Synthesis and properties of new tetrachlorocobaltate (II) and tetrachloromanganate (II) anion salts with dicationic counterions

Article abstract of DOI:10.1016/j.poly.2010.11.009

New tetrachlorocobaltate (II) and tetrachloromanganate (II) ionic compounds containing various counterdications were synthesized and characterized. These salts are soluble in polar solvents such as methanol and water. Physical properties such as thermal stability, melting point, and magnetic susceptibility of these salts depend on the cation or anion structure. The thermal stability of the phosphinium or imidazolium based salts is higher than that of the pyridinium or triethylaminonium analogues. The melting point of these compounds is following the order of triphenylphosphinium > pyridinium > imidazolium dications, and symmetrical dicationic salts > unsymmetrical ones. The magnetic susceptibility (χ_MT values) of tetrachloromanganate (II) anions-based salts is higher than that of tetrachlorocobaltate (II) anions-based salts. These dicationic salts exhibit weak antiferromagnetic interactions and have higher magnetic susceptibility than that of the previously reported tetrachloromanganate (II) and tetrachlorocobaltate(II) salts with monocationic counterion.

Full text of DOI:10.1016/j.poly.2010.11.009

Polyhedron 30 (2011) 497–507
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Polyhedron
journal homepage: www.elsevier.com/locate/poly
Synthesis and properties of new tetrachlorocobaltate (II)
and tetrachloromanganate (II) anion salts with dicationic counterions
a,
b
b
a
Jui-Cheng Chang a, Wen-Yueh Ho b, , I-Wen Sun , Yu-Kai Chou , Hsin-Hsiu Hsieh , Tzi-Yi Wu
⇑
⇑
a Department of Chemistry, National Cheng Kung University, Tainan, Taiwan
b Department of Cosmetic Science, Chia Nan University of Pharmacy and Science, Tainan, Taiwan
a r t i c l e i n f o
a b s t r a c t
Article history:
New tetrachlorocobaltate (II) and tetrachloromanganate (II) ionic compounds containing various count-
erdications were synthesized and characterized. These salts are soluble in polar solvents such as metha-
nol and water. Physical properties such as thermal stability, melting point, and magnetic susceptibility of
these salts depend on the cation or anion structure. The thermal stability of the phosphinium or imidazo-
lium based salts is higher than that of the pyridinium or triethylaminonium analogues. The melting point
of these compounds is following the order of triphenylphosphinium > pyridinium > imidazolium dica-
Received 17 October 2010
Accepted 9 November 2010
Available online 16 November 2010
Keywords:
Dication
Ionic liquid
Tetrachlorocobaltate (II) anion
Tetrachloromanganate (II) anion
Magnetic susceptibility
tions, and symmetrical dicationic salts > unsymmetrical ones. The magnetic susceptibility (vMT values)
of tetrachloromanganate (II) anions-based salts is higher than that of tetrachlorocobaltate (II) anions-
based salts. These dicationic salts exhibit weak antiferromagnetic interactions and have higher magnetic
susceptibility than that of the previously reported tetrachloromanganate (II) and tetrachlorocobaltate(II)
salts with monocationic counterion.
Ó 2010 Elsevier Ltd. All rights reserved.
1. Introduction
than 100 °C, they are still called ‘‘ionic liquids’’ for convenience
[9,10] since they are liquid at the temperatures they are employed.
Ionic compounds formed with organic cations often show much
lower melting point than the inorganic analogous. Salts are usually
defined as ionic liquids (ILs) when they are liquids at temperature
lower than 100 °C. Most of the common ILs studied so far are made
from the popular mono-cations, such as imidazolium or pyridini-
Dicationic ILs have been classified as geminal (the two mono-
cations that form the dication are the same, for example, imidazo-
lium-R-imidazolium where R is the alky linker) or unsymmetrical
(the mono-cations are different, for example, imidazolium-R-
pyridinium). While dicationic ILs in whiꢀch each dicatiꢀon is associ-
ated with two monoanions such as PF6 and/or NTf2 have been
intensively reported, dicationic ILs in which each dication is asso-
ciated with a transition metal complex dianion have not been
studied.
Compounds of tetrahalometallate (II) dianion have been studied
for their magnetic behavior in recent years. Preparation, crystal
structure, and spectra characterization of [EMIM]2[CoCl4]
(EMIM = 1-ethyl-3-methylimidazolium), was reported in 1993
[13]. Turnbull et al. studied the crystal configuration and magnetic
behavior of A2[MX4] salts (A = N-methylmorpholinium; M = Co, Cu,
Mn; X = Cl, Br) [14]. Del Sesto et al. discussed the magnetic behav-
ior of ionic liquids containing trihexyl(tetradecyl)phosphonium
[PR4], 1-decyl-3-methylimidazolium [C10mim], and 1-butyl-
3-methylimidazolium [C4mim] cations with transition metal
complex anions such as [FeCl4]ꢀ, [MnBr4]2ꢀ, and [MnCl4]2ꢀ [15].
