Selective consecutive insertion of alkynes into the B-Se bonds of 1,3,2-diselenaborolane derivatives: Synthesis and molecular structures of nine-membered rings

Article abstract of DOI:10.1002/ejic.201200471

Various alkynes have been inserted selectively and stepwise into the B-Se bond(s) of 1,3,2-diselenaboracyclopentanes {as the 4,5-[1,2-dicarba-closo- dodecaborano(12)] derivatives}. The B-phenyl derivative was much less reactive than the B-halogeno derivat

Full text of DOI:10.1002/ejic.201200471

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FULL PAPER
DOI: 10.1002/ejic.201200471
Selective Consecutive Insertion of Alkynes into the B–Se Bonds of
1,3,2-Diselenaborolane Derivatives: Synthesis and Molecular Structures of
Nine-Membered Rings
Bernd Wrackmeyer,*[a] Elena V. Klimkina,[a] and Wolfgang Milius[b]
Keywords: Carboranes / Selenium / Alkynes / Heterocycles / Insertion / NMR spectroscopy / Density functional calculations
Various alkynes have been inserted selectively and stepwise
into the B–Se bond(s) of 1,3,2-diselenaboracyclopentanes {as
the 4,5-[1,2-dicarba-closo-dodecaborano(12)] derivatives}.
The B-phenyl derivative was much less reactive than the B-
clear shielding 2Δ10/11B(13C) across weak intramolecular co-
ordinative Se–B bonding was observed in the 13C NMR spec-
tra of the nine-membered-ring compounds. The molecular
structures of two nine-membered-ring structures with B–Cl
halogeno derivatives. The proposed structures were con- and B–Br functions were determined by X-ray diffraction. In
firmed in solution by multinuclear NMR studies (1H, 11B, 13C
and 77Se NMR), also supported by DFT calculations of the
gas-phase molecular geometries and NMR parameters
[B3LYP/6-311+G(d,p) level of theory]. Isotope-induced nu-
addition, it was shown that the slow hydrolysis of these boron
halides afforded the corresponding diboroxanes and borinic
acids, the structures of the former being determined by X-
ray diffraction.
Introduction
acidic. Otherwise radical reactions may be induced, which
may lead to numerous products.[3a] To detect the first rea-
sonably stable intermediates in the course of the insertion
reactions, kinetic stabilization might be necessary. In this
respect, it is expected that the bulky annelated 1,2-di-
carba-closo-dodecaborane(12) unit[9,10] in 2 is particularly
useful.
Straightforward routes to various well-characterized, sim-
ple selenoboranes have previously been reported.[1,2] Al-
though some applications of noncyclic selenoboranes[1,2] have
been described,[3] their cyclic analogues appear to be even
more intriguing due to their potential use in heterocyclic syn-
thesis[4,5] or as ligands for transition-metal complexes.[6] The
former has been shown by the conversion of 1,3,4,2,5-triselena-
borolanes into novel ring systems through reactions with iso-
In this paper we report on the first attempts to insert
cyanates[5a] or alkynes.[5b,5c] Recently, we prepared the first alkynes into the B–Se bond(s) of 2 aiming for the synthesis
stable 1,3,2-diselenaborolane derivatives 2 (Scheme 1)[7] start- of larger ring systems in the solid state and in solution and
ing from the silane 1[8] through exchange reactions. Unsatu- their structural characterization by using multinuclear mag-
rated substrates can be inserted into the reactive B–Se bond(s) netic resonance methods as well as MO calculations at the
if the boron atom is three-coordinate and strongly Lewis- B3LYP/6-311+G(d,p) level of theory.
Scheme 1. Formation of 1,3,2-diselenaborolane derivatives 2.
Results and Discussion
[a] Anorganische Chemie II, Universität Bayreuth,
Synthesis and NMR Spectroscopy of Novel Seven- and
Nine-Membered Rings
95440 Bayreuth, Germany
Fax: +49-921-552157
E-mail: b.wrack@uni-bayreuth.de
[b] Anorganische Chemie I, Universität Bayreuth,
95440 Bayreuth, Germany
Some alkynes reacted more or less readily with 2a–2d,
and some did not react at all, for example, 2a with 1,4-
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Scheme 2. Reaction of 1,3,2-diselenaborolanes 2a,b with ethyne.
dichlorobut-2-yne or dimethyl acetylenedicarboxylate at pected, 2e was inert towards all alkynes studied, most likely
room temperature after prolonged periods of time. The re- for electronic and steric reasons.
action of 2a or 2b with ethyne (Scheme 2) proceeded slowly,
Two different terminal alkynes were used for reactions
leading to numerous decomposition products of which only with 2a (Scheme 3). In contrast to the reaction of phenyle-
the known tetraselenide 3[9] could be identified by its char- thyne, which afforded a complex mixture not analysed as
acteristic 13C and 77Se NMR spectroscopic data. As ex- yet, tert-butylethyne gave meaningful results in the first
Scheme 3. Reactions of the 1,3,2-diselenaborolanes 2a with two terminal alkynes.
Table 1. 13C, 11B and 77Se NMR spectroscopic data[a] for the ortho-carborane derivatives 4a, 5a–d and 7a in [D8]toluene.
Compound
4a
5a
5b
5c
5d[b]
7a
δ13C
[C(2,3)carb
66.4 [151.7]
{–8.8 ppb}
70.1 [169.0]
{–8.8 ppb}
164.6 [111.2]
138.1 [br.]
tBu
69.9 [165.9]
{–9.0 ppb}
70.2 [156.7]
{–7.3 ppb}
142.6 [91.5]
160.1 [br.]
Et
70.2 [163.8]
{–9.8 ppb}
73.5 [158.4]
{–8.2 ppb}
141.5 [87.4]
163.1 [br.]
Et
70.8 [161.4]
{–8.2 ppb}
79.3 [164.1]
{–11.5 ppb}
139.6 [81.6]
166.5 [br.]
Et
70.0 [164.7]
{–9.6 ppb}
71.8 [162.5]
{–9.6 ppb}
139.4 [85.3]
163.5 [br.]
Et
70.9 [165.9]
{–9.6 ppb}
71.0 [156.8]
{–9.6 ppb}
135.8 [88.1]
163.3 [br.]
Ph
]
δ13C[SeC=]
δ13C[=CB]
δ13C[SeC(R)]
41.5 [9.4]
28.4 [3.5]
29.1 [11.6]
12.8
28.4 [11.2]
12.8
27.5 [11.4]
12.6
28.0 [10.5]
13.19
128.5 (Cm)
128.8 (Co)
129.2 (Cp)
137.5 (Ci)
Et
δ13C[=C(R)B] H (δ1H)
Et
Et
26.4
Et
26.9
Et
27.4
4
6.33 J(77Se,1H) = 9.6 Hz 26.1
28.0
13.5
56.9
524.6 [br.]
h1/2 = 100 Hz
616.7
13.4
50.4
516.9 [br.]
13.1
34.2
515.2 [br.]
13.22
55.8
470.2 [br.]
13.0
52.0
508.9 [br.]
δ11B(CBSe)
δ77Se [SeB]
63.3
577.8 [br.]
h1/2 = 105 Hz
564.0
h1/2 = 110 Hz h1/2 = 150 Hz h1/2 = 60 Hz h1/2 = 85 Hz
616.7
δ77Se [SeC=]
δ11B (calcd.)
613.4
626.5
661.4
70.3
SeB
68.7
71.2
SeB
δ77Se (calcd.) SeB
553.9 [–180.1] [1J(carb)] 550.7 [–179.6] [1J(carb)]
528.3 [–184.4] [1J(carb)]
SeC=
SeC=
SeC=
561.9 [–197.2] [1J(carb)] 613.0 [–200.1] [1J(carb)]
687.9 [–200.2] [1J(carb)]
[–112.3] [1J(C=)]
[+13.5] [2J(C=)]
[+8.3] [2J(Ci)]
[–1.3] [3J(CH2)]
[–132.4] [1J(C=)]
[+2.5] [2J(C=)]
[+7.9] [2J(CMe3)]
[0.0] [3J(CH3)]
[–124.1] [1J(C=)]
[+2.9] [2J(C=)]
[+17.3] [2J(CH2)]
[–2.0] [–2.6] (3J)
[a] Coupling constants nJ(77Se,13C) are given in brackets [Ϯ0.5 Hz], 1Δ10/11B(13C(2,3)carb)Ϯ0.5 ppb are given in braces {Ϯ0.5 Hz}, isotope-
1
induced chemical shifts Δ are given in ppb, and the negative sign denotes a shift of the NMR signal of the heavy isotopomer to a lower
frequency; n.o. = not observed; [br.] denotes broad 13C or 77Se resonances of boron-bonded carbon atoms. [b] Other δ13C data: 128.7
(Cm), 132.7 (Cp), 133.8 (Co), n.o. (Ci) (for Ph).
