Electrophile-induced nucleophilic substitution of the nido- dicarbaundecaborate anion nido-7,8-c2b9h12 by conjugated heterodienes

Article abstract of DOI:10.1002/chem.201303762

Substitution of the dicarbaundecaborate anion nido-7,8-C2B9H12 (1) by precise hydride abstraction followed by nucleophilic attack usually leads to symmetric products 10-R-nido-7,8-C2B9H11. However, thioacetamide (MeC(S)NH2) as nucleophile and acetone/AlCl3 as hydride abstractor gave asymmetric 9-[MeC(NHiPr)S]-nido-7,8-C2B9H11 (2), whereas N,N-dimethylthioacetamide (MeC(S)NMe2) gave the expected symmetric 10-[MeC(NMe2)S]-nido-7,8-C2B9H11 (4). For the formation of 2, acetone and thioacetamide are assumed to give the intermediate MeC(S)N(CMe2) (3), which then attacks 1 with formation of 2. Similarly, reaction of acetyliminium chloride [MeC(O)NH(CPh2)]Cl (5) with 1 in THF gave a mixture of 9-and 10-substituted [MeC(NHCHPh2)O]-nido-7,8-C2B9H11 (6 and 7, respectively). These reactions are the first examples in which compounds (here heterodienes) that unite the functionalities of both hydride acceptor and nucleophilic site react with 1 in a bimolecular fashion. Furthermore, the analogous reaction of 1 and 5 (in an equilibrium mixture with acetyl chloride and benzophenone imine) in MeCN afforded 10-[MeC(NCPh2)NH]-nido-7,8-C2B9H11 (8) and MeC(O)NHCHPh2 (9).

Full text of DOI:10.1002/chem.201303762

DOI: 10.1002/chem.201303762
Full Paper
&
Boron Cluster Chemistry
Electrophile-Induced Nucleophilic Substitution of the
ꢀ
nido-Dicarbaundecaborate Anion nido-7,8-C B H by
2
9
12
Conjugated Heterodienes
[
a]
Renꢀ Frank, Anup Kumar Adhikari, Henry Auer, and Evamarie Hey-Hawkins*
Abstract: Substitution of the dicarbaundecaborate anion
chloride [MeC(O)NH(CPh )]Cl (5) with 1 in THF gave a mixture
2
ꢀ
nido-7,8-C B H (1) by precise hydride abstraction followed
of 9- and 10-substituted [MeC(NHCHPh )O]-nido-7,8-C B H
11
2
9
12
2
2
9
by nucleophilic attack usually leads to symmetric products
0-R-nido-7,8-C B H . However, thioacetamide (MeC(S)NH )
(6 and 7, respectively). These reactions are the first examples
in which compounds (here heterodienes) that unite the
functionalities of both hydride acceptor and nucleophilic site
react with 1 in a bimolecular fashion. Furthermore, the anal-
ogous reaction of 1 and 5 (in an equilibrium mixture with
acetyl chloride and benzophenone imine) in MeCN afforded
10-[MeC(NCPh )NH]-nido-7,8-C B H (8) and MeC(O)NHCHPh2
1
2
9
11
2
as nucleophile and acetone/AlCl as hydride abstractor gave
3
asymmetric 9-[MeC(NHiPr)S]-nido-7,8-C B H (2), whereas
2
9
11
N,N-dimethylthioacetamide (MeC(S)NMe ) gave the expected
2
symmetric 10-[MeC(NMe )S]-nido-7,8-C B H (4). For the for-
2
2
9
11
mation of 2, acetone and thioacetamide are assumed to
2
2
9
11
give the intermediate MeC(S)N(CMe ) (3), which then attacks
(9).
2
1
with formation of 2. Similarly, reaction of acetyliminium
Introduction
N-halosuccinimides, organophosphorus or organosulfur hal-
ides, attacks the most electron rich boron positions B9 (or B11)
with formation of asymmetrically substituted products, 9-R-
7
,8-Dicarba-nido-dodecahydroundecaborate(1-)
(nido-7,8-
ꢀ
[1,2]
ꢀ
C B H , 1)
has become the most studied dicarbaundeca-
nido-7,8-C B H . The mechanism is considered to be similar
2
9
12
2
9
11
[3]
borate anion due to its various modes of reactivity at the pen-
tagonal C2B3 plane, which is capped by an extra hydrogen
to electrophilic substitutions in arenes, and many examples
[5]
[6]
have been reported including halogenation, acylation, sily-
ꢀ
[7]
[8]
[9]
[10]
atom (Scheme 1). Substitution reactions with nido-7,8-C B H
12
lation, phosphanylation, alkylation, sulfonio-alkylation,
2
9
[11]
[12]
sulfenylation,
and formation of 9-Me S-nido-7,8-C B H .
2 2 9 11
Oxidative substitutions employ mild oxidants, for example,
[13]
[14]
[15]
FeCl3, CuSO4, or HgCl2, and formally oxidize the hydride
of a BꢀH moiety with concomitant substitution by a donor
molecule (e.g., MeCN, THF) to form a charge-compensated
zwitterion. The mechanism is more complex and is believed to
ꢀ
involve oxidative closure of nido-7,8-C B H
12
and re-opening
2
9
[16]
of the resulting closo species with cluster rearrangement.
A
third type of mechanism is based on a precise hydride abstrac-
tion followed by attack of a donor molecule (Scheme 1). Typi-
cal acceptors for hydrides in BꢀH moieties are Lewis acids, in-
Scheme 1. Precise hydride abstraction in 1 leads to symmetric derivatives. L
denotes a suitable Lewis base.
+
cluding BF ·OEt , AlCl , and H . Due to the cooperative action
3
2
3
of electrophilic Lewis acids and nucleophilic donors this type
of reaction is termed electrophile-induced nucleophilic substi-
[
3]
ꢀ
mostly lead to s-boron-bound substituents, which occupy one
of the three exo positions at B9 (or the equivalent B11) or
tution (EINS). For nido-7,8-C B H , precise abstraction of hy-
2 9
12
dride in the position B10 with the attack of Lewis base L has
been demonstrated in a few cases. Thus, acidic aqueous acetal-
dehyde is reported to give 10-L-nido-7,8-C B H in the pres-
[
2]
B10. Currently, three types of mechanism for substitution re-
ꢀ
[3,4]
actions with nido-7,8-C B H
have been recognized.
