Synthesis of boron-fused 1,4-dithiin via cobalt-mediated disulfuration of alkyne at the o -carborane-9,12-dithiolate unit

Article abstract of DOI:10.1021/om500411b

We present the first synthesis and characterization of a series of boron-fused 1,4-dithiin compounds through the reactions of newly established boron-substituted 16e half-sandwich complex Cp*Co(9,12-S₂C ₂B₁₀H₁₀) with alkynes. The generated C ₂S₂B₂ ring in these 1,4-dithiin species is a stable structural motif with electron-negative sulfur atoms, as evidenced by theoretical calculation and its solid-state self-assembly. Single-crystal X-ray analysis indicates that C_carb-H···S hydrogen bonding is involved in the self-assemblies of these compounds, which serves as a compatible interaction with stronger C_carb- H···π, C_carb-H···O, or C_carb-H···F hydrogen bonding. All new compounds are characterized by NMR, mass spectroscopy, and X-ray structural analysis.

Full text of DOI:10.1021/om500411b

Article
pubs.acs.org/Organometallics
Synthesis of Boron-Fused 1,4-Dithiin via Cobalt-Mediated
Disulfuration of Alkyne at the o‑Carborane-9,12-dithiolate Unit
Xiaolei Zhang, Xiaodong Zou, and Hong Yan*
State Key Laboratory of Coordination Chemistry, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing,
Jiangsu 210093, China
S
* Supporting Information
ABSTRACT: We present the first synthesis and characterization
of a series of boron-fused 1,4-dithiin compounds through the
reactions of newly established boron-substituted 16e half-sandwich
complex Cp*Co(9,12-S2C2B10H10) with alkynes. The generated
C2S2B2 ring in these 1,4-dithiin species is a stable structural motif
with electron-negative sulfur atoms, as evidenced by theoretical
calculation and its solid-state self-assembly. Single-crystal X-ray
analysis indicates that Ccarb−H···S hydrogen bonding is involved
in the self-assemblies of these compounds, which serves as a compatible interaction with stronger Ccarb−H···π, Ccarb−H···O, or
Ccarb−H···F hydrogen bonding. All new compounds are characterized by NMR, mass spectroscopy, and X-ray structural analysis.
Chart 1. Illustration of a 1,4-Dithiin Compound and Its
Derivatives Containing Benzo-Fused Dithiin Examples and
C/B-Fused o-Carboranyl Dithiin Examples
INTRODUCTION
■
1,4-Dithiin1 compounds (a class of heterocyclic compounds
with a C2S2C2 ring) have attracted renewed interest since the
discovery that plants of the sunflower family contain
dimethipin,2 a commercial plant growth regulant. These 1,4-
dithiin derivatives have been reported to exhibit a wide range of
biological activity2,3 (Chart 1a). The substitution on the 1,4-
dithiin ring plays an important role in governing the chemical
reactivity4 and biological activity5 of these compounds. On the
other hand, icosahedral carborane derivatives have been applied
in the areas of catalysis,6 materials,7 and drugs.8 These provide
significant impetus to search for an efficient synthetic strategy
for the construction of carborane-based 1,4-dithiin derivatives.
Indeed, several carbon-fused o-carboranyl-1,4-dithiin com-
pounds have already been synthesized and characterized9 that
were found to bind to myoglobin via the dithio units and
influenced the native conformation of the protein.10 Further-
more, these conjugates also show selective antineoplastic activity
and may serve as potential anticancer agents.11 Nevertheless, the
expansion of structural diversity beyond what can be achieved by
nature is one of the main goals of synthetic chemistry. Carbon or
boron fusion has emerged as a viable strategy to increase the
chemical space of compounds relevant to biomedical research
and materials science.12 If 1,4-dithiin is combined with the three-
dimensional pseudoaromatic o-carborane cluster, two structural
isomers might be generated depending on the attachment of S
atoms on carbon or boron vertexes (Chart 1b).
The known synthetic routes toward carbon-fused o-carboranyl-
1,4-dithiin compounds9 were mainly based on the square-planar
cobalt complex [Co(S2C2B10H10)2]− 9a or mononuclear 16e half-
sanwich complex [CpCo(1,2-S2C2B10H12)] [Cp = cyclopenta-
dienyl]9b,c (Chart 1c). The analogous metal complexes (Ru, Os,
Co, Rh, and Ir) containing 1,2-dicarba-closo-dodecaborane-1,2-
dithiolate ligand have exhibited rich reaction chemistries13−15
toward metal fragments, Lewis bases, alkynes, and others.
However, similar dithiolato complexes based on the o-carborane-
9,12-dithiolate ligand16 are still rare,17 and the synthesis of a
Received: April 19, 2014
Published: May 15, 2014
© 2014 American Chemical Society
2661
dx.doi.org/10.1021/om500411b | Organometallics 2014, 33, 2661−2666

Organometallics
Article
boron-fused 1,4-dithiin has remained unknown to date. In this
contribution, we first report the efficient route to boron-fused
1,4-dithiin compounds starting from the mononuclear 16e half-
sandwich cobalt complex containing an o-carborane-9,12-dithiolate.
We also demonstrate that negative charge is significantly increased
at the S atoms owing to the boron substitution. As a result, the
nonconventional Ccarb−H···S hydrogen bonding is involved in the
self-assembly of these compounds and acts in a role compatible
with the conventional Ccarb−H···O or Ccarb−H···F hydrogen
bonding.
