Molecular structures, reactivity, and NMR spectroscopic studies of cyclic and non-cyclic silyl-substituted 1, 2-dicarba-closo-dodecaborane(12) derivatives

Article abstract of DOI:10.1002/zaac.201200027

Non-cyclic and cyclic silyl-substituted 1, 2-dicarba-closo-dodecaborane(12) derivatives were prepared mainly by salt elimination methods. Several known and new compounds were structurally characterized by X-ray analysis in the solid state and by mulinuclear magnetic resonance (¹H, ¹¹B, ¹³C, ²⁹Si, ⁷⁷Se, and ¹²⁵Te NMR) in solution. This includes the 1, 2-bis(trimethylsilyl) and 1, 2- bis(chlorodimethylsilyl) derivatives as examples for non-cyclic compounds and a series of 1, 1, 3, 3-tetramethyl-4, 5-[1, 2-dicarba-closo-dodecaborano(12)]-1, 3-disila-2-element-cyclopentanes (element = S, Se, Te). Numerous spin-spin coupling constants were determined together with their signs. Molecular gas phase geometries for most compounds studied were optimized by calculations [B3Lyp/6-311+G(d, p)], and NMR parameters were calculated at the same level of theory. The conversion of silyl-substituted ortho-carboranes into their respective 7, 8-dicarba-nido-undecaborate(1-) derivatives was explored successfully for several examples.

Full text of DOI:10.1002/zaac.201200027

ARTICLE
DOI: 10.1002/zaac.201200027
Molecular Structures, Reactivity, and NMR Spectroscopic Studies of Cyclic
and Non-cyclic Silyl-substituted 1,2-Dicarba-closo-dodecaborane(12)
Derivatives
Bernd Wrackmeyer,*[a] Elena V. Klimkina,[a] and Wolfgang Milius[b]
Dedicated to Professor Wolfgang Beck on the Occasion of His 80th Birthday
Keywords: Silane; Carboranes; Selenium; Tellurium; Heterocycles; NMR spectroscopy; DFT calculations; X-ray analysis
Abstract. Non-cyclic and cyclic silyl-substituted 1,2-dicarba-closo-do-
disila-2-element-cyclopentanes (element = S, Se, Te). Numerous spin-
decaborane(12) derivatives were prepared mainly by salt elimination spin coupling constants were determined together with their signs. Mo-
methods. Several known and new compounds were structurally charac-
terized by X-ray analysis in the solid state and by mulinuclear mag-
lecular gas phase geometries for most compounds studied were opti-
mized by calculations [B3Lyp/6-311+G(d,p)], and NMR parameters
netic resonance (1H, 11B, 13C, 29Si, 77Se, and 125Te NMR) in solution. were calculated at the same level of theory. The conversion of silyl-
This includes the 1,2-bis(trimethylsilyl) and 1,2-bis(chlorodimethylsi- substituted ortho-carboranes into their respective 7,8-dicarba-nido-un-
lyl) derivatives as examples for non-cyclic compounds and a series of
1,1,3,3-tetramethyl-4,5-[1,2-dicarba-closo-dodecaborano(12)]-1,3-
decaborate(1-) derivatives was explored successfully for several exam-
ples.
In the presented work, we have set out to prepare the miss-
ing heavy homologues of 6a with sulfur (6b), selenium (6c)
and tellurium (6d), starting from 4 or 5. Some aspects of the
reactivity of 5 was addressed, and first attempts were made to
convert some of the silyl-substituted carboranes into the re-
spective 7,8-dicarba-nido-undecaborates(1-). The NMR spec-
tra of 3–6 were measured (1H, 11B, 13C, 29Si, 77Se, and 125Te
NMR), including the determination of absolute signs of spin-
spin coupling constants, if possible. The molecular structures
of 3, 4, 6c, and 6d were determined by X-ray structural analy-
sis, and the gas phase geometries of 3–6 were optimized
[B3LYP/6-311+G(d,p)] followed by calculation of NMR pa-
rameters at the same level of theory (except of 6d).
Introduction
The remarkable thermal stability and versatile chemistry of
1,2-dicarba-closo-docecaborane(12) (1) (“ortho-carborane”)
has been well documented in the last five decades.[1–3] In par-
ticular, various routes to C-derivatization were established,
such as C-lithiation (e.g. 2), which appears to be highly conve-
nient.[1–3] This has opened the way to 1,2-disilyl-substituted
carboranes, some of them (3–6a) are shown in Scheme 1. In
spite of the interest in silyl-substituted carboranes for applica-
tions in some fields of materials sciences[1,4] and numerous
fields of chemistry,[5] only few simple examples have been
structurally characterized in the solid state[6,7] (e.g. 5[8] and
6a[8]), and a fairly complete set of important solution-state
NMR spectroscopic data is not available at all. For instance,
Results and Discussion
the magnitude of spin-spin coupling constants J(29Si,13C) for
1
some diphenylsilyl-substituted carboranes[9] is smaller than ex-
pected at a first glance, considering the large magnitude of
1J(13C,1H) in 1 [1J(13C,1H) = 193 Hz][10] or in mono-substi-
tuted ortho-carboranes.[10] This was attributed to high s elec-
tron density in the C–H hybrid orbital.
Syntheses and NMR Spectroscopy
The synthetic routes are summarized in Scheme 2. Clearly,
the dichloride 4[11] offers great synthetic potential for further
transformations. It proved necessary to use the salt elimination
reaction of 4 with dilthium selenide[12] or -telluride[12] to ob-
tain pure samples of 6c and in particular of 6d. In principle,
the strained four-membered cycle in 5[8] appears to be attract-
ive for insertion reactions.[7b] However, it does not react with
tellurium, it reacts sluggishly with selenium, and somewhat
more readily with sulfur. Surprisingly, 5 does not react with
bis(trimethylsilyl)peroxide at room temp., whereas its reaction
with trimethylamine N-oxide[13] affords the known disiloxane
6a[9,11,14] quantitatively under mild conditions.
* Prof. Dr. B. Wrackmeyer
Fax: +49-921-552157
E-Mail: b.wrack@uni-bayreuth.de
[a] Anorganische Chemie II
Universität Bayreuth
95440 Bayreuth, Germany
[b] Anorganische Chemie I
Universität Bayreuth
95440 Bayreuth, Germany
Z. Anorg. Allg. Chem. 2012, 638, (᭿), 1–14
© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
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B. Wrackmeyer, E. V. Klimkina, W. Milius
ARTICLE
Scheme 1. Some known 1,2-silyl-substituted ortho-carborane derivatives, obtained from the reactions of 1,2-dilithio-1,2-dicarba-closo-dodeca-
borane(12) with various chlorosilanes.
additional conclusive structural information, both by determi-
nation of chemical shifts and various spin-spin coupling con-
stants. In all cases 3–6, the spin-spin coupling constants
1J(29Si,13C) were measured, in most cases from 13C satellites
in the 29Si NMR spectra. The 13C(carborane) NMR signals are
only slightly broadened owing to unresolved scalar 13C–11B
coupling (11B: I = 3/2; 10B: I = 3).[17] However, they are split
1
due to isotope-induced chemical shifts Δ10/11B(13C).[9] More-
over, longitudinal nuclear spin relaxation times T1(13Ccarb) are
fairly long, and therefore, the signal-to-noise ratio for these
NMR signals becomes unfavorable. However, we found that
1HǞ13C polarization transfer, using the refocused INEPT
3
pulse sequence[18] [based on J(13Ccarb,1HSiMe], can be applied
to circumvent at least the problem associated with T1(13C) (see
Figure 1).
The 29Si NMR spectrum of 6d is shown (Figure 2) as an
instructive example for the information to be gained by observ-
ing the respective satellites arising from 29Si–13C and 29Si–123/
Scheme 2. Routes to 1,1,3,3-tetramethyl-4,5-[1,2-dicarba-closo-do- 125Te spin-spin coupling.
decaborano(12)]-1,3-disila-2-chalkogena-cyclopentanes 6a–6d.
In all silyl-substituted ortho-carboranes studied here, the
magnititude of 1J(29Si,13Ccarb) is relatively small, e.g. when
compared with 1J(29Si,13CMe), although in ortho-carborane the
The compounds 6b,c,d are crystalline yellowish (6b, 6c) or
yellow (6d) solids sensitive to moisture and oxygen. In the
case of the preparation of 6c larger amounts of byproducts (ca.
10%) were observed by 29Si NMR spectroscopy in the crude
products. The products 6b,c,d are soluble in toluene and
CD2Cl2. 6b can be stored for prolonged periods as a solid or
in solution at –30 °C. Similarly, 6c can be stored as a solid or
in toluene solution at –30 °C and decomposes slowly in
CD2Cl2 at –30 °C. Compound 6d shows low thermal stability.
It decomposes under argon as a solid at room temperature and
also slowly in [D8]toluene at –30 °C with formation of a black
precipitate of elemental tellurium. On contact with moisture
and oxygen 6d decomposes almost immediately.
1
value for J(13C,1H) = 193 Hz indicates that much of the car-
bons electron density is localized in the C–H bond. However,
the Si–C(carborane) bond is polar, and polarizability reduces
positive contributions to the Fermi contact term as the domina-
ting mechanism for nuclear spin-spin coupling between nuclei
with an open s shell configuration. This is also evident by
1
1
comparing J(13C,1H) in alkynes R–CϵC–H with J(29Si,13C-
[19]
1
)
and J(29Si,13CMe) in R–CϵC–SiMe3.[20a] If this anal-
carb
ogy is correct, the comparable trend should be even more obvi-
[20]
ous for R–CХC–SnMe3
and stannyl-stubstituted ortho-car-
boranes. Therefore, we have measured the NMR spectroscopic
data of 7(Sn) and coupling constants for 7 and three alkynes
are summarized in Scheme 3. Clearly, the data for 7(Sn) follow
the pattern found for silyl-substituted ortho-carboranes.
The relative sign of coupling constants can be determined
Similar to 3–5 (Table 1), the heterocyclic compounds 6 are
readily characterized in solution by their NMR spectroscopic
data (Table 2). In the cases of 6c and 6d, the presence of mag-
netically active spin-1/2 77Se[15] and 123,125Te[16] nuclei reveals in NMR experiments involving one passive and two active
2
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Silyl-substituted 1,2-Dicarba-closo-dodecaborane(12) Derivatives
Table 1. 13C and 29Si NMR spectroscopic dataa) of the ortho-carborane derivatives 3, 4, 5, 7, and 7(Sn).
3
4
5
7b)
7(Sn)
[D8]toluene
1.2 [55.7]
[D8]toluene
4.4 [64.6]
[D8]toluene
–3.5
CD2Cl2
–2.7 [47.7]
[4.6]
[D8]toluene
–2.0 [55.7]
C6D6
–8.3 (370.2)
δ13C[SiCH3]
δ13C[C(1,2)]
74.8 [46.8]
–11.8
73.5 [55.8]
–10.8
80.1
80.9 [38.4]
59.8 (CH),
67.1 [46.6] (CSiMe3) 61.5 (CSn)
(165.0)
59.3(CH)
1Δ10/11B[13C(1,2)]
Ϯ 0.5 ppb
–12.0
17.8
–10.5
–8.5
–8.0
56.9
–
δ29Si/119Sn
10.0 [55.8]
[47.1]
–48.6 (Me)
–41.9 (C(1,2))
24.3 [64.7]
[55.8]
–56.3 (Me)
–51.7 (C(1,2))
19.1 [47.8]
[38.4]
9.7 [55.6]
[46.1]
–48.9 (Me)
–42.8 (C(1))
1J(29Si,13C) (calcd.)
–40.1 (Me) –9.9 (2J))
–34.1 (C(1,2)
a) Coupling constants nJ(29Si,13C) are given in brackets [Ϯ 0.5 Hz], coupling constants 1J(119Sn,13C) are given in parentheses (Ϯ 0.5 Hz);
isotope-induced chemical shifts 1Δ are given in ppb, and the negative sign denotes a shift of NMR signal of the heavy isotopomer to lower
frequency. b) Ref.[19]
.
Table 2. 13C, 29Si, 77Se, and 125Te / 123Te NMR spectroscopic dataa) of the cyclic ortho-carborane derivatives 6a–6d.
6a
6b
E = S
[D8]toluene
6c
6d
E = O
[D8]toluene
E = Se
[D8]toluene
E = Te
[D8]toluene
CD2Cl2
CD2Cl2
2.6
CD2Cl2
δ13C[SiCH3]
δ13C[C(1,2)]
–1.7 [66.4]
73.6 [55.7]
–1.1 [66.4] 2.1 [59.3]
3.5 [57.4] Ͻ8.5Ͼ
76.9 [51.2]
–10.5
3.5 [57.6]
Ͻ8.5Ͼ
76.9 [51.2]
Ͻ8.9Ͼ
4.6 [55.0]
Ͻ14.3Ͼ
79.3 [48.4]
Ͻ26.1Ͼ
–10.5
74.1
75.0 [53.5]
75.3
1Δ10/11B(13C(1,2)) –11.4
Ϯ 0.5 ppb
–11.1
–10.5
δ29Si
16.8
16.8
31.8
32.3
30.5
30.9 (123.4)
17.2 (328.1)
/272.2/
[66.4] [55.5]
[66.6]
[55.4]
–
[59.4] [53.4]
[123.5]
[57.6] [51.4]
[4.2]
–356.3
(123.4) {4.4} (328.4) {7.6}
–25.6
[54.8] [48.6]
δ77Se / δ125Te
–
–
–
–
–358.5
(123.7)
–22.5
–895.3b)
1Δ28/29Si(77Se /
125Te) Ϯ 1 ppb
nJ(29Si,13C)
(calcd.)
–
–
–
–36.7
–60.3 (Me)
–52.4 (Me)
–50.1 (Me)
–
δ77Se (calcd.)
–50.5 (C(1,2)) –3.3 (2J)
–
–47.3 (C(1,2)) –4.5 (2J)
–
–45.6 (C(1,2)) –4.5 (2J)
–486.8 (+155.5)
–
–
–
Ͻ+6.0Ͼ(2J(77Se,13CMe))
Ͻ–10.0Ͼ (2J(77Se,13Ccarb))
a) Coupling constants nJ(29Si,13C) are given in brackets [Ϯ 0.5 Hz]; 1J(77Se,29Si) and 1J(125Te,29Si) are given in parentheses (Ϯ 0.5 Hz);
1J(123Te,29Si) are given in / / /Ϯ 0.5 Hz/; 2J(77Se,13C) and 2J(125Te,13C) are given in Ͻ Ͼ ϽϮ 0.5 HzϾ; 3J(77Se,1H), 3J(125Te,1H) and 3J(123Te,1H)
1
in braces {Ϯ 0.5 Hz}; isotope-induced chemical shifts Δ are given in ppb, and the negative sign denotes a shift of NMR signal of the heavy
isotopomer to lower frequency. b) δ123Te: –895.0 {7.0}.
spins. This can be done using appropriate 1D heteronuclear field. Apparently the reaction with an excess of piperidine
double resonance experiments[21] or, more conveniently, 2D worked in the normal way[3,24] to give the monoanion 8, read-
heteronuclear shift correlations, observing the tilt of relevant
cross peaks.[22] If any of the nuclei have a negative gyromag-
netic ratio, such as γ(29Si) and γ(125Te), it is advisable to use
the notation of reduced coupling constants K before converting
the sign information to J (see Figure 3 and Figure 4).
ily apparent from the typical set of multinuclear magnetic reso-
nance data (Experimental Section and Table 4).
However, the procedure did not work in the case of the disil-
ane derivative 5. Instead, cleavage of one of the Si–C(carbor-
ane) bonds was observed to give 9 (Scheme 5), readily evident
from the NMR spectroscopic data set (Table 3). More bulky
secondary amines, such as dicyclohexylamine, did not react,
whereas primary amines, such as cyclohexylamine or aniline,
gave results analogous to piperidine. Traces of moisture as an
impurity in all these amines, caused also cleavage of the Si–
C(carborane) bond to give 10, present in the reaction mixtures.
The comparable reaction of 5 with ethanol has been re-
7,8-Dicarba-nido-undecaborates(1-) from Silyl-substituted
ortho-Carboranes
Decapping of the silyl-substituted ortho-carboranes to ob-
tain 7,8-dicarba-nido-undecaborate(1-) derivatives would
greatly enhance their synthetic potential. We started with 1-
trimethylsilyl-ortho-carborane 7 (Scheme 4) to explore this ported.[8] Although the desired borates were not formed, the
Z. Anorg. Allg. Chem. 2012, 1–14
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3

B. Wrackmeyer, E. V. Klimkina, W. Milius
ARTICLE
tal Section). The reactions proceed readily, as monitored by
NMR spectroscopy, accompanied by slow side reactions most
likely owing to cleavage of the Si–Se or Si–Te bonds, respec-
tively.
DFT Calculations of Molecular Geometries, Chemical
Shifts δ77Se, and Coupling Constants
The optimized calculated [B3LYP/6-311+G(d,p) level of
theory] geometries agree reasonably well with experimental
data (Table 5, Table 6) given for expected differences between
gas and solid phases. Using the calculated geometries, NMR
parameters such as nuclear shielding (chemical shift) and spin-
n
spin coupling constants J can be calculated. This works very
well for δ11B[25] and was also shown to predict δ77Se val-
ues[26,27] within an acceptable limit of error. The magnitude of
1
calculated values J(29Si,13C), at this level of theory, tends to
be smaller by about 10–15% than experimental data.[23] How-
ever, the sign and the trends are predicted correctly. This is
also the case for 1J(77Se,29Si) as well as for 2J(77Se,13CMe) and
3J(77Se,1HMe),[24b,28–30] again experimentally confirmed in this
work.
X-ray Structural Analyses of the ortho-Carborane
Derivatives
The molecular structures of the 1,2-bis(silyl)-ortho-carbor-
anes 3 and 4 are shown in Figure 5 and Figure 6, respectively.
The most notable features are the Si–C bond lengths, which
are fairly long for the Si–C(carborane) and in the normal range
for Si–C(methyl). The Si–C(carborane) distances are in the
range determined previously[5,31] which, however, was not dis-
cussed. Apparently, the longer Si–C(carborane) distances mir-
Figure 1. 125.8 MHz 13C{1H} NMR spectra of the carborane deriva-
tives 3 (right; in [D8]toluene at 23 °C) and 5 (left; in CD2Cl2, at 23 °C),
showing the 13C(carborane) signals. The typical pattern can be seen,
caused by isotope-induced chemical shifts 1Δ10/11B(13C).[9] The per-
formance of the refocused INEPT pulse sequence with 1H decoup-
ling[18] is markedly better than single pulse methods, using 30° pulses.
reactions shown in Scheme 5 provide a convenient route ror the rather small magnitude of the coupling constants
towards new disilane derivatives, of which those (e.g. 11, 12) 1J(29Si,13Ccarb) (vide supra).
derived from primary amines may be particularly useful for
further transformations.
The analogous molecular structures of the selenium and tel-
lurium containing cyclic ortho-carborane derivatives are
In contrast with 5, the cyclic derivatives 6c and 6d react shown in Figure 7. The cycles annealed to the carborane unit
with an excess of piperidine (Scheme 6) to afford the desired deviate markedly from ideal planarity (Table 6), whereas solu-
7,8-dicarba-nido-undecaborate(1-) derivatives 13 (Figure 4; tion state 1H and 13C NMR spectra indicate fast ring inversion.
see NMR spectroscopic data in Table 4 and in the Experimen- Again, the Si–C(carborane) distances are slightly elongated,
1
Figure 2. 99.4 MHz 29Si{1H} NMR spectrum (INEPT, refocused[18]) of 6d (in [D8]toluene, at 23 °C). The 125Te satellites for J(125Te,29Si) are
1
1
1
marked by asterisks; the 123Te satellites for J(123Te,29Si) are marked by filled circles; the 13C satellites for J(29Si,13CMe) and J(29Si,13Ccarb
)
are marked by arrows.
4
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Silyl-substituted 1,2-Dicarba-closo-dodecaborane(12) Derivatives
Scheme 3. Comparison of spin-spin coupling constants for alkynes and ortho-carboranes 1, 7, and 7(Sn) (Table 1).
= O, S, Se, Te), of which the selenium and tellurium com-
pounds could be structurally characterized. All cyclic com-
pounds were characterized in solution by advanced multinu-
clear magnetic resonance spectroscopic methods. The data ob-
tained were compared with those of noncyclic silyl-substituted
ortho-carboranes, of which two examples were also charac-
terized by X-ray crystallography. It was found that the compar-
atively small magnitude of one-bond 29Si–13C(carborane) spin-
spin coupling constants, measured herein for the first time in
a systematic way, is mirrored by elongated Si–C bond lengths.
The scarce data set of 13C NMR spectroscopic data of ortho-
carboranes presented in the literature could be enlarged by ap-
plication of polarization transfer techniques (INEPT). In sev-
eral cases, it could be demonstrated that the conversion of the
new ortho-carborane derivatives into 7,8-dicarba-nido-unde-
caborate(1-) derivatives proceeds in the usual way. Further ex-
ploration of this synthetic potential is in progress.
Experimental Section
General: All syntheses and handling of samples were carried out ob-
serving necessary precautions to exclude traces of air and moisture.
Carefully dried solvents and oven-dried glassware were used through-
out. CH2Cl2 and CD2Cl2 were distilled over CaH2 in an atmosphere
of argon. All other solvents were distilled from Na metal in an atmo-
sphere of argon. The starting materials were prepared as described in
the literature, i.e. 2,[33] Li2Se, Li2Te.[12] Other starting materials were
purchased from Aldrich [Me3SiCl, Me2SiCl2, (Me2SiCl)2, Li[BEt3H]
(1.0 m in THF, Super-Hydride), tellurium (powder, –200 mesh, 99.8%
metals basis), sulfur (powder, 99.98% metals basis), Me3N = O
(98%)], Fluka (selenium metal “grey”), ABCR (Me3SiOOSiMe3,
97%) and KatChem. (ortho-carborane 1), and used as received.
Figure 3. 2D 77Se/1H heteronuclear shift correlation (ν77Se = 95.4 and
ν1H
= 500.13 MHz) of 6c (in CD2Cl2, at 23 °C), based on
3J(77Se,1HMe) = 4.4 Hz. The positive tilt (dashed line) of the cross
2
peaks for the 29Si satellites indicates alike signs of K(29Si,1HMe) and
1K(77Se,29Si). Since the former is known to be negative,[23] it follows
1
1
that K(77Se,29Si) Ͻ 0 and J(77Se,29Si) Ͼ 0 [γ(29Si) Ͻ 0].
NMR measurements: Bruker DRX 500 and Bruker ARX 250: 1H, 11B,
13C, 77Se, 125Te, 123Te, and 29Si NMR [refocused INEPT[18] based on
2J(29Si,1H) = 6–7 Hz]; Varian INOVA 400: 1H, 11B, 13C, 29Si, 77Se
NMR; chemical shifts are given relative to Me4Si [δ1H (CHDCl2) 5.33,
(C6D5CD2H) = 2.08 (Ϯ 0.01); δ13C (CD2Cl2) = 53.8, (C6D5CD3) =
20.4 (Ϯ 0.1); δ29Si = 0 (Ϯ0.1) for Ξ(29Si) = 19.867184 MHz]; external
BF3-OEt2 [δ11B = 0 (Ϯ0.3) for Ξ(11B) = 32.083971 MHz], neat Me2Se
[δ77Se = 0 (Ϯ 0.1) for Ξ(77Se) = 19.071523 MHz], neat SnMe4
when compared with those of Si–C(methyl) bonds. All other
bond lengths and angles are in the usual ranges.[12,32]
Conclusions
This work has completed the series of ortho-carborane-an-
nealed 1,3-disila-2-element-cyclopentane derivatives (element [[δ119Sn = 0 for Ξ(119Sn) = 37.290665 MHz], neat Me2Te [δ125Te = 0
Z. Anorg. Allg. Chem. 2012, 1–14
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5

B. Wrackmeyer, E. V. Klimkina, W. Milius
ARTICLE
Figure 4. 2D heteronuclear shift correlations (ν1H = 500.13 MHz) of 13c (in [D8]toluene, at 25 °C), showing the expected different SiMe groups.
2
Left: 29Si/1H-HETCOR experiment using J(29Si,1HMe). The negative tilt of the 77Se satellites is indicated by dashed lines. This compares the
signs of 1K(77Se,29Si) and 3K(77Se,1HMe). Since 1K(77Se,29Si) Ͻ 0, 3K(77Se,1HMe) Ͼ 0. Right: 13C/1H-HETCOR experiment for the Si–Me
groups, using 1J(13C,1H). The positive and negative tilt of the 77Se and 29Si satellites (see expansions), respectively, is indicated by dashed lines.
3
For the 77Se satellites, this compares the signs of 2J(77Se,13CMe) and J(77Se,1HMe) which are both Ͼ 0, for both types of methyl groups, in
agreement with calculations.
slowly (30 min) through a syringe. After stirring the reaction mixture
for 20 h at room temperature, insoluble materials were separated by
centrifugation, and the clear liquid was collected. Volatile materials
were removed in vacuo to give 4 as a white solid (955 mg; 92%).
Single transparent crystals of 4 for X-ray analysis were grown from
[D8]toluene after 1 month at –30 °C; m.p. 100–103 °C. 1H{11B} NMR
(250.1 MHz; [D8]toluene; 25 °C): δ [2J(29Si,1H)] = 0.37 [7.2] (s, 12 H,
CH3Si), 2.25 (br. s, 4 H, HB), 2.47 (br. s, 2 H, HB), 2.84 (br. s, 2 H,
HB), 3.03 (br. s, 2 H, HB). 11B{1H} NMR (80.3 MHz; [D8]toluene;
25 °C): δ = –10.8 (2B), –8.8 (4B), –5.1 (2B), 3.2 (2B). 11B NMR
(80.3 MHz; [D8]toluene; 25 °C): δ = –10.8 (d, 2B, 163 Hz), –8.8 (d,
4B, 160 Hz), –5.1 (d, 2B, 150 Hz), 3.2 (d, 2B, 150 Hz). EI-MS (70 eV)
for C6H22B10Si2Cl2 (328.16): m/z (%) = 328 (2) [M+], 313 (100) [M+ –
CH3], 294 (5), 277 (4), 259 (8), 199 (10), 156 (10).
Scheme 4. Typical reaction of a monosubstituted ortho-carborane with
piperidine in excess.
for Ξ(125Te) = 31.549802 MHz], neat Me2Te [δ123Te = 0 for Ξ(123Te)
= 26.169773 MHz]. Assignments of 1H and 11B NMR signals are
1
based on selective H{11B selective} heteronuclear decoupling experi-
ments.[34] Melting points (uncorrected) were determined with a Büchi
510 melting point apparatus.
1,1,2,2-Tetramethyl-3,4-[1,2-dicarba-closo-dodecaborano(12)]-1,3-
disila-cyclobutane (5): Freshly prepared [(1,2-C2B10H10)Li2](2 Et2O)
2 (665 mg, 2.27 mmol) was taken up in Et2O (40 mL); the suspension
was cooled to 0 °C, and Me2Si(Cl)–Si(Cl)Me2 (43 mg, 0.42 mL,
2.27 mmol) was injected slowly (30 min) through a syringe. After stir-
ring the reaction mixture for 3 h at room temperature, insoluble materi-
als were separated by centrifugation, and the clear liquid was collected.
The remaining insoluble materials were washed with Et2O (15 mL)
and centrifuged. The centrifuged solutions were combined, and volatile
materials were removed in vacuo to give 5 as a white solid (551 mg;
All quantum chemical calculations were carried out using the Gaussian
09 program package.[35] Optimized geometries at the B3LYP/6-
311+g(d.p) level of theory were found to be minima by the absence of
imaginary frequencies. NMR parameters were calculated at the same
level of theory. Calculated chemical shifts δ11B and δ77Se were con-
verted by δ11B (calcd) = σ(11B) – σ(11B, B2H6), with σ(11B, B2H6) =
+84.1 [δ11B (B2H6) = 18 and δ11B (BF3-OEt2) = 0] and δ77Se(calcd)
= σ(77Se) – σ(77Se, SeMe2) with σ(77Se, SeMe2) = +1621.7.
1
94%). H{11B} NMR (250.1 MHz; CD2Cl2; 25 °C): δ [2J(29Si,1H)] =
1,2-Bis(trimethylsilyl)-1,2-dicarba-closo-dodecaborane(12) (3):[36]
Single transparent crystals of 3 for X-ray analysis were grown from
[D8]toluene after 2 weeks at –30 °C; m.p. 121–124 °C.
0.48 [6.9] (s, 12 H, CH3Si), 2.11 [br. s, 4 H, HB for δ(11B) = –9.8],
2.25 [br. s, 2 H, HB for δ(11B) = 0.0], 2.42 [br. s, 2 H, HB for δ(11B)
= –4.1], 2.49 [br. s, 2 H, HB for δ(11B) = –11.9]. 11B{1H} NMR
(80.3 MHz; CD2Cl2; 25 °C): δ = –11.9 (2B), –9.8 (4B), –4.1 (2B), 0.0
1,2-Bis[chloro(dimethyl)silyl]-1,2-dicarba-closo-dodecaborane(12)
(4): Freshly prepared [(1,2-C2B10H10)Li2](2·Et2O) (2) (919 mg, (2B). 11B NMR (80.3 MHz; CD2Cl2; 25 °C): δ = –11.9 (d, 2B,
3.14 mmol) was taken up in Et2O (20 mL); the suspension was cooled
174 Hz), –9.8 (d, 4B, 164 Hz), –4.1 (d, 2B, 147 Hz), 0.0 (d, 2B,
to 0 °C, and Me2SiCl2 (90 mg, 0.85 mL, 6.98 mmol) was injected 147 Hz).
6
www.zaac.wiley-vch.de
© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Z. Anorg. Allg. Chem. 2012, 1–14

Silyl-substituted 1,2-Dicarba-closo-dodecaborane(12) Derivatives
Scheme 5. Cleavage of the Si–C(carborane) bond in 5 with amines.
Table 3. 13C, 29Si NMR spectroscopic dataa) of the ortho-carborane derivatives 9–12.
9
11
12
10
[D8]toluene
[D8]toluene
[D8]toluene
[D8]toluene
δ13C[C(1)SiCH3]
δ13C[SiSiCH3]
δ13C[C(2)]
–1.8 [44.0] [5.4]
–1.3 [50.9] [11.1]
60.9
–2.6 [44.6] [5.6]
0.3 [50.2] [10.1]
60.9
–1.8 [45.6] [5.5]
–0.2 [51.4] [9.1]
60.5
–3.3 [45.6] [6.3]
2.7 [51.5] [10.4]
60.2
1Δ10/11B(13C(1))
Ϯ 0.5 ppb
–8.6
–7.2
–8.0
δ13C[C(1)Si]
1Δ10/11B(13C(2))
Ϯ 0.5 ppb
67.1
–12.3
67.0
–11.8
66.4
–11.2
65.6
–10.4
Other
pip:
C6H11:
25.4 (Cp)
25.8 (Cm)
38.9 (Co)
51.8 (Ci)
Ph:
–
δ13C data
25.4 (Cγ)
28.0 (Cβ)
47.3 (Cα)
117.1 (Cm)
119.2 (Cp)
129.9 (Co)
146.9 (Ci)
–6.6 [45.5] [9.2]
δ29Si [C(1)Si]
δ29Si [SiSi]
–8.3 (95.0) [44.0] [11.1]
–7.98 [45.0] [10.1]
–7.5 (106.1) [46.1]
[10.4]
6.6 (106.2) [51.5] [6.4]
–3.8 (95.0) [51.0] [5.4]
+75.0 (SiSi), –27.1 (C(1)),
–34.3 (Me), –58.4 (Me),
–13.8 (MeSiSi; J),
–5.8 (MeSiC(1), J)
–7.97 [50.1] [5.4]
–7.2 [51.4] [5.5]
1J(29Si,29Si) and J(29Si,13C)
n
(calcd.)
2
2
n
1
a) Coupling constants J(29Si,13C) are given in brackets [Ϯ 0.5 Hz]; J(29Si,29Si) are given in parentheses (Ϯ 0.5 Hz); isotope-induced chemical
1
shifts Δ are given in ppb, and the negative sign denotes a shift of NMR signal of the heavy isotopomer to lower frequency.
1,1,3,3-Tetramethyl-4,5-[1,2-dicarba-closo-dodecaborano(12)]-1,3-
disila-2-selena-cyclopentane (6c): Method A: A solution of 4
(372 mg, 1.13 mmol) in toluene (20 mL) was cooled to 0 °C and a
solution of freshly prepared Li2Se (1.13 mmol) [from Se (89 mg;
1.13 mmol), Li[BEt3H] (2.26 mL of
a 1 m solution in THF;
2.26 mmol), and THF (3 mL)[12]]; afterwards further THF (10 mL) was
added. After stirring the reaction mixture for 3h at room temperature,
volatile materials were removed in vacuo. The remaining materials
were washed with toluene (20 mL) and centrifuged. The centrifuged
solutions were combined, and volatile materials were removed in
vacuo to give a yellow solid. The residue was extracted with hexane
(20 mL), insoluble materials were centrifuged. The clear liquid after
centrifugation was dried in vacuo to give 322 mg (85%) of 6c as a
Scheme 6. Conversion of the ortho-carborane derivatives 6 into the
respective 7,8-dicarba-nido-undecaborate(1-) derivatives 13.
