Dicarba-closo-dodecaboranes with one and two ethynyl groups bonded to boron

Article abstract of DOI:10.1002/ejic.201000064

The diethynyldicarba-closo-dodecaboranes 1,2-R₂-9,12(HCC) ₂-ClOSO-1,2-C₂B₁₀H₈ [R = H (1a), Me (2a)j and 9,10(HCC)₂-closo-1,7-C₂B₁₀H ₁₀ (3a) were obtained by

Full text of DOI:10.1002/ejic.201000064

FULL PAPER
DOI: 10.1002/ejic.201000064
Dicarba-closo-dodecaboranes with One and Two Ethynyl Groups Bonded to
Boron
Alexander Himmelspach[a] and Maik Finze*[a]
Keywords: Alkynes / Boron / Boranes / Carboranes / Palladium / Cross-coupling / Structure elucidation
The diethynyldicarba-closo-dodecaboranes 1,2-R2-9,12-
(HCC)2-closo-1,2-C2B10H8 [R = H (1a), Me (2a)] and 9,10-
(HCC)2-closo-1,7-C2B10H10 (3a) were obtained by Pd-cata-
lyzed Kumada-type cross-coupling reactions of the corre-
sponding diiodinated dicarba-closo-dodecaboranes with
Me3SiCCMgBr followed by desilylation of the trimethyl-
silylalkynyl-substituted clusters. In addition, the related
{closo-C2B10} derivatives with one ethynyl group 1,2-R-9-
HCC-closo-1,2-C2B10H9 [R = H (4a), Me (5a)], 9-HCC-closo-
1,7-C2B10H11 (6a), and 2-HCC-closo-1,12-C2B10H11 (7a) were
synthesized and their spectroscopic properties were com-
alized dicarba-closo-dodecaboranes were characterized by
elemental analysis, mass spectrometry, as well as by multinu-
clear NMR, IR, and Raman spectroscopy. The assignment of
the NMR spectroscopic chemical shifts and the IR and Raman
bands is supported by theoretical values derived from den-
sity functional calculations. The crystal structures of 9,12-
(HCC)2-closo-1,2-C2B10H10
(1a), 9,10-(HCC)2-closo-1,7-
C2B10H10 (3a), and 1,2-Me-9,12-(Me3SiCC)2-closo-1,2-
C2B10H8 (2b) were determined by single-crystal X-ray dif-
fraction. Selected experimental bond properties are com-
pared to bond lengths and angles calculated at the B3LYP/
6-311++G(d,p) level of theory.
pared to those of the diethynyl-substituted {closo-C2B10
}
clusters. The ethynyl- and trimethylsilylalkynyl-function-
Introduction
On account of their potential uses as building blocks for
a wide range of applications, for example, in supramolec-
ular chemistry,[1,2] pharmaceuticals,[3,4] and dendrimers[5] or
polymers,[6] the functionalization of the three isomeric ico-
sahedral dicarba-closo-dodecaboranes (Scheme 1) has been
studied extensively.[7,8] This includes the incorporation of
functional groups at the carbon vertices that may be
achieved by deprotonation and subsequent reaction with an
electrophile, as well as the modification of the substituents
at the boron vertices (e.g., by electrophilic halogenation or
alkylation).
A versatile synthetic strategy for the preparation of
{closo-C2B10} derivatives with one or more functional
groups bonded to boron is the partial iodination[4,9–14] of
the cluster followed by transition-metal-catalyzed cross-
coupling reactions.[7] The first report on cross-coupling re-
actions using iodinated dicarba-closo-dodecaboranes as
starting materials was published in 1981,[15] and 9-Me3-
Scheme 1. Labeling of the vertices of the clusters of the three iso-
mers of the dicarba-closo-dodecaborane closo-1,2-C2B10H12 (ortho-
carborane), closo-1,7-C2B10H12 (meta-carborane), and closo-1,12-
C2B10H12 (para-carborane).
clusters and Me3SiCCMgBr in Pd-catalyzed Kumada-
type[16] coupling reactions. The desilylation of the protected
alkynes under basic conditions yielded the respective eth-
ynyl-substituted clusters.[15] Thereafter, other dicarba-closo-
dodecaboranes with alkynyl substituents bonded to boron
have been described that were either synthesized following
a Kumada-type reaction protocol or a related coupling pro-
cedure.[17–20] Furthermore, cross-coupling reactions were
employed for the preparation of other {closo-C2B10} deriva-
tives with various substituents bonded to boron, for exam-
ple, by means of a carbon[9,11,15,17–22] or a nitrogen[23] atom.
In this contribution, the syntheses of the diethynyl-
dicarba-closo-dodecaboranes 1,2-R2-9,12-(HCC)2-closo-1,2-
C2B10H8 [R = H (1a), Me (2a)] and 9,10-(HCC)2-closo-1,7-
C2B10H10 (3a) and their NMR and vibrational spectro-
scopic data are presented. Furthermore, the crystal struc-
tures of 9,12-(HCC)2-closo-1,2-C2B10H10 (1a), 9,10-
SiCC-closo-1,2-C2B10H11
and
9-Me3SiCC-closo-1,7-
C2B10H11 were obtained from the corresponding iodinated
[a] Institut für Anorganische Chemie und Strukturchemie II,
Heinrich-Heine-Universität
Universitätsstraße 1, 40225 Düsseldorf, Germany
Fax: +49-211-14146
E-mail: maik.finze@uni-duesseldorf.de
Supporting information for this article is available on the
WWW under http://dx.doi.org/10.1002/ejic.201000064.
2012
© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2010, 2012–2024

Dicarba-closo-dodecaboranes with B-Ethynyl Groups
(HCC)2-closo-1,7-C2B10H10 (3a), and 1,2-Me2-9,12-(Me3-
SiCC)2-closo-1,2-C2B10H8 (2b) are reported. In addition, se-
lected monoethynyldicarba-closo-dodecaboranes were pre-
pared and the synthetic procedures are described in this
contribution, because they differ from synthetic protocols
reported previously.[15,17–19]
Results and Discussion
Iodination Reactions of Dicarba-closo-dodecaboranes
The starting materials for the palladium-catalyzed cross-
coupling reactions used in this study are mono- and diio-
Scheme 2. Three-step synthesis of 1,2-R-9,12-(HCC)2-closo-1,2-C2B10H8 [R = H (1a), Me (2a)] and 1,2-R-9-HCC-closo-1,2-C2B10H9
[R = H (4a), Me (5a)] starting from closo-1,2-C2B10H12.
Scheme 3. Three-step synthesis of 9,10-(HCC)2-closo-1,7-C2B10H10 (3a) and 9-HCC-closo-1,7-C2B10H11 (6a) starting from closo-1,7-
C2B10H12.
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A. Himmelspach, M. Finze
FULL PAPER
Scheme 4. Synthesis of 2-HCC-closo-1,12-C2B10H11 in three steps starting from closo-1,12-C2B10H12.
dinated 1,2-dicarba-closo-dodecaboranes[4,9–12] and 1,7-di- served. These are listed in the Exp. Section and assigned to
carba-closo-dodecaboranes[4,11,12] as well as 2-I-closo-1,12- nine boron atoms indicative of a {nido-C2B9} cluster with
C2B10H11,[4,13,14] which are accessible by iodination of the local Cs symmetry.
respective {closo-C2B10} cluster either with elemental iodine
or iodine monochloride; in most reactions reported, AlCl3 decaboranes were desilylated in ethanol with 1–2 equiv. of
is used as Lewis acid.[4,9–14]
KOH per (trimethylsilyl)alkynyl group at room tempera-
The (trimethylsilyl)alkynyl-substituted dicarba-closo-do-
A different synthetic protocol was described for the prep- ture, thereby resulting in the respective mono- and dieth-
aration of mono- and diiodinated ortho-carboranes 1,2-R2- ynyl-substituted dicarba-closo-dodecaboranes in approxi-
9-I-closo-1,2-C2B10H9 and 1,2-R2-9,12-I2-closo-1,2-C2B10H9 mately 95% yield (see Schemes 2, 3, and 4). In the case of
(R = H, aryl), which employs elemental iodine in combina- the desilylation reactions of the {closo-1,2-C2B10} deriva-
tion with a mixture of concentrated H2SO4 and concen- tives, small amounts of {nido-7,8-C2B9} species (Ͻ5%) were
trated HNO3 (1:1 v/v) in glacial acetic acid.[24,25] This formed as determined by 11B{1H} NMR spectroscopy.
method was used for the preparation of the mono- and diio-
dinated 1,2-dicarba-closo-dodecaboranes 1c, 2c, 4c, and 5c
in yields of 80 to 95% as shown in Scheme 2.
Single-Crystal Structures of 1a, 3a, and 2b
This iodination reaction using elemental iodine and a 1:1
mixture of concentrated sulfuric acid and nitric acid in Me-
9,12-(HCC)2-closo-1,2-C2B10H10 (1a) crystallizes in the
monoclinic space group C2/c with 16 formula units in the
CO2H was applied for the selective preparations of 9,10-I2-
unit cell. The deviations of the bond parameters of the two
closo-1,7-C2B10H10 (3c), 9-I-closo-1,7-C2B10H11 (6c), and 2-
independent molecules in the structure of 1a are insignifi-
I-closo-1,12-C2B10H11 (7c) for the first time (see Schemes 3
cant. 9,10-(HCC)2-closo-1,7-C2B10H10 (3a) crystallizes in
and 4). This procedure enables the fast and simple prepara-
the orthorhombic space group Pnma with Z = 4. Details of
the structural determinations are given in the Exp. Section.