Scheme 1. Synthetic Route toward Boron-Substituted 1,4-
Dithiin Compounds S1−S8 via a 16e Half-Sandwich Cobalt
Dithiolato Complex 2
RESULTS AND DISCUSSION
■
The reaction of boron-substituted dithiol 1 and Cp*Co(CO)I2
[Cp* = pentamethylcyclopentadienyl] gave rise to the orange
product 2 in excellent isolated yield (90%). Note that complex
2 is stable both in solution and in the solid state, in contrast to
the similarly prepared CpCo(9,12-S2C2B10H12), which is not
stable enough in solution.17 The X-ray crystal structure of 2
(Figure 1) validates the formation of a five-membered metallacycle
Figure 2. Molecular structure of compound S1. For clarity, the
hydrogen atoms are not shown. Selected bond distances [Å] and bond
angles [deg]: C1−C2 1.625(3), B9−S1 1.852(2), B12−S2 1.854(2),
C13−S1 1.7659(19), C14−S2 1.7687(19), C13−C14 1.328(3), C13−
S1−B9 102.28(9), C14−S2−B12 103.32(9).
Table 1. Scope of Terminal Alkynes
compound
R-
T/°C
yield
90%
S1
Ph-
110
110
110
25
S2-1, S2-2, S2-3
(o, m, p)-F-Ph-
Fc-
87−90%
88%
S3
S4
S5
S6
S7
S8
Me-C(O)-
2-furyl-C(O)-
Ph-C(O)-
MeO-C(O)-
Fc-C(O)-
92%
25
93%
25
91%
Figure 1. Molecular structure of complex 2. For clarity, the hydrogen
atoms are not shown. Selected bond distances [Å] and bond angles
[deg]: C1−C2 1.632(5), B9−S1 1.843(4), B12−S2 1.844(4), Co1−S1
2.1930(10), Co1−S2 2.1745(10), S1−Co1−S2 100.14(3).
25
90%
25
89%
(<10%) with predominantly competing B−H activation.18
Therefore, the reactivity of the carbon-substituted 16e
complexes [Cp#Co{1,2-S2C2B10H10}] (Cp# = Cp, Cp*) toward
alkynes differs. Here we provide a clean reaction to boron-fused
1,4-dithiins with excellent yields from the boron-substituted 16e
complex [Cp*Co{9,12-S2C2B10H10}].
ring CoS2B2, and the electron count confirms the 16e cobalt
center. The NMR data are in agreement with the solid-state
structure. For example, the 11B NMR spectrum shows one type of
cageB−S resonance at 18.1 ppm in comparison to 8.5 ppm in the
parent ligand 1. The 1H NMR spectrum also exhibits the cageC−H
signal at 2.86 ppm. Here, the steric and electronic effect of the
Cp* unit may play an important role in stabilizing the CoS2B2 ring
in contrast to the Cp unit.
Reactions of 2 toward PhCCH in boiling toluene led to
the alkyne disulfurated product S1 as the sole product in an excellent
yield (90%) (Scheme 1 and Figure 2). The scope of alkynes was
expanded (Scheme 1), and similar reactivity was observed for (o, m,
p-F)-PhCCH and FcCCH, leading to S2-1, S2-2, S2-3, and
S3. In the case of alkynes with an electron-withdrawing group such
as HCCC(O)R, the reactions proceeded smoothly at room
temperature to give rise to S4−S8 in yields of 88−92% (Scheme 1
and Table 1). Note that boron-substituted dithiol 1 does not react
with alkynes in the absence of a metal fragment. Similar reactions of
alkynes with the carbon-substituted 16e half-sandwich complex
[Cp*Co{1,2-S2C2B10H10}] led only to double-alkyne-inserted
products at M−S bonds, and its Cp analogue, [CpCo{1,2-
S2C2B10H10}], led to carbon-fused 1,4-dithiins9 in lower yields
Single-crystal X-ray analysis ambiguously confirms the newly
formed compounds S1−S8. For example, the solid-state
structure of S1 (Figure 2) shows an alkyne added to the
o-caborane-9,12-dithiolate ligand at the two sulfur atoms. The
generated six-membered ring C(13)C(14)S(1)S(2)B(9)B(12)
is bent at the S(1)···S(2) vector at a dihedral angle of 141.8°.
The C13−C14 is measured as 1.328(3) Å, in the range of
carbon−carbon double bonds, and the C1−C2 distance of the
o-carborane is observed at 1.625(3) Å. The other X-ray
structures of S2−S8 are found in the SI, Figures s6−13. A
DFT-optimized structure of S6 based on its crystal structure
indicates that the C2S2B2 six-membered ring is a stable struc-
tural motif, as its HOMO−LUMO gap (0.142 eV) is similar to
that in the carbon-fused species (SI, Figures s2−4).
Consistent with the solid-state structures, the 1H NMR
spectra of all products show a quartet in the olefinic area, which
is assigned to the CCH unit. The splitting of the hydrogen
2662
dx.doi.org/10.1021/om500411b | Organometallics 2014, 33, 2661−2666

Organometallics
Article
signal is attributed to the remote coupling from the two B
atoms of the B−S bonds with JB−H = 5 Hz via the comparison
1
of the boron-coupled and boron-decoupled H NMR measure-
ments (SI, Figure s5). The cageC−H proton signal is observed
around 3.70 ppm. The 13C NMR signals of the newly generated
CCH unit are located in the normal range for olefinic carbon
1
atoms. Selected H, 13C, and 11B data for compounds S1−S8
are listed in Table 2.
