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J.-C. Chang et al. / Polyhedron 30 (2011) 497–507
that no tetrahalometallate (II) salts in which each tetrahalometal-
late (II) dianion is combined with a counterdication rather than
two countermonocations, this paper for the first time presents a
new series tetrachlorocobaltate (II) or tetrachloromanganate (II)
salts in which each tetrahalometallate (II) dianion is associated
with a dication formed from 1-methylimidazolium, pyridinium,
triethylammonium, and triphenylphosphinium. Due to the struc-
ture difference between the mono-cations and dications, the dicat-
ionic ILs are expected to exhibit different physical properties from
their corresponding monocationic ILs. The thermal properties, sol-
ubility in organic solvents, and magnetic susceptibility of these
dicationic ILs are discussed.
2.3.1. [1-(1-Pyridinium-yl-propyl)-3-methylimidazolium] dibromide
(2a)
Yield 88%. 1H NMR (200 MHz, D2O): d 2.70 (quin, J = 7.5 Hz, 2H),
3.92 (s, 3H), 4.43 (t, J = 7.5 Hz, 2H), 4.77 (t, J = 7.5 Hz, 2H), 7.49 (s,
1H), 7.56 (s, 1H), 8.12 (t, J = 7.1 Hz, 2H), 8.61 (t, J = 7.3 Hz, 1H),
8.84 (s, 1H), 8.92 (d, J = 6.5 Hz, 2H).
2.4. General procedure for the synthesis of bromide anions salt
containing geminal dications and propyl linkage chains (2b)
1,3-Dibromopropane (5.0 g, 24.8 mmol) was reacted with pyri-
dine (3.9 g, 49.5 mmol), stirred in methanol and refluxed for 24 h,
and then precipitated from ethyl acetate to obtain the required
products (all white solids for 2b, 8.5 g).
2. Experimental
2.4.1. [1,10-(Propane-1,3-diyl)-bis(pyridinium)] dibromide (2b)
Yield 95%. 1H NMR (200 MHz, D2O): d 2.86 (quin, J = 7.8 Hz, 2H),
4.86 (t, J = 7.8 Hz, 4H), 8.14 (t, J = 7.3 Hz, 4H), 8.62 (t, J = 7.3 Hz, 2H),
8.96 (t, J = 6.5 Hz, 4H).
2.1. General
1,3-Dibromopropane (Alfa Aesar, purity: 99.9%), 1,4-dibromo-
butane (Alfa Aesar, purity: 99.9%), pyridine (Fluka, purity: 98%),
1-methylimidazole (Fluka, purity: 99.9%), triphenylphosphine (Flu-
ka, purity: 99.9%), triethylamine (Fluka, purity: 99.9%), cobalt
dichloride hexahydrate (Showa, purity: 99.9%), manganese dichlo-
ride tetrahydrate (Showa, purity: 99.9%), methanol (J.T. Baker, ACS
grade, 60.01% H2O), and ethanol (J.T. Baker, ACS grade, 60.01%
H2O) were purchased from a commercial supplier and used with-
out any pre-treatment.
2.5. General procedure for the synthesis of bromide anions salt
containing geminal dications and butyl linkage chains (2c, 2d, 2e, and
2f)
1,4-Dibromopropane (5.0 g, 23.2 mmol) was reacted with 1-
methylimidazole (3.8 g), pyridine (3.7 g), triethylamine (4.7 g),
and triphenylphosphine (12.1 g), respectively (all using 46.3 mmol),
stirred in methanol under reflux for 24 h, and then precipitated
from ethyl acetate to obtain the required products (all white solids
for 2c (8.1 g), 2d (8.3 g), 2e (9.0 g), and 2f (15.9 g)).