Hanusa et al. reported the composition, viscosity, and thermal
behavior of ILs incorporating tetrachloronickelate [NiCl4]2ꢀ anions
[16]. In the compounds reported in the early literatures, each tet-
rahalometallate (II) dianion is almost unexceptionally combined
with two separate mono-cations as counterions. In view of the fact
um, with inorganic anions, such as Clꢀ, PF6ꢀ, or NTf2 (bis(trifluo-
ꢀ
romethanesulfonyl)amide). The physical and chemical properties
of ILs can be readily manipulated by controlling the nature and
functionality of the cations and anions to allow a myriad of appli-
cations [1–3], including organic synthesis [4], electrochemistry [5],
electrolytes for capacitors [6], dye-sensitized solar cells (DSSC) [7],
and stationary phases in gas chromatography [8], thermal stability
of the ILs also become more important.
For certain applications such as gas chromatography, the ther-
mal stability of the aforementioned ILs is often not satisfactory.
To improve the thermal stability, a series of ionic salts, in which
two mono-cations are linked together to form a dication that is
charge balanced by two separate monoanions, has been developed
and the salts are termed dicationic ILs [9–12]. By doing so the ther-
mal stability of the resulted salts is significantly improved.
Although many of the dicationic salts exhibit melting points higher
⇑
Corresponding authors.
E-mail addresses: rickho@mail.chna.edu.tw (W.-Y. Ho), iwsun@mail.ncku.edu.tw
(I-W. Sun).
0277-5387/$ - see front matter Ó 2010 Elsevier Ltd. All rights reserved.
doi:10.1016/j.poly.2010.11.009

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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).

J.-C. Chang et al. / Polyhedron 30 (2011) 497–507
499
Scheme 1. Synthesis procedures for magnetic [CoCl4]2ꢀ and [MnCl4]2ꢀ anion salts that contain (a) unsymmetrical and (b) geminal dicationic moieties.
2.6.1. [1-(1-Pyridinium-yl-propyl)-3-methylimidazolium]
tetrachlorocobaltate (II) (3a1)
2.6.2. [1,10-(Propane-1,3-diyl)-bis(pyridinium)] tetrachlorocobaltate
(II) (3b1)
Yield 85%. Elem. Anal. Calc. for C13H16Cl4CoN2ꢁ0.5H2O: C, 38.08;
H, 4.18; N, 6.83. Found: C, 38.07; H, 4.01; N, 6.89%.
Yield 82%. Elem. Anal. Calc. for C12H17Cl4CoN3ꢁ0.5H2O: C, 34.89;
H, 4.39; N, 10.17. Found: C, 34.95; H, 4.22; N, 10.25%.

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J.-C. Chang et al. / Polyhedron 30 (2011) 497–507
Table 1
Table 2
Summary of melting points and thermal decomposition temperatures of [CoCl4]2ꢀ
anion salts.
Summary of melting points and thermal decomposition temperatures of [MnCl4]2ꢀ
anion salts.
Structure
M.p. (°C) Td (°C)a Td (°C)b
Structure
M.p. (°C) Td (°C)a Td (°C)b
195–196 311
335
188–189 311
336
N
N
3a1
3a2
N
N
N
N
2
2
Cl
Co
Cl
Cl
Mn
Cl
N
N
Cl
Cl
Cl
Cl
212–213 307
326
310
268–269 306
322
318
3b1
3b2
2
2
Cl
Cl
Co
Cl
Mn
Cl
N
N
Cl
Cl
Cl
Cl
229–230 286
204–205 298
3c1
3c2
N
N
2
2
N
N
Cl
Cl
Co
Cl
Mn
Cl
Cl
Cl
Cl
Cl
Cl
Cl
202–203 336
364
300
199–200 330
360
304
N
N
3d2
3d1
N
N
N
N
N
N
2
2
Cl
Co
Cl
Cl
Mn
Cl
Cl
Cl
250–251 275
228–229 282
3e1
3e2
N
N
N
N
2
2
Cl
Cl
Co
Cl
Mn
Cl
Cl
Cl
Cl
Cl
305–306 336
366
304–305 342
375
3f1
3f2
Ph3P
2
2
Ph3P
Cl
Co
Cl
Cl
Mn
Cl
PPh3
PPh3
Cl
Cl
Cl
Cl
a
a
Td onset.
Td at 10% weight loss.
Td onset.
Td at 10% weight loss.
b
b
2.6.3. [1,10-(Butane-1,4-diyl)-bis(di-pyridinium)] tetrachlorocobaltate
(II) (3c1)
2.7. General procedure for the synthesis of [MnCl4]2ꢀ anion salts (3a2,
3b2, 3c2, 3d2, 3e2, and 3f2)
Yield 84%. Elem. Anal. Calc. for C14H18Cl4CoN2ꢁ0.5H2O: C, 39.65;
H, 4.52; N, 6.61. Found: C, 39.65; H, 4.31; N, 6.59%.
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 manganese dichloride
tetrahydrate (4.1 g, 20.7 mmol reacted with 2a; 4.1 g, 20.8 mmol
with 2b; 4.0 g, 20.0 mmol with 2c; 3.9 g, 19.7 mmol with 2d;
3.5 g, 17.9 mmol with 2e; 2.0 g, 10.1 mmol with 2f), and stirred
in ethanol at room temperature for 4 days. The required products
were then precipitated from ethanol (all white solids for 3a2
(2.5 g), 3b2 (2.5 g), 3c2 (2.4 g), 3d2 (2.6 g), 3e2 (2.4 g), and 3f2
(2.3 g)). The detailed crystal structure refinements are summarized
in the supporting information. The element analysis data are de-
scribed below.