In
2
9
12
2
9
11
[
17,18]
electrophilic substitutions, a suitable reagent, for example,
ence of a Lewis base L (L=R O, R S)
or the anion 10-HO-
2
2
ꢀ
[17]
nido-7,8-C B H in the absence of L. More recently, water-
2
9
11
[
a] Dr. R. Frank, A. K. Adhikari, H. Auer, Prof. Dr. E. Hey-Hawkins
Institut fꢀr Anorganische Chemie, Universitꢁt Leipzig
Johannisallee 29, 04103 Leipzig (Germany)
Fax: (+49)341-9739319
free alternatives employing acetone/AlCl and tritylium tetra-
3
fluoroborate as hydride acceptors have been reported, and
have expanded the scope to 10-MeCN-nido-7,8-C B H and
2
9
11
[19]
E-mail: hey@uni-leipzig.de
10-Ph S-nido-7,8-C B H , respectively.
The introduction of
2
2
9
11
Chem. Eur. J. 2014, 20, 1440 – 1446
1440
ꢁ 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Full Paper
2
9
12ꢀ
substituents into nido-7,8-C B H
has been subject of
nism was given by an experiment in which thioacetamide was
[
20]
a recent review. The reported examples of EINS-type reac-
tions in 1 employ hydride acceptors and Lewis bases as sepa-
rate compounds and have led to symmetric substitution at po-
sition B10. Herein, we report the first examples of reactions of
replaced by N,N-dimethylthioacetamide (MeC(S)NMe ), which
2
gave the symmetric B10-substituted product 4, as expected for
common EINS-type reactions (Scheme 2). The asymmetric
isomer was not observed in this case. The yields of com-
pounds 2 (30%) and 4 (25%) are similar. The reactions were
carried out in acetone as solvent and compete with the forma-
1
with heterodienes which unite the inherent function of both
hydride acceptor and Lewis base and result in asymmetric (B9)
or symmetric (B10) substitution.
ꢀ
tion of the anion 10-HO-nido-7,8-C B H ,
11
[19]
which was also
2
9
1
1
1
observed in the reaction mixture by B{ H} NMR spectroscopic
studies. In addition to unambiguous characterization by NMR
spectroscopy, the constitution of compounds 2 and 4 was con-
firmed by X-ray crystallography (Figure 1 and 2, Table 1). Single
crystals of compounds 2 and 4 could be obtained from
Results and Discussion
As reported recently, 1 undergoes symmetric (B10) EINS-type
reactions in the presence of Lewis bases facilitated by acetone,
Et O/n-hexane solution by slow solvent evaporation.
2
[
19]
which is activated by AlCl3. However, when 1 was treated
Further investigations with compounds of similar reactivity
to the suggested intermediate 3 were performed. Thus, acetyl
chloride was treated with benzophenone imine to give
with thioacetamide (MeC(S)NH ) in acetone in the presence of
2
AlCl , surprisingly the exclusive formation of asymmetric
3
B9-substituted compound 2 was observed (Scheme 2). As the
N-acetyl benzophenone iminium chloride [MeC(O)NH(CPh )]Cl
2
Figure 1. Molecular structure of 2; only the 1 enantiomer is shown. 2 crystal-
lized with four Et
Thermal ellipsoids are drawn at 50% probability. Selected bond lengths
pm) and angles (deg): C7ꢀC8 154.8(4), C8ꢀB9 159.9(5), B9ꢀB10 179.5(5),
B10ꢀB11 185.8(5), B11ꢀC7 163.4(5), B9ꢀS1 188.4(3), S1ꢀC1 171.8(3), C1ꢀC2
48.8(4), C1ꢀN1 130.4(4), B10-S1-C1 105.9(1), C2-C1-N1 118.7(3), S1-C1-N1
19.0(2), S1-C1-N2 122.4(2).
2
O molecules per unit cell, which are omitted for clarity.
(
1
1
Scheme 2. a) MeC(S)NH
2
(5 equiv), AlCl
3
(3 equiv), acetone, reflux, 3 h, 30%;
b) MeC(S)NMe (5 equiv), AlCl
2
3
(3 equiv), acetone, 458C, overnight, 25%.
isopropyl group in 2 can only originate from acetone, the ini-
tial formation of intermediate MeC(S)N(CMe ) (3) from thioace-
2
tamide and acetone is assumed. In a bimolecular fashion, the
imine moiety in compound 3 abstracts a hydride from B10 in
1
with concomitant nucleophilic attack of sulfur at position B9
forming the asymmetric derivative 2. This reaction is the first
example in which hydride acceptor and nucleophile are inher-
ent in a single compound.
However, despite several attempts, we have not been able
to detect the proposed intermediate 3, neither in reaction mix-
tures with 1 nor in its absence with sole mixtures of acetone,
Figure 2. Molecular structure of 4. Thermal ellipsoids are drawn at 50%
probability. Selected bond lengths (pm) and angles (deg): C7ꢀC8 155.4(2),
C8ꢀB9 160.3(2), B9ꢀB10 108.2(2), B10ꢀB11 185.1(2), B11ꢀC7 161.9(2), B10ꢀS1
thioacetamide and AlCl . Thus, intermediate 3 is assumed to
3
react immediately when formed in low concentrations. In the
1
88.1(2), S1ꢀC1 171.4(1), C1ꢀC2 149.2(2), C1ꢀN1 130.9(2), C1-S1-B10 108.3(1),
absence of AlCl , compound 2 is not formed and the starting
3
C1-N1-C4 121.6(1), C1-N1-C3 122.0(1), C4-N1-C3 116.4(1), N1-C1-C2 120.6(1),
N1-C1-S1 117.3(1), C2-C1-S1 122.2(1).