2
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Insertion of Alkynes into B–Se Bonds of Diselenaborolanes
Figure 1. Reaction mixture of 5d, 2d, 3 and hex-3-yne obtained from the reaction of 2d with hex-3-yne (molar ratio 1:2, in [D8]toluene)
after 2 h at 50 °C (3 is a decomposition product; see Scheme 1). (A) Part of the 125.8 MHz 13C{1H} NMR spectrum. The 77Se satellites
are marked by arrows. (B) 95.4 MHz 77Se NMR spectrum.
Figure 2. 95.4 MHz 77Se NMR spectrum of the reaction mixture of 5a together with small amounts of 6a, 6Јa and 2a (ca. 10%) obtained
from the reaction of 2a with hex-3-yne (molar ratio 1:1, in [D8]toluene) after 2 d at room temp.
step. The carborane derivative 4a, containing a seven-mem- stoichiometry. Indeed, an equilibrium exists between 2d and
bered cycle, was obtained from the slow 1:1 reaction at 5d in the presence of an excess of hex-3-yne (Scheme 4). It
1
–30 °C. According to the H, 11B, 13C and 77Se NMR spec- is conceivable that the Lewis acidity of the boron atom
tra (Table 1), the insertion of the alkyne into one of the B– plays an important role in the insertion of the alkyne into
Se bonds had taken place selectively. The 77Se NMR spec- the B–Se bond(s). In the case of a B–Ph moiety as in 2d or
tra[11] of the reaction solutions are particularly instructive, 5d, the Lewis acidity is too low to favour a second insertion,
because compounds of type 4 give rise to two signals, one and even the first insertion appears to be readily reversible.
broad[7] (B–Se–C) and one sharp (C–Se–C; see Figure 1B
When the boron halides 2a,b,c were used instead of 2d,
or Figure 2). In the presence of an excess of tert-butyl- the situation was markedly different (Scheme 5). The first
ethyne, further slow reactions occurred, accompanied by insertion products 5a,b,c were detected by NMR spec-
decomposition. The complex mixtures were not analysed.
troscopy used to monitor the reactions. It proved difficult
Even more promising results were obtained with hex-3- to obtain the products 5a,b,c of the 1:1 reactions in a pure
yne. When 2d was used, the reaction never went beyond 1:1 state (see the 77Se NMR spectra in Figure 2 and Figure 3).
Scheme 4. Reversible reaction of 1,3,2-diselenaborolane 2d with hex-3-yne.
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Scheme 5. Stepwise reactions of the 1,3,2-diselenaborolanes 2a,b,c with hex-3-yne.
Figure 3. NMR spectra of reaction solutions containing 5c together with a very small amount of 6c (in [D8]toluene, at 23 °C).
(A) 62.9 MHz 13C{1H} NMR spectrum. In the expansions, the 77Se satellites are marked by arrows. (B) 47.7 MHz 77Se NMR spectrum.
Solely in the case of the iodide 5c was the product obtained presence of isomer 6Јc could not be detected with any cer-
1
almost pure (see Figure 3). The 11B chemical shifts (Table 1) tainty in the H, 13C or 77Se NMR spectra. The solution-
indicate weak intramolecular coordinative Se–B bonds, state structures of 6a,b,c and 6Јa,b were assigned on the
slightly stronger in the bromide 5b and iodide 5c than in basis of the 1H and 13C NMR spectra with the various 77Se
the chloride 5a. In all three cases the 11B NMR signals are satellites arising from 77Se–13C spin–spin coupling across
shifted to a lower frequency with respect to the range ex- one, two and three bonds (Table 2 and Figure 4). The
1
pected[12] for trigonal boranes in which the boron atoms are 13C(CH2) signals were assigned to the H(CH2) multiplets
1
surrounded by carbon, selenium and a halogen.
(Figure 5), typical of diastereotopic H nuclei, as expected
In the presence of an excess of hex-3-yne, the second ad- for the structures 6 and 6Ј. Because pure crystalline samples
dition or insertion into the remaining B–Se bond took place of 6 could be isolated (see below for the X-ray structural
readily to give the nine-membered heterocycles 6a,b,c and analysis) and redissolved, the assignment of the NMR sig-
6Јa,b as mixtures of isomers. Nine-membered heterocycles nals was straightforward. In solution, there was no indica-
containing boron are rare[13] and so far unknown with a tion of a rapid interconversion between 6 and 6Ј.
boron–halogen bond. The amount of the isomers 6Ј
We treated 1-phenylbut-1-yne with 2a to study the selec-
changed in repeated experiments, ranging from ca. 10 to tivity of the insertion reactions (Scheme 6). The reaction
33% for X = Cl and Ͻ5–10% for X = Br. For X = I, the proved to be selective in both steps, affording at first 7a and
4
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Insertion of Alkynes into B–Se Bonds of Diselenaborolanes
Table 2. 13C, 11B and 77Se NMR spectroscopic data[a] of the ortho-carborane derivatives 6a–c, 8a, 6Јa–b and 8Јa in [D8]toluene.
Compound
6a
6b
6c
8a
6Јa
6Јb
8Јa
δ13C
[C(2,3)carb
79.2
[174.1]
75.5
[171.3]
72.7
[168.8]
{–8.7 ppb}
(+13 ppb)
138.6 [87.0]
80.1
[174.4]
59.4
[174.8]
{–9.6 ppb}
58.5
[172.0]
{–9.6 ppb}
60.6
]
{–10.4 ppb}
(+21 ppb)
136.8 [95.7]
(–12 ppb)
162.6 [br.]
Et
{–9.6 ppb}
(+12 ppb)
137.98 [91.1]
(–10 ppb)
164.0 [br.]
Et
{–10.5 ppb}
(+22 ppb)
131.8 [96.1]
(–12 ppb)
163.4 [br.]
Ph
δ13C
138.4 [94.9]
137.9
133.9
[SeC=]
δ13C[=CB]
165.3 [br.]
Et
163.6 [br.]
Et
165.0 [br.]
Et
164.4 [br.]
Ph
δ13C
[SeC(R)]
28.1 [9.7]
13.7
27.7 [10.3]
13.5
27.7 [10.5]
13.1
128.7 (Cm)
129.2 (Co)
128.6 (Cp)
139.3 [8.2] (Ci)
Et
30.3 [8.7]
13.0
32.5
12.8
139.9 (Ci)
δ13C
Et
Et
Et
Et
Et
Et
[=C(R)B]
26.0 [6.7]
14.3
42.0
556.1
61.3
548
25.8 [7.3]
14.3
27.0
25.7 [7.5]
14.3
9.0
27.6
14.0
28.0
608.4
26.6
13.7
48.5
554.7
27.9
13.5
n.o.
540.4
28.7
13.8
n.o.
574.5
δ11B (=CBC=)
δ77Se [SeC=]
δ11B (calcd.)
δ77Se (calcd.)
541.6
526.9
[a] Coupling constants nJ(77Se,13C) are given in brackets [Ϯ0.5 Hz], 1Δ10/11B(13C(2,3))Ϯ0.5 ppb are given in braces {Ϯ0.5 Hz},
2
2Δ10/11B(13C(2,3)) and Δ10/11B(13C(SeC=))Ϯ0.5 ppb are given in parentheses (Ϯ0.5 Hz), isotope-induced chemical shifts 1,2Δ are given
in ppb, and the negative sign denotes a shift of NMR signal of the heavy isotopomer to a lower frequency; n.o. = not observed; [br.]
denotes broad 13C or 77Se resonances of boron-bonded carbon atoms.