1
Table 2. H, 13C, and 11B NMR Data of the C2S2B2 Six-
Membered Rings in S1−S8
compound
CC−H (1H)
S−CC−H (13C)
B−B−S (11B)
S1
6.15
6.12
6.15
6.09
6.10
7.24
7.33
6.94
7.37
7.08
114.5, 130.8
118.2, 130.4
114.2, 130.1
114.5, 129.0
109.3, 129.2
130.8, 149.0
132.0, 151.1
118.8, 129.1
118.7, 129.2
126.2, 130.8
8.4, 7.4
8.5, 7.5
8.5, 7.4
8.2, 7.4
8.7, 8.1
7.2, 4.7
7.1, 5.0
8.4, 7.4
7.1, 5.0
7.8, 6.0
Figure 3. C−H···π and C−H···S hydrogen bonding involved in self-
assembly of S1 in the solid state. For clarity, partial hydrogen atoms
are not shown. Green: boron, black: carbon, yellow: sulfur, white:
hydrogen.
S2-1
S2-2
S2-3
S3
corresponding to the sum of the van der Waals radii of hydrogen
and sulfur atoms,20f and the nearly linear Ccarb−H···S angle
(147.66°) qualifies it to be a hydrogen bond. Another shorter
and stronger contact is also seen in S4 (Ccarb−H···S 2.518 Å,
164.68°) in a cooperative fashion with the Ccarb−H···O interac-
tion (2.255 Å, 123.42°), which leads to a one-dimensional S-type
polymeric chain (Figure 4). However, in S2-3 the Ccarb−H···S
S4
S5
S6
S7
S8
As shown in Scheme 2, a plausible mechanism has been proposed
to illustrate the disulfuration of alkyne at o-carborane-9,12-dithiolate.
Scheme 2. Proposed Mechanism for the Formation of
Boron-Fused 1,4-Dithiin Compounds
Figure 4. C−H···O and C−H···S hydrogen bonding involved in self-
assembly of S4 in the solid state. For clarity, partial hydrogen atoms
are not shown. Green: boron, black: carbon, yellow: sulfur, white:
hydrogen, red: oxygen.
The first step should be insertion of alkyne into a Co−S
bond to form the 18e species I since the addition of alkyne
to the M−E bond of the 16e half-sandwich complexes
Cp#M(1,2-E2C2B10H10) (Cp# = Cp, Cp*; M = Co, Rh, Ir;
E = S, Se) and (p-cymene)M(S2C2B10H10) (M = Ru, Os) has
been well reported.14,19 If the coordinative Co←S bonding is
not strong enough, the 16e species II might be present,
followed by loss of the Cp*Co fragment to give boron-fused
1,4-dithiin compounds. It is noteworthy that the one-fold
alkyne insertion intermediate I was not observed in this system,
probably owing to the fast Cp*Co reductive elimination. This
also might be the reason that no other competitive reactions
could occur in this reaction system.
interaction (2.944 Å, 149.71°) turns out to be very weak in
comparison with the stronger Ccarb−H···F interaction (2.347 Å,
121.21°); thus the molecules form a one-dimensional linear
polymeric chain dominated by Ccarb−H···F bonding (Figure 5).
Our results indicate that the boron-attached S atoms in 1,4-
dithiin compounds may serve as a compatible hydrogen acceptor
in multiforce-involved supramolecular self-assembly. The related
C−H···S−H···H−B hydrogen bonding interaction based on the
boron-attached SH group has been reported.24
Moreover, DFT calculations demonstrate the electron-negative
property on the S atoms in these boron-fused 1,4-dithiin
compounds, in contrast to the carbon-fused analogues
(SI, Table s1). Correspondingly, the Ccarb−H···S hydrogen
bonding20 involved in self-assembly has been observed in the
solid state, which is comparable to the Ccarb−H···π,21 Ccarb−H···
O,22 or Ccarb−H···F23 hydrogen bonding in these compounds.
For example, in S1 each molecule has been linked by one
Ccarb−H···π interaction (2.468 Å) and one Ccarb−H···S (2.678 Å)
bonding with two adjacent molecules in a triangular fashion
(Figure 3) to form a two-dimensional polymeric plane. The
observed Ccarb−H···S distance of 2.678 Å is shorter than 3.0 Å,
CONCLUSION
■
In summary, we first found an efficient synthetic route to the
boron-fused 1,4-dithiin compounds through the reactions of a
16e half-sandwich cobalt complex and alkynes in excellent
yields. The C2S2B2 six-membered ring in these species is a
thermally stable and isolatable heterocycle with considerably
negatively charged sulfur atoms. Single-crystal X-ray diffration
analysis indicates that the Ccarb−H···S hydrogen bonding is
involved in self-assemblies of these products in the solid state.
In view of the recent advances in developing new ferrocenyl-
substituted carborane conjugates as potential anticancer
2663
dx.doi.org/10.1021/om500411b | Organometallics 2014, 33, 2661−2666

Organometallics
Article
Figure 5. C−H···F hydrogen bonding involved in self-assembly of S2-3 in the solid state. For clarity, partial hydrogen atoms are not shown. Green:
boron, black: carbon, yellow: sulfur, white: hydrogen, grass green: fluorine.
(br, 8H, cage−BH). 11B{1H} NMR (CDCl3): δ 8.4 (1B, B−S), 7.4
(1B, B−S), −2.0 (2B), −11.4 (4B), −13.0 (2B). 13C NMR (CDCl3): δ
143.0 (Ph), 130.8 (S−CC) 128.1 (Ph), 127.0 (Ph), 126.7 (Ph),
114.5 (S−CCH) 47.1 (cage−C). ESI-MS (positive ion mode) m/z:
331.44 (M + Na+, 100%). IR (KBr): ν (cm−1) 2587 (B−H). Anal.