material is recovered instead. Further support for the mecha-
Chem. Eur. J. 2014, 20, 1440 – 1446
www.chemeurj.org
1441
ꢁ 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Full Paper
Table 1. Crystallographic data, details of data collection and structure re-
finement parameters for compounds 2, 4, 6 and 8
2
4
6
8
Mol. formula
C
11
H
32
B
9
NOS
C
6
H
20
B
9
NS
C
17
H
26
B
9
NO
C
17 25 9 2
H B N
ꢀ
1
M
r
(gmol
)
323.73
monoclinic monoclinic monoclinic triclinic
P2 /n P2 /n P2 /c
P1¯
1034.40(3) 1197.90(4) 964.39(5)
976.80(2) 913.80(3) 1026.86(6)
1373.60(3) 1906.70(6) 1082.63(4)
90 90 76.098(4)
106.709(3) 105.358(3) 80.825(4)
235.58
357.68
354.68
Crystal system
Space group
a (pm)
b (pm)
c (pm)
1
1
1
1273.40(4)
1260.13(4)
1280.03(4)
90
a (8)
b (8)
90.142(3)
90
2052.6(1)
4
g (8)
90
90
74.661(5)
998.36(9)
2
3
V (ꢂ )
1329.26(6) 2012.6(1)
4
1.177
Figure 3. Molecular structure of 6, only the s enantiomer is shown. Thermal
ellipsoids are drawn at the 50% level of probability. Selected bond lengths
Z
1
4
ꢀ3
(gcm
)
1.408
1.180
1.180
(
1
pm) and bond angles (deg): C1ꢀC2 154.7(3), C2ꢀB9 157.9(3), B9ꢀB10
q range (8)
No. total reflns
No. unique reflns
3.19–25.35 2.19–26.37 2.84–26.37 3.09–26.37
78.5(3), B10ꢀB11 183.7(3), B11ꢀC1 163.5(3), B9ꢀO1 147.9(2), O1ꢀC3 128.3(2),
15275
3757
10144
2714
11937
4079
6795
4066
C3ꢀC4 148.1(2), C3ꢀN1 130.5(2), C3-O1-B9 126.7(1), C3-N1-C5 123.3(2),
O1-C3-N1 116.2(2), O1-C3-C4 122.8(2), N1-C3-C4 121.0(2).
Restraints/parameters 16/303
0/223
0.0277
0.0404
0.0891
1.061
0/308
0.0366
0.0746
0.1324
1.037
0/353
0.0139
0.0472
0.1013
1.020
R
R
int
0.0232
0.0883
0.1853
1.034
1
(all reflections)
(all reflections)
Goodness of fit
Crystals of compound 6 suitable for X-ray crystallography
wR
2
could be obtained from Et O/n-hexane solution by slow sol-
2
vent evaporation (Figure 3, Table 1).
When the reaction of 1 with 5 (in equilibrium) was per-
formed in acetonitrile instead of THF, products 8 and 9 were
obtained in a ratio of approximately 1:1 (Scheme 4). Apparent-
Scheme 3. a) MeC(O)Cl (2 equiv), Ph
7% for 6, 23% for 7.
2
C(NH) (2 equiv), THF, reflux, overnight,
4
Scheme 4. a) MeC(O)Cl (2 equiv), Ph
night, 69% for 8, 67% for 9.
2
C(NH) (2 equiv), acetonitrile, reflux, over-
(
5) in an equilibrium reaction without further isolation
Scheme 3). The reaction of 5 with dicarbaundecaborate
(
ly, the cation in 5 abstracts a hydride from B10 with formation
of both 9 and the acetonitrile adduct 10-MeCN-nido-7,8-
C B H (10). Compound 8 is then formed from the reaction of
10 with benzophenone imine present in the equilibrium mix-
ture. This mechanistic view is corroborated by the fact that the
anion 1 in THF led to a mixture of 6 and 7, which could be
separated by column chromatography. Again, their formation
can be explained by hydride transfer from B10 to the conjugat-
ed system in 5 with concomitant attack of the oxygen atom in
the cation of 5. However, the occurrence of the symmetric
product 7 is surprising, as symmetric substitution was not ob-
served in the reaction with 3, but the ratio of 6:7 (ca. 2:1)
shows the asymmetric substitution to be favored.
2
9
11
isolated compound 10 (obtained from 1 and acetone/AlCl in
3
[19]
acetonitrile) also gave 8 when treated with benzophenone
imine under comparable conditions. The formation of the ace-
tonitrile adduct 10 as an intermediate is surprising, because
the same reaction in THF did not give the respective THF
Chem. Eur. J. 2014, 20, 1440 – 1446
www.chemeurj.org
1442
ꢁ 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Full Paper
[
19]
adduct, 10-[cyclo-(CH ) O]-nido-7,8-C B H . The formation of
the highest shifts observed for derivatives of 1 and can be
traced back to strong electron withdrawal of the substituent. A
similar situation is observed for B10 in compound 7.
2
4
2
9
11
1
0 is assumed to be due to the better donor properties of the
nitrogen atom in MeCN compared to the carbonyl oxygen in
the cation of 5. Crystals suitable for X-ray crystallography could
be obtained from a solution of compound 8 in Et O/n-hexane
2
by slow solvent evaporation (Figure 4, Table 1).
Conclusion
Substitution of the dicarbaundecaborate anion nido-7,8-
ꢀ
C B H
12
(1) with precise hydride abstraction led to the selec-
2
9
tive formation of symmetric products 10-R-nido-7,8-C B H , for
2
9
11
example, 10-[cyclo-(CH ) O]-nido-7,8-C B H , 10-[cyclo-(CH ) S]-
2
4
2
9
11
2 4
nido-7,8-C B H or 10-CH CN-nido-7,8-C B H . The reactions
2
9
11
3
2
9
11
follow EINS-type mechanisms with hydride acceptor and nucle-
ophile as separate compounds. However, heterodienes in
which the hydride-accepting moiety and nucleophilic site are
combined in a single molecule react with 1 in a bifunctional
fashion and shift the pronounced selectivity for the formation
of symmetric B10-substituted products in favor of asymmetric
B9-substituted derivatives. Thus, thioacetamide (MeC(S)NH2)
formed the heterodiene MeC(S)N(CMe ) (3) with acetone in
2
situ, which then reacted with 1 to form asymmetric 9-[MeC-
(
NHiPr)S]-nido-7,8-C B H (2). Support for the mechanism was
2 9 11
provided
by
employing
N,N-dimethylthioacetamide
(
MeC(S)NMe ), which is unable to form an imine, to give the
2
Figure 4. Molecular structure of 8. The thermal ellipsoids are drawn at the
5
1
1
1
0% level of probability. Selected bond lengths (pm): C1ꢀC2 155.8(2), C2ꢀB9
60.8(2), B9ꢀB10 184.3(2), B10ꢀB11 183.2(2), B11ꢀC1 160.3(2), B10ꢀN1
52.2(2), N1ꢀC3 129.4(2), C3ꢀC4 148.9(2), C3ꢀN2 136.0(2), C3-N1-B10
28.1(1), C5-N2-C3 126.2(1), N1-C3-N2 119.2(1), N1-C3-C4 122.0(1), N2-C3-C4
expected symmetric product, 10-[MeC(NMe )S]-nido-7,8-C B H
2 2 9 11
(
(
4). Analogously, acetyliminium chloride [MeC(O)NH(CPh )]Cl
5) formed in situ from acetyl chloride and benzophenone
2
imine gave 9- and 10-substituted [MeC(NHCHPh )O]-nido-7,8-
118.3(1).