Figure 4. NMR spectra of the mixture of 6a and 6Јa (ca. 3:1, in [D8]toluene, at 23 °C) obtained from the reaction of 2a with hex-3-yne
(molar ratio 1:2, in [D8]toluene) after 5 d at room temp. (A) 100.5 MHz 13C{1H} NMR spectrum. In the expansions, the 77Se satellites
are marked by arrows. (B) 95.4 MHz 77Se NMR spectrum.
then a mixture containing mainly 8a together with a small 6Ј (the 11B NMR signal of 8Јa was not observed in the
amount of its isomer 8Јa (see Table 2 for the NMR spectro- neighbourhood of the broad 11B NMR signal of 8a because
scopic data).
of the low concentration of 8Јa). In principle, this coordina-
For both 6 and 8, the 11B nuclear shielding is increased tive Se–B bonding should also be evident by isotope-in-
with respect to trigonal diorgano(seleno)boranes[12] even duced nuclear shielding (secondary isotope effects[14]), as
more significantly than for the seven-membered cycles 4a, has already been shown for 2Δ10/11B(29Si) in bridging B···E–
5a,b,c and 7a. Supported by the solid-state structures (see Si units for E = H or O.[15,16] In the present examples, we
below), this points towards marked intramolecular coordi- deal with B···Se–C units, and therefore one might expect
native Se–B interactions in which both the selenium atoms to see additional 13C NMR signals due to 2Δ10/11B(13C).
in 6 and 8 are involved. On the basis of the δ11B data, these Although neither the sign nor the magnitude of this effect
interactions appear to be somewhat weaker in the isomers can be predicted yet, it is clearly visible in the 13C NMR
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Figure 5. Contour plot of part of the 400 MHz 2D 1H–13C HSQC spectrum (in [D8]toluene, at 23 °C) of a mixture containing 6a and 6Јa (3:1).
Scheme 6. Reaction of 1,3,2-diselenaborolane 2a with 1-phenylbut-1-yne.
spectra of compounds 6 and 8 when spectra could be re-
corded with a sufficient signal-to-noise ratio and high reso- and 8 are susceptible to further transformations. First, we
lution (Figure 6). studied the slow oxidation/hydrolysis of samples with X =
Both the boron–carbon and boron–halogen bonds in 6
6
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Insertion of Alkynes into B–Se Bonds of Diselenaborolanes
Figure 6. Expansions of the 125.8 MHz 13C{1H} NMR spectrum of 6a for the 13C(carb) and the olefinic 13C(5,9) NMR signals showing
secondary isotope effects due to the presence of 10B and 11B (ratio ca. 1:4). The characteristic splitting due to 1Δ10/11B(13C) has been
2
discussed for dicarba-closo-dodecaboranes,[17] whereas the effects across selenium, Δ10/11B(13C) of opposite signs (!), were observed here
for the first time.
Scheme 7. Slow hydrolysis of the B–Cl bond affording diboroxanes or borinic acids.
Cl (Scheme 7). Toluene solutions containing mainly 6a or Table 3. 13C, 11B and 77Se NMR spectroscopic data for the ortho-
carborane derivatives 10–12 in CD2Cl2.
8a were kept unsealed for several days until a crystalline
solid separated. The supernatant solution still contained
compound 6 or 8. The solid materials were collected and
studied by X-ray crystallography (see below); they were
Compound
10
11
12
δ13C [C(2,3)carb
]
84.9
85.1
85.5
δ13C [SeC=]
140.49
161.2 [br.]
Ph
128.7 (Cm)
130.0 (Co)
128.5 (Cp)
131.2 (Ci)
Et
27.96
14.4
28.0
626.5
135.5
162.2 [br.]
Et
29.5
14.3
140.53
162.5 [br.]
Ph
128.5 (Cm)
130.3 (Co)
128.2 (Cp)
130.4 (Ci)
Et
27.93
14.1
25.0
625.6
identified as the diboroxanes 9 and 10. When 9 or 10 were δ13C[=CB]
δ13C [SeC(R)]
dissolved in CD2Cl2 and the samples again kept unsealed,
after some time (1 d for 9, 7 d for 10) traces of moisture
generated the borinic acids 11 and 12 (see Table 3 for the
NMR spectroscopic data). Thus, slow hydrolysis of the B–
δ13C [=C(R)B]
Et
Cl bond in 6 or 8 is preferred over slow oxidation.
26.2
14.6
41.8
560.5
δ11B (=CBC=)
DFT Calculations of Molecular Geometries, Chemical
δ77Se [SeC=]
Shifts δ11B and δ77Se, and Coupling Constants
The gas-phase molecular structures of the seven-mem-
bered rings 4a, 5a,b and 7a, and the nine-membered rings
6a,b, 6Јa,b and 11 were calculated and optimized at the
B3LYP/6-311+G(d,p) level of theory.[18] In the case of the
nine-membered rings, 6a is slightly more stable (by 6.7 kcal/
mol) than 6Јa. The calculated structures are similar to the
experimental solid-state structures (6a,b, see below), al-
though coordinative Se–B interactions are underestimated
in the calculations. The mean Se–B distances are longer and
the sums of bond angles deviate less from 360° for the cal-
culated structures. This is regarded as a major reason for
NMR parameters, in particular with respect to 11B(7) nu-
clear shielding. The calculated 77Se nuclear shielding[22,23]
as well as the trend in the calculated coupling constants
nJ(77Se,13C)[24,25] agree well with the experimental data
given the inaccuracy of the calculated geometries.
X-ray Structural Analyses of the ortho-Carborane
Derivatives 6a,b, 9 and 10
The molecular structures of the boron halides 6a,b and
the differences in the calculated[19–21] and experimental boroxanes 9 and 10 are shown in Figures 7, 8 and 9 (see
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Table 4 for the structural parameters). Intermolecular inter- (290.1 pm). This fits to changes in the sums of bond angles,
actions appear to be negligible in all cases studied, although which are close to 360° for the trigonal-planar surroundings
the arrangement of the molecules of 10 in the unit cell is of the boron atoms in 9 and 10 (358.7 and 359.1°), and
remarkable (Figure 9B). All the relevant structural features point towards increasing pyramidalization in 6a (356.2°)
of the carborane units agree with reported data.[10] The and 6b (352.1°). The Se(1)–B(13) bonding interaction is also
question of intramolecular Se–B bonding, already apparent mirrored by the widening of the corresponding C(1)–Se(1)–
from the δ11B data, is also answered by inspecting the C(3) angle when compared with C(12)–Se(2)–C(2), as is
changes in the mean Se–B distances and the sums of the clearly evident for 6a and 6b and expectedly less so for 9
angles at the respective boron atoms. The longest mean Se– and 10. The wide B–O–B bond angles in the diboroxanes 9
B distances are observed for the diboroxanes 9 and 10 and 10 [169.3(3) and 178.2(8)°] are typical of this class of
(313.4 and 315.4 pm) followed by 6a (299.8 pm) and 6b compounds.[26,27]
Figure 7. Molecular structures of (A) 6a and (B) 6b (ORTEP plots drawn at the 50% probability level, hydrogen atoms have been omitted
for clarity; for selected distances and angles, see Table 4). The dashed line in (B) indicates the relatively short Se–B distance, typical of a
coordinative interaction, supported by the sum of the bond angles at B(13) (356.2° for 6a and 352.7° for 6b).
Figure 8. Molecular structure of 7,7Ј-oxobis{2,3-[1,2-dicarba-closo-dodecaborano(12)]-5,6,8,9-tetraethyl-1,4-diselena-7-boracyclohepta-
5,8-diene} (9; ORTEP plots drawn at the 50% probability level, hydrogen atoms have been omitted for clarity; for selected distances and
angles, see Table 4).
8
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/KAP1
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Pages: 15
Insertion of Alkynes into B–Se Bonds of Diselenaborolanes
Figure 9. A) Molecular structure of 7,7Ј-oxybis{2,3-[1,2-dicarba-closo-dodecaborano(12)]-6,8-diethyl-5,9-diphenyl-1,4-diselena-7-boracy-
clohepta-5,8-diene} (10; ball-and-stick model, hydrogen atoms have been omitted for clarity; for selected distances and angles, see Table 4).
(B) Positions of molecules of 10 in the cryatal lattice.
Table 4. Selected bond lengths [pm] and angles [°] of the ortho-carborane derivatives 6a and 6b, (calcd. for the tetramethyl derivative), 9
(calcd. for the tetramethyl-BOH derivative) at 133 K and 10 at 293 K.
6a
X = Cl
Calcd.
X = Cl X = Br
6b
Calcd.
