Coordination chemistry in the solid state: Reactivity of manganese and cadmium chlorides with imidazole and pyrazole and their hydrochlorides

Article abstract of DOI:10.1021/ic101403j

Crystalline coordination compounds [MnCl₂(Hpz)₂] 3, [CdCl₂(Hpz)₂] 5, [MnCl₂(Him)₂] 9, and [CdCl₂(Him)₂] 13 (Him = imidazole; Hpz = pyrazole) can be synthesized in solid state reactions by grinding together the appropriate metal chloride and 2 equiv of the neutral ligand. Similarly, grinding together the metal chlorides with the ligand hydrochloride salts produces the halometallate salts [H₂pz][MnCl₃(OH₂)] 1, [H₂pz][CdCl₄] 4, [H₂im]₆[MnCl ₆][MnCl₄] 8, and [H₂im]₆[CdCl ₆][CdCl₄] 11. In contrast, reacting the metal chloride salt with the ligand in concentrated HCl solution yields a second set of salts [H₂pz][MnCl₃] 2, [H₂im][MnCl ₃(OH₂)₂] 7, and [H₂im][CdCl ₃(OH₂)]·H₂O 12. Compound 5 can be partly dehydrochlorinated by grinding with KOH to form an impure sample of the pyrazolate compound [Cd(pz)₂] 6, while recrystallizing 9 from ethanol yielded crystals of solvated [Mn₄Cl₈(Him)₈] 10. The crystal structure determinations of 1, 2, 4, 11, and 12 are reported.

Full text of DOI:10.1021/ic101403j

Inorg. Chem. 2010, 49, 10475–10485 10475
DOI: 10.1021/ic101403j
Coordination Chemistry in the Solid State: Reactivity of Manganese and Cadmium
Chlorides with Imidazole and Pyrazole and Their Hydrochlorides
Christopher J. Adams,* Mukhtar A. Kurawa, and A. Guy Orpen*
School of Chemistry, University of Bristol, Bristol BS8 1TS, U.K.
Received July 14, 2010
Crystalline coordination compounds [MnCl (Hpz) ] 3, [CdCl (Hpz) ] 5, [MnCl (Him) ] 9, and [CdCl (Him) ] 13
2
2
2
2
2
2
2
2
(Him = imidazole; Hpz = pyrazole) can be synthesized in solid state reactions by grinding together the appropriate
metal chloride and 2 equiv of the neutral ligand. Similarly, grinding together the metal chlorides with the ligand
hydrochloride salts produces the halometallate salts [H pz][MnCl (OH )] 1, [H pz][CdCl ] 4, [H im] [MnCl ][MnCl ]
4
2
3
2
2
4
2
6
6
8
solution yields a second set of salts [H pz][MnCl ] 2, [H im][MnCl (OH ) ] 7, and [H im][CdCl (OH )] H O 12.
, and [H im] [CdCl ][CdCl ] 11. In contrast, reacting the metal chloride salt with the ligand in concentrated HCl
2 6 6 4
2
3
2
3
2 2
2
3
2
3
2
Compound 5 can be partly dehydrochlorinated by grinding with KOH to form an impure sample of the pyrazolate
compound [Cd(pz) ] 6, while recrystallizing 9 from ethanol yielded crystals of solvated [Mn Cl (Him) ] 10. The crystal
structure determinations of 1, 2, 4, 11, and 12 are reported.
2
4
8
8
Introduction
The similarity of the chemistry of these two metals is well-
known, due to neither d cadmium(II) nor high-spin d
10
5
Although solid-state methods of preparation have been in
use in inorganic chemistry for many years, as in the synthesis
of mixed-metal oxides and the like, their use in coordination
chemistry is much less widespread. Recently, however, there
has been growing interest in the formation of metal-ligand
bonds by solvent-free methods. Not only do such meth-
odologies obviate the need for solvent removal and disposal,
they can result in the isolation of species which cannot be
obtained in solution, and can also confer other advantages
such as control over isomerism or polymorphism.
manganese(II) complexes having any crystal-field stabilization
effects. This leads to steric factors having an important effect
upon the geometries of their complexes, and to them being
relatively labile in solution. By utilizing solid-state methods of
complex preparation, we hoped to allow the synthesis of phases
unavailable by more traditional (solution) methods of prep-
aration.