Calcd for C10H16B10S2: C, 35.77; H, 4.86. Found: C, 35.32; H, 5.01.
Synthesis of S2-1, S2-2, and S2-3. HCC(2F-Ph) (HCC(3F-Ph)
or HCC(4F-Ph)) (0.2 mL, 2 mmol) was added to a toluene (20 mL)
agents,11 this work opens the door to the preparation of
structural diversity of these species for potential use in the
biomedical field.
EXPERIMENTAL SECTION
■
General Procedures. All workup was performed under an argon
atmosphere using standard Schlenk techniques. Solvents were dried by
refluxing over sodium (petroleum ether, ether, and toluene) or calcium
hydride (dichloromethane) under nitrogen and then were distilled
25
prior to use. Cp*Co(CO)I2 and HCCC(O)Fc26 were prepared
according to the literature methods. The other alkynes were used as
commercial products without further purification. 9,12-Dithiol-
o-carborane was prepared according to the reported literature
methods.16 Elemental analysis was performed in an Elementar
Vario EL III elemental analyzer. NMR data were recorded on a
1
Bruker DRX-500 spectrometer. H NMR and 13C NMR spectra were
reported in ppm with respect to CHCl3/CDCl3 (σ 1H = 7.24, σ
13C = 77.0), and 11B NMR spectra were reported in ppm with respect
to external Et2O·BF3 (σ 11B = 0). The IR spectra were recorded on a
Bruker Tensor 27 spectrophotometer with KBr pellets in the 4000−
400 cm−1 region. The mass spectra were recorded on a Finnigan MAT
TSQ7000 for ESI-MS.
solution of complex 2 (40.0 mg, 0.2 mmol), and the mixture was stirred
for 24 h at 110 °C. After removal of the solvent, the residue was
chromatographed on TLC. Elution with petroleum ether/CH2Cl2 (2:1)
gave compounds S2-1, S2-2, and S2-3 in yields of 87−90%. Compound
S2-1, yield: 87%. Color: white solid. Mp: 123−124 °C. 1H NMR
(CDCl3): δ 7.32−7.00 (m, 4H, Ph), 6.12 (q, JB−H = 5 Hz, 1H, CCH),
3.53 (s, 2H, cage−CH), 1.60−3.14 (br, 8H, cage−BH). 11B{1H} NMR
(CDCl3): δ 8.5 (1B, B−S), 7.5 (1B, B−S), −2.0 (2B), −11.4 (4B),
−13.0 (2B). 19F NMR (CDCl3): δ −115.1. 13C NMR (CDCl3): δ 159.3
(d, JC−F = 250 Hz, C−F), 130.4 (S−CC), 129.0 (d, JC−F = 3 Hz, Ph),
128.8 (d, JC−F = 12 Hz, Ph), 123.8 (d, JC−F = 3 Hz, Ph), 118.2 (S−C
CH), 115.7 (d, JC−F = 12 Hz, Ph), 114.9 (d, JC−F = 25 Hz, Ph), 47.1
(cage−C). ESI-MS (positive ion mode) m/z: 349.44 (M + Na+, 100%).
IR (KBr): ν (cm−1) 2587 (B−H). Anal. Calcd for C10H15B10S2F: C,
36.79; H, 4.63. Found: C, 36.46; H, 4.83. Compound S2-2, yield: 87%.
Color: white solid. Mp: 123−124 °C. 1H NMR (CDCl3): δ 7.42−7.21
(m, 4H, Ph), 6.15 (q, JB−H = 5 Hz, 1H, CCH), 3.51 (s, 2H, cage−
CH), 1.60−3.14 (br, 8H, cage−BH). 11B{1H} NMR (CDCl3): δ 8.5
(1B, B−S), 7.4 (1B, B−S), −2.1 (2B), −11.3 (4B), −13.1 (2B). 19F
NMR (CDCl3): δ −111.9. 13C NMR (CDCl3): δ 160.3 (d, JC−F = 250
Hz, C−F), 138.9 (d, JC−F = 12 Hz, Ph), 130.1 (S−CC) 128.8 (d, JC−F
= 12 Hz, Ph), 126.3 (d, JC−F = 3 Hz, Ph), 116.9 (d, JC−F = 25 Hz, Ph),
115.7 (d, JC−F = 25 Hz, Ph), 114.2 (S−CCH), 47.2 (cage−C). ESI-
MS (positive ion mode) m/z: 349.45 (M + Na+, 100%). IR (KBr): ν
(cm−1) 2587 (B−H). Anal. Calcd for C10H15B10S2F: C, 36.79; H, 4.63.
Found: C, 36.45; H, 4.80. Compound S2-3, yield: 90%. Color: white
solid. Mp: 123−124 °C. 1H NMR (CDCl3): δ 6.96−7.38 (m, 4H, Ph),
6.09 (q, JB−H = 5 Hz, 1H, CCH), 3.53 (s, 2H, cage−CH), 1.60−3.14
(br, 8H, cage−BH). 11B{1H} NMR (CDCl3): δ 8.2 (1B, B−S), 7.4 (1B,
B−S), −2.0 (2B), −11.3 (4B), −12.9 (2B). 19F NMR (CDCl3): δ
−114.9. 13C NMR (CDCl3): δ 162.5 (d, JC−F = 250 Hz, C−F), 129.0
(S−CC), 128.4 (d, JC−F = 12 Hz, Ph), 125.3 (Ph), 115.0 (d, JC−F = 25
Hz, Ph), 114.5 (S−CCH), 47.3 (cage−C). ESI-MS (positive ion mode)
m/z: 349.46 (M + Na+, 100%). IR (KBr): ν (cm−1) 2587 (B−H). Anal.