X = Br X = O
9
Calcd.
X = OH
10[a]
X = O
C(1)–Se(1)
C(2)–Se(2)
C(1)–C(2)
C(3)–Se(1)
C(12)–Se(2)
C(3)–C(6)
C(12)–C(9)
C(6)–B(13)
193.0(6)
193.7(7)
172.3(9)
193.7(7)
194.0(7)
132.4(10)
133.7(10)
158.6(10)
157.4(10)
177.7(8)
195.4
195.5
178.9
195.3
195.4
134.2
134.3
157.5
157.6
178.6
195.4(6)
193.1(5)
169.8(8)
192.8(6)
193.7(6)
134.4(9)
133.6(8)
158.0(9)
157.6(9)
198.0(6)
195.5
195.6
178.8
195.4
195.4
134.2
134.3
157.0
157.4
195.7
192.9(3)
192.1(3)
175.5(5)
194.9(3)
194.3(3)
133.6(5)
132.6(5)
157.2(5)
158.4(5)
135.7(4)
133.8(4)
306.7
195.4
195.4
179.9
195.8
195.8
133.7
133.7
158.7
158.8
136.1
C(1)–Se(1)
C(2)–Se(2)
C(1)–C(2)
C(3)–Se(1)
C(13)–Se(2)
C(3)–C(10)
C(13)–C(20)
C(10)–B(13)
C(20)–B(13)
B(13)–O
193.3(6)
194.1(6)
174.5(8)
193.3(6)
191.6(7)
132.8(8)
133.5(9)
157.4(9)
157.5(10)
134.8(6)
C(9)–B(13)
B(13)–X
B(24)–X
B(13A)–O
Se(1)···B(13)
Se(2)···B(13)
Se(1)···B(13)
264.7
334.8
316.8
320.3
247.9
332.2
315.3
322.3
307.9
318.0
310.8
320.0
Se(2)···B(13)
319.0
302.9
324.8
Se(3)···B(24)
Se(4)···B(24)
C(3)–Se(1)–C(1)
C(12)–Se(2)–C(2)
Se(1)–C(1)–C(2)
Se(2)–C(2)–C(1)
Se(1)–C(3)–C(6)
Se(2)–C(12)–C(9)
C(3)–C(6)–B(13)
C(12)–C(9)–B(13)
C(6)–B(13)–C(9)
C(6)–B(13)–X
C(9)–B(13)–X
Se(1)–C(3)–C(4)
Se(2)–C(12)–C(13)
C(7)–C(6)–B(13)
C(10)–C(9)–B(13)
B(24)–O–B(13)
109.1(3)
100.6(3)
116.0(4)
116.9(4)
107.0(5)
119.4(5)
114.6(6)
130.4(6)
117.9(6)
121.5(5)
116.8(5)
121.4(5)
112.8(5)
122.0(6)
112.2(6)
104.3
104.5
117.5
117.3
117.7
117.1
125.5
124.6
122.0
117.8
117.8
114.7
114.7
113.1
113.4
110.2(2)
101.1(2)
114.3(3)
116.9(3)
103.9(4)
118.6(5)
111.6(5)
130.2(5)
120.3(5)
119.6(4)
112.8(4)
123.1(5)
113.2(4)
125.1(5)
110.6(5)
103.8
104.5
117.7
117.3
118.0
116.9
126.0
124.2
122.6
117.3
117.3
114.7
114.7
112.8
113.6
103.39(13)
101.21(14)
116.7(2)
118.2(2)
116.5(3)
118.6(3)
121.9(3)
124.9(3)
124.8(3)
117.9(3)
116.0(3)
113.5(2)
113.8(3)
115.9(3)
114.7(3)
169.3(3)
104.8
104.5
117.2
118.0
117.2
118.8
123.5
126.4
120.3
117.0
121.3
114.5
114.0
114.6
113.1
C(3)–Se(1)–C(1)
C(13)–Se(2)–C(2)
Se(1)–C(1)–C(2)
Se(2)–C(2)–C(1)
Se(1)–C(3)–C(10)
Se(2)–C(13)–C(20)
C(3)–C(10)–B(13)
C(13)–C(20)–B(13)
C(10)–B(13)–C(20)
C(10)–B(13)–O
105.1(2)
103.8(2)
117.0(3)
116.0(4)
114.7(4)
116.8(5)
123.2(5)
125.5(6)
114.9(5)
121.4(6)
122.8(5)
117.5(4)
116.4(5)
116.3(5)
114.6(6)
178.2(8)
C(20)–B(13)–O
Se(1)–C(3)–C(4)
Se(2)–C(13)–C(14)
C(11)–C(10)–B(13)
C(21)–C(20)–B(13)
B(13)–O–B(13A)
[a] The crystal structure contains about 0.2CD2Cl2 per formula unit.
The molecule of 10 shows the symmetry C2. The two- found in the unit cell. The four molecules in the unit cell
¯
fold axis runs through the oxygen atom at the center of the are generated by a 4 axis in the center of the ab plane run-
B–O–B bond (Figure 9A). Thus, only four molecules are ning parallel to the c axis (Figure 9B).
Eur. J. Inorg. Chem. 0000, 0–0
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9

Job/Unit: I20471
/KAP1
Date: 19-07-12 10:54:50
Pages: 15
B. Wrackmeyer, E. V. Klimkina, W. Milius
FULL PAPER
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.
Conclusions
The CϵC bond of various alkynes, except those of elec-
tron-deficient alkynes, inserts readily into the B–Se bond(s)
of 1,3,2-diselenaborolanes, provided the boron atom is suffi-
ciently Lewis-acidic and preferably in the presence of a B–
X function (X = Cl, Br, I). In the first step, the reactions
afforded novel seven-membered rings, and – for the first
time – nine-membered rings containing six carbon, two se-
lenium and one boron atom were formed in the second step.
The insertion of 1-phenylbut-1-yne led selectively to hetero-
cycles in which the selenium atoms and the phenyl groups
are in geminal positions. In both the seven- and nine-mem-
bered rings, weak intramolecular coordinative Se–B interac-
tions are indicated by NMR spectroscopy, confirmed by X-
ray structural analysis. The new heterocycles are susceptible
to further transformations; in the case of the nine-mem-
bered-ring compounds, the conversion of B–Cl into B–O
functions was shown to take place selectively by slow hy-
drolysis.
5-(tert-Butyl)-7-chloro-2,3-[1,2-dicarba-closo-dodecaborano(12)]-
1,4-diselena-7-boracyclohept-3-ene (4a): A solution of 2a
(0.26 mmol) in [D8]toluene (0.6 mL) [from 1 (93.5 mg; 0.26 mmol)
and BCl3 (0.5 mL of a 1.0 m solution in toluene, 0.5 mmol)[7]] was
cooled to –50 °C, and tert-butylethyne (0.032 mL, 21 mg,
0.26 mmol) was added through a microsyringe. The progress of the
1
reaction was monitored by 11B and H NMR spectroscopy. After
2 weeks at –30 °C, volatile materials were removed in vacuo to give
4a as a white oil. 1H{11B} NMR (500.13 MHz, [D8]toluene, 25 °C):
δ = 0.79 (s, 9 H, CH3), 2.58, 2.75 [2 br. s, 3 H, 5 H, HB for δ(11B)
= –11.8, –8.5 ppm], 2.90 [br. s, 1 H, HB for δ(11B) = –3.0 ppm],
3
2.96 [br. s, 1 H, HB for δ(11B) = –0.9 ppm], 6.34 [s, J(77Se,1H) =
9.6 Hz, 1 H, SeC=CH] ppm. 11B{1H} NMR (160.5 MHz, [D8]tolu-
ene, 25 °C): δ = –11.8 (1 B), –8.5 (7 B), –3.0 (1 B), –0.9 (1 B), 63.3
(1 B, BCl) ppm. 11B NMR (160.5 MHz, [D8]toluene, 25 °C): δ =
–11.8 [d, 1J(11B,1H) = 164 Hz, 1 B], –8.5 (m, 7 B), –3.0 [d,
1
1J(11B,1H) = 151 Hz, 1 B], –0.9 [d, J(11B,1H) = 151 Hz, 1 B], 63.3
(s, 1 B, BCl) ppm.