Z. Anorg. Allg. Chem. 2012, 1–14
© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
www.zaac.wiley-vch.de
7

B. Wrackmeyer, E. V. Klimkina, W. Milius
Table 4. 13C, 29Si, 77Se, and 125Te NMR spectroscopic dataa) of the 7,8-dicarba-nido-undecaborate(1–) derivatives 8, 13c, and 13d.
ARTICLE
8
13c (E = Se)
[D8]toluene
13d (E = Te)
[D8]toluene
[D8]toluene
δ13C[SiCH3]
δ13C[C(7,8)]
–1.0 [52.8]
CH3(b): 2.9 [53.3] Ͻ11.7Ͼ
CH3(a): 6.8 [55.1] Ͻ6.0Ͼ
55.3 (br)
CH3(b): 4.5 [51.1] Ͻ23.7Ͼ
CH3(a): 8.4 [53.6] Ͻ7.5Ͼ
56.3 (br)
43.7 (br) (CSi)
46.6 (br) (CH)
pip:
23.7 (Cγ)
25.5 (Cβ)
45.6 (Cα)
1.2 [53.5]
–
Other
pip:
pip:
24.2 (Cγ)
26.5 (Cβ)
46.4 (Cα)
20.6 (273.5) /225.2/
–1006.0 (279.0) {10.5}b)
–34.5
δ13C data
23.9 (Cγ)
25.7 (Cβ)
45.7 (Cα)
29.9 (106.8)
–396.5 (106.0)
–23.0
δ29Si
δ77Se / δ125Te
1Δ28/29Si(77Se / 125Te)
Ϯ 1 ppb
–
1J(29Si,13C)(calcd.)
1J(77Se,29Si) (cacld.)
2J(77Se,13C) (calcd.)
δ77Se (calcd.)
–50.2 (Me), –66.4 [C(7)]
–44.9, –47.1[Me(b,a)], –59.5 [C(7,8)]
+130.0
+9.8, +3.4 [Me(b,a)], –8.1 [C(7,8)]
–539.0
–
–
–
a) Coupling constants nJ(29Si,13C) are given in brackets [Ϯ 0.5 Hz]; 1J(77Se,29Si) and 1J(125Te,29Si) are given in parentheses (Ϯ 0.5 Hz);
1J(123Te,29Si) are given in / / /Ϯ 0.5 Hz/; 2J(77Se,13C) and 2J(125Te,13C) are given in Ͻ Ͼ ϽϮ 0.5 HzϾ; 3J(77Se,1H), 3J(125Te,1H) and 3J(123Te,1H)
1
in braces {Ϯ 0.5 Hz}; (br) denotes broad 13C resonances due to dynamic effects; isotope-induced chemical shifts Δ are given in ppb, and the
negative sign denotes a shift of NMR signal of the heavy isotopomer to lower frequency. b) δ123Te: –1005.6.
Table 5. Selected bond lengths /pm and angles /° of the ortho-carborane derivatives 3, 3(calcd.), 4, 4(calcd.), and 5, 5(calcd.).
3
3(calcd.)
4
4(calcd.)
5a)
293 K
5(calcd.)
T /K
133 K
133 K
C(1)–Si(1)
C(2)–Si(2)
Si(1)–C(3)
Si(1)–C(4)
Si(1)–C(5)
Si(2)–C(6)
Si(2)–C(7)
Si(2)–C(8)
C(1)–C(2)
193.5(3)
193.3(3)
185.7(3)
185.9(3)
186.0(3)
185.0(3)
186.0(3)
186.3(3)
171.4(4)
195.4
195.4
188.5
188.3
188.3
188.5
188.3
188.3
172.6
C(1)–Si(1)
C(2)–Si(2)
Si(1)–C(3)
Si(1)–C(4)
Si(2)–C(5)
Si(2)–C(6)
191.5(4)
192.2(4)
186.6(4)
189.5(3)
191.7(7)
186.8(4)
194.0
194.0
187.0
186.6
186.6
187.0
193.0(2)
194.6
194.5
188.3
188.3
188.3
188.3
187.4
186.1
C(1)–C(2)
Si(1)–Si(2)
Si(1)–C(1)–
C(2)
Si(2)–C(2)–
C(1)
170.3(5)
127.2(2)
127.6(2)
171.5
128.0
128.0
170.6(3)
236.40(9)
99.81(5)
170.4
239.2
100.2
Si(1)–C(1)–
C(2)
Si(2)–C(2)–
C(1)
127.03(17)
126.31(17)
127.24
127.23
Plane
Plane
Si(1)–C(1)–
C(2)–Si(2)
0.8
3.1
Si(1)–C(1)–
C(2)–Si(2)
1.3
6.75
0.2
0.0
a) Ref.[8]
.
yellowish solid (larger amounts of byproducts were observed by 29Si –0.6 (2B). 11B NMR (128.3 MHz; CD2Cl2; 25 °C): δ = –12.3 (d, 2B,
NMR spectroscopy in the crude products). Yellowish single crystals
B3,6, 170 Hz), –10.2 (d, 4B, B4,5,7,11, 156 Hz), –3.7 (d, 2B, 151 Hz),
of 6c for X-ray analysis were grown from [D8]toluene solution after 7 –0.6 (d, 2B, 156 Hz). EI-MS (70 eV) for C6H22B10Si2Se (338.14): m/z
d at –30 °C; m.p. 118–122 °C.
(%) = 338 (65) [M+], 323 (100) [M+ – CH3], 275 (5), 259 (18), 210
(10).
Method B: A solution of 5 (90 mg, 0.35 mmol) in [D8]toluene (1 mL)
was added at room temperature to an excess of dry and degassed ele-
mental selenium (40 mg). The progress of the reaction was monitored
by 29Si NMR spectroscopy. After 7 d at 95 °C, the solution was centri-
fuged from selenium. The clear liquid was dried in vacuo to give 6c
as a yellowish solid (the solid thus obtained contained about 10% of
6a).
1,1,3,3-Tetramethyl-4,5-[1,2-dicarba-closo-dodecaborano(12)]-1,3-
disila-2-tellura-cyclopentane (6d):
A solution of 4 (255 mg,
0.77 mmol) in THF (8 mL) was cooled to 0 °C and a solution of
freshly prepared Li2Te (0.77 mmol) [from Te (99 mg; 0.77 mmol) and
Li[BEt3H] (1.55 mL of a 1 m solution in THF; 1.55 mmol)[12]] was
added. After stirring the reaction mixture for 2h at 0 °C, volatile mate-
rials were removed in vacuo. The remaining materials were washed
6c: 1H{11B} NMR (399.8 MHz; CD2Cl2; 25 °C): δ = 0.67 (s, 12 H, with toluene (20 mL) and centrifuged. The clear liquid was dried in
CH3Si), 2.16 [br. s, 4 H, HB4,5,7,11 for δ(11B) = –10.2], 2.29 [br. s, 2
vacuo to give 241 mg (81%) of 6d as a yellow solid. Yellowish single
H, HB3,6 for δ(11B) = –12.3], 2.33 [br. s, 2 H, HB for δ(11B) = –0.6], crystals of 6d for X-ray analysis were grown from [D8]toluene solution
2.52 [br. s, 2 H, HB for δ(11B) = –3.7]. 11B{1H} NMR (128.3 MHz; after 3 d at –30 °C; m.p. 135–139 °C. 6d decomposes slowly in an
CD2Cl2; 25 °C): δ = –12.3 (2B, B3,6), –10.2 (4B, B4,5,7,11), –3.7 (2B),
argon atmosphere as a solid at room temperature and also slowly in
8
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© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Z. Anorg. Allg. Chem. 2012, 1–14

Silyl-substituted 1,2-Dicarba-closo-dodecaborane(12) Derivatives
Table 6. Selected bond lengths /pm and angles /° of the cyclic ortho-carborane derivatives 6 and 6(calcd.).
6aa)
(E = O)
198 K
6a(calcd.)
(E = O)
6b(calcd.)
(E = S)
6c
(E = Se)
133 K
6c(calcd.)
(E = Se)
6d
(E = Te)
133 K
T /K
C(1)–Si(1)
C(2)–Si(2)
Si(1)–C(3)
Si(1)–C(4)
Si(2)–C(5)
Si(2)–C(6)
C(1)–C(2)
E–Si(1)
191.4(2)
193.1
193.1
186.6
186.6
186.6
186.6
169.2
167.4
167.4
109.34
109.34
98.12
98.12
125.09
0
192.6
192.6
187.3
187.3
187.3
187.3
167.2
217.4
217.4
115.81
115.81
103.83
103.83
100.72
0
190.3(4)
190.2(4)
185.1(5)
185.1(5)
184.9(5)
185.1(5)
168.5(5)
226.30(14)
227.24(13)
117.3(2)
116.0(2)
104.02(12)
104.47(12)
96.70(4)
0.2
192.9
192.9
187.5
187.5
187.5
187.5
167.6
231.5
231.5
117.31
117.31
104.62
104.62
96.15
0
191.0(3)
191.0(3)
185.0(3)
185.4(3)
185.7(3)
185.2(3)
167.8(4)
249.07(10)
248.87(9)
119.90(18)
119.09(18)
103.86(9)
104.22(9)
91.26(3)
0.4
183.3
184.2
183.3
184.2
169.1(4)
164.2(1)
E–Si(2)
Si(1)–C(1)–C(2)
Si(2)–C(2)–C(1)
C(1)–Si(1)–E
C(2)–Si(2)–E
Si(1)–E–Si(2)
Plane Si(1)–C(1)–C(2)–Si(2)
Distance of E from the plane
Si(1)–C(1)–C(2)–Si(2)
Plane C(1)–Si(1)–E–Si(2)–C(2)
108.97(6)
98.15(9)
125.84(13)
0
8.0
0
0
31.9
0
37.2
2.2
0
0
7.6
0
8.4
a) Ref.[8]
.
Figure 6. Two views of the ORTEP plots (50% probabilities; hydrogen
atoms are omitted for clarity) of the molecular structure of the 1,2-
bis(chloro-dimethysilyl)-1,2-dicarba-closo-dodecaborane(12) 4 (for se-
lected distances and angles see Table 5). In one of the dimethylchlo-
rosilyl groups disorder [between Cl(2) and C(5)] was observed.
Figure 5. ORTEP plot (50% probabilities; hydrogen atoms are omitted
for clarity) of the molecular structure of the 1,2-bis(trimethysilyl)-1,2-
dicarba-closo-dodecaborane(12) 3 (for selected distances and angles
see Table 5).
(br. s, 6 H, HB), 2.93 (br. s, 2 H, HB), 2.99 (br. s, 2 H, HB). 11B{1H}
NMR (128.3 MHz; [D8]toluene; 25 °C): δ = –12.5 (2B, B), –10.1 (4B,
B), –3.3 (2B), 0.1 (2B). 11B NMR (128.3 MHz; [D8]toluene; 25 °C):
δ = –12.5 (d, 2B, 170 Hz), –10.1 (d, 4B, 164 Hz), –3.3 (d, 2B, 149 Hz),
0.1 (d, 2B, 152 Hz). EI-MS (70 eV) for C6H22B10Si2S (290.20): m/z
(%) = 290 (30) [M+], 275 (100) [M+ – CH3], 259 (5), 211 (4), 137
(7).
[D8]toluene at –30 °C with formation of a black precipitate of elemen-
tal tellurium. 1H{11B} NMR (399.8 MHz; [D8]toluene; 25 °C): δ
[2J(29Si,1H)] = 0.38 [7.6] (s, 12 H, CH3Si), 2.22 (br. s, 6 H,), 2.72 (br.
s, 2 H, HB), 2.91 (br. s, 2 H, HB). 11B{1H} NMR (128.3 MHz; [D8]tol-
uene; 25 °C): δ = –12.3 (2B, B3,6), –9.9 (4B, B), –3.1 (2B), –0.1 (2B).
11B NMR (128.3 MHz; [D8]toluene; 25 °C): δ = –12.3 (d, 2B, B,
162 Hz), –9.9 (d, 4B, B, 160 Hz), –3.1 (d, 2B, 148 Hz), –0.1 (d, 2B,
150 Hz).
1,1,3,3-Tetramethyl-4,5-[1,2-dicarba-closo-dodecaborano(12)]-1,3-
disila-2-oxa-cyclopentane (6a): A solution of 5 (70 mg, 0.27 mmol)
in [D8]toluene (1 mL) was added at room temperature to Me3N=O
(25 mg; 0.33 mmol). Volatile materials were removed in vacuo to give
6a as a white oil (the solid thus obtained contained about 10% of
1,1,3,3-Tetramethyl-4,5-[1,2-dicarba-closo-dodecaborano(12)]-1,3-
disila-2-thia-cyclopentane (6b): A solution of 5 (70 mg, 0.27 mmol)
in [D8]toluene (1 mL) was added at room temperature to an excess of
dry and degassed elemental sulfur (10 mg). The progress of the reac-
tion was monitored by 29Si NMR spectroscopy. After 7 d at 85 °C, the
Me3N=O). 1H{11B} NMR (500.1 MHz; [D8]toluene; 25 °C):
[2J(29Si,1H)] = 0.03 [7.0] (s, 12 H, CH3Si), 2.21 (br. s, 2 H, HB), 2.26
δ
solution was centrifuged from sulfur. The clear liquid was dried in (br. s, 4 H, HB), 2.99 (br. s, 2 H, HB), 3.04 (br. s, 2 H, HB). 11B{1H}
vacuo to give 6b as a yellowish solid. 1H{11B} NMR (399.8 MHz;
NMR (160.5 MHz; [D8]toluene; 25 °C): δ = –12.5 (2B, B), –10.5 (4B,
[D8]toluene; 25 °C): δ [2J(29Si,1H)] = 0.2 [6.8] (s, 12 H, CH3Si), 2.22 B), –3.2 (2B), 0.2 (2B). 11B NMR (160.5 MHz; [D8]toluene; 25 °C):
Z. Anorg. Allg. Chem. 2012, 1–14
© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
www.zaac.wiley-vch.de
9

B. Wrackmeyer, E. V. Klimkina, W. Milius
ARTICLE
Figure 7. ORTEP plot (50% probabilities; hydrogen atoms are omitted for clarity) of the molecular structure of the 1,1,3,3-tetramethyl-4,5-[1,2-
dicarba-closo-dodecaborano(12)]-1,3-disila-2-selenacyclopentane (6c) and of the 1,1,3,3-tetramethyl-4,5-[1,2-dicarba-closo-dodecaborano(12)]-
1,3-disila-2-telluracyclopentane (6d) (for selected distances and angles see Table 6).
δ = –12.5 (d, 2B, 165 Hz), –10.5 (d, 4B, 157 Hz), –3.2 (d, 2B, 145 Hz),
0.2 (d, 2B, 145 Hz).
10: 1H NMR (500.1 MHz; [D8]toluene; 25 °C): δ [2J(29Si,1H)] = –0.06
[6.4] (s, 6 H, SiCH3), 0.12 [6.4] (s, 6 H, SiCH3), 2.94 (s, 1H, CH). 1H
NMR (500.1 MHz; CD2Cl2; 25 °C): δ [2J(29Si,1H)] = 0.27 (s, 6 H,
SiCH3), 0.33 (s, 6 H, SiCH3), 3.48 (s, 1H, CH). 11B{1H} NMR
(160.5 MHz; [D8]toluene; 25 °C): δ = –13.3 (2B), –11.8 (2B), –10.7
(2B), –6.6 (2B), –1.1 (1B), 0.1 (1B). 11B NMR (160.5 MHz; [D8]tol-
uene; 25 °C): δ = –13.3 (d, 2B, 179 Hz), –11.8 (d, 2B, 173 Hz), –10.7
(d, 2B, 165 Hz), –6.6 (d, 2B, 150 Hz), –1.1 (d, 1B, 157 Hz), 0.1 (d,
1B, 174 Hz).