Calcd for C10H15B10S2F: C, 36.79; H, 4.63. Found: C, 36.48; H, 4.74.
Synthesis of S3. Compound S3 was synthesized similarly to S1 by
using HCCFc. Yield: 88%. Color: yellow solid. Mp: 187−188 °C.
Synthesis of 16e Complex 2 [Cp*Co(9,12-S2C2B10H10)]. 9,12-Dithiol-
1,2-o-carborane (60 mg, 0.3 mmol) was dissolved in CH2Cl2 (30 mL),
Et3N (90 μL, 0.6 mmol) was added to the solution, and the mixture
was stirred for 20 min at room temperature. A CH2Cl2 solution of
Cp*Co(CO)I2 (144 mg, 0.3 mmol) was added to the mixture. The
resulting solution turned orange instantly. After 30 min, the solvent
was removed in vacuo and the residue was chromatographed on silica
gel by CH2Cl2 to give complex 2 (108 mg, 90%). Single crystals
suitable for single-crystal analysis were obtained by slow evaporation of
1
a solution of CH2Cl2/hexanes. Color: orange. Mp: 234−235 °C. H
NMR (CDCl3): δ 2.86 (s, 2H, cage−CH), 1.70−2.81 (br, 8H, cage−
BH), 1.68 (s, 15H, CH3), 11B{1H} NMR (CD2Cl2): δ 18.1 (2B, B−S),
−6.0 (2B), −11.5 (4B), −13.5 (2B). 13C NMR (CDCl3): δ 89.9
(Cp*), 37.1 (cage−C), 10.6 (Cp*). ESI-MS (positive ion mode) m/z:
423.50 (M + Na+, 100%). IR (KBr): ν (cm−1) 2557 (B−H). Anal.
Calcd for C12H25B10S2Co: C, 35.99; H, 6.29. Found: C, 35.63; H, 6.18.
Synthesis of S1. HCCPh (0.2 mL, 2 mmol) was added to a
toluene (20 mL) solution of complex 2 (40.0 mg, 0.2 mmol), and the
mixture was stirred for 24 h at 110 °C. After removal of the solvent,
the residue was chromatographed on TLC. Elution with petroleum
ether/CH2Cl2 (2:1) gave compound S1 in a yield of 90%. Color: white
solid. Mp: 117−118 °C. 1H NMR (CDCl3): δ 7.42−7.21 (m, 5H, Ph),
6.15 (q, JB−H = 5 Hz, 1H, CCH), 3.51 (s, 2H, cage−CH), 1.60−3.14
2664
dx.doi.org/10.1021/om500411b | Organometallics 2014, 33, 2661−2666

Organometallics
Article
1H NMR (CDCl3): δ 6.10 (q, JB−H = 5 Hz, 1H, CCH), 4.40
(m, 2H, Fc−CH), 4.19 (s, 5H, Fc−Cp), 4.16 (m, 2H, Fc−CH), 3.51
(s, 2H, cage−CH), 1.70−3.02 (br, 8H, cage−BH). 11B{1H} NMR
(CDCl3): δ 8.7 (1B, B−S), 8.1 (1B, B−S), −2.2 (2B), −11.4 (4B),
−12.9 (2B). 13C NMR (CDCl3): δ 129.2 (S−CC), 109.3 (S−CCH),
89.8 (Fc−C), 69.4 (Fc−Cp), 68.2 (Fc−CH), 66.1 (Fc−CH), 46.6
(cage−C). ESI-MS (positive ion mode) m/z: 439.41 (M + Na+, 100%). IR
(KBr): ν (cm−1) 2592 (B−H). Anal. Calcd for C14H20B10S2Fe: C, 40.38;
H, 4.84. Found: C, 40.11; H, 5.02.
Synthesis of S4−S8. Alkyne (1 mmol) was added to a CH2Cl2
(20 mL) solution of complex 2 (40.0 mg, 0.2 mmol), and the mixture
was stirred at 25 °C for 4 h. After removal of the solvent, the residue
was chromatographed on TLC. Elution with petroleum ether/CH2Cl2
(1:2) gave compounds S4−S8.
Compound S7, yield: 90%, white solid. Mp: 105−106 °C. 1H NMR
(CDCl3): δ 7.37 (q, JB−H = 5 Hz, 1H, CCH), 3.75 (s, 3H, OCH3),
3.58 (s, 2H, cage−CH), 1.63−3.39 (br, 8H, cage−BH). 11B{1H} NMR
(CDCl3): δ 7.1 (1B, B−S), 5.0 (1B, B−S), −1.1 (2B), −11.5 (4B),
−12.6 (2B). 13C NMR (CDCl3): δ 165.3 (CO), 129.2 (S−C
CH), 118.7 (S−CC), 52.6 (OCH3), 48.9 (cage−C), 48.5 (cage−C).