2
C B H (6 and 7, respectively) with 1 in THF. The influence of
2
9
11
the solvent is apparent from the reaction of 1 with iminium
1
1
1
The chemical shifts in the B{ H} NMR spectra of the charge-
salt 5 in MeCN instead of THF. In this case, 10-[MeC(NCPh )NH]-
2
ꢀ
compensated derivatives of 7,8-nido-C B H 2, 4 and 6–8 are
nido-7,8-C B H (8) and MeC(O)NHCHPh2 (9) are obtained,
2
9
12
2
9
11
summarized in a stick-diagram representation (Figure 5). The
whereas 9 results from reduction of the iminium cation
MeC(O)NH(CPh2) by hydride acceptance and 8 from reaction
+
substitution pattern (asymmetric for 2 and 6; symmetric for 4,
11
1
7
and 8) is obvious from the respective B{ H} NMR spectra.
of 10-MeCN-nido-7,8-C B H (10) with benzophenone imine.
2
9
11
Compound 7 shows a coincidence of the signals for B2, B3,
The formation of 10 as an intermediate is due to the better
electron-donating ability of the nitrogen atom in MeCN com-
pared to the carbonyl oxygen atom in the cation of 5.
and B4, which does not originate from the molecular symme-
11
try. The chemical shift of B9 in 6 (d( B)=7.1 ppm) is among
11
1
Figure 5. B{ H} NMR stick diagram of the charge-compensated products 2, 4, and 6–8.
Chem. Eur. J. 2014, 20, 1440 – 1446 www.chemeurj.org
1443
ꢁ 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Full Paper
3
7.6 (m, cage-CH), 50.7 (CHCH ), 53.5 (m, cage-CH), 197.2 (CH C-
Experimental Section
3
3
(
NHiPr)S); IR: 3330 (s, n(NꢀH)), 3038 (w, n(cage-CꢀH)), 2969 (w,
The anion 1 was synthesized as its tetramethylammonium salt,
n(CꢀH)), 2596 (s), 2558 (s), 2520 (s, all three n(BꢀH)), 1676 (s, n(C=
[1]
NMe (7,8-nido-C B H ). All manipulations were carried out in ni-
4
2
9
12
N)), 1563 (m), 1383 (m), 1345 (m), 1028 (m), 1016 (m), 801 (m); MS
trogen atmosphere. Solvents were dried and distilled prior to use
ꢀ
(
ESIꢀ): m/z 249.1 ([MꢀH] , 100%); elemental analysis calcd (%) for
[21]
as mentioned in the literature. All chemicals were obtained from
commercial sources and used without further purification. Thin-
layer chromatography (TLC) was performed on precoated glass
plates (0.25 mm, silica gel 60 F254). Visualization of compounds on
C H B NS: C 56.18, H 8.90, N 5.61, S 12.84; found: C 56.07, H 8.95,
7
22 9
N 5.53, S 12.86.
TLC plates was achieved by treatment with a solution of PdCl (1%
2
in MeOH) and gentle heating or by UV light (254 nm). Column
chromatography was carried out with silica gel (0.035–0.070 mm,
Synthesis of 10-[CH C{N(CH ) }S]-nido-7,8-C B H (4)
3
3 2
2
9
11
The NMe4 salt of 1 (500 mg, 2.41 mmol) and AlCl3 (963 mg,
7.22 mmol) were thoroughly mixed. Acetone (30 mL) and N,N-di-
methylthioacetamide (MeC(S)NMe2, 1.24 g, 12.04 mmol) were
added, and the solution was heated to 458C overnight. Progress of
the reaction was monitored by TLC in EtOAc. The solvent was re-
6
4
0 ꢂ). All NMR spectra were recorded on a Bruker AVANCE DRX
00 spectrometer. The chemical shifts of H, B, and C NMR spec-
1
11
13
tra are reported in parts per million (ppm) at 400.13, 128.38 and
00.63 MHz, respectively, with tetramethylsilane as internal stan-
1
[22]
dard and referencing to the unified X scale. The presence of
moved in vacuo. The residue was suspended in Et O (100 mL) and
acidic protons was demonstrated by exchange with D O. Complete
2
2
extracted with water (4ꢃ30 mL). The organic phase was dried over
assignment of all boron atoms to the respective signals in the
1
1
1
11 11
1
MgSO . The solvent was removed in vacuo, and the residue was
B{ H} NMR spectra was achieved by B- B{ H} COSY NMR spec-
troscopy. FTIR spectra were recorded on a Perkin Elmer Spectrum
4
subjected to column chromatography (EtOAc/n-hexane, 1:2, v/v),
ꢀ1
which gave 4 (142 mg, 25%) as a colorless solid. R (EtOAc/n-
2
000 FTIR spectrometer, scanning between 400 and 4000 cm , by
using KBr discs. Mass spectra (ESI) were recorded on an ESQUIRE
000 plus. Elemental analyses were carried out in a Heraeus VARIO
f
1
hexane, 1:1, v/v) 0.50; m.p. 2398C; H NMR (CD CN): d=ꢀ1.33 (br,
3
1
H, extra-H), 0.10 to 2.80 (br, 10H, BH), 2.16 (s, 2H, cage-CH), 3.07
3
11
(
(
s, 3H, CH ), 3.38 (s, 3H, NCH ), 3.43 (s, 3H, NCH ); B NMR
3 3 3
EL oven. The melting points were measured in sealed capillaries.