1,2
Results
Within this context, we have recently reported on our
studies of the solid-state preparations of imidazolium and
Pyrazole and Pyrazolium Compounds. Attempts to
synthesize the apparently previously unknown salt bis-
2-
pyrazolium salts of tetrachlorometallate anions [MCl4]
M=Co, Cu, Zn) and their solid-state conversion into the
appropriate coordination compounds ML Cl (L = Him,
(pyrazolium) tetrachloromanganate(II) [H pz] [MnCl ]
by reaction of MnCl 4H O with two molar equivalents
2 2 4
(
2
3
2
2
2
of pyrazole in 2 M HCl solution afforded instead colorless
needle-like crystals of the novel compound [H pz][MnCl -
imidazole; Hpz, pyrazole) by dehydrochlorination, either
thermally (by simply heating the salts) or mechanochemically
2
3
3
,4
(OH
ganate(II) species by grinding MnCl 4H O with two
)] (1). Attempts to synthesize the tetrachloroman-
2
(
by grinding the salts with a base such as KOH). These
2
3
2
methods have proved remarkably general, and have in certain
cases allowed the isolation of compounds that are not acces-
sible by solution-based methods.
molar equivalents of pyrazolium chloride and by expos-
ing the coordination compound [MnCl (Hpz) ] 3 to dry
2
2
HCl gas resulted in the formation of a (or several) com-
pound(s) of unknown composition, whereas exposure of 3to
vapors from concentrated HCl solution also resulted in the
formation of 1 (presumably accompanied by pyrazolium
chloride), and a deliberate attempt to synthesize 1 mechano-
chemically by grinding MnCl 4H O with [H pz]Cl in a
We report below on our extension of these studies to salts
and coordination compounds of manganese and cadmium.
*
To whom correspondence should be addressed. E-mail: chcja@bris.ac.uk.
(
(
1) Garay, A. L.; Pichon, A.; James, S. L. Chem. Soc. Rev. 2007, 36, 846.
2) Braga, D.; Giaffreda, S. L.; Grepioni, F.; Pettersen, A.; Maini, L.;
2
3
2
2
Curzi, M.; Polito, M. Dalton Trans. 2006, 1249.
3) Adams, C. J.; Kurawa, M. A.; Orpen, A. G. Dalton Trans. 2010, 39,
1:1 ratio afforded it in quantitative yield. The compound
crystallizes in the Pbca space group, and the asymmetric
(
6
974.
unit contains one pyrazolium cation and a [MnCl -
3
(
4) Adams, C. J.; Kurawa, M. A.; Lusi, M.; Orpen, A. G. CrystEngComm
-
2
008, 10, 1790.
(H O)] moiety.
2
r 2010 American Chemical Society
Published on Web 10/14/2010
pubs.acs.org/IC

1
0476 Inorganic Chemistry, Vol. 49, No. 22, 2010
Adams et al.
Figure 3. Part of the anionic {MnCl -
} double chain motif in 2.
3 n
þ
Figure 1. Hydrogen bonding between [H pz] cations and the manga-
2
nese chloride chains in [H pz][MnCl (OH )] 1.
2
2
3
2 2 n
Figure 4. {MnCl (Hpz) } chain in 3.
needle-like crystals in the C2/c space group were obtained,
containing an asymmetric unit consisting of one [H pz]
cation and an [MnCl ] moiety. These [MnCl ] units are
3 3
þ
2
Figure 2. Ion packing in [H pz][MnCl
2
(OH )] 1 (left) and [Hpy]-
3 2
-
-
5
[
3 2
MnCl (OH )] (right).
polymerized to form a chain in which the metal atoms are
octahedrally coordinated by chlorine atoms and adjacent
octahedra are linked along b by trans-edge sharing. Two
In the crystal structure the manganese ions are coordi-
nated in a distorted octahedral fashion by five chloride ions
and one water molecule. Adjacent octahedra share two
μ-chlorine ligands, forming an infinite chain of edge-sharing
˚
such chains run parallel to each other and offset by 1.87 A
(they are symmetry related by the crystallographic 21
screw axis) and are linked by cis-edge sharing (Figure 3)
to give a double chain which can be formally derived from
{
MnCl (H O)} octahedra along the crystallographic a-axis,
5 2
with the water molecules occupying alternate trans-axial
positions. The water ligands form an in-chain O-H Cl
6
,7
the MnCl structure by dimensional reduction, and which
2
3
3 3
8
is identical to that seen in NH CdCl . The Mn Mn
hydrogen bond with a chloride ion on the adjacent manga-
nese atom, and another with the axial chloride atom on a
neighboring chain (Figure 1). The pyrazolium ions in 1 lie
4
3
3 3 3
˚
distance within the chain is 3.74 A along the b-axis, and
˚
3.89 A between chains. These distances are longer than
˚
found in 1 (3.629 A) but close to the distance in MnCl
between parallel anionic chains, forming two N-H Cl
3
3 3
2
9
˚
(3.71 A).