ESI-MS (positive ion mode) m/z: 314.50 (M + Na+, 100%). IR (KBr):
ν (cm−1) 2579 (B−H). Anal. Calcd for C6H14B10S2O2: C, 24.81; H,
4.86. Found: C, 24.69; H, 5.05.
1
Compound S4, yield: 92%, white solid. Mp: 97−98 °C. H NMR
(CDCl3): δ 7.24 (q, JB−H = 5 Hz, 1H, CCH), 3.70 (s, 2H, cage−
CH), 1.70−3.12 (br m, 8H, cage−BH), 2.32 (s, 3H, CH3). 11B{1H}
NMR (CDCl3): δ 7.2 (1B, B−S), 4.7 (1B, B−S), −1.1 (2B), −5.6
(1B), −11.1 (3B), −11.6 (2B). 13C NMR (CDCl3): δ 193.8 (CO),
149.0 (S−CC), 130.8 (S−CCH), 48.6 (cage−C), 49.1 (cage−C),
26.2 (CH3). ESI-MS (positive ion mode) m/z: 298.92 (M + Na+,
100%). IR (KBr): ν (cm−1) 2578 (B−H). Anal. Calcd for
C6H14B10S2O: C, 26.26; H, 5.14. Found: C, 26.02; H, 5.34.
1
Compound S8, yield: 89%, red solid. Mp: 125−126 °C. H NMR
(CDCl3): δ 7.08 (q, JB−H = 5 Hz, 1H, CCH), 4.81 (m, 2H, Fc−
CH), 4.50 (m, 2H, Fc−CH), 4.23 (s, 5H, Fc−Cp), 3.70 (s, 2H, cage−
CH), 1.93−3.49 (br, 8H, cage−BH). 11B{1H} NMR (CDCl3): δ 7.8
(1B, B−S), 6.0 (1B, B−S), −1.6 (2B), −11.3 (4B), −12.6 (2B). 13C
NMR (CDCl3): δ 195.5 (CO), 130.8 (S−CCH), 126.2 (S−C
C), 72.2 (Fc−CH), 71.2 (Fc−CH), 70.3 (Fc−Cp), 48.6 (cage−C),
48.2 (cage−C). ESI-MS (positive ion mode) m/z: 468.50 (M + Na+,
100%). IR (KBr): ν (cm−1) 2572 (B−H). Anal. Calcd for
C15H20B10S2OFe: C, 40.54; H, 4.53. Found: C, 40.33; H, 4.39.
ASSOCIATED CONTENT
* Supporting Information
Calculation details and crystallographic data (CIF, CCDC Nos.
996700−996710). This material is available free of charge via
the Internet at http://pubs.acs.org.
■
S
Compound S5, yield: 93%, white solid. Mp: 133−134 °C. 1H NMR
(CDCl3): δ 7.59 (m, 1H, furyl −CH), 7.33 (q, JB−H = 5 Hz, 1H, C
CH), 7.08 (m, 1H, furyl −CH), 6.50 (m, 1H, furyl −CH), 3.83 (s, 1H,
cage−CH), 3.78 (s, 1H, cage−CH) 1.90−3.42 (br, 8H, cage−BH).
11B{1H} NMR (CDCl3): δ 7.1 (1B, B−S), 5.0 (1B, B−S), −1.3 (2B),
−11.3 (4B), −12.6 (2B). 13C NMR (CDCl3): δ 179.6 (CO), 151.1
(S−CC), 146.1 (furyl−CH), 132.0 (S−CCH), 128.9 (furyl−C),
119.6 (furyl−CH), 112.2 (furyl−CH), 49.3 (cage−C), 48.8 (cage−C).
ESI-MS (positive ion mode) m/z: 350.58 (M + Na+, 100%). IR (KBr):
ν (cm−1) 2583 (B−H). Anal. Calcd for C9H14B10S2O2: C, 33.11; H,
4.32. Found: C, 32.89; H, 4.49.
AUTHOR INFORMATION
Corresponding Author
*E-mail: hyan1965@nju.edu.cn.
Notes
■
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
This work was supported by the National Basic Research
Program of China (2010CB923303 and 2013CB922101), the
National Science Foundation of China (21271102), the Natural
Science Foundation of Jiangsu Province (BK20130054), and
Graduate Innovation Fund of China (2012CL03). We are
grateful to the High Performance Computing Center (HPCC)
of Nanjing University for calculations.
REFERENCES
■
Compound S6, yield: 91%, white solid. Mp: 125−126 °C. 1H NMR
(CDCl3): δ 7.54−7.38 (m, 5H, Ph), 6.94 (q, JB−H = 5 Hz, 1H, C
CH), 3.80 (s, 1H, cage−CH), 3.75 (s, 1H, cage−CH), 1.63−3.39 (br,
8H, cage−BH). 11B{1H} NMR (CDCl3): δ 8.4 (1B, B−S), 7.4 (1B,
B−S), −1.2 (2B), −11.4 (4B), −12.5 (2B). 13C NMR (CDCl3): δ
193.7 (CO), 143.0 (Ph), 129.1 (S−CCH), 118.8 (S−CC),
131.4 (Ph), 129.8 (Ph), 129.8 (Ph), 128.2 (Ph), 49.3 (cage−C), 48.7
(cage−C). ESI-MS (positive ion mode) m/z: 360.50 (M + Na+,
100%). IR (KBr): ν (cm−1) 2572 (B−H). Anal. Calcd for
C11H16B10S2O: C, 39.26; H, 4.79. Found: C, 38.99; H, 4.66.
(1) (a) Kobayashi, K. J.; Gajurel, C. L. Sulfur Rep. 1986, 7, 123−148.
(b) Klar, G. In Methods of Organic Chemistry, Vol. E9a; Schauruann, E.,
Ed.; Thierue: Stuttgart, 1997; pp 250−407.
(2) Ames, R. B. Proc. Plant Growth Regul. Soc. Am. 1996, 23, 243−
248.
