126
G.J. Meyer et al. / Polyhedron 86 (2015) 125–132
NMR (500 MHz, CD2Cl2) d 5.04 (s, 1H), 6.87 (t, J = 7.0 Hz, 1H),
7.52 (d, J = 7.0 Hz, 2H); IR (KBr) 1400, 1421, 1543, 2553 (SH),
3064, 3458 cmÀ1
2. Materials and methods
.
2.1. General methods and instrumentation
2.2.3. 2,6-Dibromo-1-(tert-butylthio)benzene
All reactions were carried out under inert atmosphere with
standard Schlenk techniques. THF and hexane were dried and
distilled prior to use according to standard methods. Thin layer
chromatography (TLC) was carried out on EMD Chemical, Inc.
TLC Plastic Sheets Si 60 F254. Column chromatography was
performed using Dynamic Adsorbents 32–63 micron flash silica
gel. 2,6-Dibromoaniline and tert-butyl lithium were purchased
from Alfa Aesar Chemical Company. All other reagents were pur-
chased from Aldrich Chemical Co. and were used without further
purification unless otherwise stated. tert-Butanol was purchased
from J.T. Baker Inc., 200 proof ethanol was purchased from Decon
Laboratories, Inc. and all other solvents were purchased from
EMD Chemical, Inc. Tetrabutylammonium tetrakis(pentafluor-
ophenyl)borate was supplied by Boulder Scientific Co. Proton and
carbon-13 nuclear magnetic resonance (NMR) spectra were
recorded on Varian-300, Bruker DRX-500 and Bruker DRX-600
spectrometers. Chemical shifts are reported in parts per million
using residual NMR solvent as reference. Infrared spectra were
recorded on a Nicolet Impact-410 spectrophotometer. All melting
points are uncorrected and were recorded on Thomas Hoover
Uni-Melt apparatus. All mass spectra were done at the University
of Arizona Mass Spectrometry Facility using a JEOL HX110A high
resolution mass spectrometer.
This compound was prepared using modified procedures
[33,34].
A
solution of 2,6-dibromothiophenol (180 mg,
0.671 mmol), t-butanol (0.332 mL, 3.49 mmol), AcOH (2.7 mL),
and acetic anhydride (0.387 mL) was stirred at 0 °C for 20 min
under argon, and then 70% aqueous HClO4 (0.108 mL) was added.
The solution was allowed to warm to room temperature and
stirred overnight. After t-butanol was removed under reduced
pressure, water (50 mL) was added to the solution. The solution
was extracted with CH2Cl2 (3 Â 50 mL). The combined organic
layer was washed with NaOH (50 mL), brine (50 mL), dried with
anhydrous MgSO4, filtered and evaporated under reduced pressure.
The resulting crude product was purified by silica gel chromatogra-
phy using hexanes as eluent to give 2,6-dibromo-1-(tert-butyl-
thio)benzene as a slightly yellow oil (87%-quantitative yield): 1H
NMR (600 MHz, CD2Cl2) d 1.41 (s, 9H), 7.02 (t, J = 9.0 Hz, 1H),
7.68 (d, J = 9.0 Hz, 2H); 13C NMR (600 MHz, CD2Cl2) d 32.22,
52.71, 131.64, 133.44, 135.50, 136.38; IR (neat) 1413, 1542,
2959 cm–1
; HRMS (GCT MS EI+, m/z): Calcd for C10H12Br2S,
321.9026; Found: 321.9013.
2.2.4. 2,6-Diferrocenyltoluene (2)
To a solution of 2,6-dibromotoluene (15 mg, 0.06 mmol) in dis-
tilled 1,4-dioxane (0.08 mL) under argon, were added a 3 M aque-
ous solution of NaOH (0.11 mL), ferroceneboronic acid (90 mg,
0.4 mmol), and Pd(PPh3)4 (13 mg, 0.011 mmol). The reaction was
stirred for 16 h. H2O (15 mL) was added to the resulting suspension
and extracted with dichloromethane (10 mL). The organic layer
was washed successively with 1 M NaOH (10 mL), brine (10 mL),
and H2O (10 mL), dried with anhydrous MgSO4, filtered and evap-
orated under reduced pressure. The crude product was purified by
flash silica gel chromatography using 15% dichloromethane in hex-
anes as eluent to give 2,6-bisferrocenyltoluene as a red–orange
solid (78%, Rf = 0.25): m.p. 139.5–141.0 °C (decomposition at
205 °C); 1H NMR (500 MHz, CDCl3) d 2.27 (3 H, s), 4.22 (10 H, s),
4.26 (4H, J = 1.8 Hz, t), 4.42 (4H, J = 1.9 Hz, t), 7.21 (1H, J = 7.7 Hz,
t), 7.73 (2H, J = 7.6 Hz, d); 13C NMR d 13.14, 67.54, 69.49, 70.59,
89.03, 124.59, 124.59, 129.50, 134.63, 137.98; IR: 1413, 1542,
2857, 2959 cmÀ1; HRMS (m/z): Calcd for C27H24Fe2, 460.0576;
Found: 460.05687.