7-Chloro-2,3-[1,2-dicarba-closo-dodecaborano(12)]-5,6-diethyl-1,4-
diselena-7-boracyclohept-3-ene (5a): A solution of 2a (0.24 mmol)
in [D8]toluene (0.6 mL) [from 1 (85 mg; 0.24 mmol) and BCl3
(0.45 mL of a 1.0 m solution in toluene, 0.45 mmol)[7]] was cooled
to –50 °C, and hex-3-yne (0.027 mL, 19.5 mg, 0.24 mmol) was
added through a microsyringe. The progress of the reaction was
monitored by 11B and 1H NMR spectroscopy. After 1 h at room
temp., the mixture contained 5a together with 2a (ca. 5%, by 77Se
Experimental Section
General: All syntheses and the handling of the samples were carried
out observing necessary precautions to exclude traces of air and
moisture. Carefully dried solvents and oven-dried glassware were
used throughout. The solvents CH2Cl2 and CD2Cl2 were distilled
from CaH2 under argon. All other solvents were distilled from Na
under argon. The starting materials, that is, 2a–e, were prepared as
described previously.[7] Dried [D8]toluene was saturated with acetyl-
ene (1 atm) at 0 °C. Other starting materials were purchased from
Aldrich [hex-3-yne (99%), 3,3-dimethylbut-1-yne (98%), 1-phen-
ylbut-1-yne (99%), 1,4-dichlorobut-2-yne (99%), phenylethyne
(98%), dimethyl acetylenedicarboxylate (99%)], and used as re-
ceived. NMR measurements: Bruker DRX 500 and Bruker ARX
1
NMR). H{11B} NMR (500.13 MHz, [D8]toluene, 25 °C): δ = 0.71
3
3
[t, J(H,H) = 7.4 Hz, 3 H, C(5)CCH3], 0.83 [t, J(H,H) = 7.6 Hz,
2
3
3 H, C(6)CCH3], 1.85 [dq, J(H,H) = 14.8 Hz, J(H,H) = 7.4 Hz,
1 H, C(5)CH(a)], 1.91 [dq, J(H,H) = 15.2 Hz, J(H,H) = 7.6 Hz,
1 H, C(6)CH(a)], 2.03 [dq, J(H,H) = 15.2 Hz, J(H,H) = 7.6 Hz,
2
3
2
3
2
3
1 H, C(6)CH(b)], 2.12 [dq, J(H,H) = 14.8 Hz, J(H,H) = 7.4 Hz,
1 H, C(5)CH(b)], 2.50 [br. m, 1 H, HB for δ(11B) = –9.3 ppm], 2.55
[br. m, 2 H, HB for δ(11B) = –6.3, –12.0 ppm], 2.63 [br. m, 1 H,
HB for δ(11B) = –8.8 ppm], 2.68 [br. m, 2 H, HB for δ(11B) = –7.9,
–8.8 ppm], 2.72 [br. m, 1 H, HB for δ(11B) = –7.9 ppm], 2.83 [br. s,
1 H, HB for δ(11B) = –7.9 ppm], 2.86 [br. s, 1 H, HB for δ(11B) =
–3.3 ppm], 3.00 [br. s, 1 H, HB for δ(11B) = –0.8 ppm] ppm.
11B{1H} NMR (160.5 MHz, [D8]toluene, 25 °C): δ = –12.0 (1 B),
–9.3 (1 B), –8.8 (2 B), –7.9 (3 B), –6.3 (1 B), –3.3 (1 B), –0.8 (1 B),
57.2 (1 B, BCl) ppm. 11B NMR (160.5 MHz, [D8]toluene, 25 °C):
δ = –12.0 [d, 1J(11B,1H) = 194 Hz, 1 B], –9.3 [d, 1J(11B,1H) =
169 Hz, 1 B], –8.8 [d, 1J(11B,1H) = 150 Hz, 2 B], –7.9 [d, 1J(11B,1H)
1
1
250: H, 10B, 11B, 13C, 29Si and 77Se; Varian INOVA 400: H, 11B,
13C and 77Se; chemical shifts are given relative to Me4Si [δ1H
(CHDCl2) = 5.33, (C6D5CD2H) = 2.08 (Ϯ0.01) ppm; δ13C
(CD2Cl2) = 53.8, (C6D5CD3) = 20.4 (Ϯ0.1) ppm], external
BF3·OEt2 [δ11B = 0 (Ϯ0.3) ppm for Ξ(11B) = 32.083971 MHz], ex-
ternal BF3·OEt2 [δ10B
=
0
(Ϯ0.3) ppm for Ξ(10B)
=
10.743657 MHz], neat Me2Se [δ77Se = 0 (Ϯ0.1) ppm for Ξ(77Se) =
19.071523 MHz]. 10B NMR spectra were recorded to observe the
extremely broad 10B NMR signals of diluted samples. In the 11B
NMR spectra, these signals were partially covered by the probe
1
= 145 Hz, 3 B], –6.3 (d, 1 B), –3.3 [d, J(11B,1H) = 150 Hz, 1 B],
head background signal. Assignments of H and 11B NMR signals
1
1
–0.8 [d, J(11B,1H) = 151 Hz, 1 B], 57.2 (s, 1 B, BCl) ppm.
are based on selective 1H{11B selective} heteronuclear decoupling
experiments.[28] Mass spectra (EI, 70 eV): Finnigan MAT 8500 with
7-Bromo-2,3-[1,2-dicarba-closo-dodecaborano(12)]-5,6-diethyl-1,4-
diselena-7-boracyclohept-3-ene (5b): A solution of 2b (0.24 mmol)
in [D8]toluene (0.6 mL) [from 1 (85 mg; 0.24 mmol) and BBr3
(0.4 mL of a 1.0 m solution in hexane, 0.4 mmol)[7]] was cooled to
–50 °C, and hex-3-yne (0.027 mL, 19.5 mg, 0.24 mmol) was added
through a microsyringe. The progress of the reaction was moni-
1
direct inlet (data for 12C, H, 11B, 16O and 80Se). Routinely carried
out elemental analyses of the products as bulk samples did not give
satisfactory and reproducible results. Possible reasons for this are
the formation of boron carbide, the great sensitivity of the com-
pounds (see the formation of 9–12), and the presence of minor
impurities (e.g., 3). Melting points were determined with a Büchi
510 melting point apparatus. All quantum chemical calculations
were carried out by using the Gaussian 09 program package.[29] Op-
timized geometries at the B3LYP/6-311+g(d.p) level of theory[18]
were found to be minima by the absence of imaginary frequencies.
NMR parameters were calculated[21,30] at the same level of theory.
Calculated nuclear magnetic shieldings σ11B and σ77Se were con-
verted into δ values by using δ11B (calcd.) = σ(11B) – σ(11B, B2H6)
1
tored by 11B and H NMR spectroscopy. After 1 h at room temp.,
the mixture contained 5b together with 6b (Ͻ5%, by 77Se NMR).
1H{11B} NMR (250.13 MHz, [D8]toluene, 25 °C): δ = 0.71 [t,
3J(H,H) = 7.5 Hz, 3 H, C(5)CCH3], 0.88 [t, 3J(H,H) = 7.6 Hz, 3
2
3
H, C(6)CCH3], 1.84 [dq, J(H,H) = 15.0 Hz, J(H,H) = 7.5 Hz, 1
2
3
H, C(5)CH(a)], 1.95 [dq, J(H,H) = 14.8 Hz, J(H,H) = 7.6 Hz, 1
H, C(6)CH(a)], 2.11 [m, 2 H, C(6)CH(b), C(5)CH(b)], 2.45–2.80
[br. m, 8 H, HB for δ(11B) = –8.6, –12.7 ppm], 2.83 [br. s, 1 H, HB
10
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Insertion of Alkynes into B–Se Bonds of Diselenaborolanes
for δ(11B) = –3.3 ppm], 2.98 [br. s, 1 H, HB for δ(11B) = –1.2 ppm]