(3) (a) Arora, S. K.; Bates, R. B.; Kriek, G. R.; Brewer, A. D. Acta
Crystallogr. 1978, B34, 2918−2920. (b) Bates, R. B.; Kriek, G. R.;
Brewer, A. D. Acta Crystallogr. 1980, B36, 736−738. (c) Brewer, A. D.;
Neidermyer, R. W.; McIntire, W. S. US Patent 3920438, 1975.
(d) Brewer, A. D.; Neidermyer, R. W.; McIntire, W. S. US Patent
2665
dx.doi.org/10.1021/om500411b | Organometallics 2014, 33, 2661−2666

Organometallics
Article
3997323, 1976. (e) Ferguson, G.; Lough, A. J.; Brewer, A. D. Acta
Crystallogr. 1990, C46, 1287−1289. (f) Ferguson, G.; Kaitner, B.;
Brewer, A. D. Acta Crystallogr. 1990, C46, 1284−1287.
(16) Plese
Commun. 1980, 45, 1775−1779.
(17) Zhang, X. L.; Tang, X.; Yang, J. J.; Li, Y. Z.; Yan, H.; Bregadze,
V. I. Organometallics 2013, 32, 2014−2018.
̌
k, J.; Janousek, Z.; Hermanek, S. Collect. Czech. Chem.
(4) (a) Scott, M. K.; Ross, T. M.; Lee, D. H. S.; Wang, H. Y.; Shank,
R. P.; Wild, K. D.; Davis, C. B.; Crooke, J. J.; Potocki, A. C.; Reitz, A.
B. Bioorg. Med. Chem. 2000, 8, 1383−1391. (b) Nakayama, J.;
Nakamura, Y.; Hoshino, M. Heterocycles 1985, 23, 1119−1122.
(5) (a) Chee, G. L.; Bhattarai, B.; Nash, J. D.; Madec, K.; Hasinoff, B.
B.; Brewer, A. D. Can. J. Chem. 2013, 91, 649−655. (b) Metzger, J. D.;
Keng, J. J. Plant Growth Regul. 1984, 3, 141−143. (c) Metzger, J. D.;
Keng, J. J. Plant Growth Regul. 1987, 6, 33−35.
(18) (a) Li, Y. G.; Ye, H. D.; Guoyiqibayi, G.; Jiang, Q. B.; Li, Y. Z.;
Yan, H. Sci. China: Chem. 2010, 53, 2129−2138. (b) Zhang, R.; Zhu,
L.; Lu, Z. Z.; Yan, H.; Bregadze, V. I. Dalton Trans. 2012, 41, 12054−
12063. (c) Bai, W. J.; Liu, G. F.; Guoyiqibayi, G.; Yan, H.
Organometallics 2011, 30, 5188−5195.
(19) (a) Xu, B. H.; Peng, X. Q.; Li, Y. Z.; Yan, H. Chem.Eur. J.
2008, 14, 9347−9356. (b) Ye, H. D.; Ding, G. Y.; Xie, M. S.; Li, Y. Z.;
Yan, H. Dalton Trans. 2011, 40, 2306−2313.
(6) Valliant, J. F.; Guenther, K. J.; King, A. S.; Morel, P.; Schaffer, P.;
Sogbein, O. O.; Stephenson, K. A. Coord. Chem. Rev. 2002, 232, 173−
230.
́ ́
(20) (a) Cocinero, E. J.; Sanchez, R.; Blanco, S.; Lesarri, A.; Lopez, J.
C.; Alonso, J. L. Chem. Phys. Lett. 2005, 402, 4−6. (b) Desiraju, G. R.;
Steiner, T. The Weak Hydrogen Bond in Structural Chemistry and
Biology; Oxford University Press: Oxford, 2001. (c) Steiner, T. Angew.
Chem., Int. Ed. 2002, 41, 48−76. (d) Desiraju, G. R. Acc. Chem. Res.
2002, 35, 565−573. (e) Jetti, R. K. R.; Boese, R.; Thakur, T. S.;
Vangala, V. R.; Desiraju, G. R. Chem. Commun. 2004, 2526−2527.
(f) Van den Berg, J. A.; Seddon, K. R. Cryst. Growth Des. 2003, 3, 643−
661.
(7) (a) Grimes, R. N. Carboranes, 2nd ed.; Elsevier, 2011. (b) Grimes,
R. N. Coord. Chem. Rev. 2000, 200, 773−811. (c) Plesek, J. Chem. Rev.
1992, 92, 269−278. (d) Hawthorne, M. F. Angew. Chem., Int. Ed. 1993,
32, 950−984. (e) Wedge, T. J.; Hawthorne, M. F. Coord. Chem. Rev.
2003, 240, 111−128. (f) Saxena, A. K.; Maguire, J. A.; Hosmane, N. S.
Chem. Rev. 1997, 97, 2421−2462. (g) Bregadze, V. I. Chem. Rev. 1992,
92, 209−223. (h) Masalles, C.; Llop, J.; Teixidor, F. Adv. Mater. 2002,
14, 826−829.
(21) Hardie, M. J.; Raston, C. L. Eur. J. Inorg. Chem. 1999, 1, 195−
200.
(8) (a) Hosmane, N. S. Boron Science: New Technologies and
Applications; CRC Press, 2011. (b) Hawthorne, M. F.; Maderna, A.
Chem. Rev. 1999, 99, 3421−3434. (c) Bregadze, V. I.; Sivaev, I. B.;
Glazun, S. A. Anti-Cancer Agents Med. Chem. 2006, 6, 75−109.