2.6.4. [1,10-(Butane-1,4-diyl)-bis(3-methylimidazolium)]
tetrachlorocobaltate (II) (3d1)
Yield 86%. Elem. Anal. Calc. for C12H20Cl4CoN4ꢁ0.5H2O: C, 33.51;
H, 4.92; N, 13.03. Found: C, 33.54; H, 4.78; N, 13.13%.
2.6.5. [1,10-(Butane-1,4-diyl)-bis(triethylaminonium)]
tetrachlorocobaltate (II) (3e1)
Yield 83%. Elem. Anal. Calc. for C16H38Cl4CoN2ꢁ1H2O: C, 40.27; H,
8.45; N, 5.87. Found: C, 40.17; H, 8.09; N, 5.80%.
2.6.6. [1,10-(Butane-1,4-diyl)-bis(triphenylphosphonium)]
tetrachlorocobaltate (II) (3f1)
2.7.1. [1-(1-Pyridinium-yl-propyl)-3-methylimidazolium]
tetrachloromanganate (II) (3a2)
Yield 80%. Elem. Anal. Calc. for C40H38Cl4CoP2ꢁ1H2O: C, 60.10; H,
Yield 75%. Elem. Anal. Calc. for C12H17Cl4MnN3: C, 36.03; H,
4.28; N, 10.50. Found: C, 35.58; H, 4.29; N, 10.43%.
5.04. Found: C, 60.25; H, 4.83%.

J.-C. Chang et al. / Polyhedron 30 (2011) 497–507
501
Fig. 1. ORTEP diagrams of magnetic [CoCl4]2ꢀ and [MnCl4]2ꢀ anion salts (the thermal ellipsoids of all molecular structures (3a1–3f1 and 3a2–3f2) are drawn at the 50%
probability level). (a) Compound 3a1, (b) compound 3b1, (c) compound 3c1, (d) compound 3d1, (e) compound 3e1, (f) compound 3f1, (g) compound 3a2, (h) compound 3b2,
(i) compound 3c2, (j) compound 3d2, (k) compound 3e2, and (l) compound 3f2.
2.7.2. [1,10-(Propane-1,3-diyl)-bis(pyridinium)] tetrachloromanganate
(II) (3b2)
2.7.6. [1,10-(Butane-1,4-diyl)-bis(triphenylphosphonium)]
tetrachloromanganate (II) (3f2)
Yield 75%. Elem. Anal. Calc. for C13H16Cl4MnN2ꢁ0.5H2O: C, 38.45;
Yield 73%. Elem. Anal. Calc. for C40H38Cl4MnP2ꢁ1H2O: C, 60.40;
H, 4.22; N, 6.90. Found: C, 38.43; H, 4.04; N, 6.80%.
H, 5.07. Found: C, 60.77; H, 4.86%.
3. Results and discussion
2.7.3. [1,10-(Butane-1,4-diyl)-bis(di-pyridinium)]
tetrachloromanganate (II) (3c2)
Yield 74%. Elem. Anal. Calc. for C14H18Cl4MnN2: C, 40.91; H,
4.41; N, 6.81. Found: C, 40.57; H, 4.46; N, 6.84%.
3.1. Synthesis of compounds and structure characterization of Co (II)
anion and Mn (II) anion systems
The synthesis procedure and the product yields are summarized
in Scheme 1a and b. The chemical structures are shown in Tables 1
and 2. Target dicationic salts, 3a1–3f1 and 3a2–3f2, were prepared
using previously reported protocols [9,10,17]. To synthesize
unsymmetrical dicationic compounds 3a1 and 3a2 the weak nucle-
ophile, pyridine, was used in the first step to react with a dibromo
reagent (1,3-dibromopropane or 1,4-dibromobutane) because it at-
taches to only one side of the dibromo reagent (a stronger nucleo-
phile such as 1-methylimidazole would attack both sides of the
dibromo reagent). The product 1 from this step was then reacted
with a base or nucleophile to conduct the SN2 substitution reaction
2.7.4. [1,10-(Butane-1,4-diyl)-bis(3-methylimidazolium)]
tetrachloromanganate (II) (3d2)
Yield 78%. Elem. Anal. Calc. for C12H20Cl4MnN4: C, 34.56; H,
4.83; N, 13.43. Found: C, 34.27; H, 4.78; N, 13.31%.
2.7.5. [1,10-(Butane-1,4-diyl)-bis(triethylaminonium)]
tetrachloromanganate (II) (3e2)
Yield 72%. Elem. Anal. Calc. for C16H38Cl4MnN2ꢁ2H2O: C, 39.12;
H, 8.62; N, 5.70. Found: C, 38.92; H, 8.21; N, 5.69%.