tion of 3c, 6c, and 7c in yields of up to 95% and does
not require inert reaction conditions. Diiodination of 1,12-
9,12-(HCC)2-closo-1,2-C2B10H10 (1a) and 9,10-(HCC)2-
dicarba-closo-dodecaboranes was also achieved, thereby re-
closo-1,7-C2B10H10 (3a) are the first structurally charac-
sulting in a mixture of regioisomers similar to the reaction
terized dicarba-closo-dodecaboranes with ethynyl groups
bonded to boron. Only two structures of related {closo-
of closo-1,12-C2B10H12 with ICl in the presence of AlCl3.[13]
C2B10} clusters with alkynyl groups bonded to boron have
been previously reported: 2,9-(Me3SiCC)2-closo-1,12-
C2B10H10 and 1,4-(closo-1Ј,12Ј-C2B10H11-2Ј-yl)2-1,3-buta-
Synthesis of Alkynyl-Substituted {closo-C2B10} Derivatives
Mono- and diiodinated dicarba-closo-dodecaboranes diyne.[19] In contrast, a number of dicarba-closo-dodecabo-
were converted into the corresponding trimethylsilylalk- ranes with ethynyl groups or other alkynyl substituents
ynyl-functionalized clusters with Me3SiCCMgBr and bonded to carbon were structurally characterized.[2,27–32] In
[PdCl2(Ph3P)2] as a catalyst (see Schemes 2, 3, and 4). Figure 1 the diethynyl-substituted clusters 1a and 3a are de-
For the first examples of Pd-catalyzed Kumada-type cross- picted. The CϵC and B–C bond lengths of 1a and 3a are
coupling reactions of monoiodinated dicarba-closo-dodeca- similar (Table 1) and they are also similar to bond lengths
boranes that were described in the early 1980s, similar reac- determined for ethynyl groups bonded to boron of different
tion conditions were reported.[15,17,21,26] The yields of the clusters, for example, in the anion [12-HCC-closo-1-
{closo-C2B10} clusters with one and two trimethylsilylalk- CB11H11]– [d(CϵC) = 1.172(10) Å; d(B–C) = 1.568(8) Å][33]
ynyl substituents depicted in Schemes 2, 3, and 4 are in the (Table 1) and in [1-(η5-C5H5)-2-Ph-6-(HCC)-closo-1,2,3,4-
range of 73 to 83%. The only exception is the synthesis FeC3B7H8] [d(CϵC) = 1.188(3) Å; d(B–C) = 1.542(3) Å].[34]
of 9,12-(Me3SiCC)2-closo-1,2-C2B10H10 (1b) starting from The differences of the experimentally determined d(CϵC)
9,12-I2-closo-1,2-C2B10H10 (1c) and Me3SiCCMgBr that re- of the ethynyl-functionalized boron clusters listed in Table 1
sulted in a significantly lower yield of 40%. A yellow side- are small and not significant (Ͻ3σ). Bond lengths derived
product was obtained that slowly decomposes. In the 11B from density functional theory (DFT) calculations are more
NMR spectrum of this yellow substance, six signals are ob- reliable for comparisons: d(CϵC) and d(B–C) of 1a, 3a, and
2014
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Dicarba-closo-dodecaboranes with B-Ethynyl Groups
Table 1. Selected experimental and calculated[a] bond parameters and vibrational spectroscopic data of ethynyl and trimethylsilylalkynyl
substituents bonded to boron or carbon in dicarba-closo-dodecaboranes or carba-closo-dodecaborate anions.
Compound/anion
d(CϵC)
[Å]
d(B–CC)/d(C–CC)
[Å]
d(CC–Si)
[Å]
Є(B–CϵC)/Є(C–CϵC)
[°]
ν(CϵC)
ν(C–H)
Ref.
˜
˜
[cm–1]
[cm–1]
[c]
[c]
9,12-(HCC)2-closo-1,2-C2B10H10 (1a) exp.
calcd.
1.161(7)[b]
1.207
1.557(7)[b]
1.529
–
–
177.7(4)[b]
179.7
2074
2175/2174
3287/3269
3469
1,2-Me2-9,12-(Me3SiCC)2-closo-1,2-
[c]
[c]
C2B10H8 (2b)[d,e]
exp.
calcd.
1.193(5)[b]
1.217
1.180(3)
1.207
1.206(7)
1.185(2)
1.200
1.180(3)
1.201
1.536(5)[b]
1.529
1.542(3)
1.528
1.532(7)
1.441
1.433
1.831(4)[b]
1.842
178.1(3)[b]
179.4
178.7(2)
179.8
178.5(3)
178.3
179.7
2137
2232/2231
2072
–
–
3276
3469
n.r.
3297
3473
3305/3294
3476
[c]
9,10-(HCC)2-closo-1,7-C2B10H10 (3a) exp.
calcd.
2,9-(Me3SiCC)2-closo-1,12-C2B10H10 exp.
–
–
[c]
2177/2176
[19]
[35,28]
[c]
1.837(5)
n.r.[f]
1-HCC-closo-1,2-C2B10H11
exp.
calcd.
exp.
–
–
–
–
2140
2231
n.r.
2227/2229
[32]
[c]
1,12-(HCC)2-closo-1,12-C2B10H10
1.451(2)
1.438
179.2
180.0
calcd.
1,12-(Me3SiCC)2-closo-1,12-
C2B10H10
[32,30]
[33]
exp.
exp.
1.193(3)
1.172(10)
1.211
1.452(2)
1.568(8)
1.857(2)
179.1(2)
178.7(7)
180.0
2178
2055
2145
2064
2150/2152
–
3272
3474
3278/3264
3475/3475
[12-HCC-closo-1-CB11H11]–
–
–
–
–
[33]
calcd.
1.545
[7,12-(HCC)2-closo-1-CB11H10]–
exp.[f]
1.01(2)[b,g]
1.62(3)[b,g]
1.541/1.542
177.3(1)[b,g]
179.7
[33]
[33]
calcd. 1.210/1.210
[a] B3LYP/6-311++G(d,p). [b] Averaged value. [c] This work. [d] Only the bond lengths of the molecule that is not disordered were
considered. [e] d(Ccluster–CH3)exp. = 1.529(5) Å; d(Ccluster–CH3)calcd. = 1.520 Å. [f] n.r. = not reported. [g] The anion is disordered over two
positions, thereby resulting in relatively imprecise bond parameters.[33]
Figure 1. One of the two independent molecules of 9,12-(HCC)2-
closo-1,2-C2B10H10 (1a) in the crystal (left) and the molecule of
9,10-(HCC)2-closo-1,7-C2B10H10 (3a) in the crystal (right) (dis-
Figure 2. One of the two independent molecules of 1,2-Me2-9,12-
(Me3SiCC)2-closo-1,2-C2B10H8 (2b) in the crystal (displacement el-
lipsoids at the 30% probability level).
placement ellipsoids at the 40% probability level).
monoethynyldicarba-closo-dodecaboranes with the CCH
The experimentally determined bond lengths of the
group bonded to boron are very similar (Table S1 in the {closo-C2B10} clusters of 1a, 2b, and 3a are in good agree-
Supporting Information). In contrast, calculated d(CϵC) as ment with values calculated at the B3LYP/6-311++G(d,p)
well as d(B–C) of the anions [12-HCC-closo-1-CB11H11]– level of theory. In Table S2 in the Supporting Information,
and [7,12-(HCC)2-closo-1-CB11H10]– are slightly longer,[33] the C–C, C–B, and B–B bond lengths of 1a and 2b are
whereas d(CϵC) of ethynyl groups bonded to carbon of compared to those of the parent carba-closo-dodecaboranes
[36]
{closo-C2B10} clusters are shorter (Table 1).
closo-1,2-C2B10H12
and 1,2-Me2-closo-1,2-C2B10H10,[37]
The bis[(trimethylsilyl)alkynyl]-functionalized molecule and in Table S3 in the Supporting Information, the cluster
1,2-Me2-9,12-(Me3SiCC)2-closo-1,2-C2B10H8 (2b) crys- bond lengths of 3a are compared to d(C–B) and d(B–B) of
tallizes in the orthorhombic space group Pnma with Z = closo-1,7-C2B10H12.[38,39] The substitution of the 1,2- as well
8. Experimental details of the structure determination are as 1,7-dicarba-closo-dodecaboranes with two alkynyl
presented in the Experimental Section. In Figure 2 one of groups results in slightly longer bonds between the func-
the two independent molecules of 2b is depicted. The Me3- tionalized boron atoms, d(B9–B12) in 1a and 2b and d(B9–
SiCC groups of the second independent molecule in the B10) in 3a, in comparison to the parent clusters, respec-
crystal of 2b are disordered. The bond lengths of the alk- tively. The bonds of the alkynyl-substituted boron atoms to
ynyl groups in 2b are similar to values reported for 2,9- their nonfunctionalized neighbor boron atoms are slightly
[19]
(Me3SiCC)2-closo-1,12-C2B10H8 (Table 1).
longer as well. The differences of the remaining cluster
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A. Himmelspach, M. Finze
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bonds in the dialkynyldicarba-closo-dodecaboranes com-
pared to the respective parent clusters are small (Tables S2
and S3).
In the crystal of 3a the molecules form layers parallel
to the a–c plane with weak hydrogen contacts between the
hydrogen atoms of the cluster carbon atoms and the CϵC
bonds as depicted in Figure 3. For the structure of
1,4-(closo-1Ј,12Ј-C2B10H11-2Ј-yl)2-1,3-butadiyne,
similar
Ccluster–H···CϵC have been discussed.[38] The layers in the
crystal of 3a are interconnected by further weak C–
H···CϵC interactions of the acetylenic hydrogen atoms of
one layer and the CϵC bonds of the molecules of the neigh-
boring layer, thereby resulting in a three-dimensional net-
work. Related Cethynyl–H···π hydrogen contacts are well
known from crystal structures of terminal alkynes.[40]
In the structure of 1a, similar weak hydrogen contacts
are observed as discussed for 3a; the shortest distance for a
hydrogen contact is d(H–M) = 2.73(3) Å for Ccluster–H···
CϵC. Although molecules 1a and 3a are very similar, their
crystal structures are different (see Figures 3 and S1, the
latter is available in the Supporting Information). This can
probably be attributed to the different positions of the clus-
ter carbon atoms in 1a and 3a, which result in differences
in the weak hydrogen bridges formed between the acidic
Figure 3. Partial packing diagram and unit cell of the crystal struc-
ture of 9,10-(HCC)2-closo-1,7-C2B10H10 (8) and weak hydrogen
contacts: Cethynyl–H···CϵC: d(H–M) = 3.118(13) Å, d(Cethynyl–M)
= 4.020(2) Å, Є(CϵC–M) = 171.7(2)°; Ccluster–H···CϵC: d(H–M)
= 2.91(2) and 3.10(2) Å (M = center of the carbon CϵC bond).
Table 2. Selected experimental[a] and calculated[b] NMR spectroscopic data of ethynyl and trimethylsilylalkynyl-substituted dicarba-closo-
dodecaboranes and carba-closo-dodecaborate anions.
Compound/anion
δ(13C)
δ(13C)
δ(11B)
δ(1H)
1J(13C,11B)
2J(13C,11B)
1J(13C,1H) 2J(13C,1H)
3J(11B,1H)
Ref.
B–13CϵC B–Cϵ13C 11B–CϵC CϵC–1H 11B–13CϵC 11B–Cϵ13C Cϵ13C–1H 13CϵC–1H 11B–CϵC–1H
[ppm]
[ppm]
[ppm]
[ppm]
[Hz]
[Hz]
[Hz]
[Hz]
[Hz]
9-HCC-closo-1,2-C2B10H11
(4a)
[d]
[d]
exp.
calcd.
88.0
91.0
88.1
91.0
–3.3
–3.2
2.58
1.96
107
113.9
19
23.6
240.2
238.6
45.2
46.1
n.o.[c]
3.9
9,12-(HCC)2-closo-1,2-
C2B10H10 (1a)
[d]
[d]
exp.
calcd.
87.0
89.6
89.1
92.5
–2.9
–2.8
2.68
2.07
111
115.2
20
23.5
240.5
239.1
45.5
46.1
n.o.
4.0
9-HCC-closo-1,7-C2B10H11
(6a)
[d]
[d]
exp.
calcd.
85.7
89.8
86.2
88.5
–10.0
–11.2
2.56
1.74
110
114.8
20
23.7
243.7
239.0
46
46.3
n.o.