bonds to chloride ions on different chains. Similar poly-
meric manganese anionic species, which possess magnetic
properties of interest and which have the same coordina-
tion environment as 1 have been reported with pyridinium
þ
-
Each [H pz] cation in 2 is associated with {MnCl }n
2
3
chains through N-H Cl hydrogen bonds (isomorphous
3
3 3
to those shown in Figure 5 for the cadmium analogue).
One of the principal features of the crystal structure of 2 is
the columnar packing along the b-axis; these columns
are connected by the hydrogen-bond network with the
pyrazolium cations.
(
CSD refcode: PYMNCH10) and quinolinium (CSD
5
efcode: QUMNCL) as the counter-cations, and these
structures have their protonated nitrogen-donor cations
in similar positions to the cations in 1 (Figure 2).
The salt [H pz][MnCl ] (2) was formed when MnCl and
2
3
2
pyrazole were reacted in concentrated aqueous HCl in an
attempt to synthesize [H pz] [MnCl ]. Upon slow eva-
poration of the solution at room temperature, colorless
(
6) Thorn, A.; Willett, R. D.; Twamley, B. Cryst. Growth Des. 2006, 6,
2
2
4
1
134.
(
(
(
7) Tulsky, E. G.; Long, J. R. Chem. Mater. 2001, 13, 1149.
8) Brasseur, H.; Pauling, L. J. Am. Chem. Soc. 1938, 60, 2886.
9) Tornero, J. D.; Fayos, J. Z. Kristallogr. -New Cryst. Struct. 1990,
(
5) Caputo, R.; Willett, R. D.; Morosin, B. J. Chem. Phys. 1978, 69, 4976.
192, 17.

Article
Inorganic Chemistry, Vol. 49, No. 22, 2010 10477
Figure 5. (a) Packing and hydrogen bonding in [H pz][CdCl
2
3
] 4 (which is isostructural with 2) viewed down the crystallographic b-axis. The M-Cl chains
1
pz] ] (CSD refcode: GADYUF) (b) and [4,5-dihydro-3H -1,3-
4
þ
run directly into the page. The packing motif is very similar to that observed in [H
2
2
[Cu Cl
2
6
1
1
thiazolium][CdCl
3
] (CSD refcode: CAXLES) (c), and is related to that observed in [CdCl (Him)] (CSD refcode: CLIMZC) (d).
2
Grinding MnCl 4H O with two molar equivalents
2
Thermogravimetric analysis was performed on 3 to
study its thermal behavior. Mass losses, each of about
26%, were observed at 450 and in the range 527-561 K
(the latter apparently being a two-step process). These
percentages are in close agreement with that calculated
for the removal of one pyrazole ligand from 3 in each step,
leading first to formation of a phase of stoichiometry
MnCl (Hpz) and then to MnCl (the latter step presum-
3
2
of pyrazole gave [MnCl (Hpz) ] 3 as an off-white poly-
2
2
crystalline powder, as did grinding MnCO with two
3
molar equivalents of [H pz]Cl (with concomitant elimina-
2
tion of CO and water) or grinding 2 with 1 equiv of each of
2
KOH and pyrazole (with concomitant formation of water
and KCl). The crystal structure of this compound (CSD
1
0
refcode: DCPZMN) consists of rows of octahedral manga-
nese(II) units (Figure 4) with trans pyrazole ligands, which
share equatorial chlorine atoms to form one-dimensional
chains. The pyrazole ligands are not coplanar but have an
angle of approximately 47° between them, which leads to
each being nearly eclipsed with one of the Mn-Cl bonds,
and allows formation of an intramolecular NH-Cl hydrogen
bond; there are also hydrogen bonds from the NH donors
of pyrazole ligands in one chain to Cl acceptors in
neighboring chains.
2
2
ably with an intermediate phase).
Slow evaporation of a concentrated aqueous HCl
solution of pyrazole and CdCl resulted in the formation
2
of colorless needle-like crystals of [H pz][CdCl ] 4, whose
3
2
structure is isomorphous with its manganese analogue 2.