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J.-C. Chang et al. / Polyhedron 30 (2011) 497–507
Fig. 1 (continued)
Table 3
For the synthesis of geminal compounds 3b1–3f1 and 3b2–3f2,
1-methylimidazole, pyridine, triethylamine, and triphenylphos-
phine, respectively, were reacted with the dibromo reagent to form
the geminal dicationic bromide salts. The bromide anions were
then anion exchanged with [CoCl4]2ꢀ or [MnCl4]2ꢀ to give com-
pounds 3b1–3f1 and compounds 3b2–3f2, respectively. The
unsymmetrical dicationic compounds 3a1 and 3a2 have pyridini-
um on one side and 1-methylimidazolium on the other side,
whereas geminal compounds have the di-pyridinium group (3b1,
3b2, 3c1 and 3c2), the di-1-methylimidazolium group (3d1 and
3d2), the di-triethylammonium (3e1 and 3e2), and the di-triphe-
nylphosphinium group (3f1 and 3f2). The linkage chain system is
a propyl chain (–(CH2)3–) in compounds 3a1–3a2 and 3b1–3b2,
and a butyl chain (–(CH2)4–) in compounds 3c1–3g1 and 3c2–
3g2. The anion is [CoCl4]2ꢀ in synthesized products 3a1–3g1, and
[MnCl4]2ꢀ in compounds 3a2–3g2.
Selected bond lengths (Co–Cl or Mn–Cl) and bond angles (Cl–Co–Cl or Cl–Mn–Cl) for
[CoCl4]2ꢀ and [MnCl4]2ꢀ anions. (a) [CoCl4]2ꢀ anions for compounds 3a1–3f1 and (b)
[MnCl4]2ꢀ anions for compounds 3a2–3f2.
Compound
(a)
Co–Cl (Å)
a(Cl–Co–Cl) (°)
3a1
3b1
3c1
3d1
3e1
3f1
2.2623–2.3068
2.2825–2.2961
2.2697–2.2975
2.2789–2.3011
2.2771–2.3285
2.2706–2.3116
105.62(2)–112.30(2)
105.61(3)–115.47(3)
107.39(3)–111.21(2)
106.43(2)–112.16(2)
106.25(5)–112.65(5)
106.56(3)–113.88(4)
(b)
Mn–Cl (Å)
a(Cl–Mn–Cl) (°)
3a2
3b2
3c2
3d2
3e2
3f2
2.3485–2.3886
2.3731–2.3830
2.3537–2.3843
2.3634–2.3834
2.3634–2.4257
2.3562–2.3946
105.65(17)–112.34(18)
104.70(3)–115.71(3)
105.93(18)–112.15(19)
105.64(2)–113.07(2)
105.97(5)–112.68(5)
106.54(3)–114.51(3)
The structures of the synthesized products were determined
using an X-ray single-crystal diffractometer. Their ORTEP pictures
are shown in Fig. 1a–l. The anion in all the synthesized dicationic
ionic liquids consists of a [CoCl4]2ꢀ or [MnCl4]2ꢀ unit. Table 3
shows the bond lengths of Co–Cl and Mn–Cl, and the bond angles
of Cl–Co–Cl and Cl–Mn–Cl, respectively. Table 4 shows some
to give the dicationic bromide salt 2a. Finally, the bromide anions
of the dicationic salts were exchanged with [CoCl4]2ꢀ or [MnCl4]2ꢀ
dianion by reacting with CoCl2ꢁ6H2O or MnCl2ꢁ4H2O in ethanol.

Table 4
Summary of crystal data for [CoCl4]2ꢀ anions with propyl linkage chains in compounds 3a1 and 3b1; [CoCl4]2ꢀ anions with butyl linkage chains in compounds 3c1, 3d1, 3e1, and 3f1; [MnCl4]2ꢀ anions with propyl linkage chains in
compounds 3a2 and 3b2; [MnCl4]2ꢀ anions with butyl linkage chains in compounds 3c2, 3d2, 3e2, and 3f2.
Compound
Formula
3a1
3b1
3c1
3d1
3e1
3f1
3a2
3b2
3c2
3d2
3e2
3f2
C
12H17Cl4CoN3 C13H16Cl4CoN2 C14H18Cl4CoN2 C12H20Cl4CoN4 C16H38Cl4CoN2 C40H38Cl4CoP2 C12H17Cl4MnN3 C13H16Cl4MnN2 C14H18Cl4MnN2 C12H20Cl4MnN4 C16H38Cl4MnN2 C40H38Cl4MnP2
Formula weight (g) 404.02
401.01
296(2)
monoclinic
P21/c
7.8794(4)
14.8229(6)
14.2899(7)
90
94.759(2)
90
1663.24(14)
4
415.03
100(2)
triclinic
421.05
100(2)
459.21
296(2)
orthorhombic triclinic
781.37
296(2)
400.03
100(2)
397.02
100(2)
monoclinic
P21/c
7.9833(13)
14.732(2)
14.466(2)
90
94.952(2)
90
1695.0(5)
4
411.04
100(2)
triclinic
417.06
100(2)
monoclinic
P21/c
11.0006(16)
12.2642(18)
13.960(2)
90
103.866(2)
90
1828.5(5)
4
455.22
296(2)
orthorhombic
Pbca
777.38
296(2)
triclinic
T (K)
100(2)
Crystal system
Space group
a (Å)
b (Å)
c (Å)
monoclinic
P21/c
8.1478(7)
14.9562(13)
13.6105(12)
90
monoclinic
P21/c
10.9168(3)
12.2499(3)
13.8504(4)
90
103.6000(10) 90
90
1800.28(8)
4
1.553
1.544
monoclinic
P21/c
8.2137(5)
15.0267(10)
13.7001(9)
90
ꢀ
ꢀ
ꢀ
ꢀ
Pbca
P1
P1
P1
P1
8.1738(16)
9.0003(18)
12.500(2)
91.140(3)
93.257(3)
109.133(3)
866.7(3)
2
13.6560(2)
13.5245(2)
25.1136(5)
90
9.6141(2)
13.3044(3)
15.2883(4)
97.3730(10)
8.2396(9)
9.0275(9)
12.5475(13)
91.4490(10)
93.2350(10)
108.8410(10)
880.97(16)
2
13.7487(4)
13.6444(4)
25.1227(7)
90
90
90
4712.8(2)
8
1.283
9.6370(2)
13.3708(3)
15.3247(3)
97.1610(10)
100.7600(10)
97.0230(10)
1903.23(7)
2
a
(°)
b (°)
96.5970(10)
90
1647.6(2)
4
1.629
1.682
100.8520(10) 96.9140(10)
c
(°)
90
96.9490(10)
1883.40(8)
2
1.378
0.852
90
V (Å3)
4638.25(13)
8
1.315
1678.64(19)
4
1.583
Z
Dcalc (mg/m3)
Absorption
coefficient
1.601
1.664
1.590
1.600
1.556
1.400
1.550
1.349
1.515
1.304
1.357
0.739
1.202
1.415
1.015
(mmꢀ1
)
F(0 0 0)
820
812
422
860
1944
806
812
804
418
852
1928
802
Reflections
collected
12088
16653
10226
17031
25358
32931
12297
12458
10442
13378
26143
34711
Goodness-of-fit
(GOF)
1.080
1.075
1.089
1.083
1.092
1.069
1.049
1.057
1.075
1.054
0.998
1.077
R1, wR2 [I > 2
r
(I)]
0.0319,
0.0871
0.0349,
0.0894
0.0345,
0.1039
0.0375,
0.1058
0.0344,
0.0916
0.0377,
0.0947
0.0315,
0.0819
0.0417,
0.0867
0.0608,
0.1971
0.1039,
0.2297
0.0501,
0.1370
0.0909,
0.1566
0.0303, 0.0842 0.0427, 0.1201 0.0299, 0.0768 0.0349, 0.0904 0.0687, 0.1953 0.0432, 0.1141
0.0330, 0.0863 0.0497, 0.1265 0.0342, 0.0801 0.0417, 0.0948 0.1544, 0.2502 0.0786, 0.1297
R1, wR2 (all data)

504
J.-C. Chang et al. / Polyhedron 30 (2011) 497–507
Table 5
crystal data and structure refinements details, and Table 5 shows
the stacking distance between the dicationic moieties and
Hydrogen bonding and intermolecular p–p
stacking distances for (a) [CoCl4]2ꢀ anions
p–p
in compounds 3a1–3f1 and (b) [MnCl4]2ꢀ anions in compounds 3a2–3f2.
the M (M = Co or Mn)–Clꢁ ꢁ ꢁH–C–X (X = N or P) hydrogen bonding
distance between the [CoCl4]2ꢀ or [MnCl4]2ꢀ anions and the dicat-
ionic moiety in the crystal packing (other detailed crystallographic
data and structure refinements are shown in the supporting infor-
mation, Fig. S1a–l and Table S1–S60).
Compound
p–
p
stacking distance, (Å)a
Hydrogen bonding distance, (Å)a
3a1
3b1
3c1
3d1
3e1
3f1
5.775 (3)
5.799 (2)
4.526 (2)
8.577 (2)b
2.870 (3)
2.676 (3)
2.755 (3)
2.821 (3)
2.775 (3)
2.719 (3)d
Take compound 3b1 as an example of [CoCl4]2ꢀ anion based
dicationic salts. Diffraction-quality crystals of compound 3b1 were
obtained from methanol/ethyl ether at 25 °C. The Co–Cl bonds vary
in length from 2.2825 Å to 2.2961 Å with a mean trans angle of
108.06°. The bond lengths of this complex are longer than those
of previously reported monocationic salts containing [CoCl4]2ꢀ an-
ion (for example: for bis(N-methylmorpholinium) tetrachloroco-
baltate (II), (nmmH)2[CoCl4] [14], the Co–Cl bonds vary in length
from 2.2703 Å to 2.2887 Å with a mean trans angle of 114.02°). It
is likely that these differences are due to the temperature of
data collections (room temperature for 3b1 and 158 K for
(nmmH)2[CoCl4]). The tetrahedral geometry in 3b1 is less distorted
than that in (nmmH)2[CoCl4], as expected for the d7 tetrahedral ion.
Take compound 3b2 as an example of [MnCl4]2ꢀ anion based
dicationic salts. The Mn–Cl bonds vary in length from 2.3731 Å to
2.3830 Å with a mean trans angle of 106.75°. Again, the bond
lengths are longer than those for [MnCl4]2ꢀ anion-containing
c
NA
4.186 (2), 13.304 (3)
3a2
3b2
3c2
3d2
3e2
3f2
5.867 (3)
5.912 (2)
4.440 (2)
8.607 (2)b
2.923 (3)
2.685 (3)
2.747 (3)
2.725 (3)
2.770 (3)
2.720 (3)e
c
NA
4.229 (2), 13.371 (3)
a
Study on crystal packing, distances were calculated using MERCURY and DIAMOND
programs. The hydrogen bonding distance is defined as M (Co or Mn)–Clꢁ ꢁ ꢁH–C–X
(N or P), the distances of hydrogen bonding and stacking are shown in
p–p
Fig. S1(a–l)). Estimated standard deviations (ESDs) are given in parenthesis.
b
Two 1-methylimidazolium rings are partially stacked.
c
No
p-aromatic ring is stacked.
d
Hydrogen bonding distance between the chloride in [CoCl4]2ꢀ anion and PCH in
dicationic moiety.
e
Hydrogen bonding distance between the chloride in [MnCl4]2ꢀ anion and PCH
in dicationic moiety.
Fig. 2. TGA curves for magnetic [CoCl4]2ꢀ anion salts at a heating rate of 10 °C minꢀ1. (a) Propyl chain compounds (3a1 and 3b1), and (b) butyl chain compounds (3c1, 3d1,
3e1, and 3f1).
Fig. 3. TGA curves for the magnetic [MnCl4]2ꢀ anion salts at a heating rate of 10 °C minꢀ1. (a) Propyl chain (3a2 and 3b2), and (b) butyl chain (3c2, 3d2, 3e2, and 3f2).

J.-C. Chang et al. / Polyhedron 30 (2011) 497–507
505
monocationic salts previously studied (for example: for bis(N-
methylmorpholinium) tetrachloromanganate (II), (nmmH)2[MnCl4]
[14], the Mn–Cl bonds vary in length from 2.3670 Å to 2.3470 Å
with a mean trans angle of 114.97°). The tetrahedron is slightly
more distorted in 3b2 than in 3b1, but not nearly as much as
in (nmmH)2[MnCl4]. For compounds 3a1–3f1 and 3a2–3f2, the
Cl–Co–Cl bond angles vary from 105.61° to 115.47° whereas the
Cl–Mn–Cl bond angles vary from 104.70° to 115.71°. This discrep-
ancy may be due to the formation of H-bonds between the chloride
atom in [CoCl4]2ꢀ or [MnCl4]2ꢀ anion and the NCH in the dicationic
moiety (see Table 5; the defined range of the hydrogen bonding
distance is 2.0–3.1 Å [9]), and to the cationic functional groups,
such as pyridinium, 1-methylimidazolium, triethylammonium,
and triphenylphosphinium, being close to the cobalt or manganese
center in the [CoCl4]2ꢀ or [MnCl4]2ꢀ structure, resulting in the
slight distortion of the Cl–Co–Cl and Cl–Mn–Cl bond angles in
[CoCl4]2ꢀ and [MnCl4]2ꢀ anions, respectively. This behavior is alike
to that the ligand approaches metal center would cause the distor-
tion of the metal complex [18].
3.2. Thermal stability
As shown by the TGA curves in Figs. 2 and 3, the dicationic salts
that contain [CoCl4]2ꢀ and [MnCl4]2ꢀ based anions exhibit good
thermal stability in the range 300–375 °C. As indicated by the data
in Tables 1 and 2, these salts that contain the triphenylphosphinium
group (3f1 and 3f2) or the 1-methylimidazolium group (3d1 and
3d2) are thermally more stable than those containing the pyridini-
um ring (3c1 and 3c2). This may be due to the fact that the triphe-
nylphosphinium and 1-methylimidazolium groups have better
positive charge dispersion than does the pyridine group, which
give them a stronger attraction to anions [19].
Fig. 4.
v
MT versus T plot for magnetic [CoCl4]2ꢀ (compounds 3a1–3g1) and [MnCl4]2ꢀ (compounds 3a2–3g2) anion salts at 1000 G. (a) [CoCl4]2ꢀ and (b) [MnCl4]2ꢀ anions.
Table 6
Comparison of the magnetic susceptibility and Weiss constant (fit with Curie–Weiss formula) between (a) the compounds 3a1–3f1 and [CoCl4]2ꢀ salts (b) the compounds 3a2–
3f2 and [MnCl4]2ꢀ salts reported in the previous literature.a
Compound
b
(a)
3a1
3b1
3c1
3d1
3e1
v
MT (emu K molꢀ1
)
leff
Co–Clꢁ ꢁ ꢁCl–Co (Å)c
4.388, 6.408
7.830, 5.998
7.430
5.534, 8.636
6.244, 6.531
12.116
H
(K)d
R2
References
This work
This work
This work
This work
This work
This work
[15]
[14]
[23]
[22]
[22]
3.16
2.95
3.26
2.98
3.10
3.24
2.48
2.76
2.00
2.61
2.68
2.45
5.03
4.86
5.11
4.88
4.98
5.09
4.45
4.70
4.00
4.57
4.63
4.43
ꢀ7.88
ꢀ4.81
ꢀ4.93
ꢀ6.39
ꢀ5.97
ꢀ6.30
ꢀ3.7
0.99821
0.99896
0.99842
0.99843
0.99811
0.99758
nr
nr
nr
nr
nr
3f1
[PR4]2[CoCl4]e
nr
[nmmH]2[CoCl4]f
5.592, 5.611
nr
3.809, 5.924
nr
ꢀ18
[(CH3)2NH2]2[CoCl4]
[NH3(CH2)5NH3][CoCl4]
[NH3(CH2)8NH3][CoCl4]
[NH3(CH2)10NH3][CoCl4]
(b)
3a2
3b2
3c2
ꢀ31
ꢀ3.62
ꢀ2.70
ꢀ4.06
nr
nr
[22]
Mn–Clꢁ ꢁ ꢁCl–Mn (Å)c
4.984, 5.604
7.949, 6.568
7.453
4.72
4.96
4.80
4.64
4.74
4.84
4.22
4.32
6.14
6.30
6.20
6.09
6.16
6.22
5.81
5.88
ꢀ1.86
ꢀ0.99
ꢀ1.78
ꢀ1.86
ꢀ1.83
ꢀ2.44
ꢀ0.1
0.99982
0.99997
0.99976
0.99973
0.99973
0.99947
nr
This work
This work
This work
This work
This work
This work
[15]
3d2
3e2
3f2
6.235, 7.242
6.459, 7.292
12.107
[PR4]2[MnCl4]e
[nmmH]2[MnCl4]f
nr
5.591, 5.562
nr
nr
[14]
a
b
c
d
e
f
Abbreviation: nr = not reported.