(22) Harakas, G.; Vu, T.; Knobler, C. B.; Hawthorne, M. F. J. Am.
Chem. Soc. 1998, 120, 6405−6406.
(23) Lee, H.; Knobler, C. B.; Hawthorne, M. F. Chem. Commun.
2000, 2485−2486.
̌
̌
̌ ́
(d) Cigler, P.; Kozisek, M.; Kral, V.; Konvalinka, J. Proc. Natl. Acad. Sci.
(24) Planas, J. G.; Vinas, C.; Teixidor, F.; Comas-Vives, A.; Ujaque,
̃
U.S.A. 2005, 102, 15394−15399. (e) Wu, C. H.; Shi, L. X.; Yan, H.;
Wang, X. M. Nanomedicine 2012, 8, 860−869. (f) Dash, B. P.;
Satapathy, R.; Hosmane, N. S. J. Am. Chem. Soc. 2010, 132, 6578−
6587. (g) Zhu, Y. H.; Peng, A. T.; Carpenter, K. J.; Maguire, A.;
Hosmane, N. S. J. Am. Chem. Soc. 2005, 127, 9875−9880. (h) Wee, K.
R.; Han, W. S.; Kang, S. O. Angew. Chem., Int. Ed. 2012, 51, 2677−
2680.
́
G.; Lledos, A.; Light, M. E.; Hursthouse, M. B. J. Am. Chem. Soc. 2005,
127, 15976−15982.
(25) Zhang, J. S.; Jin, G. X. Inorg. Chem. Commun. 2008, 11, 145−
147.
(26) Barriga, S.; Marcos, C. F.; Riant, O.; Torroba, T. Tetrahedron
2002, 58, 9785−9792.
(9) (a) Xu, B. H.; Peng, X. Q.; Xu, Z. W.; Li, Y. Z.; Yan, H. Inorg.
Chem. 2008, 47, 7928−7933. (b) Ye, H. D.; Xu, B. H.; Xie, M. S.; Li,
Y. Z.; Yan, H. Dalton Trans. 2011, 40, 6541−6546. (c) Bai, W. J.; Liu,
G. F.; Guoyiqibayi, G.; Yan, H. Organometallics 2011, 30, 5188−5195.
(10) Wu, C.; Xu, B.; Zhao, J.; Jiang, Q.; Wei, F.; Jiang, H.; Wang, X.;
Yan, H. Chem.Eur. J. 2010, 16, 8914−8922.
(11) Wu, C. H.; Ye, H. D.; Bai, W. J.; Li, Q. N.; Guo, D. D.; Lv, G.;
Yan, H.; Wang, X. M. Bioconjugate Chem. 2011, 22, 16.
(12) (a) Bosdet, M. J. D.; Piers, W. E. Can. J. Chem. 2009, 87, 8−29.
(b) Liu, Z.; Marder, T. B. Angew. Chem., Int. Ed. 2008, 47, 242−244.
(c) Spokoyny, A. M.; Machan, C. W.; Clingerman, D. C.; Rosen, M. S.;
Wiester, M. J.; Kennedy, R. D.; Sarjeant, A. A.; Stern, C. L.; Mirkin, C.
A. Nat. Chem. 2011, 3, 590−596. (d) Spokoyny, A. M.; Lewis, C. D.;
Teverovskiy, G.; Buchwald, S. L. Organometallics 2012, 31, 8478−
8481.
(13) (a) Won, J. H.; Kim, D. H.; Kang, S. O. Organometallics 2002,
21, 1443−1453. (b) Herberhold, M.; Yan, H.; Milius, W.;
Wrackmeyer, B. J. Organomet. Chem. 1999, 587, 252.
(14) (a) Herberhold, M.; Yan, H.; Milius, W.; Wrackmeyer, B. Angew.
Chem., Int. Ed. 1999, 38, 3689−3691. (b) Herberhold, M.; Yan, H.;
Milius, W.; Wrackmeyer, B. Chem.Eur. J. 2002, 8, 388−395.
(c) Zhong, W.; Xie, M. S.; Jiang, Q. B.; Li, Y. Z.; Yan, H. Chem.
Commun. 2012, 48, 2152−2154. (d) Zhang, R.; Zhu, L.; Liu, G. F.;
Dai, H. M.; Lu, Z. Z.; Zhao, J. B.; Yan, H. J. Am. Chem. Soc. 2012, 134,
10341−10344. (e) Wang, Z. J.; Ye, H. D.; Li, Y. G.; Li, Y. Z.; Yan, H. J.
Am. Chem. Soc. 2013, 135, 11289−11298. (f) Liu, G. F.; Hu, J. R.; Yan,
H. Inorg. Chem. 2011, 50, 4187−4194. (g) Li, Y. G.; Jiang, Q. B.;
Zhang, X. L.; Yan, H.; Bregadze, V. I. Inorg. Chem. 2010, 49, 3911−
3917.
(15) (a) Liu, S.; Han, Y. F.; Jin, G. X. Chem. Soc. Rev. 2007, 36,
1543−1560. (b) Meng, X.; Wang, F. S.; Jin, G. X. Coord. Chem. Rev.
2010, 254, 1260−1272. (c) Yao, Z. J.; Jin, G. X. Organometallics 2012,
31, 1767−1774. (d) Wang, X.; Jin, G. X. Organometallics 2004, 23,
6319−6322. (e) Wang, X.; Jin, G. X. Chem.Eur. J. 2005, 11, 5758.
2666
dx.doi.org/10.1021/om500411b | Organometallics 2014, 33, 2661−2666