ppm. 11B{1H} NMR (80.25 MHz, [D8]toluene, 25 °C): δ = –12.7 (1
B), –8.6 (7 B), –3.3 (1 B), –1.2 (1 B), 50.3 (1 B, BBr) ppm. 11B
NMR (80.25 MHz, [D8]toluene, 25 °C): δ = –12.7 (d, 1 B), –8.6 (7
B), –3.3 [d, 1J(11B,1H) = 156 Hz, 1 B], –1.2 [d, 1J(11B,1H) = 156 Hz,
1 B], 50.3 (s, 1 B, BBr) ppm.
of 5a [0.24 mmol; [together with 2a (ca. 5%), see above] in [D8]-
toluene (0.6 mL) was cooled to –50 °C, and hex-3-yne (0.03 mL,
21.5 mg, 0.26 mmol) was added through a microsyringe. The pro-
gress of the reaction was monitored by 11B, 1H and 77Se NMR
spectroscopy. After 2 d at room temp., the mixture contained 6a,
6Јa and hex-3-yne. Volatile materials were removed in vacuo (3 h,
8ϫ10–3 Torr). The resulting mixture thus obtained contained 6a
(ca. 70%) and 6Јa (ca. 30%). Transparent single crystals of 6a for
X-ray analysis were grown from [D8]toluene after 3 weeks at
–30 °C; m.p. 100–103 °C. Data for 6a: 1H NMR (399.8 MHz, [D8]-
2,3-[1,2-Dicarba-closo-dodecaborano(12)]-5,6-diethyl-7-iodo-1,4-di-
selena-7-boracyclohept-3-ene 5c): A solution of 2c (0.20 mmol) in
[D8]toluene (0.5 mL) [from 1 (85 mg; 0.20 mmol) and BI3
(0.2 mmol)[7]] was cooled to –50 °C, and hex-3-yne (0.023 mL,
16.8 mg, 0.20 mmol) was added through a microsyringe. The pro-
gress of the reaction was monitored by 11B and 1H NMR spec-
troscopy. After 3 h at room temp., the mixture contained 5c to-
gether with 6c (Ͻ5%, by 77Se NMR). 1H{11B} NMR (250.13 MHz,
[D8]toluene, 25 °C): δ = 0.67 [t, 3J(H,H) = 7.4 Hz, 3 H, C(5)CCH3],
0.90 [t, 3J(H,H) = 7.6 Hz, 3 H, C(6)CCH3], 1.81 [dq, 2J(H,H) =
3
toluene, 25 °C): δ = 0.91 [t, J(H,H) = 7.5 Hz, 6 H, C(5,9)CCH3],
3
2
0.94 [t, J(H,H) = 7.5 Hz, 6 H, C(6,8)CCH3], 1.94 [dq, J(H,H) =
3
2
15.0 Hz, J(H,H) = 7.5 Hz, 2 H, C(6,8)CH(a)], 2.05 [dq, J(H,H)
= 15.0 Hz, 3J(H,H) = 7.5 Hz, 2 H, C(6,8)CH(b)], 2.09 [dq, 2J(H,H)
= 15.0 Hz, 3J(H,H) = 7.5 Hz, 2 H, C(5,9)CH(a)], 2.45 [dq, 2J(H,H)
= 15.0 Hz, 3J(H,H) = 7.5 Hz, 2 H, C(5,9)CH(b)] ppm. Data for
6Јa: 1H NMR (399.8 MHz, [D8]toluene, 25 °C): δ = 0.93 [t, 3J(H,H)
= 7.5 Hz, 6 H, C(5,9)CCH3], 0.94 [t, 3J(H,H) = 7.5 Hz, 6 H, C(6,8)-
CCH3], 2.26 [dq, 2J(H,H) = 15.0 Hz, 3J(H,H) = 7.5 Hz, 2 H,
C(6,8)CH(a)], 2.28 [dq, 2J(H,H) = 15.0 Hz, 3J(H,H) = 7.5 Hz, 2 H,
C(5,9)CH(a)], 2.39 [dq, 2J(H,H) = 15.0 Hz, 3J(H,H) = 7.5 Hz, 2 H,
C(6,8)CH(b)], 2.65 [dq, 2J(H,H) = 15.0 Hz, 3J(H,H) = 7.5 Hz, 2
H, C(5,9)CH(b)] ppm. Data for 6a + 6Јa: 11B{1H} NMR
(160.5 MHz, [D8]toluene, 25 °C): δ = –12.0 to –5.0 (8 B), –1.6 (2
B) for the mixture of 6a and 6Јa (overlapping signals), 42.0 (1 B,
BCl for 6a), 48.5 (1 B, BCl for 6Јa) ppm.
3
2
14.8 Hz, J(H,H) = 7.4 Hz, 1 H, C(5)CH(a)], 1.94 [dq, J(H,H) =
3
15.2 Hz, J(H,H) = 7.6 Hz, 1 H, C(6)CH(a)], 2.11 [m, 2 H, C(6)-
CH(b), C(5)CH(b)], 2.50–2.80 [br. m, 8 H, HB for δ(11B) = –8.6,
–11.5 ppm], 2.80 [br. s, 1 H, HB for δ(11B) = –3.2 ppm], 2.94 [br. s,
1 H, HB for δ(11B) = –1.6 ppm] ppm. 11B{1H} NMR (80.25 MHz,
[D8]toluene, 25 °C): δ = –11.5 (1 B), –8.8 (7 B), –3.2 (1 B), –1.6 (1
B), 34.1 (1 B, BI) ppm. 11B NMR (80.25 MHz, [D8]toluene, 25 °C):
1
δ = –11.5 (d, 1 B), –8.8 (7 B), –3.2 [d, J(11B,1H) = 147 Hz, 1 B],
1
–1.6 [d, J(11B,1H) = 142 Hz, 1 B], 34.1 (s, 1 B, BI) ppm.
2,3-[1,2-Dicarba-closo-dodecaborano(12)]-5,6-diethyl-7-phenyl-1,4-
diselena-7-boracyclohept-3-ene (5d): A solution of 2d (0.28 mmol)
in [D8]toluene (0.6 mL) was cooled to –50 °C, and hex-3-yne
(0.031 mL, 23 mg, 0.28 mmol) was added through a microsyringe.
7-Bromo-2,3-[1,2-dicarba-closo-dodecaborano(12)]-5,6,8,9-tetraeth-
yl-1,4-diselena-7-boracyclohepta-5,8-diene (6b and 6Јb): A solution
of 5b (0.24 mmol; see above) in [D8]toluene (0.6 mL) was cooled to
–50 °C, and hex-3-yne (0.03 mL, 21.7 mg, 0.26 mmol) was added
through a microsyringe. The progress of the reaction was moni-
tored by 11B, 1H and 77Se NMR spectroscopy. After 5 d at room
temp., the mixture contained 6b, 6Јb and hex-3-yne. Volatile materi-
als were removed in vacuo (3 h, 8ϫ10–3 Torr). The resulting mix-
ture thus obtained contained 6b (ca. 90%) and 6Јb (ca. 5–10%)
together with tetraselenide 3 (2–3%). Transparent single crystals of
6b for X-ray analysis were grown from [D8]toluene after 2 weeks at
–30 °C; m.p. 115–120 °C. Data for 6b: 1H{11B} NMR (399.8 MHz,
[D8]toluene, 25 °C): δ = 0.88 [t, 3J(H,H) = 7.4 Hz, 6 H, C(5,9)-
CCH3], 1.01 [t, 3J(H,H) = 7.6 Hz, 6 H, C(6,8)CCH3], 2.03 [m, 6 H,
1
The progress of the reaction was monitored by 11B and H NMR
spectroscopy. After 4 d at room temp., the mixture contained 5d
(ca. 50%) and 2d (ca. 50%) together with hex-3-yne. After 20 h at
50 °C, the mixture contained 5d (ca. 40%) and 2d (ca. 60%) to-
gether with tetraselenide 3, hex-3-yne and (PhBO)3. Data for 5d:
3
1H NMR (500.13 MHz, [D8]toluene, 25 °C): δ = 0.81 [t, J(H,H) =
3
7.5 Hz, 3 H, CH3], 0.85 [t, J(H,H) = 7.5 Hz, 3 H, CH3], 1.98 [m,
2 H, C(5)CH(a), C(6)CH(a)], 2.14, 2.39 [2 dq, 3J(H,H) = 7.5 Hz,
3J(H,H) = 7.5 Hz, 1 H, 1 H, C(5)CH(b), C(6)CH(b)], 7.10 (m, 2
H, Hm from Ph), 7.18 (m, 1 H, Hp from Ph), 7.51 (m, 2 H, Ho from
Ph) ppm. 11B{1H} NMR (160.5 MHz, [D8]toluene, 25 °C): δ = –18
to 0 for the mixture of 5d and 2d (overlapping signals), 56.4 (PhBSe
for 5d), 76.2 (PhBSe for 2d) ppm.