Compound 4 can also be made by grinding CdCl and
2
-
[H pz]Cl in a 1:1 ratio. A similar polymeric [CdCl ]
2
chain has been reported with 2-amino-4,5-dihydro-3H -1,
3-thiazolium cations (CSD refcode: CAXLES), and a
3
þ
1
1
(
10) Gorter, S.; Vaningen, A. D.; Verschoo, G. C. Acta Crystallogr. 1974,
(11) Kubiak, M.; Glowiak, T.; Kozlowski, H. Acta Crystallogr. 1983,
C39, 1637.
B30, 1867.

1
0478 Inorganic Chemistry, Vol. 49, No. 22, 2010
Adams et al.
related one (where the terminal chloride ions are replaced
with imidazole) is found in [CdCl (Him)] (CSD refcode:
2
12
CLIMZC) (Figure 5). Grinding CdCl with two equiv of
2
[
H pz]Cl produced a material whose powder pattern re-
2
vealed it to contain 4 and unreacted pyrazolium chloride. A
similar mixture is produced by exposure of 5 to HCl gas.
Mechanochemical grinding of CdCl with two molar
2
equivalents of pyrazole resulted in the formation of
[
CdCl (Hpz) ] (5), and the use of an “internal base” to
2 2
afford coordination compounds from crystalline salts
could also be exploited. Thus, mechanochemical reaction
of pyrazolium chloride with either Cd(OH) or CdCO
2
3
formed 5 with concomitant elimination of water (and also
CO in the latter case). The crystal structure of 5determined
at room temperature has been reported (CSD refcode:
2
13
LEDQIV), and it is again isomorphous with its manga-
nese analogue, in this case 3. In addition, their thermal
behaviors are also similar, with thermogravimetric analysis
of 5 showing two distinct mass losses of 21.21% and
21.09%, consistent with sequential loss of two pyrazole
molecules and intermediate formation of CdCl (Hpz).
The cadmium pyrazolate compound [Cd(pz) ] (6) has
2
Figure 6. XRPDpatterns for [{Cd(pz)
2
}
n
] 6. Blue= calculated fromthe
2
15
crystal structure; pink = mixture of 5, 6 and KCl from grinding 5 with
KOH; green = [CdCl (Hpz) ] 5.
2
2
previously been prepared by the addition of aqueous NH3
(as the deprotonating agent) to aqueous solutions of
CdCl or Cd(ClO ) and pyrazole. Compound 6 was
structurally characterized by ab initio XRPD analysis,
2
4 2
1
5
and was found to contain tetrahedral metal centers
coordinated to four pyrazolate ions through the nitrogen
atoms. Attempted mechanochemical elimination of two
molecules of HCl from [CdCl (Hpz) ] (5) by grinding with
2
2
two molar equivalents of KOH resulted in the formation
of a mixture of [Cd(pz) ] (6), KCl, and some unreacted
2
starting material 5 (Figure 6). Attempts to obtain 6 in a
phase-pure form invariably yielded mixtures of product
and starting material.
Imidazole and Imidazolium Compounds. An attempt to
afford a single crystal sample of [H im] [MnCl ] by slow
evaporation of a solution of MnCl 4H O and two molar
2
2
4
2
3
2
equivalents of imidazolium chloride in concentrated hy-
drochloric acid resulted in the formation of [H im]
2
[MnCl (H O) ] (7), whose structure has been previously
3 2 2
reported to consist of discrete imidazolium cations and a
n-
polymeric {[MnCl (H O) ] } anionic chain (CSD ref-
3
Figure 7. XRPD patterns of [H
2
7im]
6
[MnCl
4 6
][MnCl ] 8. Blue = calcu-
2
2 n
1
lated from the crystal structure; green = mechanochemical (MnCl
1
6
code: ADEPOP). Recrystallization of a sample of 7 by
diffusion of diethyl ether into an ethanol solution yielded
the perchloromanganate species [H im] [MnCl ][MnCl ]
2
3
4
absorption by 9. Key: * = peaks from 9.