1
1
CD CN): d=ꢀ37.9 (d, JBH =134 Hz, B1), ꢀ25.7 (d, JBH =53 Hz,
3
X-ray data were collected on an Oxford Diffraction CCD Xcalibur-S
1
1
B10), ꢀ20.3 (d, J =153 Hz, B2, B4), ꢀ18.1 (d, J =161 Hz, B3),
[23]
BH
BH
diffractometer (data reduction with CrysAlis Pro including the
1
1
ꢀ
14.0 (d,
J
=138 Hz, B5, B6), ꢀ11.1 (d,
J =141 Hz, B9, B11);
BH
C{ H} NMR (CD CN): d=24.3 (CH ), 44.0 to 46.0 (m, 2ꢃNCH ,
[24]
BH
program SCALE3 ABSPACK for empirical absorption correction)
1
3
1
3
3
3
with MoKa radiation (l=0.71073 ꢂ) and w-scan rotation. The struc-
cage-CH), 194.7 (CH C(N(CH ) )S); IR: 3046 (w, n(cage-CꢀH)), 2936
[25]
3
3 2
tures were solved with the SIR tool, and the refinement of all
(
1
w, n(CꢀH)), 2542 (s, n(BꢀH)), 1584 (s, n(C=N)), 1408 (m, n(CꢀN)),
[26]
non-hydrogen atoms was performed with SHELXL97. Non-hydro-
gen atoms were refined anisotropically. Hydrogen atoms were cal-
culated by both free refinement and constrained methods with
283 (s, d(NCH )), 1141 (m), 1090 (w), 1018 (s), 964 (w), 824 (m); MS
3
ꢀ
(
ESIꢀ): m/z 235.2 ([MꢀH] , 100%); elemental analysis calcd (%) for
C H B NS: C 30.58, H 8.57, N 5.94, S 13.69; found: C 30.49, H 8.63,
6
20 9
a riding model. The refinement was carried out with the least-
N 6.02, S 13.58.
2
squares method on F . Final R indices were calculated as R =
1
2
2 2
2 2 1/2
ꢀ
j jF jꢀjF j j/ꢀjF j and wR ={ꢀ[w(F ꢀF ) ]/ꢀw(F ) }
. The
o
c
o
2
o
c
o
[27]
structure figures were drawn with the program ORTEP. Supple-
mentary crystallographic data are deposited in the CCDC data base
and are registered as stated: CCDC 924104 (2), CCDC 924105 (4),
CCDC 924106 (6), CCDC 924107 (8). These data can be obtained
free of charge from The Cambridge Crystallographic Data Centre
via www.ccdc.cam.ac.uk/data_request/cif. Crystallographic data are
summarized in Table 1.
Synthesis of 9-[CH C(NHCHPh )O]-nido-7,8-C B H (6)
3
2
2
9
11
Benzophenone imine (Ph C(NH), 873 mg, 4.82 mmol) was dissolved
2
in anhydrous THF (50 mL), and acetyl chloride (MeC(O)Cl, 378 mg,
340 mL, 4.82 mmol) was added dropwise. A colorless precipitate
formed. NMe salt of 1 (500 mg, 2.41 mmol) was added. The result-
4
ing suspension was heated to reflux overnight. The solution was
cooled to ambient temperature and the solvent evaporated in
vacuo to near dryness. CH Cl (100 mL) was added, and the organic
Synthesis of 9-[CH C{NHCH(CH ) }S]-nido-7,8-C B H (2)
3
3 2
2
9
11
2
2
The NMe4 salt of 1 (500 mg, 2.41 mmol) and AlCl3 (963 mg,
.22 mmol) were thoroughly mixed. Acetone (30 mL) and thioacet-
phase was extracted with water (2ꢃ50 mL) and dried over MgSO4.
Column chromatography (CH Cl /n-hexane, 2:1, v/v) gave
7
6
2
2
amide (MeC(S)NH , 904 mg, 12.04 mmol) were added, and the solu-
tion was heated to reflux for 3 h. Progress of the reaction was
monitored by TLC in EtOAc. The solvent was removed in vacuo.