2
3
C(6,8)CH2, C(5,9)CH(a)], 2.42 [dq, J(H,H) = 14.8 Hz, J(H,H) =
7.4 Hz, 2 H, C(5,9)CH(b)], 2.61 [br. m, 6 H, HB for δ(11B) =
–9.4 ppm], 2.80 [br. m, 2 H, HB for δ(11B) = –8.0 ppm], 2.94 [br.
m, 2 H, HB for δ(1 1B) = –1.6 ppm] ppm. 11 B{1H} NMR
(160.5 MHz, [D8]toluene, 25 °C): δ = –9.4 (6 B), –8.0 (2 B), –1.5 (2
7-Chloro-2,3-[1,2-dicarba-closo-dodecaborano(12)]-6-ethyl-5-phenyl-
1,4-diselena-7-boracyclohept-3-ene (7a): A solution of 2a
(0.23 mmol) in [D8]toluene (0.5 mL) [from 1 (85 mg; 0.24 mmol)
and BCl3 (0.5 mL of a 1.0 m solution in toluene, 0.5 mmol)[7]] was
cooled to –50 °C, and 1-phenylbut-1-yne (0.033 mL, 29.9 mg,
0.23 mmol) was added through a microsyringe. The progress of the
1
B), 28.0 (1 B, BBr) ppm. H and 11B NMR signals for 6Јb could
not be assigned with certainty owing to low concentration and se-
vere overlap with signals for 6b.
2,3-[1,2-Dicarba-closo-dodecaborano(12)]-5,6,8,9-tetraethyl-7-iodo-
1,4-diselena-7-boracyclohepta-5,8-diene (6c): A solution of 5c
(0.20 mmol; see above) in [D8]toluene (0.6 mL) was cooled to
–50 °C, and hex-3-yne (0.025 mL, 18 mg, 0.22 mmol) was added
through a microsyringe. The progress of the reaction was moni-
tored by 11B, 1H and 77Se NMR spectroscopy. After 5 d at room
temp., volatile materials were removed in vacuo (3 h, 8ϫ10–3 Torr).
The resulting mixture thus obtained contained 6c (ca. 90%) to-
1
reaction was monitored by 11B and H NMR spectroscopy. After
1 h at room temp., the mixture contained 7a together with 8a and
2a (ca. 5%, by 77Se NMR). 1H NMR (500.13 MHz, [D8]toluene,
25 °C): δ = 0.86 [t, 3J(H,H) = 7.6 Hz, 3 H, CH3], 2.21 [dq, 2J(H,H)
3
2
= 15.2 Hz, J(H,H) = 7.6 Hz, 1 H, C(6)CH(a)], 2.29 [dq, J(H,H)
= 15.2 Hz, 3J(H,H) = 7.6 Hz, 1 H, C(6)CH(b)], 6.95–7.00 (m, 5 H,
Ph) ppm. 11B{1H} NMR (160.5 MHz, [D8]toluene, 25 °C): δ =
–11.7 (1 B), –8.5 (7 B), –3.0 (1 B), –1.2 (1 B), 52.3 (1 B, BCl) ppm.
11B NMR (160.5 MHz, [D8]toluene, 25 °C): δ = –11.7 [d, 1J(11B,1H)
1
gether with several unidentified side-products (ca. 10%). H{11B}
NMR (399.8 MHz, [D8]toluene, 25 °C): δ = 0.82 [t, 3J(H,H) =
1
= 164 Hz, 1 B], –8.5 (7 B), –3.0 [d, J(11B,1H) = 155 Hz, 1 B], –1.2
3
7.4 Hz, 6 H, C(5,9)CCH3], 1.02 [t, J(H,H) = 7.6 Hz, 6 H, C(6,8)-
1
[d, J(11B,1H) = 150 Hz, 1 B], 52.3 (s, 1 B, BCl) ppm.
2
CCH3], 2.02 [m, 6 H, C(6,8)CH2, C(5,9)CH(a)], 2.36 [dq, J(H,H)
3
7-Chloro-2,3-[1,2-dicarba-closo-dodecaborano(12)]-5,6,8,9-tetraeth-
yl-1,4-diselena-7-boracyclohepta-5,8-diene (6a and 6Јa): A solution
= 14.8 Hz, J(H,H) = 7.4 Hz, 2 H, C(5,9)CH(b)], 2.45–2.80 (m, 8
H, HB), 2.94 [br. m, 2 H, HB for δ(11B) = –1.6 ppm] ppm. 11B{1H}
Eur. J. Inorg. Chem. 0000, 0–0
© 0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
11

Job/Unit: I20471
/KAP1
Date: 19-07-12 10:54:50
Pages: 15
B. Wrackmeyer, E. V. Klimkina, W. Milius
FULL PAPER
NMR (160.5 MHz, [D8]toluene, 25 °C): δ = –12.0 to –5.0 (8 B),
1
3 d at room temp.; m.p. 210–213 °C. H{11B} NMR (500.13 MHz,
CD2Cl2, 25 °C): δ = 0.98 [t, 3J(H,H) = 7.6 Hz, 12 H, CH3], 1.56
(br. m, 4 H, HB), 1.90 (br. m, 6 H, HB), 2.22 (br. m, 6 H, HB),
2.38 [dq, 2J(H,H) = 14.5 Hz, 3J(H,H) = 7.6 Hz, 4 H, C(6,8)CH(a)],
2.46 (br. m, 4 H, HB), 2.70 [dq, 2J(H,H) = 14.5 Hz, 3J(H,H) =
7.6 Hz, 4 H, C(6,8)H(b)], 7.32–7.45 (m, 20 H, Ph) ppm. 11B{1H}
NMR (160.5 MHz, CD2Cl2, 25 °C): δ = –10.6 (6 B), –8.5 (4 B),
–7.4 (4 B), –2.2 (6 B), 28.0 (v. br., 2 B, BOB) ppm. 10B{1H} NMR
(53.7 MHz, CD2Cl2, 25 °C): δ = –10.6 (6 B), –8.7 (8 B), –2.4 (6 B),
28.0 (br., 2 B, BOB) ppm.
–1.6 (2 B), 9.0 (1 B, BI) ppm.
7-Chloro-2,3-[1,2-dicarba-closo-dodecaborano(12)]-6,8-diethyl-5,9-
diphenyl-1,4-diselena-7-boracyclohepta-5,8-diene (8a and 8Јa): A
solution of 7a (0.23 mmol) [together with 8a and 2a (ca. 5%), see
above] in [D8]toluene (0.6 mL) was cooled to –50 °C, and 1-phen-
ylbut-1-yne (0.035 mL, 32.0 mg, 0.25 mmol) was added through a
microsyringe. The progress of the reaction was monitored by 11B,
1H and 77Se NMR spectroscopy. After 3 d at room temp., the mix-
ture contained 8a, 8Јa and 1-phenylbut-1-yne. Volatile materials
were removed in vacuo (5 h, 8 ϫ10–3 Torr). The resulting mixture
thus obtained contained 8 (ca. 90%) and 8Јa (ca. 5–10%). Data for
2,3-[1,2-Dicarba-closo-dodecaborano(12)]-5,6,8,9-tetraethyl-7-hy-
droxy-1,4-diselena-7-boracyclohepta-5,8-diene (11): Compound 9 is
moisture-sensitive and decomposed in CD2Cl2 (1 d) at room temp.