At 300 K.
Study on crystal packing, distances were calculated using MERCURY software (one M–Cl bond to another M–Cl bond, shown in Fig. S1(a–l)).
Susceptibility data 5–300 K.
[PR4]+ = trihexyl(tetradecyl)phosphonium.
nmm = N-methylmorpholinium.

506
J.-C. Chang et al. / Polyhedron 30 (2011) 497–507
3.3. Melting point
from 3.16 emu K molꢀ1 for compound 3a1 and 4.72 emu K molꢀ1
for compound 3a2 at 300 K to 1.26 emu K molꢀ1 and 3.56 emu
All the dicationic compounds synthesized in this study are blue
([CoCl4]2ꢀ based anion) or white ([MnCl4]2ꢀ based anion) solids at
room temperature. The melting points of the [CoCl4]2ꢀ and
[MnCl4]2ꢀ based dicationic salts were determined using a capillary
melting point apparatus. As indicated in Tables 1 and 2, these
dicationic salts containing the triphenylphosphinium group (com-
pounds 3f1 and 3f2) have the highest melting point among these
dicationic compounds. Geminal salts containing two pyridinium
groups have higher melting points than those containing two
1-methylimidazolium groups (compound 3c1 > 3d1; 3c2 > 3d2).
The unsymmetrical dicationic salts have lower melting points than
those of geminal ILs (3b1 > 3a1; 3b2 > 3a2).
K molꢀ1 at 2 K, respectively. The other compounds (3b1–3f1 and
3b2–3f2) display similar temperature dependence. The vMT (mag-
netic susceptibility) values estimated from Fig. 4a and b are shown
in Table 6.
The spin-only effective magnetic susceptibility value,
leff, can
be defined [20] by the anisotropy, g, and the total quantum number
of electron spin, S, as described by Eq. (1):
1=2
1=2
g½SðS þ 1Þꢂ
¼
leff ¼ 2:828ð
v
MTÞ
ð1Þ
The experimentally determined leff values of compounds
3a1–3f1 and 3a2–3f2 are interestingly higher than the theoretical
spin-only values (3.87 for the [CoCl4]2ꢀ anion and 5.92 for the
[MnCl4]2ꢀ anion) with noninteracting metal centers with S = 3/2
for [CoCl4]2ꢀ (S = 5/2 for [MnCl4]2ꢀ) (g = 2.0). The magnetism of
the [CoCl4]2ꢀ and the [MnCl4]2ꢀ anion is well established and
described by Curie–Weiss Eq. (2) [21].
The higher melting points of 3f1, 3f2, 3c1, and 3c2 compared to
those of 3d1 and 3d2 may be attributed to the added
p–p stacking
(p–p
stacking distances are shown in Table 5) [10]. Unsymmetrical
dicationic compounds 3a1 and 3a2 have relatively poor p–p stack-
ing, and thus lower melting points.
vꢀM1 ¼ ðT ꢀ
H
Þ=C
ð2Þ
3.4. Solubility description
In Eq. (2), C represents the Curie constant and
constant.
stant according to the Eq. (3):
H
is the Weiss
All synthesized [CoCl4]2ꢀ or [MnCl4]2ꢀ based anion dicationic
salts exhibited good solubility in high polar solvents such as di-
methyl sulfoxide (DMSO), N,N-dimethyl formamide (DMF), aceto-
nitrile (CH3CN), water (H2O), and methanol (MeOH). They cannot
be dissolved in ethanol, acetone, ethyl acetate, and ethyl ether. This
may be attributed to the basic dipole force between these ionic
compounds and polar solvents.
H
can be also on behalf of the magnetic coupling con-
H
¼ zJSðS þ 1Þ=3 k
ð3Þ
J is the magnetic coupling constant. The values for the Weiss
constant,
H, obtained from the fitting (shown in Fig. 5a and b)
for the compounds containing [CoCl4]2ꢀ or [MnCl4]2ꢀ anion are
collected in Table 6. The negative Weiss constants of these com-
pounds indicate that these salts have very weak antiferromagnetic
interaction. As expected from Eq. (3) and S = 5/2 in [MnCl4]2ꢀ anion
Although these [CoCl4]2ꢀ or [MnCl4]2ꢀ anion based dicationic
ILs can only be dissolved in high polar solvents, they have better
solubility than that of Co2O3 and Mn2O3 particles, which are not
soluble in any polar or non-polar solvent. This advantage is impor-
tant for blending with polymers to develop magnetic composites
which have high thermal stability and good solubility in polar or-
ganic solvents.
versus S = 3/2 in [CoCl4]2ꢀ anion, the
H
values of [MnCl4]2ꢀ anion-
based salts are lower than those of [CoCl4]2ꢀ anion-based ones.