(405 mg, 47%) as a colorless solid. R (CH Cl /n-hexane, 4:1, v/v):
f 2 2
2
1
0.05. Mp: 1968C. H NMR (CD CN): d ꢀ3.20 (br, 1H, extra-H), ꢀ0.20
3
to 2.85 (br, 10H, BH), 1.87 (s, 1H, cage-CH), 2.40 (s, 1H, cage-CH),
The residue was suspended in Et O (100 mL) and extracted with
2.67 (s, 3H, CH ), 6.22 (s, CHPh ), 7.30 to 7.41 (m, 10H, aryl-CH),
2
3
2
11
1
water (4ꢃ30 mL). The organic phase was dried over MgSO . The
9.47 (br, s, 1H, NH). B NMR (CD CN): d ꢀ40.0 (d, J =141 Hz, B1),
4
3
BH
1
1
solvent was removed in vacuo, and the residue was subjected to
ꢀ33.3 (d, J =107 Hz, B10), ꢀ27.5 (d, J =139 Hz, B6), ꢀ23.4 (m,
1
BH
BH
column chromatography (Et O), which gave 2 (180 mg, 30%) as
B4), ꢀ21.2 (m, B2), ꢀ19.8 (m, B3), ꢀ18.1 (m, B11), ꢀ8.1 (d, J
=
BH
2
1
13
1
a colorless solid. R (Et O) 0.25; m.p. 1878C. H NMR (CD CN): d=
135 Hz, B5), 7.1 (s, B9). C{ H} NMR (CD CN): d 20.0 (CH ), 32.9 (br,
3 3
f
2
3
3
ꢀ
3.15 (br, 1H, extra-H), 0.10 to 2.75 (br, 10H, BH), 1.37 (d, J
=
cage-CH), 48.1 (br, cage-CH), 60.3 (CHPh ) 127.5, 128.3, 128.9, 138.5
HH
2
3
5
Hz, 3H, CHCH ), 1.38 (d, JHH =5 Hz, 3H, CHCH ), 2.12 (s, 1H,
(all four aryl-C), 177.7 (CH C(NCHPh )O). IR: 3340 (s, n(N-H)), 3048
3
3
3
2
cage-CH), 2.55 (s, 1H, cage-CH), 2.85 (s, 3H, CH ), 4.26 (m, 1H,
(w), 3031 (w, both n(aryl-CꢀH) and n(cage-CꢀH)), 2929 (w, n(CꢀH)),
2548 (s, n(BꢀH)), 1617 (s, n(C=N) and n(C=C)), 1543 (s, n(C=C)),
1433 (m, n(C=C)), 1377 (m), 1353 (m), 1116 (s), 1024 (m), 869 (s),
755 (s), 745 (s), 704 (s, all three g(aryl-CꢀH)). MS (ESIꢀ): m/z 356.2
3
11
1
CHCH ), 9.51 (br, s, 1H, NH); B NMR (CD CN): d=ꢀ37.3 (d, J
=
BH
3
3
1
1
1
42 Hz, B1), ꢀ28.5 (d, J =132 Hz, B10), ꢀ25.5 (d, J =140 Hz,
BH
BH
1
B6), ꢀ22.3 (d,
J
BH
=150 Hz, B4), ꢀ18.2 (m, B3), ꢀ17.6 (m, B11),
1
1
ꢀ
ꢀ
14.6 (d, J =150 Hz, B2), ꢀ7.5 (s, B9), ꢀ4.1 (d, J =139 Hz, B5);
([MꢀH] , 100%). Elemental analysis calculated in% for C H B NO:
BH
BH
17 26 9
1
3
1
C{ H} NMR (CD CN): d=19.5 (CHCH ), 19.6 (CHCH ), 27.8 (CH ),
C 57.07, H 7.34, N 3.92; found: C 56.96, H 7.28, N 3.88.
3
3
3
3
Chem. Eur. J. 2014, 20, 1440 – 1446
www.chemeurj.org
1444
ꢁ 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Full Paper
Synthesis of 10-[CH C(NHCHPh )O]-nido-7,8-C B H (7)
analysis calcd (%) for C15
9.89, H 6.63, N 6.30.
H15NO: C 79.96, H 6.72, N 6.22; found: C
3
2
2
9
11
7
Compound 7 was eluted as the first fraction in the chromatograph-
ic purification of 6. 7 was obtained as a colorless solid (198 mg,
1
2
3%). Rf (CH Cl /n-hexane, 4:1, v/v) 0.15; m.p. 1608C; H NMR
2
2
(
(
(
CD CN): d=ꢀ0.05 (br, 1H, extra-H), 0.30 to 2.85 (br, 10H, BH), 1.87
3
Acknowledgements
1
s, 2H, cage-CH), 2.67 (s, 3H, CH ), 6.06 (d, J =8 Hz, CHPh ), 7.25
3
HH
2
1
d, J =7 Hz, 4H, aryl-CH), 7.32 to 7.41 (m, 6H, aryl-CH), 9.45 (br,
HH
We gratefully acknowledge financial support of the Fonds der
Chemischen Industrie (FCI, doctoral grant R.F.), the European
Union and the Free State of Saxony (EFRE) and the Graduate
School Leipzig School of Natural Sciences—Building with Mole-
cules and Nano-objects (BuildMoNa). We thank Regina Zꢄbe,
Ramona Oehme and Stefanie Mꢄrcker for analytical measure-
ments.
11
1
s, 1H, NH); B NMR (CD CN): d=ꢀ39.8 (d, J =141 Hz, B1), ꢀ22.6
3
BH
1
(
m, B2, B3, B4), ꢀ15.9 (d,
J
BH
=142 Hz, B5, B6), ꢀ14.8 (s, B10),
1
13
1
ꢀ
11.0 (d,
J
=139 Hz, B9, B11); C{ H} NMR (CD CN): d=19.5
BH
3
(
CH ), 41.9 (br, cage-CH), 60.2 (CHPh ) 127.4, 128.3, 128.8, 138.3 (all
3 2
four aryl-C), 177.1 (CH C(NCHPh )O); IR: 3342 (s, n(NꢀH)), 3050 (w),
3
2
3
032 (w, both n(aryl-CꢀH) and n(cage-CꢀH)), 2932 (w, n(CꢀH)), 2523
(
s, n(BꢀH)), 1616 (s, n(C=N) and n(C=C)), 1546 (s, n(C=C)), 1434 (m,
n(C=C)), 1376 (m), 1353 (m), 1100 (s), 1023 (m), 868 (s), 755 (s), 745
ꢀ
(
1
7
s), 702 (s, all three g(aryl-CꢀH)); MS (ESIꢀ): m/z 356.2 ([MꢀH] ,
00%); elemental analysis calcd (%) for C H B NO: C 57.07, H
Keywords: boron · carbaboranes · carboranes · conjugated
heterodienes · EINS-type reactions · hydride abstraction
17
26 9
.34, N 3.92; found: C 57.18, H 7.36, N 3.79.
Synthesis of 10-[CH C(NCPh )NH]-nido-7,8-C B H (8)
[1] a) R. A. Wiesboeck, M. F. Hawthorne, J. Am. Chem. Soc. 1964, 86, 1642–
3
2
2
9
11
1
643; b) M. F. Hawthorne, D. C. Young, P. M. Garrett, D. A. Owen, S. G.
Benzophenone imine (Ph C(NH), 873 mg, 4.82 mmol) was dissolved
in anhydrous MeCN (50 mL), and acetyl chloride (MeC(O)Cl,
2
Schwerin, F. N. Tebbe, P. A. Wegner, J. Am. Chem. Soc. 1968, 90, 862–
868.
3
78 mg, 340 mL, 4.82 mmol) was added dropwise. A colorless pre-
[2] R. N. Grimes, Carboranes, 2nd ed., Elsevier, Amsterdam, 2011, p. 197.