The 1H spectra of the purified products (for 1, 2a–2f) were re-
corded in D2O (Cambridge Isotope Laboratories Inc., 99.9% D) on
a Bruker Avance 200 spectrometer at 200 MHz at a temperature
of 25 °C. The crystal structures, which were dissolved in methanol
and crystallized by ethyl ether, were characterized with an X-ray
single-crystal diffractometer (model: Siemens Smart CCD,
Germany). Elemental analyses were conducted using an Elementar
analyzer (model: Vario EL III), thermal decomposition tempera-
tures were measured using a thermogravimetic analyzer (TGA,
model: TGA-50, Shimadzu) with a heating rate of 10 °C/min (the
Td was selected at a temperature corresponding to 10% weight
loss), melting points were measured using a capillary melting point
apparatus (model: Buchi B-540) with a heating rate of 10 °C/min,
2.5.1. [1,10-(Butane-1,4-diyl)-bis(di-pyridinium)] dibromide (2c)
Yield 94%. 1H NMR (200 MHz, D2O): d 2.14 (quin, J = 7.3 Hz, 4H),
4.70 (t, J = 7.3 Hz, 4H), 8.09 (t, J = 7.1 Hz, 4H), 8.57 (t, J = 7.1 Hz, 2H),
8.87 (t, J = 7.1 Hz, 4H).
2.5.2. [1,10-(Butane-1,4-diyl)-bis(3-methylimidazolium)] dibromide
(2d)
Yield 94%. 1H NMR (200 MHz, D2O): d 1.94 (quin, J = 7.3 Hz, 4H),
3.91 (s, 6H), 4.28 (t, J = 7.3 Hz, 4H), 7.47 (s, 2H), 7.50 (s, 2H), 8.58 (s,
2H).
and direct current magnetic susceptibility (called
vMT value) was
measured using a superconducting quantum interference device
(SQUID, model: MPMS7, Quantum Design).
2.5.3. [1,10-(Butane-1,4-diyl)-bis(triethylaminonium)] dibromide (2e)
Yield 93%. 1H NMR (200 MHz, D2O): d 1.27–1.39 (m, 18H), 1.79–
1.90 (m, 4H), 3.29–3.43 (m, 16H).
2.2. General procedure for the synthesis of 1
2.5.4. [1,10-(Butane-1,4-diyl)-bis(triphenylphosphonium)] dibromide
(2f)
Pyridine (5.0 g, 63.2 mmol) was mixed with 1,3-dibromopro-
pane (19.1 g, 94.8 mmol) and stirred under neat condition at room
temperature for 4 days, and then washed using ethyl acetate to ob-
tain the required products (white solids for 1, 17.6 g).
Yield 93%. 1H NMR (200 MHz, D2O): d 1.74–1.78 (m, 4H), 3.24–
3.30 (m, 4H), 7.64–7.86 (m, 30H).
2.6. General procedure for the synthesis of [CoCl4]2ꢀ anion salts (3a1,
3b1, 3c1, 3d1, 3e1, and 3f1)
2.2.1. [1-(3-Bromopropyl)pyridinium] bromide (1)
Yield 99%. 1H NMR (200 MHz, D2O): d 2.58 (quin, J = 6.6 Hz, 2H),
3.48 (t, J = 6.6 Hz, 2H), 4.85 (t, J = 6.6 Hz, 2H), 8.08 (t, J = 6.8 Hz, 2H),
8.54 (t, J = 7.2 Hz, 1H), 8.89 (d, J = 6.3 Hz, 2H).
Compounds 2a (3.0 g, 8.3 mmol), 2b (3.0 g, 8.3 mmol), 2c (3.0 g,
8.0 mmol), 2d (3.0 g, 7.9 mmol), 2e (3.0 g, 7.2 mmol), and 2f (3.0 g,
4.1 mmol), respectively, were reacted with cobalt dichloride hexa-
hydrate (4.9 g, 20.7 mmol reacted with 2a; 5.0 g, 20.8 mmol with
2b; 4.8 g, 20.0 mmol with 2c; 4.7 g, 19.7 mmol with 2d; 4.3 g,
17.9 mmol with 2e; 2.4 g, 10.1 mmol with 2f), and stirred in etha-
nol at room temperature for 4 days. The required products were
then precipitated from ethanol (all blue solids for 3a1 (2.7 g),
3b1 (2.8 g), 3c1 (2.8 g), 3d1 (2.9 g), 3e1 (2.7 g), and 3f1 (2.5 g)).
The detailed crystal structure refinements are summarized in sup-
porting information. The element analysis data are described
below.
2.3. General procedure for the synthesis of bromide anion salts
containing unsymmetrical dications (2a)
Compound 1 (5.0 g, 17.8 mmol) was reacted with 1-methylim-
idazole (2.9 g, 35.6 mmol), and stirred in methanol under reflux
for 24 h, and then precipitated from ethyl acetate to obtain the re-
quired products (white solids for 2a, 5.7 g).