Piperidinium 9,10-μ-hydro-7-trimethylsilyl-7,8-dicarba-nido-unde-
caborate(1-) Piperidine Adduct, [(C5H10NH)2H]+[7-Si(CH3)3-nido-
7,8-C2B9H10]– (8): A solution of 1-trimethylsilyl-1,2-dicarba-closo-
dodecaborane(12) (100 mg; 0.46 mmol) in [D8]toluene (0.6 mL) was
cooled to 0 °C, and piperidine (0.02 mL; 17 mg; 2.0 mmol) was added
through a syringe. The progress of the reaction was monitored by 11B
and 29Si NMR spectroscopy. After 60 h at room temp., volatile materi-
als were removed in vacuo, and the remaining oil was washed with Reaction of 5 with Dicyclohexylamine: 1,1,3,3-Tetramethyl-1,3-
hexane (1 mL), dried in vacuo to give a white oil of 8. 1H NMR
(500.1 MHz; [D8]toluene; 25 °C): δ [2J(29Si,1H)] = –2.15 [br. m, 1 H,
bis(1,2-dicarba-closo-dodecaborane(12)-1-yldimethylsilyl)
disiloxane (10): A suspension of 5 (50 mg, 0.19 mmol) in [D8]toluene
B(10)Hbridge for δ(11B) = –32.1], 0.15 [6.8] (s, 9 H, SiCH3), 1.33 (m, (0.7 mL) was cooled to –10 °C and dicyclohexylamine (0.08 mL;
H-pip), 2.54 (m, H-pip), 6.18 (br. s, NH). 11B{1H} NMR (160.5 MHz; 73 mg; 0.4 mmol) was added through a microsyringe. The progress of
[D8]toluene; 25 °C): δ = –36.0 [1B, B(1)], –32.1 [1B, B(10)], –21.0 the reaction was monitored by 29Si NMR spectroscopy. After 24 h at
(1B), –18.8 (1B), –17.2 (1B), –16.0 (1B), –12.6 (1B), –9.7 (1B), –8.7
(1B). 11B NMR (160.5 MHz; [D8]toluene; 25 °C): δ = –36.0 [d, 1B,
B(1), 140 Hz], –32.1 [d, 1B, B(10), 129 Hz], –21.0 (d, 1B, 129 Hz),
room temp., the solution contained only 5 and dicyclohexylamine. Af-
ter 24 h at 95 °C, the solution contained 5 (ca. 70%), 10 (ca. 30%),
and dicyclohexylamine. EI-MS (70 eV) for C12H26Si4OB20 (514.9):
–18.8 (d, 1B, 130 Hz), –17.2 (d, 1B), –16.0 (d, 1B), –12.6 (d, 1B, m/z (%) = 350 (10), 334 (100) [M+ – C4H17B10Si], 250 (10), 238 (32),
128 Hz), –9.7 (d, 1B, 150 Hz), –8.7 (d, 1B, 145 Hz).
200 (5).
1-(1,1,2,2-Tetramethyl-2-(N-piperidinyl)disilanyl)-1,2-dicarba-
1-(2-(Cyclohexylamino)-1,1,2,2-tetramethyl-disilanyl)-1,2-dicarba-
closo-dodecaborane(12) (9): A suspension of 5 (150 mg, 0.58 mmol) closo-dodecaborane(12) (11): A suspension of 5 (66 mg, 0.26 mmol)
in [D8]toluene (3.0 mL) was cooled to –10 °C and piperidine in [D8]toluene (0.7 mL) was cooled to –20 °C and cyclohexylamine
(0.079 mL; 68 mg; 0.80 mmol) was added through a microsyringe. The (0.055 mL; 48 mg; 0.48 mmol) was added through a microsyringe. The
progress of the reaction was monitored by 29Si NMR spectroscopy. progress of the reaction was monitored by 29Si NMR spectroscopy.
After 30 min at room temp., the transparent solution contained 9 to-
gether with 10 (ca. 25%) and piperidine. Volatile materials were re-
moved in vacuo (1 h, 8ϫ10–3 Torr). The mixture thus obtained con-
After 1 h at room temp., the transparent solution contained 11 together
with 10 (ca. 20%) and cyclohexylamine. Volatile materials were re-
moved in vacuo (3 h, 8ϫ10–3 Torr). The mixture thus obtained con-
tained 9 (60%) and 10 (40%) (29Si, 13C, H NMR).
tained 11 (80%) and 10 (20%) (29Si, 13C, H NMR). H{11B} NMR
(500.1 MHz; [D8]toluene; 25 °C): δ [2J(29Si,1H)] = 0.00 [6.2] (s, 6 H,
SiCH3), 0.05 [6.4] (s, 6 H, SiCH3), 0.78 (m, 2H, cyclohexyl), 0.91 (m,
1H, cyclohexyl), 1.12 (m, 2H, cyclohexyl), 1.45 (m, 1H, cyclohexyl),
1.58 (m, 4H, cyclohexyl), 2.18 (br. s, 2 H, HB for δ(11B) = –13.3 and
–10.8), 2.25 [br. s, 2 H, HB for δ(11B) = –13.3 and –10.8], 2.33 [br. s,
2 H, HB for δ(11B) = –11.8], 2.33 (m, 1H, cyclohexyl), 2.73 [br. s, 2
H, HB for δ(11B) = –6.6], 2.80 [br. s, 1 H, HB for δ(11B) = –1.1], 2.86
[br. s, 1 H, HB for δ(11B) = 0.0], 3.41 (s, 1H, CH). 11B{1H} NMR
(160.5 MHz; [D8]toluene; 25 °C): δ = –13.3 (2B), –11.8 (2B), –10.8
(2B), –6.6 (2B), –1.1 (1B), 0.0 (1B). 11B NMR (160.5 MHz; [D8]tol-
uene; 25 °C): δ = –13.3 (d, 2B, 179 Hz), –11.8 (d, 2B, 170 Hz), –10.8
(d, 2B, 165 Hz), –6.6 (d, 2B, 150 Hz), –1.1 (d, 1B, 160 Hz), 0.0 (d,
1B, 170 Hz).
1
1
1
1
9: H{11B} NMR (500.1 MHz; [D8]toluene; 25 °C): δ [2J(29Si,1H)] =
–0.01 [6.4] (s, 6 H, SiCH3), –0.02 [6.5] (s, 6 H, SiCH3), 1.20 (m, 4H,
Hβ-pip), 1.37 (m, 2H, Hγ-pip), 2.17 [br. s, 1 H, HB for δ(11B) = –13.3],
2.22 [br. s, 2 H, HB for δ(11B) = –13.3 and –10.7], 2.25 [br. s, 1 H,
HB for δ(11B) = –10.7], 2.35 [m, 1H, HB for δ(11B) = –11.8], 2.39 [br.
s, 1 H, HB for δ(11B) = –1.8], 2.51 (m, 4H, Hα-pip), 2.78 [br. s, 2 H,
HB for δ(11B) = –6.6], 2.84 [br. s, 1 H, HB for δ(11B) = –1.1], 2.91
[br. s, 1 H, HB for δ(11B) = 0.1], 3.42 (s, 1H, CH). 1H NMR
(500.1 MHz; CD2Cl2; 25 °C): δ [2J(29Si,1H)] = 0.23 [6.4] (s, 6 H,
SiCH3), 0.27 (s, 6 H, SiCH3), 1.39 (m, 4H, Hβ-pip), 1.55 (m, 2H, Hγ-
pip), 2.76 (m, 4H, Hα-pip), 3.87 (s, 1H, CH). 11B{1H} NMR
(160.5 MHz; [D8]toluene; 25 °C): δ = –13.3 (2B), –11.8 (2B), –10.7
(2B), –6.6 (2B), –1.1 (1B), 0.1 (1B). 11B NMR (160.5 MHz; [D8]tol-
uene; 25 °C): δ = –13.3 (d, 2B, 179 Hz), –11.8 (d, 2B, 173 Hz), –10.7 1-(1,1,2,2-Tetramethyl-2-(phenylamino)disilanyl)-1,2-dicarba-
(d, 2B, 165 Hz), –6.6 (d, 2B, 150 Hz), –1.1 (d, 1B, 157 Hz), 0.1 (d,
1B, 174 Hz).
closo-dodecaborane(12) (12): A suspension of 5 (56 mg, 0.22 mmol)
in [D8]toluene (0.7 mL) was cooled to 0 °C and aniline (0.1 mL;
10
www.zaac.wiley-vch.de
© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Z. Anorg. Allg. Chem. 2012, 1–14

Silyl-substituted 1,2-Dicarba-closo-dodecaborane(12) Derivatives
102 mg; 1.1 mmol) was added through a syringe. The progress of the
reaction was monitored by 29Si NMR spectroscopy. After 40 h at room
Piperidinium 9,10-μ-Hydro-7,8-μ-(1Ј,1Ј,3Ј,3Ј-tetramethyl-1Ј,3Ј-dis-
ila-2Ј-tellura-1Ј,3Ј-diyl)-7,8-dicarba-nido-undecaborate(1-) Piperi-
temp., the transparent solution contained 12 together with 10 (ca. 25%) dine Adduct, [(C5H10NH)2H]+[7,8-μ-Si(CH3)2TeSi(CH3)2-nido-7,8-
and aniline. Volatile materials were removed in vacuo (5 h, 8ϫ10–
3 Torr). The mixture thus obtained contained 12 (75%) and 10 (25%)
(29Si, 13C, 1H NMR). 1H{11B} NMR (500.1 MHz; [D8]toluene; 25 °C):
δ [2J(29Si,1H)] = –0.03 [5.7] (s, 6 H, SiCH3), 0.15 (6.0) (s, 6 H, SiCH3),
2.08 [br. s, 1 H, HB for δ(11B) = –13.3], 2.19 [br. s, 2 H, HB for δ(11B)
= –13.3 and –10.8], 2.22 [br. s, 1 H, HB for δ(11B) = –10.8], 2.26 [m,
1 H, HB for δ(11B) = –11.7], 2.35 [br. s, 1 H, HB for δ(11B) = –11.7],
2.73 [br. s, 1 H, HB for δ(11B) = –6.7], 2.78 [br. s, 1 H, HB for δ(11B)
= –6.7], 2.85 [br. s, 1 H, HB for δ(11B) = –1.1], 2.86 [br. s, 1 H, HB
for δ(11B) = 0.1], 2.92 (s, 1H, CH), 6.37 (m, 2H, Ph), 6.68 (m, 1H,
Ph), 7.03 (m, 2H, Ph). 11B{1H} NMR (160.5 MHz; D8]toluene; 25 °C):
δ = –13.3 (2B), –11.7 (2B), –10.8 (2B), –6.7 (2B), –1.1 (1B), 0.1 (1B).