4.0
9,10-(HCC)2-closo-1,7-
C2B10H10 (3a)
[d]
[d]
exp.
calcd.
85.5
88.3
87.9
89.7
–9.5
–10.8
2.65
1.87
110
116.1
19–20
23.7
241.1
239.4
45.9
46.3
n.o.
4.0
2-HCC-closo-1,12-
C2B10H11 (7a)
[d]
[d]
exp.
calcd.
83.3
88.0
96.0
86.5
89.7
80.9
74.5
–14.3
–10.8
–7.5
2.69
1.87
1.87
0.97
110
≈19
24.9
19.1
21.8
242
47
n.o.
4.2
4
121.8
101.5
105.4
240.5
234.3
228.6
46.6
45.4
43.8
[12-HCC-closo-1-CB11H11]– exp.
calcd.
[33]
[33]
104.2
–9.5
3.5
[7,12-(HCC)2-closo-1-
CB11H10]–[e]
[33]
[33]
exp.
94.6/93.4
82.1/80.9 –6.7/–12.6
1.97/1.95
1.13/1.04
103.1/104.1
107.3/108.4
19.0/18.8
21.9/22.0
234.0/235.7
229.6/230.0
46.0/43.5
44.1/44.3
4/4
3.6/3.6
calcd. 102.3/101.3 76.8/75.1 –7.4/–14.0
9,12-(Me3SiCC)2-closo-1,2-
C2B10H10 (1b)
[d]
[d]
exp.
calcd.
111.0
115.7
106.9
113.8
–4.9
–1.5
–
–
104
110.4
14–20
19.8
–
–
–
–
–
–
9,10-(Me3SiCC)2-closo-1,7-
C2B10H10 (3b)
[d]
[d]
exp.
calcd.
109.7
114.4
105.4
111.0
–9.5
–10.1
–
–
≈105
111.3
15–20
20.0
–
–
–
–
–
–
[12-Me3SiCC-closo-1-
CB11H11]–
[43]
[43]
exp.
calcd.
122.4
138.3
97.1
91.0
–7.9[f]
–10.1
–
–
≈100
110.0
≈18
21.8
–
–
–
–
–
–
[a] Solvent: (CD3)2CO. [b] GIAO/B3LYP/6-311++G(2d,p)//6-311++G(d,p). [c] n.o. = not observed. [d] This work. [e] The first value listed
for the chemical shifts and coupling constants corresponds to the B12–CϵC–H group, and the second value to the B7–CϵC–H group.
[f] Solvent: CD3CN.
2016
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Eur. J. Inorg. Chem. 2010, 2012–2024

Dicarba-closo-dodecaboranes with B-Ethynyl Groups
hydrogen atoms of the cluster carbon atoms and the acet-
ylenic hydrogen atoms with the electron-rich triple bonds
of the ethynyl groups.
NMR Spectroscopy
The mono- and dialkynyl-substituted dicarba-closo-do-
1
decaboranes were characterized by 11B, H, and 13C NMR
1
spectroscopy. The assignment of the 11B and H NMR sig-
nals presented in the Experimental Section and in Table 2
is aided by 11B{1H}-1H{11B} 2D[41] and 11B{1H}-11B{1H}
COSY[42] experiments. The experimental chemical shifts
and coupling constants are well reproduced by theoretical
studies at the gauge-including atomic orbital (GIAO)/
B3LYP-6-311++G(2d,p) level of theory (Table 2). The 11B
and 11B{1H} NMR spectra of 1a and 3a depicted in Fig-
ure 4 are in agreement with disubstitution at the positions
9 and 12 for 1a and 9 and 10 for 3a, respectively, and C2v
symmetry of the clusters.
Figure 5. 13C and 13C{1H} NMR spectra of 9,12-(HCC)2-closo-1,2-
C2B10H10 (1a) and 9,10-(HCC)2-closo-1,7-C2B10H10 (3a).
Vibrational Spectroscopy
The ethynyl- and (trimethylsilyl)alkynyl-functionalized
dicarba-closo-dodecaboranes were studied by IR and Ra-
man spectroscopy and the experimental band positions of
the most characteristic vibrations [ν(CϵC), ν(CC–H),
˜
˜
ν(C
˜
–H), ν(B–H)] are compared to wavenumbers de-
˜
cluster
rived from DFT calculations in Table S4 in the Supporting
Information. The wavenumbers of the CϵC and CC–H
stretches of the ethynyl groups bonded to a boron atom of
dicarba-closo-dodecaboranes exhibit only small differences
in agreement with earlier reports.[45] For ethynyl groups
Figure 4. 11B NMR spectra of 9,12-(HCC)2-closo-1,2-C2B10H10
(1a) and 9,10-(HCC)2-closo-1,7-C2B10H10 (3a).
bonded to cluster carbon atoms, ν(CϵC) is shifted to
˜
In Figure 5 the 13C and 13C{1H} NMR spectra of the higher wavenumbers by approximately 70 cm–1 (Table 1).[45]
diethynyldicarba-closo-dodecaboranes 1a and 3a are shown. In contrast, for the ethynyl groups that are bonded to boron
The signals of the cluster carbon atoms are singlets in the in the anions [12-HCC-closo-1-CB11H11]– and [7,12-
13C NMR spectra and they are split into doublets in the (HCC)2-closo-1-CB11H10]–, slightly smaller wavenumbers
proton-coupled spectra. Both 13C signals that correspond are observed and predicted by DFT calculations as well (ca.
to the ethynyl groups are split into quartets due to the cou- 10–20 cm–1).[33] These differences in experimental as well as
pling to 11B (I = 3/2), and the coupling to the acetylenic theoretical ν(CϵC) display the trend in calculated d(CϵC)
˜
proton results in a further splitting into doublets. The sig- discussed in this contribution and they can be interpreted
nals assigned to the carbon atoms bonded to boron exhibit in terms of decreasing triple bond strengths in the following
larger coupling constants with 11B [1J(13C,11B) ≈ 110 Hz] order: ethynyl groups bonded to cluster carbon atoms of
and smaller coupling constants with 1H [2J(13C,1H) ≈ {closo-C2B10} clusters Ͼ ethynyl groups bonded to boron
46 Hz], compared to the signals of the terminal carbon atoms in {closo-C2B10} clusters Ͼ ethynyl groups bonded
1
atoms [2J(13C,11B) ≈ 21 Hz, J(13C,1H) ≈ 241 Hz]. The dis- to boron atoms of anionic {closo-CB11} clusters.
tortion of the quartets of the 13C signals of the terminal
In Figure 6 the vibrational spectra of 1a and 3a are de-
carbon atoms, as exemplified by the spectra in Figure 5, is picted. ν(CC–H) and ν(Ccluster–H) in the IR and Raman
˜
˜
typical of signals of nuclei that couple to 11B and it is an spectrum of 1a are split in contrast to single bands that are
2
indication that the respective coupling constant J(13C,11B) found in the respective spectra of 3a. This difference reflects
is similar to the inverse spin-lattice relaxation rate σ1 of the the different arrangement of the isoelectronic molecules 1a
11B nucleus.[33,44]
and 3a that is presumably a result of the different intermo-
Eur. J. Inorg. Chem. 2010, 2012–2024
© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
2017

A. Himmelspach, M. Finze
FULL PAPER
400 spectrometer operating at 400.17 (1H), 128.39 (11B), and
100.62 MHz (13C). The NMR spectroscopic signals were referenced
against TMS (1H, 13C) and BF3·OEt2 in CD3CN (11B) as external
standards. Infrared and Raman spectra were recorded at room tem-
perature with an Excalibur FTS 3500 spectrometer (Digilab, Ger-
many) with an apodized resolution of 2 cm–1 (IR) and 4 cm–1 (Ra-
man), respectively. IR spectra were measured in the attenuated total
reflection (ATR) mode in the region of 4000–530 cm–1. Raman
spectra were measured using the 1064 nm excitation line of a Nd/
YAG laser on crystalline samples contained in melting point capil-
laries in the region of 3500–80 cm–1. EI mass spectra were recorded
with a Finnigan MAT 8200 spectrometer. Elemental analyses
lecular hydrogen bridges in the solid state, as evident from
the crystal structures (see Figures 3 and S1, S: Supporting
Information).
(C, H, N) were performed with
(HEKA-Tech, Germany).
a Euro EA3000 instrument
Chemicals: All standard chemicals were obtained from commercial
sources. Tetrahydrofuran was distilled from K/Na alloy under a
nitrogen atmosphere and stored in a flask equipped with a valve
with a polytetrafluoroethylene (PTFE) stem (Young, London) over
molecular sieves (4 Å) under an argon atmosphere. A solution of
Me3SiCCMgBr in THF (0.75 molL–1) was prepared from trimeth-
ylsilylacetylene and EtMgBr (1 molL–1 in THF) and kept in a
250 mL round-bottomed flask with a valve with a PTFE stem
(Young, London) at 4 °C. 1,2-, 1,7-, and 1,12-Dicarba-closo-do-
decaborane were obtained from Katchem spol. s.r.o. (Prague, Czech
Republic) and used as received. 1,2-Me2-closo-1,2-C2B10H10 was
prepared by a modified literature procedure.[49] The partially iodin-
ated {closo-1,2-C2B10} derivatives 9-I-closo-1,2-C2B10H11 (4c) and
9,12-I2-closo-1,2-C2B10H10 (1c) were synthesized from closo-1,2-
C2B10H12 and elemental iodine in glacial acetic acid by slow ad-
dition of a mixture of concentrated H2SO4 and concentrated HNO3
(50:50 v/v) according to a literature procedure in yields of 80–
95%.[24,25]
Figure 6. IR and Raman spectra of 9,12-(HCC)2-closo-1,2-
C2B10H10 (1a) and 9,10-(HCC)2-closo-1,7-C2B10H10 (3a).
General Protocol for the Iodination Reactions: The iodination reac-
tions were performed similar to the syntheses described for some
mono- and diiodinated 1,2-dicarba-closo-dodecaboranes in the lit-
erature.[24,25]
Conclusion
The 1,2- and 1,7-dicarba-closo-dodecaboranes with two
and one ethynyl substituents bonded to boron that are com-
prehensively characterized by structural and spectroscopic
methods in this study are attractive starting materials for
the further derivatization of the {closo-C2B10} cage and po-
tential ligands for coordination chemistry. Their application
in coordination chemistry is especially promising, as sug-
gested by a comparison to related compounds: (i) dicarba-
closo-dodecaboranes with ethynyl groups bonded to the
cluster carbon atoms have been successfully used as li-
gands,[2,25,27,29,46] for example, in [{Ru(dppe)Cp*}2{µ-1,12-
(CϵC)2-closo-1,12-C2B10H10}][27] (dppe = 1,2-bis(diphenyl-
phosphanyl)ethane) and (ii) 9,12-(HCC)2-closo-1,2-
C2B10H10 (1a) as well as 9,10-(HCC)2-closo-1,7-C2B10H10
(3a) reveal structural similarities to 1,2-diethynylbenzene
that has proven to be a versatile bridging ligand, for exam-
ple, in metallamacrocycles.[47] Furthermore, with the
ethynyl-functionalized carba-closo-dodecaborate anions
[12-HCC-closo-1-CB11H11]– and [7,12-(HCC)2-closo-1-
CB11H10]–, isoelectronic anionic counterparts[33,48] are
available for comparative studies.
In a typical diiodination experiment, a 50 mL round-bottomed
flask equipped with a dropping funnel was charged with the respec-
tive dicarba-closo-dodecaborane (2.1 mmol), elemental iodine
(270 mg, 2.1 mmol), and glacial acetic acid (16 mL). The solution
was warmed to 60 °C and then a mixture of concentrated H2SO4
and concentrated HNO3 (6 mL; 50:50 v/v) was added dropwise in
40 min. After complete addition, the reaction mixture was stirred
at 80 °C for 1 h. The mixture was cooled to room tempertaure and
ice-cold water (200 mL) was added. During this addition, a color-
less precipitate formed that was isolated by filtration through a
glass frit. The crude product was washed with water (100 mL) and
dissolved in diethyl ether (100 mL). The solution was treated with
a dilute aqueous solution of sodium sulfite (10 mL, 0.1 molL–1).
The solution was dried with MgSO4, filtered, and the solvent was
removed using a rotary evaporator to result in a colorless solid.
1,2-Me2-9-I-closo-1,2-C2B10H9 (5c): Yield 2.92 g (9.8 mmol, 84%).
C4H15B10I (298.17): calcd. C 16.11, H 5.07; found C 16.22, H 4.97.
1H{11B} NMR [(CD3)2CO]: δ = 2.71 (s, 2 H, BH, 7-H and 11-H),
2.55 (s, 1 H, BH, 12-H), 2.48 (s, 2 H, BH, 4-H and 5-H), 2.34 (s,
2 H, BH, 3-H and 6-H), 2.30 (s, 2 H, BH, 8-H and 10-H), 2.22 (s,
3 H, CH3), 2.06 (s, 3 H, CH3) ppm. 13C{1H} NMR [(CD3)2CO]: δ
= 74.4 (s, 1 C, Ccluster), 69.8 (s, 1 C, Ccluster), 21.1 (s, 1 C, CH3), 20.9
(s, 1 C, CH3) ppm. 11B NMR [(CD3)2CO]: δ = –4.1 [d, 1J(11B,1H) =
152.1 Hz, 1 B, B-12], –7.9 [d, 1J(11B,1H) = overlapped, 2 B, B-8
and B-9], –8.7 [d, 1J(11B,1H) = overlapped, 2 B, B-7 and B-11], –8.9
Experimental Section
General Remarks: 1H, 11B, and 13C NMR spectra were recorded at
25 °C either in (CD3)2CO or [D8]THF with a Bruker Avance III
1
1
[d, J(11B,1H) = overlapped, 2 B, B-3 and B-6], –9.2 [d, J(11B,1H)
2018
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Eur. J. Inorg. Chem. 2010, 2012–2024

Dicarba-closo-dodecaboranes with B-Ethynyl Groups
= overlapped, 2 B, B-4 and B-5], –18.3 (s, 1 B, B-9) ppm. MS (EI):
m/z (isotopic abundance) calcd. for 6 (C4H15B10I): 294 (2), 295 (8),
296 (28), 297 (66), 298 (100), 299 (91), 300 (39), 301 (2); found 294
(11), 295 (18), 296 (35), 297 (78), 298 (100), 299 (87), 300 (40), 301
(Ͻ1).
General Procedure for the Kumada-Type Cross-Coupling Reactions:
The iodinated dicarba-closo-dodecaboranes were weighed in a
round-bottomed flask equipped with a valve with a PTFE stem
(Young, London) and fitted with a magnetic stirring bar. Dry tetra-
hydrofuran was added under an argon atmosphere to result in a
clear colorless solution with a concentration of approximately
2 molL–1 of the respective dicarba-closo-dodecaborane. A solution
of Me3SiCCMgBr in THF (2.5 equiv. per iodine atom) was added
at room temperature. The resulting suspension was transferred by
means of a cannula into a second round-bottomed flask equipped
with a valve with a PTFE stem (Young, London) and fitted with a
magnetic stirring bar that contained [PdCl2(Ph3P)2] (5 mol% per
iodine atom). The reaction mixture was stirred at 40–50 °C. (The
reactions of the monoiodinated dicarba-closo-dodecaboranes were
complete within 12 h; in contrast, the diiodinated molecules re-
quired reaction times of 48–72 h.) The progress of the reaction was
checked by 11B{1H} NMR spectroscopy. The resulting reaction
mixture was poured into ice-cold hydrochloric acid (10% v/v;
10 mL per mmol of cluster) while stirring. The organic layer was
separated and the aqueous phase was extracted two times with di-
ethyl ether. The combined organic fractions were dried with
MgSO4, filtered, and the solvents were removed using a rotary
evaporator. The crude product was purified by column chromatog-
raphy on silica gel (Kieselgel 60, Merck KGaA, Germany) as sta-
tionary phase and a mixture of hexane and benzene (70:30 v/v) as
mobile phase.
1,2-Me2-9,12-I2-closo-1,2-C2B10H8 (2c): Yield 4.28 g (10.1 mmol,
86%). C4H14B10I2 (424.07): calcd. C 11.33, H 3.33; found C 11.46,
1
H 3.34. H{11B} NMR ([D8]THF): δ = 2.79 (s, 4 H, BH, 4-H, 5-
H, 7-H, and 11-H), 2.69 (s, 2 H, BH, 8-H and 10-H), 2.29 (s, 2 H,
BH, 3-H and 6-H), 2.03 (s, 6 H, CH3) ppm. 13C{1H} NMR ([D8]-
THF): δ = 72.2 (s, 2 C, Ccluster), 21.8 (s, 2 C, CH3) ppm. 11B NMR
([D8]THF): δ = –8.9 [d, 1J(11B,1H) = 153.6 Hz, 2 B, B-8 and B-10],
–9.5 [d, 1J(11B,1H) ≈ 173 Hz, 2 B, B-3 and B-6], –10.5 [d, 1J(11B,1H)
≈ 167 Hz, 4 B, B-4, B-5, B-7, and B-11], –17.8 (s, 2 B, B-9 and B-
12) ppm. MS (EI): m/z (isotopic abundance) calcd. for
7
(C4H14B10I2): 420 (2), 421 (8), 422 (28), 423 (66), 424 (100), 425
(91), 426 (39), 427 (2); found 420 (7), 421 (15), 422 (34), 423 (75),
424 (100), 425 (85), 426 (34), 427 (1).
9-I-closo-1,7-C2B10H11 (6c): Yield 540 mg (2.0 mmol, 95%).
C2H11B10I (270.12): calcd. C 8.89, H 4.10; found C 9.27, H 3.97.
1H{11B} NMR [(CD3)2CO]: δ = 3.86 (s, 2 H, CclusterH), 3.08 (s, 1
H, BH, 2-H), 2.71 (s, 1 H, BH, 3-H), 2.68 (s, 2 H, BH, 5-H and
12-H), 2.58 (s, 2 H, BH, 4-H and 8-H), 2.45 (s, 1 H, BH, 10-H),
2.24 (s, 2 H, BH-6 and BH-11) ppm. 13C{1H} NMR [(CD3)2CO]:
δ = 58.3 (s, 2 C, Ccluster) ppm. 11B NMR [(CD3)2CO]: δ = –5.7 [d,
1J(11B,1H) = 165.4 Hz, 2 B, B-5 and B-12], –8.6 [d, 1J(11B,1H) = 9-Me3SiCC-closo-1,2-C2B10H11 (4b): Yield 2.13 g (8.9 mmol, 73%).
1
152.4 Hz, 1 B, B-10], –11.8 [d, J(11B,1H) ≈ 161 Hz, 2 B, B-4 and
C7H20B10Si (240.43): calcd. C 34.97, H 8.38; found C 33.61, H 8.35.
1H{11B} NMR [(CD3)2CO]: δ = 4.52 [pseudosextet, 3J(1H,1H) =
3.4 Hz, 1 H, CclusterH], 4.43 [pseudosextet, 3J(1H,1H) = 3.5 Hz, 1
H, CclusterH], 2.36 (s, 1 H, BH, 12-H), 2.31 (s, 2 H, BH, 3-H and
6-H), 2.25 (s, 2 H, BH, 8-H and 10-H), 2.22 (s, 2 H, BH, 4-H and 5-
H), 2.05 (s, 2 H, BH, 7-H and 11-H), 0.10 [s, 1J(13C,1H) = 119.7 Hz,
2J(29Si,1H) = 7.1 Hz, 9 H, Me3Si] ppm. 13C NMR [(CD3)2CO]: δ
= 112.3 [q, 1J(13C,11B) = 101 Hz, 1 C, B13CϵC], 105.2 [q,
2J(13C,11B) ≈ 15–21 Hz, 1 C, BCϵ13C], 55.4 [d, 1J(13C,1H) =
196.0 Hz, 1 C, Ccluster], 52.2 [d, 1J(13C,1H) = 198.2 Hz, 1 C, Ccluster],
0.1 [q of septets, 1J(29Si,13C) = 56.1 Hz, 1J(13C,1H) = 119.7 Hz,
3J(13C,1H) = 2.0 Hz, 3 C, Me3Si] ppm. 11B NMR [(CD3)2CO]: δ =
1
B-8], –13.0 [d, J(11B,1H) ≈ 161 Hz, 2 B, B-6 and B-11], –16.5 [d,
1
1J(11B,1H) = 183.2 Hz, 1 B, B-3], –18.6 [d, J(11B,1H) = 182.9 Hz,
1 B, B-2], –23.6 (s, 1 B, B-9) ppm. MS (EI): m/z (isotopic abun-
dance) calcd. for 6 (C2H11B10I): 266 (2), 267 (8), 268 (29), 269 (66),
270 (100), 271 (90), 272 (38), 273 (1); found 266 (5), 267 (13), 268
(30), 269 (72), 270 (100), 271 (87), 272 (36), 273 (Ͻ1).
9,10-I2-closo-1,7-C2B10H10 (3c): Yield 810 mg (2.0 mmol, 90%).
C2H10B10I2 (396.01): calcd. C 6.07, H 2.55; found C 6.04, H 2.54.
1H{11B} NMR [(CD3)2CO]: δ = 4.08 (s, 2 H, CclusterH), 3.17 (s, 2
H, BH, 2-H and 3-H), 2.85 (s, 2 H, BH, 5-H and 12-H), 2.70 (s, 4
H, BH, 4-H, 6-H, 8-H, and 11-H) ppm. 13C{1H} NMR [(CD3)2-
CO]: δ = 59.1 (s, 2 C, Ccluster) ppm. 11B NMR [(CD3)2CO]: δ = –4.5
1
–2.6 [d, J(11B,1H) ≈ 158 Hz, 1 B, B-12], –3.2 (s, 1 B, B-9), –8.9 [d,
1J(11B,1H) = 151 Hz, 2 B, B-8 and B-10], –13.4 [d, 1J(11B,1H) =
1
1
[d, J(11B,1H) = 168.3 Hz, 2 B, B-5 and B-12], –11.8 [d, J(11B,1H)
1
overlapped, 2 B, B-4 and B-5], –14.5 [d, J(11B,1H) = overlapped,
= 168.9 Hz, 4 B, B-4, B-6, B-8, and B-11], –18.4 [d, J(11B,1H) =
1
1
2 B, B-7 and B-11], –15.2 [d, J(11B,1H) = 185 Hz, 2 B, B-3 and B-
185.1 Hz, 2 B, B-2 and B-3], –20.8 (s, 2 B, B-9 and B-10) ppm. MS
(EI): m/z (isotopic abundance) calcd. for 7 (C2H10B10I2): 293 (2),
393 (8), 394 (29), 395 (66), 396 (100), 397 (90), 398 (38), 399 (1);
found 293 (9), 393 (17), 394 (38), 395 (79), 396 (100), 397 (91), 398
(41), 399 (4).
6] ppm. IR (ATR): ν = 3070 (m, Ccluster–H), 3042 (w, sh, Ccluster
–
˜
H), 2635–2584 (vs, B–H), 2132 (w, CϵC) cm–1. Raman: ν = 3069
˜
(m, Ccluster–H), 3043 (w, Ccluster–H), 2638–2573 (vs, B–H), 2132 (vs,
CϵC) cm–1. MS (EI): m/z (isotopic abundance) calcd. for 7
(C7H20B10Si): 236 (2), 237 (8), 238 (27), 239 (64), 240 (100), 241
(96), 242 (47), 243 (8), 244 (2); found 236 (1), 237 (9), 238 (27), 239
(65), 240 (100), 241 (95), 242 (49), 243 (10), 244 (2).
2-I-closo-1,12-C2B10H11 (7c): Yield 300 mg (1.1 mmol, 90%).
C2H11B10I (270.12): calcd. C 8.89, H 4.10; found C 8.88, H 3.97.
3
1H{11B} NMR [(CD3)2CO]: δ = 3.92 [pseudoquintet, J(1H,1H) =
1,2-Me2-9-Me3SiCC-closo-1,2-C2B10H9
(5b):
Yield
1.51 g
4.0 Hz, 1 H, CclusterH, 1-H], 3.62 [pseudosextet, 3J(1H,1H) = (5.6 mmol, 83%). C9H24B10Si (268.49): calcd. C 40.26, H 9.01;
3.9 Hz, 1 H, CclusterH, 12-H], 2.61 (s, 1 H, BH, 9-H), 2.59 (s, 2 H, found C 40.55, H 8.94. H{11B} NMR [(CD3)2CO]: δ = 2.40 (s, 2
1
BH), 2.55 (s, 2 H, BH), 2.30 (s, 2 H, BH), 2.26 (s, 2 H, BH) ppm.
H, BH), 2.26 (s, 2 H, BH), 2.22 (s, 3 H, BH), 2.18 (s, 2 H, BH),
1
1
13C{1H} NMR [(CD3)2CO]: δ = 66.9 (s, 1 C, Ccluster), 64.9 (s, 1 C, 2.17 [s, J(13C,1H) = 133.3 Hz, 3 H, MeCcluster], 2.16 [s, J(13C,1H)
Ccluster) ppm. 11B NMR [(CD3)2CO]: δ = –11.8 [d, 1J(11B,1H) = = 133.4 Hz, 3 H, MeCcluster], 0.10 [s, 1J(13C,1H) = 119.6 Hz,
1
overlapped, 2 B], –13.2 [d, J(11B,1H) = overlapped, 2 B], –13.5 [d,
1J(11B,1H) = overlapped, 2 B], –14.1 [d, 1J(11B,1H) = overlapped, 2
B], –16.4 [d, 1J(11B,1H) = 168.0 Hz, 1 B, B-9], –28.4 (s, 1 B, B-2)
ppm. MS (EI): m/z (isotopic abundance) calcd. for 8 (C2H11B10I):
266 (2), 267 (8), 268 (29), 269 (66), 270 (100), 271 (90), 272 (38),
273 (1); found 266 (4), 267 (13), 268 (41), 269 (80), 270 (100), 271
(85), 272 (36), 273 (1).
2J(29Si,1H) = 7.0 Hz, 9 H, Me3Si] ppm. 13C{1H} NMR [(CD3)2-
1
CO]: δ = 111.9 [q, J(13C,11B) ≈ 103 Hz, 1 C, B13CϵC], 105.8 [q,
2J(13C,11B) ≈ 17–21 Hz, 1 C, BCϵ13C], 74.0 (s, 1 C, Ccluster), 70.8
(s, 1 C, Ccluster), 23.4 (s, 1 C, MeCcluster), 22.7 (s, 1 C, MeCcluster),
0.1 [s, 1J(29Si,13C) = 55.7 Hz, 3 C, Me3Si] ppm. 11B NMR
1
[(CD3)2CO]: δ = –4.7 [d, J(11B,1H) = overlapped, 1 B, B-12], –3.2
1
(s, 1 B, B-9), –5.1 (s, 1 B, B-9), –8.8 [d, J(11B,1H) = overlapped, 2
Eur. J. Inorg. Chem. 2010, 2012–2024
© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
2019

A. Himmelspach, M. Finze
FULL PAPER
B] –9.2 [d, 1J(11B,1H) = overlapped, 2 B], –10.1 [d, 1J(11B,1H) =
1J(11B,1H) = 162 Hz, 2 B, B-6 and B-11], –17.4 [d, 1J(11B,1H) =
184 Hz, 1 B, B-3], –19.0 [d, 1J(11B,1H) = 185 Hz, 1 B, B-2] ppm.
1
overlapped, 2 B], –10.2 [d, J(11B,1H) = overlapped, 2 B] ppm. IR
(ATR): ν = 2612–2574 (vs, B–H), 2136 (w, CϵC) cm–1. Raman: ν =
IR (ATR): ν = 3056 (w, Ccluster–H), 3037 (m, Ccluster–H), 2628–
˜
˜
˜
2615–2580 (vs, B–H), 2137 (vs, CϵC) cm–1. MS (EI): m/z (isotopic 2606 (vs, B–H), 2135 (w, CϵC) cm–1. Raman: ν = 3065 (m, C
–
˜
cluster
abundance) calcd. for 7 (C9H24B10Si): 264 (2), 265 (8), 266 (27),
267 (64), 268 (100), 269 (97), 270 (49), 271 (9), 272 (2); found 264
(5), 265 (15), 266 (30), 267 (66), 268 (100), 269 (94), 270 (45), 271
(8), 272 (1).
H), 2637–2612 (s, B–H), 2137 (vs, CϵC) cm–1. MS (EI): m/z (iso-
topic abundance) calcd. for 7 (C7H20B10Si): 236 (2), 237 (8), 238
(27), 239 (64), 240 (100), 241 (96), 242 (47), 243 (8), 244 (2); found
236 (6), 237 (10), 238 (25), 239 (65), 240 (100), 241 (96), 242 (50),
243 (12), 244 (3).
9,12-(Me3SiCC)2-closo-1,2-C2B10H10 (1b): Yield 1.01 g (3.0 mmol,
40%). C12H28B10Si2 (336.64): calcd. C 42.82, H 8.38; found C
9,10-(Me3SiCC)2-closo-1,7-C2B10H10 (3b): Yield 456 mg (1.9 mmol,
1
1
41.44, H 8.14. H{11B} NMR [(CD3)2CO]: δ = 4.46 [s, J(13C,1H)
75%). C12H28B10Si2 (336.64): calcd. C 42.82, H 8.38; found C
= 199.7 Hz, 2 H, CclusterH], 2.30 (s, 2 H, BH, 8-H and 10-H), 2.25 41.89, H 8.29. H{11B} NMR [(CD3)2CO]: δ = 3.65 [s, J(13C,1H)
1
1
(s, 2 H, BH, 3-H and 6-H), 2.16 (s, 4 H, BH, 4-H, 5-H, 7-H, and
= 183.2 Hz, 2 H, CclusterH], 2.50 (s, 2 H, BH, 2-H and 3-H), 2.48
1
2
11-H), 0.12 [s, J(13C,1H) = 119.7 Hz, J(29Si,1H) = 7.2 Hz, 18 H, (s, 2 H, BH, 5-H and 12-H), 2.24 (s, 4 H, BH, 4-H, 6-H, 8-H, and
1
1
2
Me3Si] ppm. 13C{1H} NMR [(CD3)2CO]: δ = 111.3 [q, J(13C,11B) 11-H), 0.16 [s, J(13C,1H) = 119.8 Hz, J(29Si,1H) = 7.1 Hz, 18 H,
≈ 100 Hz, 2 C, B13CϵC], 106.3 [q, 2J(13C,11B) ≈ 15–20 Hz, 2 C, Me3Si] ppm. 13C{1H} NMR [(CD3)2CO]: δ = 109.7 [q, J(13C,11B)
1
1
BCϵ13C], 50.9 (s, 2 C, Ccluster), 0.1 [s, J(29Si,13C) = 56.0 Hz, 6 C,
Me3Si] ppm. 11B NMR [(CD3)2CO]: δ = –2.9 (s, 2 B, B-9 and B-
12), –8.2 [d, 1J(11B,1H) = 148 Hz, 2 B, B-8 and B-10], –14.2 [d,
1J(11B,1H) = 167 Hz, 4 B, B-4, B-5, B-7, and B-11], –16.1 [d,
≈ 105 Hz, 2 C, B13CϵC], 105.4 [q, 2J(13C,11B) ≈ 15–20 Hz, 2 C,
1
BCϵ13C], 53.6 (s, 2 C, Ccluster), 0.2 [s, J(29Si,13C) = 55.9 Hz, 6 C,
Me3Si] ppm. 11B NMR [(CD3)2CO]: δ = –6.0 [d, 1J(11B,1H) =
160 Hz, 2 B, B-5 and B-12], –9.5 (s, 2 B, B-9 and B-10), –13.6 [d,
1J(11B,1H) = 162 Hz, 4 B, B-4, B-6, B-8, and B-11], –19.7 [d,
1J(11B,1H) = overlapped, 2 B, B-3 and B-6] ppm. IR (ATR): ν =
˜
3064 (w, sh, Ccluster–H), 3039 (m, Ccluster–H), 2639–2589 (vs, B–H), 1J(11B,1H) = 177 Hz, 2 B, B-2 and B-3] ppm. IR (ATR): ν = 3057
˜
2131 (vw, CϵC) cm–1. Raman: ν = 3063 (w, sh, Ccluster–H), 3038
(w, Ccluster–H), 3038 (m, Ccluster–H), 2653–2607 (vs, B–H), 2133 (w,
˜
(w, Ccluster–H), 2651–2590 (s, B–H), 2133 (vs, CϵC) cm–1. MS (EI):
m/z (isotopic abundance) calcd. for 7 (C12H28B10Si2): 332 (2), 333
(8), 334 (26), 335 (62), 336 (99), 337 (100), 338 (57), 339 (16), 340
(4), 341 (1); found 332 (4), 333 (7), 334 (28), 335 (65), 336 (95), 337
(100), 338 (56), 339 (16), 340 (10), 341 (2). 11B NMR spectroscopic
data of the side product of the cross-coupling reaction: [(CD3)2CO]:
δ = –9.8 [d, 1J(11B,1H) = 141 Hz, 2 B], –13.5 (s, 2 B, B–CϵCR),
CϵC) cm–1. Raman: ν = 3056 (w, Ccluster–H), 3036 (w, Ccluster–H),
˜
2641–2606 (s, B–H), 2130 (vs, CϵC) cm–1. MS (EI): m/z (isotopic
abundance) calcd. for 7 (C12H28B10Si2): 332 (2), 333 (8), 334 (26),
335 (62), 336 (99), 337 (100), 338 (57), 339 (16), 340 (4), 341 (1);
found 332 (2), 333 (9), 334 (28), 335 (70), 336 (98), 337 (100), 338
(61), 339 (21), 340 (8), 341 (2).
2-Me3SiCC-closo-1,12-C2B10H11 (7b): Yield 2.12 g (8.8 mmol,
80%). C7H20B10Si (240.43): calcd. C 34.97, H 8.38; found C 35.79,
H 8.10. 1H{11B} NMR [(CD3)2CO]: δ = 3.58 [pseudoquintet,
3J(1H,1H) = 3.8 Hz, 1 H, CclusterH, 1-H], 3.43 [pseudosextet,
1
1
–16.5 [d, J(11B,1H) = 166 Hz, 1 B], –21.6 [d, J(11B,1H) = 157 Hz,
2 B], –31.3 [dd, 1J(11B,1H) = 138 Hz; nJ(11B,1H) = 60 Hz, 1 B],
1
–36.4 [d, J(11B,1H) = 144 Hz, 1 B] ppm.
1,2-Me2-9,12-(Me3SiCC)2-closo-1,2-C2B10H8 (2b): Yield 1.42 g 3J(1H,1H) = 3.7 Hz, 1 H, CclusterH, 12-H], 2.31 (s, 2 H, BH), 2.26
(3.9 mmol, 80%). C14H32B10Si2 (364.69): calcd. C 46.11, H 8.84;
(s, 2 H, BH), 2.18 (s, 2 H, BH), 2.13 (s, 2 H, BH), 2.02 (s, 1 H,
1
found C 46.99, H 8.81. H{11B} NMR [(CD3)2CO]: δ = 2.36 (s, 4 BH, 9-H), 0.16 [s, 1J(13C,1H) = 119.9 Hz, 2J(29Si,1H) = 6.5 Hz, 9
1
H, BH), 2.24 (s, 2 H, BH), ca. 2.2 (s, 2 H, BH), 2.17 [s, J(13C,1H) H, Me3Si] ppm. 13C{1H} NMR [(CD3)2CO]: δ = 107.3 (very br. q,
= 133.6 Hz, 6 H, MeCcluster], 0.12 [s, 1J(13C,1H) = 119.7 Hz, 1 C, B13CϵC), 105.0 [q, J(13C,11B) ≈ 18 Hz, 1 C, BCϵ13C], 67.4
2
2J(29Si,1H) = 7.1 Hz, 18 H, Me3Si] ppm. 13C{1H} NMR [(CD3)2-
(s, 1 C, Ccluster), 64.4 (s, 1 C, Ccluster), –0.2 [s, 1J(29Si,13C) = 56.3 Hz,
1
1
CO]: δ = 111.0 [q, J(13C,11B) = 104 Hz, 2 C, B13CϵC], 106.9 [q, 3 C, Me3Si] ppm. 11B NMR [(CD3)2CO]: δ = –13.2 [d, J(11B,1H)
2J(13C,11B) = 14–20 Hz, 2 C, BCϵ13C], 69.6 (s, 2 C, Ccluster), 22.8 = overlapped, 2 B], –14.2 (s, 1 B, B-2), –14.2 [d, 1J(11B,1H) = over-
1
(s, 2 C, MeCcluster), 0.2 [s, J(29Si,13C) = 55.9 Hz, 6 C, Me3Si] ppm. lapped, 2 B], –14.7 [d, 1J(11B,1H) = overlapped, 2 B], –14.9 [d,
11B NMR [(CD3)2CO]: δ = –4.9 (s, 2 B, B-9 and B-12), –9.3––10.0 1J(11B,1H) = overlapped, 2 B], –16.7 [d, J(11B,1H) = overlapped, 1
1
(m, 8 B) ppm. IR (ATR): ν = 2613–2582 (vs, B–H), 2139 (w, CϵC) B] ppm. IR (ATR): ν = 3059 (w, Ccluster–H), 2606 (vs, B–H), 2141
˜
˜
cm–1. Raman: ν = 2622–2582 (s, B–H), 2137 (vs, CϵC) cm–1. MS (vvw, CϵC) cm–1. Raman: ν = 3059 (m, Ccluster–H), 2625–2614 (s,
˜
˜
(EI): m/z (isotopic abundance) calcd. for 7 (C14H32B10Si2): 360 (2),
361 (7), 362 (25), 363 (61), 364 (98), 365 (100), 366 (58), 367 (17),
368 (5), 369 (1); found 360 (4), 361 (15), 362 (38), 363 (55), 364
(95), 365 (100), 366 (62), 367 (19), 368 (5), 369 (3).
B–H), 2140 (vs, CϵC) cm–1. MS (EI): m/z (isotopic abundance)
calcd. for 7 (C7H20B10Si): 236 (2), 237 (8), 238 (27), 239 (64), 240
(100), 241 (96), 242 (47), 243 (8), 244 (2); found 236 (5), 237 (11),
238 (32), 239 (68), 240 (100), 241 (98), 242 (52), 243 (12), 244 (1).
9-Me3SiCC-closo-1,7-C2B10H11 (6b): Yield 1.99 g (8.3 mmol, 75%). Desilylation Reactions: The trimethylsilylalkynyl-substituted di-
C7H20B10Si (240.43): calcd. C 34.97, H 8.38; found C 35.48, H 8.28.
carba-closo-dodecaborane was placed in a round-bottomed flask.
A solution of KOH (1–2 equiv. per Me3Si group) in a mixture of
1
1H{11B} NMR [(CD3)2CO]: δ = 3.64 [s, J(13C,1H) = 181.7 Hz, 2
H, CclusterH], 2.60 (s, 1 H, BH, 3-H), 2.53 (s, 1 H, BH, 2-H), 2.39 water and methanol (1:4 v/v, 10 mL per mmol of the cluster) was
(s, 2 H, BH, 5-H and 12-H), 2.29 (s, 2 H, BH, 4-H and 8-H), 2.16 added and the resulting solution was stirred for 2 h. Water was
(s, 1 H, BH, 10-H), 2.12 (s, 2 H, BH, 6-H and 11-H), 0.13 [s,
added to the reaction mixture (30 mL per mmol of the cluster) to
result in a colorless suspension. The precipitate was filtered off and
the aqueous solution was extracted with diethyl ether. The ether
solution was dried with MgSO4, filtered, and the solvent was re-
moved under reduced pressure. The solid residue and the filtered
precipitate were combined. In general, a further purification of the
primary alkynes was not necessary. Some substances were recrys-
tallized or sublimed.
1J(13C,1H) = 119.8 Hz, 2J(29Si,1H) = 7.0 Hz, 9 H, Me3Si] ppm.
1
13C{1H} NMR [(CD3)2CO]: δ = 110.6 [q, J(13C,11B) = 104 Hz, 1
2
C, B13CϵC], 104.2 [q, J(13C,11B) ≈ 16–20 Hz, 1 C, BCϵ13C], 55.6
(s, 2 C, Ccluster), 0.1 [s, 1J(29Si,13C) = 56.1 Hz, 3 C, Me3Si] ppm. 11
B
1
NMR [(CD3)2CO]: δ = –6.5 [d, J(11B,1H) = 162 Hz, 2 B, B-5 and
1
B-12], –9.8 [d, J(11B,1H) = overlapped, 1 B, B-10], –9.9 (s, 1 B, B-
9), –12.8 [d, 1J(11B,1H) = 161 Hz, 2 B, B-4 and B-8], –14.0 [d,
2020
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© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2010, 2012–2024

Dicarba-closo-dodecaboranes with B-Ethynyl Groups
9-HCC-closo-1,2-C2B10H11 (4a): Yield 320 mg (1.9 mmol, 95%).
C4H12B10 (168.25): calcd. C 28.56, H 7.19; found C 28.47, H 7.09.
1H{11B} NMR [(CD3)2CO]: δ = 4.53 [pseudosextet, 3J(1H,1H) =
3.7 Hz, 1 H, CclusterH], 4.44 [pseudosextet, 3J(1H,1H) = 3.6 Hz, 1
found 188 (8), 189 (19), 190 (45), 191 (72), 192 (100), 193 (90), 194
(38), 195 (Ͻ1).
1,2-Me2-9,12-(HCC)2-closo-1,2-C2B10H8 (2a): Yield 640 mg
(2.9 mmol, 91%). C8H16B10 (220.33): calcd. C 43.61, H 7.32; found
C 43.93, H 7.43. 1H{11B} NMR [(CD3)2CO]: δ = 2.70 [s, 1J(13C,1H)
H, CclusterH], 2.58 [s, J(13C,1H) = 240.2 Hz, J(13C,1H) = 45.2 Hz,
1 H, CϵCH], 2.37 (s, 1 H, BH, 12-H), 2.32 (s, 2 H, BH, 3-H and
6-H), 2.26 (s, 2 H, BH, 8-H and 10-H), 2.23 (s, 2 H, BH, 4-H and
5-H), 2.06 (s, 2 H, BH, 7-H and 11-H) ppm. 13C NMR [(CD3)2-
1
2
2
= 238.0 Hz, J(13C,1H) = 49.6 Hz, 2 H, CϵCH], 2.38 (s, 4 H, BH,
4-H, 5-H, 7-H, and 11-H), 2.23 (s, 2 H, BH), 2.18 (s, 2 H, BH),
2.17 [s, 1J(13C,1H) = 133.9 Hz, 6 H, MeCcluster] ppm. 13C NMR
1
2
CO]: δ = 88.1 [dq, J(13C,1H) = 244 Hz, J(13C,11B) = 19 Hz, 1 C,
1
2
[(CD3)2CO]: δ = 89.8 [dq, J(13C,1H) = 242 Hz, J(13C,11B) ≈ 17–
1
BCϵ13C], 88.0 [qd, J(13C,11B) = 107 Hz, 2J(13C,1H) = 51 Hz, 1 C,
1
2
22 Hz, 1 C, BCϵ13C], 86.6 [qd, J(13C,11B) = 110 Hz, J(13C,1H) ≈
B13CϵC], 55.6 [d, 1J(13C,1H) = 198.5 Hz, 1 C, Ccluster], 52.3 [d,
1J(13C,1H) = 197.5 Hz, 1 C, Ccluster] ppm. 11B NMR [(CD3)2CO]: δ
1
50 Hz, 2 C, B13CϵC], 69.9 (s, 2 C, Ccluster), 22.7 [q, J(13C,1H) =
133.8 Hz, 2 C, MeCcluster] ppm. 11B NMR [(CD3)2CO]: δ = –5.0 (s,
= –2.6 [d, J(11B,1H) = 160 Hz, 1 B, B-12], –3.3 (s, 1 B, B-9), –8.9
1
1
2 B, B-9 and B-12), –9.5 [d, J(11B,1H) = overlapped, 4 B], –9.9 [d,
[d, 1J(11B,1H) = 148 Hz, 2 B, B-8 and B-10], –13.4 [d, 1J(11B,1H) =
1J(11B,1H) = overlapped, 4 B] ppm. IR (ATR): ν = 3280 (s, CC–
˜
overlapped, 2 B, B-4 and B-5], –14.4 [d, J(11B,1H) = overlapped,
1
H), 2647–2582 (vs, B–H), 2072 (w, CϵC) cm–1. Raman: ν = 3280
˜
2 B, B-7 and B-11], –15.2 [d, 1J(11B,1H) = 182 Hz, 2 B, B-3 and B-
(vw, CC–H), 2658–2581 (vs, B–H), 2069 (s, CϵC) cm–1. MS (EI):
m/z (isotopic abundance) calcd. for 7 (C8H16B10): 216 (2), 217 (8),
218 (28), 219 (65), 220 (100), 221 (93), 222 (42), 223 (3); found 216
(10), 217 (25), 218 (40), 219 (70), 220 (100), 221 (95), 222 (49), 223
(6).
6] ppm. IR (ATR): ν = 3285 (m, CC–H), 3057 (s, Ccluster–H), 2601–
˜
2573 (vs, B–H), 2072 (vw, CϵC) cm–1. Raman: ν = 3282 (vvw, CC–
˜
H), 3060 (s, Ccluster–H), 2652–2579 (vs, B–H), 2069 (s, CϵC) cm–1.
MS (EI): m/z (isotopic abundance) calcd. for 7 (C4H12B10): 164 (2),
165 (8), 166 (28), 167 (66), 168 (100), 169 (91), 170 (39), 171 (2);
found 164 (8), 165 (18), 166 (31), 167 (80), 168 (100), 169 (94), 170
(48), 171 (5).
9-HCC-closo-1,7-C2B10H11 (6a): Yield 455 mg (2.7 mmol, 95%).
C4H12B10 (168.25): calcd. C 28.56, H 7.19; found C 28.92, H 7.21.
1
1H{11B} NMR [(CD3)2CO]: δ = 3.66 [s, J(13C,1H) = 183.1 Hz, 2
H, CclusterH], 2.62 (s, 1 H, BH, 3-H), 2.56 [s, 1J(13C,1H) = 243.7 Hz,
2J(13C,1H) = 46 Hz, 1 H, CϵCH], 2.54 (s, 1 H, BH, 2-H), 2.40 (s,
2 H, BH, 5-H and 12-H), 2.30 (s, 2 H, BH, 4-H and 8-H), 2.16 (s,
1 H, BH, 10-H), 2.13 (s, 2 H, BH, 6-H and 11-H) ppm. 13C NMR
[(CD3)2CO]: δ = 86.2 [dq, 1J(13C,1H) = 241 Hz, 2J(13C,11B) =
1,2-Me2-9-HCC-closo-1,2-C2B10H9 (5a): Yield 627 mg (3.2 mmol,
96%). C6H16B10 (196.30): calcd. C 36.71, H 8.22; found C 36.87,
H 8.19. 1H{11B} NMR [(CD3)2CO]: δ = 2.60 [s, 1J(13C,1H) =
2
238.2 Hz, J(13C,1H) = 45.7 Hz, 1 H, CϵCH], 2.42 (s, 2 H, BH),
2.26 (s, 2 H, BH), 2.23 (s, 3 H, BH), 2.19 (s, 2 H, BH), 2.18 [s,
1J(13C,1H) = 133.4 Hz, 3 H, MeCcluster], 2.16 [s, 1J(13C,1H) =
133.3 Hz, 3 H, MeCcluster] ppm. 13C NMR [(CD3)2CO]: δ = 88.7
2
20 Hz, 1 C, BCϵ13C], 85.7 [qd, 1J(13C,11B) = 110 Hz, J(13C,1H) =
1
46 Hz, 1 C, B13CϵC], 55.0 [d, J(13C,1H) = 183.6 Hz, 2 C, Ccluster
]
ppm. 11B NMR [(CD3)2CO]: δ = –6.4 [d, 1J(11B,1H) = 163 Hz, 2
B, B-5 and B-12], –9.8 [d, 1J(11B,1H) = overlapped, 1 B, B-10],
1
2
[dq, J(13C,1H) = 239 Hz, J(13C,11B) ≈ 18 Hz, 1 C, BCϵ13C], 87.9
1
2
[qd, J(13C,11B) ≈ 104 Hz, J(13C,1H) ≈ 47 Hz, 1 C, B13CϵC], 74.1
–10.0 (s, 1 B, B-9), –12.7 [d, J(11B,1H) = 161 Hz, 2 B, B-4 and B-
1
(s, 1 C, Ccluster), 70.9 (s, 1 C, Ccluster), 23.4 [q, 1J(13C,1H) = 133.6 Hz,
8], –14.0 [d, 1J(11B,1H) = 161 Hz, 2 B, B-6 and B-11], –17.3 [d,
1J(11B,1H) = 188 Hz, 1 B, B-3], –18.9 [d, 1J(11B,1H) = 185 Hz, 1 B,
1 C, MeCcluster], 22.7 [q, 1J(13C,1H) = 133.2 Hz, 1 C, MeCcluster
]
ppm. 11B NMR [(CD3)2CO]: δ = –4.9 [d, J(11B,1H) = overlapped,
1 B, B-12], –5.1 (s, 1 B, B-9), –8.7 [d, 1J(11B,1H) = overlapped, 2
B], –9.3 [d, 1J(11B,1H) = overlapped, 2 B], –9.9 [d, 1J(11B,1H) =
1
B-2] ppm. IR (ATR): ν = 3280 (s, CC–H), 3068 (w, sh, Ccluster–H),
˜
3057 (m, Ccluster–H), 2658–2578 (vs, B–H), 2074 (w, CϵC) cm–1.
Raman: ν = 3269 (vw, CC–H), 3066 (m, Ccluster–H), 3057 (m,
˜
overlapped, 2 B], –10.2 [d, J(11B,1H) = overlapped, 2 B] ppm. IR
1
Ccluster–H), 2657–2577 (vs, B–H), 2073 (s, CϵC) cm–1. MS (EI):
m/z (isotopic abundance) calcd. for 7 (C4H12B10): 164 (2), 165 (8),
166 (28), 167 (66), 168 (100), 169 (91), 170 (39), 171 (2); found 164
(5), 165 (16), 166 (38), 167 (76), 168 (100), 169 (91), 170 (40), 171
(5).
(ATR): ν = 3291 (s, CC–H), 2616–2555 (vs, B–H), 2074 (w, CϵC)
˜
cm–1. Raman: ν = 2616–2567 (vs, B–H), 2072 (s, CϵC) cm–1. MS
˜
(EI): m/z (isotopic abundance) calcd. for 7 (C6H16B10): 192 (2), 193
(8), 194 (28), 195 (65), 196 (100), 197 (92), 198 (41), 199 (3); found
192 (8), 193 (20), 194 (45), 195 (80), 196 (100), 197 (79), 198 (45),
199 (5).
9,10-(HCC)2-closo-1,7-C2B10H10 (3a): Yield 308 mg (1.6 mmol,
92%). C6H12B10 (192.27): calcd. C 37.48, H 6.29; found C 37.21,
H 6.15. 1H{11B} NMR [(CD3)2CO]: δ = 3.67 [s, 1J(13C,1H) =
184.1 Hz, 2 H, CclusterH], 2.65 [s, 1J(13C,1H) = 241.1 Hz, 2J(13C,1H)
= 45.9 Hz, 2 H, CϵCH], 2.53 (s, 2 H, BH, 2-H and 3-H), 2.51 (s,
2 H, BH, 5-H and 12-H), 2.28 (s, 4 H, BH, 4-H, 6-H, 8-H, and 11-
9,12-(HCC)2-closo-1,2-C2B10H10 (1a): Yield 250 mg (1.3 mmol,
94%). C6H12B10 (192.27): calcd. C 37.48, H 6.29; found C 37.00,
H 6.52. 1H{11B} NMR [(CD3)2CO]: δ = 4.49 [s, 1J(13C,1H) =
199.7 Hz, 2 H, CclusterH], 2.68 [s, 1J(13C,1H) = 240.5 Hz, 2J(13C,1H)
= 45.5 Hz, 2 H, CϵCH], 2.33 (s, 2 H, BH, 8-H and 10-H), 2.29 (s, H) ppm. 13C NMR [(CD3)2CO]: δ = 87.9 [dq, 1J(13C,1H) = 241 Hz,
2 H, BH, 3-H and 6-H), 2.21 (s, 4 H, BH, 4-H, 5-H, 7-H, and 11- 2J(13C,11B) ≈ 19–22 Hz, 2 C, BCϵ13C], 85.5 [qd, 1J(13C,11B) =
H) ppm. 13C NMR [(CD3)2CO]: δ = 89.1 [dq, 1J(13C,1H) = 240 Hz, 110 Hz, J(13C,1H) = 46 Hz, 2 C, B13CϵC], 53.8 [d, J(13C,1H) =
2J(13C,11B) = 20 Hz, 2 C, BCϵ13C], 87.0 [qd, 1J(13C,11B) = 111 Hz, 184.4 Hz, 2 C, Ccluster] ppm. 11B NMR [(CD3)2CO]: δ = –5.9 [d,
2
1
2J(13C,1H) = 50 Hz, 2 C, B13CϵC], 51.2 [d, 1J(13C,1H) = 199.2 Hz,
2 C, Ccluster] ppm. 11B NMR [(CD3)2CO]: δ = –2.9 (s, 2 B, B-9 and
1J(11B,1H) = 164 Hz, 2 B, B-5 and B-12], –9.5 (s, 2 B, B-9 and B-
1
10), –13.3 [d, J(11B,1H) = 166 Hz, 4 B, B-4, B-6, B-8, and B-11],
1
1
B-12), –8.2 [d, J(11B,1H) = 151 Hz, 2 B, B-8 and B-10], –14.1 [d,
–19.4 [d, J(11B,1H) = 181 Hz, 2 B, B-2 and B-3] ppm. IR (ATR):
1J(11B,1H) = 167 Hz, 4 B, B-4, B-5, B-7, and B-11], –16.0 [d,
ν = 3276 (vs, CC–H), 3058 (s, Ccluster–H), 2636–2588 (vs, B–H),
˜
1J(11B,1H) = 187 Hz, 2 B, B-3 and B-6] ppm. IR (ATR): ν = 3287
2074 (w, CϵC) cm–1. Raman: ν = 3280 (s, CC–H), 3058 (m,
˜
˜
(s, CC–H), 3269 (s, CC–H), 3067 (w, sh, Ccluster–H), 3053 (s, Ccluster–H), 2640–2589 (s, B–H), 2072 (vs, CϵC) cm–1. MS (EI):
Ccluster–H), 2643–2586 (vs, B–H), 2074 (vw, CϵC) cm–1. Raman: ν m/z (isotopic abundance) calcd. for 7 (C6H12B10): 188 (2), 189 (8),
˜
= 3057 (m, Ccluster–H), 2643–2586 (s, B–H), 2074 (vs, CϵC) cm–1. 190 (28), 191 (65), 192 (100), 193 (92), 194 (40), 195 (3); found 188
MS (EI): m/z (isotopic abundance) calcd. for 7 (C6H12B10): 188 (2),
(10), 189 (20), 190 (50), 191 (82), 192 (100), 193 (90), 194 (40), 195
189 (8), 190 (28), 191 (65), 192 (100), 193 (92), 194 (40), 195 (3);
(5).
Eur. J. Inorg. Chem. 2010, 2012–2024
© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
2021

A. Himmelspach, M. Finze
FULL PAPER
2-HCC-closo-1,12-C2B10H11 (7a): Yield 538 mg (3.2 mmol, 96%).
Table 3. Crystal data and structure refinement details for 9,12-
(HCC)2-closo-1,2-C2B10H10 (1a), 9,10-(HCC)2-closo-1,7-C2B10H10
(3a), and 1,2-Me2-9,12-(Me3SiCC)2-closo-1,2-C2B10H8 (2b).
C4H12B10 (168.25): calcd. C 28.56, H 7.19; found C 29.00, H 7.03.
3
1H{11B} NMR [(CD3)2CO]: δ = 3.60 [pseudoquintet, J(1H,1H) =
4.0 Hz, 1 H, CclusterH, 1-H], 3.42 [pseudosextet, 3J(1H,1H) =
3.9 Hz, 1 H, CclusterH, 12-H], 2.69 [s, 1J(13C,1H) = 242 Hz,
2J(13C,1H) = 47 Hz, 1 H, CϵCH], 2.32 (s, 2 H, BH), 2.27 (s, 2 H,
BH), 2.20 (s, 2 H, BH), 2.15 (s, 2 H, BH), 2.06 (s, 1 H, BH, 9-H)
ppm. 13C NMR [(CD3)2CO]: δ = 86.5 [dq, 1J(13C,1H) = 243 Hz,
2J(13C,11B) ≈ 19 Hz, 1 C, BCϵ13C], 83.3 [br. qd, 1J(13C,11B) =
110 Hz, 2J(13C,1H) = not resolved, 2 C, B13CϵC], 66.6 [d,
1J(13C,1H) = 181.7 Hz, 1 C, Ccluster], 63.7 [d, 1J(13C,1H) = 181.8 Hz,
1a
3a
2b
Chemical formula
Mr [gmol–1]
T [K]
C6H12B10
192.272
123
C6H12B10
192.272
123
C14H32B10Si2
364.692
293
Color
colorless
colorless
colorless
Crystal system
Space group
a [Å]
b [Å]
c [Å]
monoclinic orthorhombic orthorhombic
C2/c
Pnma
Pnma
25.253(5)
9.577(3)
22.923(4)
122.40(3)
4281(3)
16
1.091
0.049
1568
4.13–25.25
15976
13.1791(10)
13.2512(13)
6.8310(8)
–
1193.0(2)
4
1.070
0.048
392
3.07–24.98
6547
17.221(3)
13.763(3)
21.512(4)
–
5098.6(17)
8
0.950
0.136
1552
4.24–25.00
41277
1
1 C, Ccluster] ppm. 11B NMR [(CD3)2CO]: δ = –13.4 [d, J(11B,1H)
= overlapped, 2 B], –14.3 (s, 1 B, B-2), –14.3 [d, 1J(11B,1H) = over-
lapped, 2 B], –14.7 [d, 1J(11B,1H) = overlapped, 2 B], –15.0 [d,
1J(11B,1H) = overlapped, 2 B], –16.8 [d, 1J(11B,1H) = overlapped, 1
β [°]
Volume [Å3]
Z
B, B-9] ppm. IR (ATR): ν = 3298 (m, CC–H), 3050 (m, C
–
˜
cluster
Dcalcd. [Mgm–3]
H), 2615–2601 (vs, B–H), 2086 (w, CϵC) cm–1. Raman: ν = 3051
˜
µ [mm–1]
(m, Ccluster–H), 2626–2606 (vs, B–H), 2085 (vs, CϵC) cm–1. MS
(EI): m/z (isotopic abundance) calcd. for 7 (C4H12B10): 164 (2), 165
(8), 166 (28), 167 (66), 168 (100), 169 (91), 170 (39), 171 (2); found
164 (12), 165 (26), 166 (42), 167 (78), 168 (100), 169 (80), 170 (36),
171 (2).
F(000)
θ Range [°]
Reflections collected
Independent reflections
R(int) [%]
4195
4.83
1088
8.65
4668
11.47
Data/restraints/parameters
R1 [IϾ2σ(I)][a]
wR2 (all)[b]
GOF on F2[c]
4195/0/309
0.0781
0.1981
1.112
1088/0/104
0.0488
0.0911
1.015
4668/34/312
0.0758
0.1596
1.083
Crystal Structure Determinations: Colorless crystals of 9,12-
(HCC)2-closo-1,2-C2B10H10 (1a) and its isomer 9,10-(HCC)2-closo-
1,7-C2B10H10 (3a) suitable for X-ray diffraction were obtained from
solutions in diethyl ether by slow uptake of hexane vapor, and col-
orless crystals of 1,2-Me2-9,12-(Me3SiCC)2-closo-1,2-C2B10H8 (2b)
were obtained from hexane by slow evaporation of the solvent. A
crystal of 1a and a crystal of 3a were investigated with an imaging
plate diffraction system (IPDS, Stoe & Cie) at 123 K and a crystal
of 2b was studied with a Stoe STADI CCD diffractometer at 293 K
using Mo-Kα radiation (λ = 0.71073 Å). All three structures were
solved by direct methods,[50,51] and the refinements are based on
full-matrix least-squares calculations on F2.[51,52] 9,12-(HCC)2-
closo-1,2-C2B10H10 (1a) crystallizes in the monoclinic space group
C2/c (no. 15). Both other compounds 3a and 2b crystallize in the
orthorhombic space group Pnma (no. 62). In the crystal structure
of 2b in one of the two independent molecules, the Me3SiCC group
is disordered over two positions with occupancies of 0.25 and 0.75.
The positions of almost all hydrogen atoms in the crystal structures
of 1a, 3a, and 2b were located by means of ∆F syntheses, with the
only exceptions being the hydrogen atoms of the trimethylsilyl
groups of 2b. All non-hydrogen atoms were refined anisotropically.
The hydrogen atoms bonded to the boron and carbon cluster atoms
were freely refined, except for those in 1a, which were refined using
soft restraints and their isotropic displacement parameters were
fixed to Ueq of the respective parent atom (130%). For most of the
hydrogen atoms of the ethynyl substituents calculated positions
were chosen; only d(C–H) of the terminal alkynyl group in 3a was
refined freely. The isotropic displacement parameters of all ethynyl
hydrogen atoms were kept equal to 140% of the Ueq of the respec-
tive parent carbon atom. The hydrogen atoms of the methyl groups
in 2b were refined using restraints and their isotropic displacement
parameters were kept equal to 140% of the Ueq of the respective
parent carbon atom.
Largest diff. peak/hole [eÅ–3] 0.763/–0.230 0.232/–0.124
0.189/–0.204
[a] R1 = (Σ||Fo| – |Fc||)/Σ|Fo|. [b] wR2 = [Σw(F2o – F2c)2/Σw(F2o)2]0.5
,
weight scheme w = [σ2Fo + (aP)2 + bP]–1; P = [max(0,F2o) + 2F2c]/
3; 1a: a = 0.0710, b = 9.5; 2b: a = 0.0278, b = 0; 3a: a = 0.0308, b
= 3.292. [c] GOF: S = Σw(F2o – F2c)2/(m – n); (m = reflections, n =
variables).
Quantum Chemical Calculations: Density functional (DF) calcula-
tions[55] were carried out using Becke’s three-parameter hybrid
functional and the Lee–Yang–Parr correlation functional
(B3LYP).[56] Geometries were optimized, and energies were calcu-
lated with the 6-311++G(d,p) basis sets. Diffuse functions were in-
corporated because improved energies are obtained for anions.[57]
All structures represent true minima with no imaginary frequency
on the respective hypersurface. DFT-GIAO[58] NMR spectroscopic
shielding constants σ(11B), σ(13C), and σ(1H) as well as spin–spin
coupling constants[59] were calculated at the B3LYP/6-
311++G(2d,p) level of theory using the geometries computed at
the B3LYP/6-311++G(d,p) level of theory. The 11B, 13C, and 1H
NMR spectroscopic shielding constants were calibrated to the re-
spective chemical shift scale δ(11B), δ(13C), and δ(1H) using predic-
tions on diborane(6) and Me4Si with chemical shifts of –16.6 ppm
[60]
for B2H6 and 0 ppm for Me4Si.[61] All calculations were carried
out with the Gaussian 03 program suite.[62]
Supporting Information (see also the footnote on the first page of
this article): Tables containing selected experimental and calculated
bond lengths and angles and a table containing experimental and
calculated IR and Raman spectroscopic data of dicarba-closo-do-
decaboranes with one and two alkynyl substituents, as well as fig-
ures of the projections along the unit cell axes of 9,12-(HCC)2-
closo-1,2-C2B10H10 (1a).
All calculations were carried out with the WinGX program pack-
age.[53] Molecular structure diagrams were drawn with the program
Diamond 3.2c.[54] Experimental details and crystal data are col-
lected in Table 3.
Acknowledgments
CCDC-752151 (for 1a), -752152 (for 3a), and -752150 (for 2b) con-
tain the supplementary crystallographic data for this paper. These
data can be obtained free of charge from The Cambridge Crystallo-
graphic Data Centre via www.ccdc.cam.ac.uk/data_request/cif.
This work was supported by the Fonds der Chemischen Industrie
(FCI). The authors thank Professor W. Frank for generous support
2022
www.eurjic.org
© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2010, 2012–2024

Dicarba-closo-dodecaboranes with B-Ethynyl Groups
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Eur. J. Inorg. Chem. 2010, 2012–2024
© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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Received: January 21, 2010
Published Online: March 31, 2010
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