[3] A. A. Semioshkin, I. B. Sivaev, V. I. Bregadze, Dalton Trans. 2008, 977–
cipitate formed. The NMe salt of 1 (500 mg, 2.41 mmol) was dis-
4
992.
solved in anhydrous MeCN (15 mL) and added. The resulting sus-
pension was heated to reflux overnight with dissolution of the pre-
cipitate and formation of an intense yellow solution. The solution
was cooled to ambient temperature and the solvent evaporated in
vacuo to near dryness. Et O (100 mL) was added, and the organic
phase was extracted with water (2ꢃ50 mL) and dried over MgSO4.
[
4] An example of Pd mediated BꢀH bond-activation with substitution at
the B9 can be found in: S. A. Jasper Jr., J. Mattern, J. C. Huffman, L. J.
Todd, Polyhedron 2007, 26, 3793–3798.
[
5] a) F. P. Olsen, M. F. Hawthorne, Inorg. Chem. 1965, 4, 1839–1840; b) R. H.
Pak, R. R. Kane, C. B. Knobler, M. F. Hawthorne, Inorg. Chem. 1994, 33,
5355–5357; c) E. A. Mizusawa, M. R. Thompson, M. F. Hawthorne, Inorg.
Chem. 1985, 24, 1911; d) E. C. Santos, A. B. Pinkerton, S. A. Kinkead, P. K.
Hurlburt, S. A. Jasper, C. W. Sellers, J. C. Huffman, L. J. Todd, Polyhedron
2000, 19, 1777–1781; e) D. A. Rudakov, V. L. Shirokii, V. I. Potkin, E. A. Di-
kusar, V. I. Bragin, P. V. Petrovskii, I. B. Sivaev, V. I. Bregadze, A. V. Kisin,
Russ. J. Electrochem. 2006, 42, 280–284; f) V. L. Shirokii, D. A. Rudakov,
A. V. Bazhanov, E. G. Zalesskaya, V. I. Potkin, N. A. Maier, S. V. Timofeev,
P. V. Petrovskii, V. I. Bregadze, Russ. J. Elektrochem. 2004, 40, 212–214;
g) D. A. Rudakov, V. I. Potkin, E. A. Dikusar, P. V. Petrovskii, I. B. Sivaev, V. I.
Bregadze, Russ. Chem. Bull. 2007, 56, 922–925; h) D. A. Rudakov, V. I.
Potkin, I. V. Lantsova, Russ. J. Electrochem. 2009, 45, 813–817.
2
Column chromatography (Et O/n-hexane, 1:2.5, v/v) gave
8
2
(
589 mg, 69%) as a yellow solid. R (Et O/n-hexane, 2:3, v/v) 0.35;
f 2
1
m.p. 2088C; H NMR (CD CN): d=ꢀ0.75 (br, 1H, extra-H), 0.30 to
3
2
7
.80 (br, 10H, BH), 1.83 (s, 2H, cage-CH), 2.04 (s, 3H, CH ), 7.52 to
3
11
.69 (m, 10H, aryl-CH), 8.16 (br, s, 1H, NH); B NMR (CD CN): d=
3
1
1
ꢀ
39.0 (d, J =141 Hz, B1), ꢀ24.1 (d, J =47 Hz, B10), ꢀ22.2 (d,
BH
BH
1
1
1
J
=151 Hz, B2, B4), ꢀ19.8 (d, J =150 Hz, B3), ꢀ16.0 (d, J
=
BH
BH
BH
1
13
1
1
35 Hz, B5, B6), ꢀ10.5 (d,
J =142 Hz, B9, B11); C{ H} NMR
BH
(
CD CN): d=21.4 (CH ), 42.5 (br, cage-CH), 128.9, 129.5, 132.7,
3 3
1
35.3 (all four aryl-C), 170.1, 177.4 (both CH C(NCPh )NH); IR: 3362
[6] V. A. Brattsev, S. P. Knyazev, V. I. Stanko, Zh. Obshch. Khim. 1976, 46,
1419.
[7] L. I. Zakharkin, N. V. Grandberg, V. A. Antonovich, Izv. Akad. Nauk SSSR
Ser. Khim. 1976, 8, 1830–1833.
3
2
(
2
s, n(NꢀH)), 3054(w), 3039 (w, both n(aryl-CꢀH) and n(cage-CꢀH)),
927 (w, n(CꢀH)), 2561 (s, n(BꢀH)), 1644 (s, n(C=N)), 1609 (s, n(C=N)
and n(C=C)), 1446 (m, n(C=C)), 1415 (m), 1366 (m), 1322 (s), 1230
[
8] L. I. Zakharkin, V. A. Ol’shevskaya, G. G. Zhigareva, V. A. Antonovich, P. V.
Petrovskii, A. I. Yanovskii, A. V. Polyakov, Yu. T. Struchkov, Metalloorg.
Khim. 1989, 2, 1274–1282.
(
m), 1154 (m), 1029 (m), 1001 (m), 944 (s), 786 (m), 705 (s), 693 (s,
ꢀ
both g(aryl-CꢀH)), 649 (s); MS (ESIꢀ): m/z 354.2 ([MꢀH] , 100%);
elemental analysis calcd (%) for C H B N : C 57.57, H 7.12, N 7.90;
17
25
9
2
[
9] a) V. A. Brattsev, S. P. Knyazev, V. I. Stanko, Zh. Obshch. Khim. 1975, 45,
found: C 57.63, H 6.99, N 8.03.
1192; b) S. P. Knyazev, V. A. Brattsev, V. I. Stanko, Dokl. Akad. Nauk SSSR
1
977, 234, 837–840; c) S. P. Knyazev, V. A. Brattsev, V. I. Stanko, Dokl.
Akad. Nauk SSSR 1977, 234, 1093–1096; d) L. I. Zakharkin, G. G. Zhigare-
va, V. A. Antonovich, A. I. Yanovskii, Yu. T. Struchkov, Zh. Obshch. Khim.