2 2
H O þ 3[H im]Cl); orange = MnCl
2
4H
2
O þ 2[H
2
im]Cl; pink = HCl
3
2
6
4
6
(
8) whose structure is also known (CSD recode: DEF-
indicating that a phase of composition [H
not formed (Figure 7).
im] [MnCl ] is
2 2 4
1
7
WOB), and which could more simply be prepared by
mechanochemical grinding of MnCl 4H O with 3 equiv
of imidazolium chloride. Exposure of the coordination
Grinding MnCl
gave [MnCl (Him)
2 2
4H
O with 2 equiv of imidazole
] (9) as a white polycrystalline pow-
der. Similarly, grinding MnCO with two molar equiva-
lents of [H im]Cl afforded 9 in quantitative yield, with
concomitant elimination of CO and water (removed in
2
3
2
2
3
2
compound [MnCl (Him) ] (9) (vide infra) to vapors from
2
3
2
concentrated aqueous HCl in a sealed vial and analysis of
the product by PXRD (Figure 8) revealed the presence of
both 8 and 9; this mixture was also observed on grinding
MnCl 4H O with two equiv of imidazolium chloride,
2
2
vacuo). Figure 8 compares the X-ray diffraction powder
patterns of 9 formed by these synthetic routes. Compar-
ison of these patterns with that of [CdCl (Him) ] (13) does
2
3
2
2
2
(
(
12) Nassimbeni, L. R.; Rodgers, A. L. Acta Crystallogr. 1976, B32, 257.
not show any similarity, an indication that 9 and 13 are
not isostructural. Other manganese chloride-imidazole
phases are known, including [MnCl (Him) (H O) ]
13) da Silva, P. B.; Frem, R. C. G.; Netto, A. V. G.; Mauro, A. E.;
Ferreira, J. G.; Santos, R. H. A. Inorg. Chem. Commun. 2006, 9, 235.
14) Casellato, U.; Graziani, R. Z. Kristallogr. -New Cryst. Struct. 1998,
13, 363.
15) Masciocchi, N.; Ardizzoia, G. A.; Maspero, A.; LaMonica, G.;
Sironi, A. Inorg. Chem. 1999, 38, 3657.
2
2
2
2
(
18
2
(CSD refcode: POVXAA), [Mn(Him) (H O) ]Cl (CSD
4 2 2 2
(
(
(
16) Zhang, H.; Wu, Y. M.; Fang, L. Acta Crystallogr. 2006, E62, M1459.
17) Zhang, H.; Chen, P.; Fang, L. Acta Crystallogr. 2006, E62, M658.
(18) Hachula, B.; P ^e dras, M.; Pentak, D.; Nowak, M.; Kusz, J.; Borek, J.
Acta Crystallogr. 2009, C65, m215.

Article
Inorganic Chemistry, Vol. 49, No. 22, 2010 10479
4 8 8
Figure 9. Structure of the [Mn Cl (Him) ] molecule in 10.
2 2
Figure 8. XRPD patterns for [MnCl (Him) ] 9. Green = mechano-
chemical; brown = MnCO
3
2
þ 2[H im]Cl.
1
refcode: CAFXEM), and [Mn(Him) ]Cl 4H O (CSD
9
6
2
3
2
20
refcode: CABPEA), but none of these generate a powder
pattern that matches that of 9 (or 13). Thermogravimetric
analysis of 9 revealed processes at 455 K, with a mass loss
corresponding to one imidazole ligand, and at 592 and
658 K. The combined mass loss of the two latter processes
is again close to that expected for loss of an imidazole
ligand, implying formation of MnCl above 658 K.
2
The crystal structure of 9 is still unknown. Attempts
to grow single crystals by dissolving MnCl 4H O and
2
3
2
imidazole in absolute ethanol gave colorless crystals
whose structure contains the tetranuclear manganese(II)
cluster [Mn Cl (Him) ] (10) (Figure 9) with ethanol in the
4
8
8
2
1
lattice (CSD refcode: NOJCIZ). The cluster is based
upon two Mn Cl cubes which share one face, and which
each lack one manganese vertex, giving a Mn Cl unit.
2 6 4 6
Figure 10. XRPD patterns for [H im] [CdCl ][CdCl ] 11. Green =2:1
4
4
mechanochemical synthesis; pink = HCl absorption by 13; black =
calculated from the crystal structure; red =3:1 mechanochemical synth-
esis.
4
6
This contains two different octahedral coordination en-
vironments for the manganese atoms, one of which is
coordinated by four bridging chloride ligands and two
imidazole nitrogen atoms, while the other is coordinated
by three bridging and one terminal chloride atoms and
two imidazole nitrogen atoms. The remaining two metal
centers are generated by inversion symmetry. A partial
occupancy ethanol solvent molecule is present, and the
observed in M Cl (thf) (M = Co, Fe) and Mn Cl -
4
8
6
5
10
23
(thf)8.