2.2. Synthesis
2.2.1. 1,3-Diferrocenyl benzene (1)
This known compound was synthesized using a modification of
the procedure reported by Patoux et al. [32]. 1,3-Diferrocenylben-
zene was prepared from the Suzuki–Miyaura cross coupling
reaction of 5 eq. of ferrocenylboronic acid in 1,4-dioxane and 3 M
NaOH in the presence of a Pd(PPh3)2Cl2 catalyst to afford the
desired product as a red solid.
2.2.2. 2,6-Dibromobenzenethiol
A solution of NaNO2 (205 mg, 2.97 mmol) in H2O (1.5 mL) was
added dropwise to a suspension of 2,6-dibromoaniline (678 mg,
2.70 mmol) in 12 M aqueous HCl (2.6 mL) at 0 °C. The mixture
was stirred at 0 °C for 90 min. Additional NaNO2 (55 mg,
0.80 mmol) was added. The mixture was stirred for an additional
45 min at 0 °C and then the resulting cold solution was added
2.2.5. 2,6-Bisferrocenyl-1-(tert-butylthio)benzene (3)
dropwise to
a
stirred solution of potassium ethylxanthate
To a solution of 2,6-dibromo(tert-butylthio)benzene (50 mg,
0.21 mmol) in distilled 1,2-dimethoxyethane (0.2 mL) under argon,
were added a 3 M aqueous solution of NaOH (0.25 mL), ferroceneb-
oronic acid (230 mg, 1.05 mmol), and Pd(PPh3)4 (17 mg,
0.021 mmol). The mixture was stirred at reflux for 24 h. H2O
(15 mL) was added to the resulting suspension and extracted with
dichloromethane (2 Â 15 mL). The organic layer was washed suc-
cessively with water (15 mL) and brine (30 mL), dried with anhyd
MgSO4, filtered and evaporated under reduced pressure. The crude
product was purified by flash silica gel chromatography using 15%
CH2Cl2 in hexanes as eluent to give 2,6-bisferrocenyl-1-(tert-butyl-
thio)benzene as a red–orange solid (62% yield, Rf = 0.15). The prod-
uct was further purified by recrystallization twice using hexanes:
m.p. 184.3–185.2 °C (decomposition at 240 °C); 1H NMR
(500 MHz, CDCl3) d 0.65 (9 H, s), 4.18 (10 H, s), 4.26 (2H, br s),
4.30 (2H, br s), 4.40 (2H, br s), 5.00 (2H, br s), 7.34 (1H,
J = 7.7 Hz, t), 7.83 (2H, J = 7.6 Hz, d); 13C NMR d 30.86, 49.26,
67.15, 67.48, 69.58, 72.27, 73.24, 89.11, 127.44, 129.79, 131.08,
146.36; IR: 1413, 1535, 2857, 2960 cmÀ1; HRMS (GCT MS EI+, m/
z): Calcd for C30H30SFe2, 534.0767; Found: 534.07623.
(525 mg, 3.27 mmol) in H2O (0.65 mL) at 45 °C through a glass
pipet with a plug of glass wool. The reaction mixture was stirred
for 30 min at this temperature and then allowed to cool to room
temperature. The reaction mixture was extracted with diethyl
ether (3 Â 50 mL). The combined organic extracts were washed
successively with 1 M NaOH solution (100 mL), water
(3 Â 50 mL), brine (50 mL), dried over anhyd MgSO4, filtered and
evaporated under reduced pressure. The resulting crude product
was dissolved in ethanol (8 mL) and heated to reflux. Potassium
hydroxide pellets (654 mg, 11.6 mmol) were added and refluxing
continued overnight. After cooling to room temperature, the
ethanol was evaporated under reduced pressure. The residue was
dissolved in water and washed with diethyl ether (100 mL). The
aqueous layer was acidified with 1 M HCl to pH 2 and extracted
with diethyl ether (3 Â 50 mL). The organic extracts were washed
with water (50 mL), brine (50 mL), dried over anhydr MgSO4, fil-
tered and evaporated under reduced pressure. The residue was
purified by silica gel chromatography using hexanes as eluent to
give the product as a slightly yellow solid (518 mg, 72%): 1H