11B NMR (160.5 MHz; D8]toluene; 25 °C): δ = –13.3 (d, 2B, 180 Hz),
–11.7 (d, 2B, 158 Hz), –10.8 (d, 2B, 155 Hz), –6.7 (d, 2B, 150 Hz),
–1.1 (d, 1B, 158 Hz), 0.0 (d, 1B, 175 Hz).
C2B9H10]– (13d): A solution of 6d (90 mg; 0.23 mmol) in [D8]toluene
(0.6 mL) was cooled to 0 °C, and piperidine (0.07 mL; 60 mg;
0.71 mmol) was added through a microsyringe. The formation of a
crimson dark solution was observed. The progress of the reaction was
monitored by 11B and 29Si NMR spectroscopy. After 40 h at room
temp., the mixture contained 13d together with (C5H10N)2BH, piperi-
dine and larger amounts of byproducts. 13d decomposes in an argon
atmosphere slowly and in [D8]toluene at –30 °C with formation of a
black precipitate of elemental tellurium. 1H NMR (500.1 MHz;
[D8]toluene; 25 °C): δ [2J(29Si,1H)] {3J(125Te,1H)} = –2.03 [br. m, 1
H, B(10)Hbridge for δ(11B) = –29.7], 0.60 [7.2] {10.5} [s, 6 H,
SiCH3(b)], 0.88 [7.0] [s, 6 H, SiCH3(a)], 1.35 (m, H-pip), 1.55 (m, H-
pip), 3.00 (m, Hα-pip), 4.16 (br. s, NH). 11B{1H} NMR (160.5 MHz;
[D8]toluene; 25 °C): δ = –34.0 [1B, B(1)], –29.7 [1B, B(10)], –13–
0 (overlapping signals for 13d and byproducts), 27.3 [1B, (C5H10N)
2BH].
Piperidinium 9,10-μ-Hydro-7,8-μ-(1Ј,1Ј,3Ј,3Ј-tetramethyl-1Ј,3Ј-dis-
ila-2Ј-selena-1Ј,3Ј-diyl)-7,8-dicarba-nido-undecaborate(1-) Piperi-
dine Adduct, [(C5H10NH)2H]+[7,8-μ-Si(CH3)2SeSi(CH3)2-nido-7,8-
C2B9H10]– (13c): A solution of 6c (80 mg; 0.24 mmol) in [D8]toluene
(0.6 mL) was cooled to 0 °C, and piperidine (0.07 mL; 60 mg;
0.71 mmol) was added through a microsyringe. The formation of a
orange solution was observed. The progress of the reaction was moni-
tored by 11B and 29Si NMR spectroscopy. After 40 h at room temp.,
the mixture contained 13c together with (C5H10N)2BH and piperidine.
Crystal Structure Determination of 3, 4, 6c, and 6d: Structure solu-
tions and refinements were carried out with the program package
SHELXTL-PLUS V.5.1.[37] Details pertinent to the crystal structure
determination are listed in Table 7. Crystals of appropriate size were
sealed in an argon atmosphere in Lindeman capillaries and the data
collections were carried out at 133 K.[38]
1H NMR (500.1 MHz; [D8]toluene; 25 °C):
δ
[2J(29Si,1H)]
Crystallographic data (excluding structure factors) for the structures in
this paper have been deposited with the Cambridge Crystallographic
Data Centre, CCDC, 12 Union Road, Cambridge CB21EZ, UK. Copies
of the data can be obtained free of charge on quoting the depository
numbers CCDC-862717 (3), -862719 (4), -862720 (6c), and -862718
(6d) (Fax: +44-1223-336-033; E-Mail: deposit@ccdc.cam.ac.uk,
http://www.ccdc.cam.ac.uk).
{3J(77Se,1H)} = –1.94 [br. m, 1 H, B(10)Hbridge for δ(11B) = –29.7],
0.52 [7.2] {4.6} [s, 6 H, SiCH3(b)], 0.75 [7.2] [s, 6 H, SiCH3(a)], 1.35
(m, H-pip), 1.52 (m, H-pip), 3.02 (m, Hα-pip), 5.90 (br. s, NH).
11B{1H} NMR (160.5 MHz; [D8]toluene; 25 °C): δ = –33.9 [1B, B(1)],
–29.7 [1B, B(10)], –17.6 (2B), –14.0 (3B), –11.4 (1B), –8.4 (1B), 27.8
[1B, (C5H10N)2BH].
Table 7. Crystallographic data of the ortho-carborane derivatives 3, 4, 6c, and 6d.
3
4
6c
6d
Formula
Crystal
C8H28B10Si2
colorless prism
0.28ϫ0.22ϫ0.20
133(2)
monoclinic
P21/n
C6H22B10Cl2Si2
colorless block
0.18ϫ0.16ϫ0.15
133(2) K
monoclinic
P21/n
C6H22B10SeSi2
yellowish prism
0.29ϫ0.24ϫ0.22 0.25ϫ0.19ϫ0.18
133(2) K
monoclinic
P21/c
C6H22B10Si2Te
yellowish prism
Dimensions /mm3
Temperature /K
Crystal system
133(2) K
monoclinic
P21/c
Space group
Lattice parameters
a /pm
b /pm
c /pm
β /deg
908.56(18)
1447.2(3)
1346.1(3)
90.42(3)
4
904.43(18)
1445.8(3)
1337.0(3)
90.69(3)
4
686.94(14)
1404.8(3)
1776.1(4)
96.90(3)
4
683.52(14)
1445.0(3)
1771.9(4)
96.27(3)
4
Z
Absorption coefficient μ /mm–1
Diffractometer
0.180
0.486
2.322
1.823
STOE IPDS II, Mo-Kα, λ = 71.073 pm, graphite monochromator
Measuring range (ϑ) /deg
Reflections collected
Independent reflections [I Ն 2σ(I)]
Absorption correctiona)
Refined parameters
wR2/R1 [I Ն 2σ(I)]
Max./min. residual electron density /e·pm–
3·10–6
2.07–25.74
20647
2569
none
181
2.07–25.73
21647
2836
none
185
1.85–25.75
18333
2470
none
172
1.82–25.60
22839
3009
none
172
0.129 / 0.058
0.525 / –0.237
0.173 / 0.063
0.719 / –0.612
0.125 / 0.055
0.848 / –0.393
0.081 / 0.032
1.497 / –0.956
a) Absorption corrections did not improve the parameter set.
Z. Anorg. Allg. Chem. 2012, 1–14
© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
www.zaac.wiley-vch.de
11

B. Wrackmeyer, E. V. Klimkina, W. Milius
ARTICLE
[16] H. C. E. McFarlane, W. McFarlane, Multinuclear NMR (Ed.: J.
Mason) Plenum Press, New York, 1987, chapter 15.
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[19] B. Wrackmeyer, E. V. Klimkina, W. Milius, Z. Anorg. Allg. Chem.
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Received: January 22, 2012
Published Online: ᭿
Z. Anorg. Allg. Chem. 2012, 1–14
© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
www.zaac.wiley-vch.de
13

B. Wrackmeyer, E. V. Klimkina, W. Milius
ARTICLE
B. Wrackmeyer,* E. V. Klimkina, W. Milius ................... 1–14
Molecular Structures, Reactivity, and NMR Spectroscopic
Studies of Cyclic and Non-cyclic Silyl-substituted 1,2-Di-
carba-closo-dodecaborane(12) Derivatives
14
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© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Z. Anorg. Allg. Chem. 2012, 1–14