to form 11; m.p. 190–195 °C. 1H{11B} NMR (500.13 MHz,
1
8a: H{11B} NMR (500.13 MHz, [D8]toluene, 25 °C): δ = 0.88 [t,
3J(H,H) = 7.6 Hz, 6 H, CH3], 2.06 [dq, 2J(H,H) = 15.2 Hz, 3J(H,H)
= 7.6 Hz, 2 H, C(6,8)CH(a)], 2.49 [dq, 2J(H,H) = 15.2 Hz, 3J(H,H)
= 7.6 Hz, 2 H, C(6,8)CH(b)], 2.89 (m, 10 H, BH), 6.98 (m, 2 H,
Hp), 7.07 (m, 4 H, Hm), 7.16 (m, 4 H, Ho) ppm. 11B{1H} NMR
(160.5 MHz, [D8]toluene, 25 °C): δ = –9.8 (4 B), –8.0 (4 B), –1.4
(2 B), 28.0 (v. br., 1 B, BCl) ppm. Data for 8Јa: 1H{11B} NMR
3
CD2Cl2, 25 °C): δ = 1.06 [t, J(H,H) = 7.5 Hz, 12 H, CH3], 1.07 [t,
3J(H,H) = 7.4 Hz, 12 H, CH3], 1.97 [br. m, 2 H, HB for δ(11B) =
–10.5 ppm], 2.07 [br. m, 2 H, HB for δ(11B) = –8.6 ppm], 2.21 [dq,
2J(H,H) = 15.0 Hz, 3J(H,H) = 7.5 Hz, 4 H, CH from CH2], 2.27
[dq, 2J(H,H) = 14.8 Hz, 3J(H,H) = 7.4 Hz, 4 H, CH from CH2],
2.40 [dq, 2J(H,H) = 15.0 Hz, 3J(H,H) = 7.5 Hz, 4 H, CH from
CH2], 2.42 [br. m, 6 H, HB for δ(11B) = –2.3 ppm], 2.51 [br. m, 4
H, HB for δ(11B) = –10.5 ppm], 2.69 [br. m, 6 H, HB for δ(11B) =
–6.3 ppm], 2.85 [dq, 2J(H,H) = 15.0 Hz, 3J(H,H) = 7.5 Hz, 4 H,
CH from CH2], 5.66 (s, 1 H, BOH) ppm. 11 B{1H} NMR
(160.5 MHz, CD2Cl2, 25 °C): δ = –10.5 (6 B), –8.7 (2 B), –6.3 (6
B), –2.3 (6 B), 41.8 (br., 2 B, BOB) ppm. MS (EI, 70 eV): calcd.
for C14H31B11Se2O 492; m/z (%) = 493 (30) [MH]+, 463 (50) [M –
EtH]+, 329 (70).
3
(500.13 MHz, [D8]toluene, 25 °C): δ = 0.87 [t, J(H,H) = 7.6 Hz, 6
H, CH3], 2.19 [dq, 2J(H,H) = 15.2 Hz, 3J(H,H) = 7.6 Hz, 2 H,
C(6,8)CH(a)], 2.60 [dq, 2J(H,H) = 15.2 Hz, 3J(H,H) = 7.6 Hz, 2 H,
C(6,8)CH(b)], 2.89 (m, 10 H, BH), 7.01 (m, 2 H, Hp), 7.11 (m, 4
H, Hm), 7.38 (m, 4 H, Ho) ppm.
7,7Ј-Oxybis{2,3-[1,2-dicarba-closo-dodecaborano(12)]-5,6,8,9-tetra-
ethyl-1,4-diselena-7-boracyclohepta-5,8-diene} (9): The mixture con-
taining 6a and 6Јa slowly formed the anhydride 9 on standing in
toluene. Transparent single crystals of 9 for X-ray analysis were
grown from CD2Cl2 after 1 d at room temp.; m.p. 210–213 °C. MS
(EI, 70 eV): calcd. for C28H60B21Se4O 956; m/z (%) = 956 (10)
[M]+, 927 (5) [M – Et]+, 876 [M – SeH]+.
2,3-[1,2-Dicarba-closo-dodecaborano(12)]-6,8-diethyl-7-hydroxy-5,9-
diphenyl-1,4-diselena-7-boracyclohepta-5,8-diene (12): Compound
10 is moisture-sensitive and decomposed slowly (7 d) in CD2Cl2 at
1
7,7Ј-Oxybis{2,3-[1,2-dicarba-closo-dodecaborano(12)]-6,8-diethyl-
5,9-diphenyl-1,4-diselena-7-boracyclohepta-5,8-diene} (10): The mix-
ture containing 8a and 8Јa slowly formed the anhydride 10 on
standing at –30 °C in [D8]toluene. Insoluble materials were sepa-
rated by centrifugation and redissolved in CD2Cl2. Transparent sin-
room temp. to form 12; m.p. 170–172 °C. H NMR (500.13 MHz,
CD2Cl2, 25 °C): δ = 0.93 [t, 3J(H,H) = 7.5 Hz, 6 H, CH3], 2.32 [dq,
2J(H,H) = 14.3 Hz, 3J(H,H) = 7.5 Hz, 2 H, C(6,8)CH(a)], 2.58 [dq,
2J(H,H) = 14.3 Hz, J(H,H) = 7.5 Hz, 2 H, C(6,8)H(b)], 6.19 (s, 1
3
H, BOH), 7.32–7.45 (m, 20 H, Ph) ppm. 10B{1H} NMR
gle crystals of 10 for X-ray analysis were grown from CD2Cl2 after (53.7 MHz, CD2Cl2, 25 °C): δ = –10.6 (6 B), –8.7 (8 B), –2.3 (6 B),
Table 5. Crystallographic data for the ortho-carborane derivatives 6a, 6b, 9 and 10.
6a
6b
9
10
Empirical formula
Crystal
Dimensions [mm]
T [K]
C14H30B11ClSe2
colourless prism
0.22ϫ0.18ϫ0.16
133(2)
C14H30B11BrSe2
colourless prism
0.24ϫ0.19ϫ0.18
133(2)
C28H60B22OSe4
colourless block
0.30ϫ0.23ϫ0.20
133(2)
C44H60B21OSe4·0.2CD2Cl2
colourless block
0.30ϫ0.26ϫ0.24
293(2)
Crystal system
Space group
monoclinic
P21/n
monoclinic
P21/n
monoclinic
Cc
tetragonal
P4n2
¯
Lattice parameters
a [pm]
b [pm]
c [pm]
β [°]
707.66(14)
1789.2(4)
1821.1(4)
100.49(3)
4
1053.8(2)
1984.7(4)
1128.4(2)
100.54(3)
4
1201.9(2)
1815.6(4)
2137.3(4)
100.73(3)
4
2368.4(3)
1114.6(2)
Z
8
μ [mm–1]
3.379
4.909
3.228
2.466
Diffractometer
θ range [°]
STOE IPDS II, Mo-Kα, λ = 71.073 pm, graphite monochromator
1.61–25.69
8071
2.05–25.70
27639
1.94–25.70
29173
1.72–29.44
118921
5035
Reflections collected
Independent reflections [IՆ2σ(I)]
Absorption correction
Max./min. transmission
Refined parameters
wR2/R1 [IՆ2σ(I)]
Flack parameter
3230
3294
8091
none[a]
none[a]
numerical
0.9371/0.7414
500
none[a]
253
253
329
0.1588/0.0726
0.0925/0.0546
0.0606/0.0280
–0.001(7)
0.529/–0.317
0.1248/0.0497
0.000(17)
0.505/–0.447
Max./min. residual electron density [10–6 epm–3] 1.576/–0.807
[a] Absorption corrections did not improve the parameter set.
0.758/–0.574
12
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Eur. J. Inorg. Chem. 0000, 0–0

Job/Unit: I20471
/KAP1
Date: 19-07-12 10:54:50
Pages: 15
Insertion of Alkynes into B–Se Bonds of Diselenaborolanes
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2 B, BOB) ppm. MS (EI, 70 eV): calcd. for
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Date: 19-07-12 10:54:50
Pages: 15
B. Wrackmeyer, E. V. Klimkina, W. Milius
FULL PAPER
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Received: May 7, 2012
Published Online: ᭿
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Eur. J. Inorg. Chem. 0000, 0–0

Job/Unit: I20471
/KAP1
Date: 19-07-12 10:54:50
Pages: 15
Insertion of Alkynes into B–Se Bonds of Diselenaborolanes
Alkyne Insertion
B. Wrackmeyer,* E. V. Klimkina,
W. Milius ........................................ 1–15
Selective Consecutive Insertion of Alkynes
into the B–Se Bonds of 1,3,2-Diselenabor-
olane Derivatives: Synthesis and Molecular
Structures of Nine-Membered Rings
Keywords: Carboranes / Selenium / Alk-
ynes / Heterocycles / Insertion / NMR spec-
troscopy / Density functional calculations
After two insertions of non-terminal alk-
ynes into the B–Se bonds of 2-halogeno-
1,3,2-diselenaborolanes novel nine-mem-
bered rings are formed. The reactions were
shown to proceed stepwise and also selec-
tively.
Eur. J. Inorg. Chem. 0000, 0–0
© 0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
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