The data in Table 6 also disclose several interesting facts relat-
ing the
cal dicationic compounds (3a1 and 3a2) show larger (more
negative) values than the geminal compounds (3b1 and 3b2),
H values to the dication structures. First, the unsymmetri-
3.5. Magnetic properties
H
i.e. 3a1 > 3b1; 3a2 > 3b2. Second, geminal compounds containing
imidazolium group (3d1 and 3d2) or triphenylphosphine group
The temperature dependence of the DC magnetic susceptibili-
ties for powder samples of compounds 3a1–3f1 and 3a2–3f2 mea-
sured in the temperature range of 2.0–300 K in a 1.0 kG magnetic
field are illustrated in Fig. 4a and b. The values steadily decrease
(3f1 and 3f2) have
ylaminonium (3e1 and 3e2) or pyridinium group (3c1 and 3c2),
i.e. 3d1 > 3f1 > 3e1 > 3c1; 3f2 > 3d2 > 3e2 > 3c2. Third, the val-
H values higher than those containing trieth-
H
Fig. 5.
anion salts at 1000 G. (a) [CoCl4]2ꢀ and (b) [MnCl4]2ꢀ anions.
v
MTꢀ1 versus T plot (fit with Curie–Weiss formula, susceptibility data 5–300 K) for magnetic [CoCl4]2ꢀ (compounds 3a1–3g1) and [MnCl4]2ꢀ (compounds 3a2–3g2)

J.-C. Chang et al. / Polyhedron 30 (2011) 497–507
507
ues of the dicationic salts containing [CoCl4]2ꢀ anion synthesized
in this work are comparable to those of the dicationic
[NH3(CH2)xNH3][CoCl4] and monocationic [PR4][CoCl4] salts but
obviously lower than the [nmmH]2[CoCl4] and [(CH3)2NH2]2[CoCl4]
salts. It has been suggested [22] that the antiferromagnetic path-
way through the superexchange interactions between the nearest
neighbours should be of the type M–Clꢁ ꢁ ꢁCl–M (M = Co or Mn),
National Taiwan University (Mr. Un-Cheong Sou for the magnetic
susceptibility data), National Tsing Hua University (Mrs. Pei-Lin
Chen for the X-ray single crystal data), and National Cheng Kung
University (Mr. Shr-Tza Lin for the magnetic susceptibility
data, Mrs. Chia-Chen Tsai for the element analysis data, and Mrs.
Ru-Rong Wu for NMR measurements). We would also like to thank
professor Hua-Fen Hsu, Dr. Chen-I Yang, and Yi-Fang Tsai for their
advice of magnetic discussions.
and consequently the
H value may be correlated to the M–
Clꢁ ꢁ ꢁCl–M distance. The theoretical values of the M–Clꢁ ꢁ ꢁCl–M
distance calculated for the dicationic tetrahalometallate (II) com-
pounds using the MERCURY program are listed in Table 6. Examining
Appendix A. Supplementary data
the M–Clꢁ ꢁ ꢁCl–M distances and the
H
values of the compounds
value is somewhat
CCDC 799156, 799157, 799158, 799159, 799160, 799161,
799162, 799163, 799164, 799165, 799166, and 799167 contains
the supplementary crystallographic data for (3a1), (3b1), (3c1),
(3d1), (3e1), (3f1), (3a2), (3b2), (3c2), (3d2), (3e2), and (3f2). These
data can be obtained free of charge via http://www.ccdc.cam.ac.uk/
conts/retrieving.html, or from the Cambridge Crystallographic
Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: (+44)
1223-336-033; or e-mail: deposit@ccdc.cam.ac.uk. Supplementary
data associated with this article can be found, in the online version,
at doi:10.1016/j.poly.2010.11.009.
synthesized in this work reveals that the
H
related to the M–Clꢁ ꢁ ꢁCl–M distance; i.e. a shorter M–Clꢁ ꢁ ꢁCl–M
distance in general results in a larger
ylphosphine containing compounds.
H value except the triphen-
Another attractive feature observed in Table 6 is that the dicat-
ionic salts synthesized in this work exhibit higher magnetic
susceptibility than those of previous reported monocationic com-
pounds. The structure–magnetism relationship is, however, not
simply determined by a single factor. It is the result of combined
effects of several factors such as weak hydrogen bonding between
the [CoCl4]2ꢀ or [MnCl4]2ꢀ anion and the dicationic moiety, and
conformational arrangement in space (or called steric effect, it
seems to be related to the Cl–Co–Cl and Cl–Mn–Cl bond angles,
References
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A new type of dicationic salt, which contains [CoCl4]2ꢀ or
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good thermal stability and are soluble in water and methanol.
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Acknowledgments
The financial support from the National Science Council of the
Republic of China is gratefully acknowledged (NSC-96-2113-M-
006-014-MY3). We would like to thank the instrument centers of