Grinding imidazolium chloride and CdCl led to the
2
formation of a white crystalline powder, which was
recrystallized from acetonitrile solution to give colorless
crystals of [H im] [CdCl ][CdCl ] (11); this could be
2
6
6
4
deliberately synthesized in the solid state by grinding
CdCl and [H im]Cl in a 1:3 ratio, whereas use of a 1:2
crystal structure displays several N-H
Cl and
O hydrogen bonds. The structure and magnetic
3
3 3 3
2
2
N-H
properties of a similar chlorido-bridged tetranuclear cluster
3
3 3 3
ratio resulted in the formation of a mixture of 11 and an
unidentified second product. The same mixture of known
and unknown products was also observed on exposing
the coordination compound 13 to vapors from concen-
trated HCl solution or to dry HCl gas. Figure 10 com-
pares the calculated and the observed X-ray powder
diffraction patterns for this compound.
0
0
of cadmium(II) with 2(2-pyridyl)-4,4 ,5,5 -tetramethyl-4,5-
dihydro-1H-imidazol-1-oxy-3-N-oxide (NIToPY) have
2
been reported, and the M Cl core is similar to that
2
4
8
(
19) Garrett, T. P. J.; Guss, J. M.; Freeman, H. C. Acta Crystallogr. 1983,
C39, 1031.
The crystal structure of 11 is isomorphous with that of
2
-
(
20) Garrett, T. P. J.; Guss, J. M.; Freeman, H. C. Acta Crystallogr. 1983,
8
and [CdCl6]
, containing imidazolium cations and discrete [CdCl ]
4
C39, 1027.
4-
anions. In the structure, N-H
Cl
(
21) Kurawa, M. A.; Adams, C. J.; Orpen, A. G. Acta Crystallogr. 2008,
3 3 3 3
E64, m1276.
hydrogen bonds link (rotationally disordered) imidazo-
lium cations and both kinds of anion, forming hydro-
gen bonded chains along the c-axis (Figure 11). Two
such chains are connected to each other via another
(
22) Lee, C. J.; Wei, H. H.; Lee, G. H.; Wang, Y. Inorg. Chem. Commun.
2
000, 3, 690.
(
23) Zhao, H.; Cl ꢀe rac, R.; Sun, J.-S.; Ouyang, X.; Clemente-Juan, J. M.;
G oꢀ mez-Garcı
´
a, C. J.; Coronado, E.; Dunbar, K. R. J. Solid State Chem.
2
001, 159, 281.
N-H
3 3 3 Cl hydrogen bond, involving (ordered) cations
3

1
0480 Inorganic Chemistry, Vol. 49, No. 22, 2010
Adams et al.
2-
4-
Figure 11. N-H
Cl bridges between [CdCl
4
]
and [CdCl
6
]
along the crystallographic c-axis in 11.
3
3 3 3
Figure 12. Linked chains in 11.
þ
Figure 13. Packing of [H
2
im] cations between Cd-Cl chains in 12.
4
-
and equatorial chlorine atoms on the [CdCl6] anions,
effectively forming a 2-dimensional network (Figure 12).
An attempt to synthesize [H im] [CdCl ] from solution
(Figure 13). Two different lattice water environments are
present in the asymmetric unit and contribute to the various
N-H
Cl, N-H
O and O-H
Cl inter-
2
2
4
3 3 3 3 3 3
3 3 3 3 3 3
3 3 3 3 3 3
by reacting CdCl with 2 equiv of imidazole in concen-
2
trated HCl acid gave colorless crystals of [H im][Cd-
2
Cl (OH )] H O (12), containing discrete imidazolium
3
actions which form a three-dimensional hydrogen bond
network (see below). Similar anionic cadmium-contain-
24
ing chains have been reported with ephedrinium cations.