Synthesis of CH C(O)NHCHPh (9)
3
2
1
986, 56, 2066–2077; e) L. I. Zakharkin, G. G. Zhigareva, V. A. Antono-
Compound 9 was eluted as the second fraction in the chromato-
graphic purification of 8. Compound 9 (364 mg, 67%) was ob-
tained as a colorless solid. R (Et O/n-hexane, 2:3, v/v) 0.20; m.p.
vich, A. I. Yanovskii, Yu. T. Struchkov, Izv. Akad. Nauk SSSR Ser. Khim.
1984, 1672; f) Yu. T. Struchkov, M. Yu. Antipin, V. I. Stanko, V. A. Brattsev,
N. I. Kirillova, S. P. Knyazev, J. Organomet. Chem. 1977, 141, 133–139;
g) L. I. Zakharkin, V. A. Ol’shevskaya, G. G. Zhigareva, P. V. Petrovskii, L. E.
Vinogradova, Russ. J. Gen. Chem. 2002, 72, 741–743; h) L. I. Zakharkin,
G. G. Zhigareva, Russ. Chem. Bull. 1996, 45, 2012–2014; i) L. I. Zakharkin,
G. G. Zhigareva, V. A. Antonovich, Zh. Obshch. Khim. 1980, 50, 1026–
f
2
1
3
1
458C; H NMR (CD CN): d=1.95 (s, 3H, CH ), 6.10 (d, J =8 Hz,
3 3 HH
1
H, CHPh ), 7.15 (br, s, 1H, NH), 7.23 to 7.35 (m, 10H, aryl-CH);
2
1
3
1
C{ H} NMR (CD CN): d=22.0 (CH ), 56.9 (CHPh ), 127.1, 127.2,
3
3
2
1
3
28.5, 142.5 (all four aryl-C), 169.0 (CH C(O)); IR: 3361 (s, n(NꢀH)),
3
1031.
052 (m), 3029 (m, both n(aryl-CꢀH)), 2922 (w, n(CꢀH)), 1645 (s,
[
10] J. Ple sˇ ek, T. Jelꢅnek, F. Mare sˇ , S. He rˇ mꢆnek, Collect. Czech. Chem.
Commun. 1993, 58, 1534–1547.
n(C=O)), 1543 (s, n(C=C)), 1495 (m, n(C=C)), 1453 (m), 1373 (m),
1
290 (m, n(CꢀN), 1117 (m), 1029 (m), 744 (m), 698 (s, both g(aryl-
[11] R. Frank, T. Grell, M. Hiller, E. Hey-Hawkins, Dalton Trans. 2012, 41,
ꢀ
CꢀH)), 649 (s). MS (ESIꢀ): m/z 224.1 ([MꢀH] , 100%); elemental
6155–6161.
Chem. Eur. J. 2014, 20, 1440 – 1446
www.chemeurj.org
1445
ꢁ 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Full Paper
[
[
[
[
12] a) J. Ple sˇ ek, Z. Janou sˇ ek, S. He rˇ mꢆnek, Collect. Czech. Chem. Commun.
978, 43, 2862–2868; b) J. Ple sˇ ek, Z. Janou sˇ ek, S. He rˇ mꢆnek, Inorg.
Synth. 1984, 22, 239–241.
13] a) D. C. Young, D. V. Howe, M. F. Hawthorne, J. Am. Chem. Soc. 1969, 91,
[19] R. Frank, H. Auer, E. Hey-Hawkins, J. Organomet. Chem. 2013, 747, 217–
1
224.
[20] D. Olid, R. NfflÇez, C. ViÇas, F. Teixidor, Chem. Soc. Rev. 2013, 42, 3318–
3336.
[21] W. L. F. Armarego, C. L. L. Chai, Purification of Laboratory Chemicals,
5th ed., Butterworth-Heinemann, Amsterdam, 2003.
859–862; b) H. C. Kang, S. S. Lee, C. B. Knobler, M. F. Hawthorne, Inorg.
Chem. 1991, 30, 2024–2031.
[
22] R. K. Harris, E. D. Becker, S. M. Cabral de Menezes, R. Goodfellow, P.
Granger, Pure Appl. Chem. 2001, 73, 1795–1818.
14] V. I. Meshcheryakov, P. S. Kitaev, K. A. Lyssenko, Z. A. Starikova, P. V. Pet-
rovskii, Z. Janou sˇ ek, M. Corsini, F. Laschi, P. Zanello, A. R. Kudinov, J. Or-
ganomet. Chem. 2005, 690, 4745–4754.
15] a) L. I. Zakharkin, V. N. Kalinin, G. G. Zhigareva, Izv. Akad. Nauk SSSR Ser.
Khim. 1979, 2376–2377; b) L. I. Zakharkin, V. N. Kalinin, G. G. Zhigareva,
Bull. Acad. Sci. USSR Ch. 1979, 28, 2198–2199.
[
[
[
23] CrysAlis Pro 2010, Oxford Diffraction Ltd., Oxfordshire (UK).
24] SCALE3 ABSPACK 2010, Oxford Diffraction Ltd., Oxfordshire (UK).
25] SIR92: A. Altomare, G. Cascarano, C. Giacovazzo, A. Guagliardi, J. Appl.
Crystallogr. 1993, 26, 343–350.
[
26] G. M. Sheldrick, SHELXL97, release 97–2, Universitꢄt Gçttingen, Gçttin-
gen (Germany), 1997; includes SHELXS97 and SHELXL97.
16] B. Grꢇner, J. Holub, J. Ple sˇ ek, B. Stꢅbr, M. Thornton-Pett, J. D. Kennedy,
Dalton Trans. 2007, 4859–4865.
ˇ
[
[
[
[
27] ORTEP3 for Windows: L. J. Farrugia, J. Appl. Crystallogr. 1997, 30, 565.
17] J. Ple sˇ ek, T. Jelꢅnek, F. Mare sˇ , S. He rˇ mꢆnek, Collect. Czech. Chem.
Commun. 1993, 58, 1534–1547.
18] O. Tutusaus, F. Teixidor, R. NfflÇez, C. ViÇas, R. Sillanpꢄꢄ, R. Kivekꢄs, J. Or-
ganomet. Chem. 2002, 657, 247–255.
Received: September 25, 2013
Published online on December 20, 2013
Chem. Eur. J. 2014, 20, 1440 – 1446
www.chemeurj.org
1446
ꢁ 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim