dissolved in both
-
the (a) bmpyBF4 and (b) toluene layers. Spectrum a also shows the BF4
resonance of the ionic liquid at -1.7 ppm. (To record spectrum a, some
CH2Cl2 was added to the NMR tube to reduce the viscosity of the
solution).
(17) Brown, H. C.; Knights, E. F.; Scouten, C. G. J. Am. Chem. Soc. 1974,
96, 7765–70.
9210 Inorganic Chemistry, Vol. 47, No. 20, 2008

Polyborane Reactions in Ionic Liquids
Figure 4. ORTEP drawing of the structure of 6-[CH3C(O)(CH2)4]-B10H13
(15). Selected bond lengths (Å) and angles (deg): C6-C5, 1.497(3); C5-O,
1.216(2); C5-C4, 1.493(3); C1-C2, 1.519(3); C1-B6, 1.565(3); B6-B2,
1.739(3); B6-B7, 1.791(3); B6-B5, 1.791(3); B7-B8, 1.965(4); B8-B9,
1.771(4); C6-C5-C4, 117.1(2); C6-C5-O, 121.1(2); O-C5-C4, 121.9(2);
C5-C4-C3, 115.1(2); C2-C1-B6, 116.4(2); C1-B6-B7, 129.2(2);
C1-B6-B5, 125.7(2); C1-B6-B2, 131.4(2); B6-B2-B3, 111.5(2);
B6-B2-B1, 111.3(2); B6-B5-B10, 118.3(2); B6-B7-B8, 117.1(2);
B7-B8-B9, 117.5(2).
heating, even toluene solutions of many soluble salts
containing halides and tetrafluoroborates, including Bu4NBF4,
Bu4NF, Bu4NCl, Bu4NBr, Bu4NSCN, and PPNCl, formed
“ionic liquid”-like biphasic mixtures that showed good
reactivities for decaborane olefin-hydroboration, whereas the
Bu4NPF6 salt did not. For reactions with the tetrabutylam-
monium cation, the reaction rates decreased in the order: F-
> Cl- > SCN-. On the other hand, toluene/decaborane/olefin
solutions in the presence of high melting, toluene-insoluble
salts, such as NaBF4, NH4BF4, and Me4NBF4, showed no
reactivity.
Figure 2. Reaction progression for the reaction of B10H14 with 1-octene
in bmpyBF4/toluene, as measured by the 11B{1H} NMR spectra of the
toluene layer versus time. 1 ) (6-octyl-B10H13) resonances.
When used in catalytic amounts (∼0.2-0.5 equiv relative
to B10H14), bmimCl proved to be the most versatile reagent
for inducing decaborane olefin-hydroboration, but its use in
larger ratios resulted in lower product yields because of
B10H14 degradation reactions. No B10H14 degradation was
observed when using ionic liquids containing the BF4- anion,
even at high stoichiometries. For both bmimCl and bmpyBF4,
the rate of 1-octene hydroboration was faster at higher
temperatures with the upper reaction temperatures (∼125-140
°C) only limited by the olefin and solvent boiling points.
The possible role of Cl- impurities in bmimBF4, bmpyBF4,
and Bu4NBF4, in activating the B10H14 olefin-hydroboration
reactions in these ionic liquids was also considered, but it
was found that reactions in low-chloride content (10 ppm)
bmimBF4 (Fluka catalytic grade) showed no decrease in rate.
While many olefins reacted in both bmimCl and bmpyBF4,
some olefins showed significant reactivity in only one of
them. For example, 6-bromo-hexene and allylbenzene reacted
more effectively in bmpyBF4, while allyl propyl and allyl
benzyl ether had much higher reactivity in bmimCl. Like-
wise, while the hydroboration rates of terminal olefins in
bmimCl were significantly higher than those of internal
olefins, both terminal and internal olefins reacted at similar
rates in bmpyBF4 and bmimBF4 with both the cis- and trans-
internal olefins showing comparable rates in bmpyBF4 (Table
S5, Supporting Information). As previously observed for
Figure 3. ORTEP representation of the structure of 6-[(CH3)3Si(CH2)3]-
B10H13 (2). Selected bond lengths (Å) and bond angles (deg): C6-Si,
1.860(2); C4-Si, 1.862(2); C5-Si, 1.864(2); Si-C3, 1.870(2); C1-B6,
1.574(3); B6-B5, 1.800(3); B5-B10, 1.983(3); B6-B7,1.805(3); B7-B8,
1.977(3); B10-B9, 1.790(3); C4-Si-C5, 108.78(13); C6-Si-C3,
110.02(12); C5-Si-C3, 109.09(10); C2-C1-B6, 114.0(2); C1-B6-B2,
132.1(2); C1-B6-B7, 127.6(2); C1-B6-B5, 127.5(2); B6-B7-B8,
118.25(14); B6-B5-B10, 117.41(14).
including the imidazolium and pyridinium halides (bmimCl,
bmimBr, bmimI, and bmpyCl), acetates (bmimOAc), and
tetrafluoroborates (bmimBF4 and bmpyBF4), but no reactions
were observed in the phosphorus hexafluorides (bmimPF6
or bmpyPF6) or the trifluoromethanesulfonate (bmimOTf).
For the reactions of 1-octene in ionic liquids containing the
bmim cation, the relative hydroboration rates were Cl-
>
Br- ≈ OAc- > BF4- > I-. When salts containing halide or
acetate anions, for example, Bu4NF, NaF, NaCl, NH4Cl, or
NaOAc, were added to the “inert” bmimPF6 and bminOTf
ionic liquids, these new mixed systems became active for
hydroboration reactions. Likewise, it was found that upon
Inorganic Chemistry, Vol. 47, No. 20, 2008 9211

Kusari et al.
monoborane-olefin hydroborations,18 decaborane hydrobo-
ration of strained cyclic olefins, like cis-cyclooctene, pro-
ceeded at a higher rate than those of terminal olefins.
Cyclohexene hydroboration was slow, possibly because of
lower ring-strain and hence a lower reactivity. Hydrobora-
tions of olefins containing acid, acid chloride, thiol, thioether,
and aldehyde groups were unsuccessful in either bmimCl or
bmpyBF4.
Several of the ionic-liquid-mediated hydroboration systems
were shown to be reusable and active over reasonable periods
of time. As summarized in Tables S1 and S4, Supporting
Information, reactions involving the sequential additions of
∼5 mmol of decaborane (20 mmol total) every ∼3-15 h to
either excess 1-octene in bmpyBF4/toluene or excess 1,7-
octadiene in a Bu4NF/bmimOTf/toluene mixture showed only
small decreases in rate and ultimately gave 84 or 87% final
yields of the 6-R-B10H13 products.
products, no reactions were observed upon heating 6-R-
B10H13 derivatives with olefins in biphasic mixtures of an
ionic liquid (either bmimCl or bmpyBF4) and toluene (eq
4).
6-R-B10H13 Syntheses via the Reactions of Olefins
with B10H13-. To test the possible role of the B10H13- anion
in the ionic-liquid-mediated reactions, the reactions of
6-R-B10H13 + 1-octene bmimcl or bmpBF /toluene8 no reaction
4
125 °C, 4 h
-
B10H13 with 1-octene, either starting with the isolated
(4)
[Et3NH+][B10H13-] salt or by in situ generation of the B10H13
-
anion from B10H14 in the presence of bases such as Et3N or
Proton Sponge, were investigated and were found (eq 2) in
each case to result in olefin-hydroboration to produce a
mixture of the neutral 6-octyl-B10H13 product 1, along with
its 6-octyl-B10H12- conjugate anion (1-). While acidification
of these mixtures gave 6-octyl-B10H13 in yields comparable
to the ionic-liquid reactions, the yields obtained for the
reactions starting with the B10H13- anion with most internal
and functional olefins were much lower than those obtained
from the bmimCl reactions discussed in the previous section.
Likewise, no dialkyl-products were produced when toluene
solutions of 1-octene and either the [Bu4N+][6-R-B10H12
]
-
or [Et3NH+][6-R-B10H12-] salts were heated at 90 °C.
Reactions 6-R-B10H13 with Alkynes: Ionic-Liquid-
Mediated Syntheses of 3-R-1,2-Et2-1,2-C2B10H9 Carbo-
ranes. Previous routes to boron-substituted o-carboranes have
been limited in their scope and yields, having involved for
example the reactions of RBX2 compounds with the dicar-
bollide anion19 or the metal-catalyzed reactions of Grignard
reagents with iodocarboranes.20 On the other hand, following
the procedures that are described in the preceding paper,1
the 6-R-B10H13 compounds were found to react with 3-hex-
yne in a biphasic mixture of a bottom 1-butyl-3-methylimi-
dazolium chloride layer and a top alkyne-toluene layer to
give boron-functionalized ortho-carboranes 3-R-1,2-Et2-1,2-
C2B10H9 in high yields (eq 5).
As expected, given the absence of an acidic hydrogen on
the ammonium cation, reactions of [Bu4N+][B10H13-] with
1-octene gave exclusively the [Bu4N+][6-octyl-B10H12-] salt
(eq 3). Nevertheless, subsequent acidification again converted
this salt to the neutral 6-octyl-B10H13.
Vigorously stirred reactions at ∼100 °C using an excess
of 3-hexyne were typically complete in ∼3-4 h. The
biphasic system enabled facile product separation by simply
pipetting the organic layer from the reaction mixture and
then extracting any residual product in the ionic-liquid layer
with ether. Flash filtration of these combined solutions
through a silica gel plug, afforded high final yields for most
substituted decaboranes. For example, the reaction of 3-hex-
-
Attempted Reactions of 6-R-B10H13 and 6-R-B10H12
with Olefins. Consistent with the fact that the ionic-liquid-
mediated decaborane olefin-hydroboration reactions were
highly selective for the formation of only monosubstituted
(18) Brown, H. C.; Liotta, R.; Scouten, C. G. J. Am. Chem. Soc. 1976, 98,
(19) Chen, W.; Rockwell, J. J.; Knobler, C. B.; Harwell, D. E.; Hawthorne,
5297–5301.
M. F. Polyhedron 1999, 18, 1725–1734.
9212 Inorganic Chemistry, Vol. 47, No. 20, 2008

Polyborane Reactions in Ionic Liquids
Table 3. Summary of 3-R-1,2-Et2-1,2-C2B10H9 Syntheses
yne with 6-[CH3(CH2)7]-B10H13 in biphasic bmimCl/toluene
gave 3-[CH3(CH2)7]-1,2-Et2-1,2-C2B10H9 (17) in ∼90%
yields in only ∼4 h. As seen in Table 3, 6-R-B10H13
derivatives with a wide range of functionalities could be
converted into their ortho-carborane analogues 3-R-1,2-Et2-
1,2-C2B10H9 17-31, in isolated yields ranging from 89 to
92%.
Compounds 17-31 were stable in air and soluble in
organic solvents like benzene, toluene, methylene chloride,
and ethyl acetate. Their 11B NMR spectra showed peaks
characteristic of 3-R-1,2-Et2-1,2-C2B10H9 derivatives.19,20 The
1H NMR spectra of all compounds showed the resonances
of the substituents attached at B3 and the Et-groups at the
C1 and C2 atoms.
Discussion
The experimental observations for both the ionic-liquid-
mediated decaborane dehydrogenative alkyne-insertion reactions
reported in the preceding paper1 and the olefin-hydroboration
reactions presented in this paper, support overall reaction
schemes, such as depicted in Figure 5 for an olefin hydrobo-
-
ration, where the ionic-liquid-mediated formation of the B10H13
anion is the essential first step in these reactions. For the-olefin-
hydroboration reactions, this initial step is then followed by (2)
(20) (a) Li, J.; Logan, C. F.; Jones, M., Jr. Inorg. Chem. 1991, 30, 4866–
4868. (b) Zheng, Z.; Jiang, W.; Zinn, A. A.; Knobler, C. B.;
Hawthorne, M. F. Inorg. Chem. 1995, 34, 2095–2100. (c) Vinas, C.;
Barbera, G.; Oliva, J. M.; Teixidor, F.; Welch, A. J.; Rosair, G. M.
Inorg. Chem. 2001, 40, 6555–6562.
-
addition of the B10H13 anion to the olefin to form a 6-R-
-
-
B10H12 anion and, finally, (3) protonation of 6-R-B10H12 to
form the final neutral 6-R-B10H13 product.
Inorganic Chemistry, Vol. 47, No. 20, 2008 9213

Kusari et al.
-
B10H14 in bmimCl would lead to the formation of B10H13
and HCl. While HCl, HBr, and HI are of course strong acids
in water, they are only partially disassociated in many organic
solvents (for example, in DCE, pKa ) 10.8, HCl; 8.7, HBr;
7.9, HI),24 and the acidic pH observed for the DCE layer
after heating B10H14 in a bmimCl/DCE mixture is consistent
with the presence of dissolved HCl that could then serve as
the protonating acid for the final step.
The formation of the protonated neutral 6-octyl-B10H13 (1)
product in both the ionic-liquid and [Et3NH+][B10H13
reactions with 1-octene suggests that the 6-octyl-B10H12
]
-
-
anion is a stronger base than the B10H13- anion, and indeed,
it was found in a separate experiment that the reaction of
6-(octyl)-B10H12 with B10H14 resulted in proton transfer to
-
-
produce neutral 6-(octyl)-B10H13 and the B10H13 anion (eq
Figure 5. Possible reaction scheme for ionic-liquid-promoted B10H14 olefin-
7). Likewise, equimolar bmimCl solutions of B10H14 exhib-
ited a significantly lower pH (pH ∼2) than those of 6-(octyl)-
B10H13 (pH∼3.5).
hydroboration.
Decaborane has been shown to be a monoprotic Brφnsted
acid21 (eq 6) as a result of ionization of one bridging proton
in either water (pKa ) 2.7) or polar nonaqueous solutions.
-
6-octyl-B10H12- + B10H14 f 6-octyl-B10H13 + B10H13
B10H14 + H2O h B10H13- + H3O+
(6)
(7)
The stronger basicity of 6-(octyl)-B10H12- compared to that
As described in the Experimental Section and in the
Supporting Information, the observations that (1) while
decaborane remained largely undissociated in pure toluene
or dichloroethane solvents, it ionized to produce acidic
solutions in the presence of ionic liquids or salts containing
the conjugate anion of a weak acid; (2) the hydroboration
activity of both the ionic liquid and the Bu4N+X- salts
increased as the conjugate base strength of the anionic
component increased; and (3) the decaborane olefin-hy-
droboration reaction was retarded by the addition of acids
that were stronger than decaborane, all suggest that B10H14
ionization was enhanced in the ionic liquids and that the
B10H13- anion was the key reactive intermediate in the olefin
hydroboration reaction.
-
of B10H13 could explain the different reactivities of the
Et3NH+ and Bu4N+ salts of B10H13 and 6-(octyl)-B10H12
-
-
salts toward olefins and alkynes. Thus, while [Et3NH+]-
[B10H13-] reacted with 1-octene and 3-hexyne in DCE to
produce 6-(octyl)-B10H13 and 1,2-Et2-1,2-C2B10H10, respec-
tively, [Et3NH+][6-(octyl)-B10H12-] reacted with neither,
becoming reprotonated instead to form neutral 6-octyl-B10H13
with loss of triethylamine. Likewise, [Bu4N+][6-(octyl)-
B10H12-] did not react with 1-octene, whereas [Bu4N+]-
[B10H13-] reacted to give [Bu4N+][6-(octyl)-B10H12-]. The
-
-
stronger basicity of 6-(octyl)-B10H12 compared to B10H13
should also result in a corresponding decrease in its elec-
trophilicity and in the degree of 6-(octyl)-B10H13 ionization.
All of these differences could play a role in the fact that
higher alkylated products were not observed in the ionic-
liquid-mediated reactions with olefins. Thus, once formed
Supporting the above hypothesis, it was found that the
reactions of B10H13- salts with 1-octene, either starting with
the isolated [Et3NH+][B10H13-] salt or by in situ generation
-
-
of the B10H13 anion from B10H14 in the presence of bases
in the sequence in Figure 5, protonation of the 6-R-B10H12
such as Et3N or Proton Sponge, resulted in 1-octene
hydroboration to produce a mixture of the neutral 6-octyl-
B10H13 product (1), along with its 6-octyl-B10H12- conjugate
anion (1-).
anions by HCl or decaborane would be expected to be more
favorable than an electrophilic attack at the olefin. These
factors would also seem to disfavor the reactions of 6-R-
B10H13 with alkynes, but, it was found that the 6-R-B10H13
derivatives underwent ionic-liquid-mediated dehydrogenative
alkyne-insertion reactions in biphasic bmimCl/toluene mix-
tures to produce 3-R-1,2-R′2-1,2-C2B10H9 ortho-carborane
derivatives in high yields. Thus, the reasons for observed
The key question that then arises is what is the nature of
the attack of the B10H13- anion at the olefins? The following
paper22 uses computational methods to explore this question.
While a fuller discussion of the possible mechanisms will
be presented there, the essential finding is that in these
reactions it is energetically feasible for the B10H13- anion to
rearrange to an electrophilic-type structure (Figure 5), similar
to that of the isoelectronic electrophilic SB9H11 thiaborane
cluster, having a LUMO orbital highly localized at the B6
boron and that olefin binding at this site, as for SB9H11,23
serves as a prelude to hydroboration.
-
differences in the reactivities of the 6-R-B10H12- and B10H13
anions toward olefins and alkynes in the presence of ionic
liquids is even more complex, with the ionic liquid possibly
playing an additional role in alkyne activation.
(21) (a) Guter, G. A.; Schaeffer, G. W. J. Am. Chem. Soc. 1956, 78, 3546.
(b) Hawthorne, M. F.; Pitochelli, A. R.; Strahm, R. D.; Miller, J. J.
J. Am. Chem. Soc. 1960, 82, 1825–1829. (c) Hermanek, S.; Plotova,
H. Collect. Czech. Chem. Commun. 1971, 36, 1639–1643.
(22) Yoon, C. W.; Kusari, U.; Sneddon, L. G. Inorg. Chem. 2008, 47, 9216–
9227.
Following hydroboration, the final step (3) in the scheme
in Figure 5 involves the protonation of the 6-R-B10H12- anion
to form the neutral product 6-R-B10H13. The dissociation of
9214 Inorganic Chemistry, Vol. 47, No. 20, 2008

Polyborane Reactions in Ionic Liquids
In summary, the ionic-liquid-promoted decaborane olefin-
hydroboration reactions now provide general, one-step, high
yield routes to many substituted decaboranes with a wide
range of functionalities including, alkenyl, halide, phenyl,
ether, ester, pinacolborane, ketone, and alcohol groups.
Likewise, this method can be used to hydroborate olefins
with terminal, internal, or cyclic double bonds in both their
cis and trans geometries, with high yields and reasonable
derivatives with different functionalities at the B3-boron and
the cage-carbons. Finally, these results suggest that the
unique properties of ionic liquids might be beneficial for
other polyborane reactions.
Acknowledgment. We thank the National Science Foun-
dation for the support of this project.
Supporting Information Available: X-ray crystallographic data
for structure determinations of compounds 2 and 15 in CIF format,
IR data for all compounds, tables summarizing olefin-hydroboration
activities of different substrates, ionic-liquids, and salts under
various conditions, and summary of qualitative solution pH
measurements. This material is available free of charge via the
Internet at http://pubs.acs.org.
-
reaction times. While B10H13 salts also exhibited activity
for decaborane olefin-hydroboration with 1-octene, the ionic-
liquid-based systems provide the most general synthetic route
to 6-R-B10H13 derivatives. The subsequent ionic-liquid-
promoted dehydrogenative alkyne-insertion reactions of these
derivatives also provide high yield routes to B-functionalized
ortho-carborane derivatives. The combination of the new
ionic-liquid-mediated decaborane olefin-hydroboration and
dehydrogenative alkyne-insertion reactions has the potential
to provide a wide range of more complex ortho-carborane
IC801000C
(23) Meneghelli, B. J.; Bower, M.; Canter, N.; Rudolph, R. W. J. Am. Chem.
Soc. 1980, 102, 4355–4360.
(24) Bos, M.; Dahmen, A. M. F. Anal. Chim. Acta 1973, 63, 185–196.
Inorganic Chemistry, Vol. 47, No. 20, 2008 9215