The imidazolium cations lie between parallel {CdCl -
2
3
2
cations and a polymeric chain of stoichiometry
[
3
-
-
CdCl (H O)] . The cadmium centers are coordinated
3
(H O) } chains, forming N-H
Cl bonds with the
2
2
n
3 3 3 3
by one water and five chloride ligands, leading to a
distorted octahedral coordination sphere. Adjacent octa-
hedra are bridged by two μ-chloride ligands, forming an
infinite -Cd-Cl -Cd-Cl - chain along the a-axis with
axial chloride ligands of one chain and N-H O bonds
with water ligands on the other chain, effectively forming
3
3 3 3
2
2
(24) Charles, N. G.; Rodesiler, P. F.; Griffith, E. A. H.; Amma, E. L. Acta
Crystallogr. 1984, C40, 1676.
water ligands occupying alternate trans-axial positions

Article
Inorganic Chemistry, Vol. 49, No. 22, 2010 10481
Figure 14. O-H
Cl and O-H
3 3 3 3 3 3
O hydrogen bonds in 12.
3
3 3 3 3 3
Figure 15. O3-H
Cl and O3-H
3 3 3 3
O hydrogen bonds in 12.
3
3 3 3
Figure 16. O4-H
Cl and O4-H
3 3 3 3
O hydrogen bonds in 12.
3
3 3 3
-
the chains into a two-dimensional network through hy-
drogen bonding (Figure 13).
{CdCl (H O) } chains oriented perpendicular to each
2
3
n
other (Figure 15), and O4 connects parallel {CdCl -
3
(H O) } chains in a similar fashion to the imidazolium
2 n
cations (Figure 16).
Grinding of CdCl2 with two molar equivalents of
imidazole affords [CdCl (Him) ] (13), as does treatment
of either of the internal bases Cd(OH) or CdCO with
-
The water ligands form intramolecular O-H Cl
3
3 3
hydrogen bonds with the chloride ions on the adjacent
cadmium atom and O-H O bonds with the lattice
3
3 3
water molecules (Figure 14). The lattice water molecules
form further hydrogen bonds; O3 bridges between two
2
2
2
3
chains via O-H
Cl and O-H
3 3 3 3 O to connect the
2 equiv of [H im]Cl with the elimination of water
2
3
3 3 3

1
0482 Inorganic Chemistry, Vol. 49, No. 22, 2010
Adams et al.
3,4,26,27
compounds.
Thus, we were able to synthesize all four
of the coordination compounds MCl L (L = Hpz or Him)
2
2
by simply grinding together in a mortar and pestle 2 equiv of
the ligand L with one of the metal precursor MCl , and it was
2
also possible to form the salts [H pz][MnCl (OH )] 1,
2
3
2
[
H pz][CdCl ] 4, [H im] [MnCl ][MnCl ] 8, and [H im] [Cd-
2 3 2 6 4 6 2 6
Cl ][CdCl ] 11 by reaction of the protonated ligand H L with
4
6
2
the metal chlorides under the same conditions. Schemes 1-4
summarize the outcomes of our solid-state and solid-gas
reactions. We note that some of the reactions presented
herein do form pastes upon grinding, which then require
further drying to yield analytically pure products. As no
attempts were made to try and control the environment
experienced by the reactions it is possible that moisture
may be playing a part in them, either adventitiously during
the grinding process, by having previously been absorbed by
hygroscopic reagents, or even by being present in hydrated
metals salts (such as MnCl 4H O) used as starting materi-
2
3
2
Figure 17. XRPD patterns for [{CdCl
from the crystal structure; green = CdCl
CdCO ; turquoise = 2 H
2
(Him)
2
}
n
] 13. Blue = Calculated
als. This is most obviously the case for formation of the aqua-
ted compound 1.
2
þ 2 Him; brown = 2 H imCl þ
2
3
2
imCl þ Cd(OH)
2
.
Our previous work has dealt with metals such as platinum
26
4
and palladium and cobalt which generally (for reasons of
crystal-field stability) have more predictable coordination
geometries and environments than the cadmium and man-
ganese compounds presented herein. All of the halide-
bridged polymeric structures encountered herein belong to
28
common general structure types, but we would not have
been able to predict in advance which one would be found.
When performing solid-state synthesis, if the product formed
is not that anticipated, then characterization of the phase(s)
produced is challenging. Thus, although it is possible to
cleanly generate 1, 4, 8, and 11 in the solid-state, it would
not be straightforward to confirm their structure without the
a priori knowledge of their stoichiometry from single-crystal
studies since none of them have the anticipated [H L] [MCl ]
2
2
4
formulation. The matter is complicated further when it is
realized that a second series of salts [H pz][MnCl ] 2,
2
3
2
5
Figure 18. {CdCl (Him)
2
2
}
n
chain in 13.
[H im][MnCl (OH ) ] 7, and [H im][CdCl (OH )] H O 12
2 3 2 2 2 3 2 2
3
also exists; these were all crystallized from concentrated HCl
solutions, and none of them have been formed by grinding,
implying that they are probably the results of a series of
complex equilibria in the chloride rich solutions.
(
removed in vacuo) and carbon dioxide (in the latter).
XRPD patterns (Figure 17) and elemental analyses con-
firmed the products from these synthetic routes to be
identical to the known structure of 13 (CSD refcode:
CLIMCD), which consists of cadmium atoms which are
linked to their neighbors in the a direction by double
In thecasesof the ML Cl coordination compounds 3, 5, 9,
2
2
and 13, thermogravimetric analysis suggests loss of organic
ligands upon heating. They all first lose the appropriate mass
for one heterocyclic ligand, leading to phases of composition
2
5
chloride bridges in infinite -Cd-Cl -Cd-Cl - ribbons.
2
2
Octahedral coordination at cadmium is completed by two
Cd-N (imidazole) bonds which are perpendicular to the
plane of the Cd and Cl atoms (Figure 18). As for other the
other MCl L compounds herein, 13 showed successive
29
12,30
MLCl . Both manganese and cadmium
are known to
2
form phases of this stoichiometry upon heating ML Cl (e.g.,
2
2
for L = pyridine), and it seems likely that similar compounds
are being formed in the current systems. The loss of the
second organic ligand apparently occurs in two steps for 3, 9,
and 13, with 60% of the mass being lost first and the
remaining 40% following between 30 and 60 degrees higher,
implying intermediate formation of compounds of stoichi-
2
2
mass losses corresponding to loss of the organic ligands
upon heating and eventual formation of the metal
dichloride.
Discussion and Conclusions
ometry ML0.4Cl . Again, ligand-poor phases (for example of
2
The work presented herein extends our recent investigations
into the solid-state preparation of perchlorometallate salts of
protonated nitrogen bases and of metal-halide coordination
stoichiometry ML0.66Cl ) have been observed in the thermal
2
29-31
decomposition of related pyridine compounds.
It has
been postulated that phases with stoichiometries between
(
25) Flook, R. J.; Freeman, H. C.; Huq, F.; Rosalky, J. M. Acta
Crystallogr. 1973, B29, 903.
26) Adams, C. J.; Haddow, M. F.; Hughes, R. J. I.; Kurawa, M. A.;
Orpen, A. G. Dalton Trans. 2010, 39, 3714.
27) Adams, C. J.; Colquhoun, H. M.; Crawford, P. C.; Lusi, M.; Orpen,
A. G. Angew. Chem., Int. Ed. 2007, 46, 1124.
(28) Englert, U. Coord. Chem. Rev. 2010, 254, 537.
(29) Allen, J. R.; Brown, D. H.; Nuttall, R. H.; Sharp, D. W. A. J. Inorg.
Nucl. Chem. 1965, 27, 1865.
(30) Allan, J. R.; Brown, D. H.; Nuttall, R. H.; Sharp, D. W. A. J. Chem.
Soc. A 1966, 1031.
(
(

Article
Inorganic Chemistry, Vol. 49, No. 22, 2010 10483
Scheme 1. Outcomes of the Solid-State Manganese-Pyrazole Reac-
tions
for CdCl L compounds (L = a pyridine or substituted
2
2
3
3
pyridine), and indeed all three MCl L species of known
2
2
structure herein adopt it (the structure of 9 is not known).
A similar principle seems to be at work in the polymeric
salts. We have previously shown how the close proximity of
H and Cl atoms within the crystal structures of hydrogen-
bonded salts can be exploited in the elimination of HCl with
associated formation of coordination complexes, especially
in cases where the salt and coordination complex have similar
2
7,34
packing motifs.
Hpz) is not known, the similarities (shown in Figure 5)
between the packing motifs observed for the salt
H pz][CdCl ] 4 and CdCl (Him) imply that the thermal
Thus, although the structure of CdCl2-
(
Scheme 2. Outcomes of the Solid-State Cadmium-Pyrazole Reac-
tions
a
[
2
3
2
decomposition of the former may well lead to a phase
CdCl (Hpz) with a structure similar to the latter. However,
2
as the coordination compounds 3, 5, 9, and 13 are all of
stoichiometry MCl L (i.e., a M:L ratio of 1:2) but none of
2
2
the salts have that ratio (M:L ratios of 1:1 for 1, 2, 4, 7, and
2, and 2:3 for 8 and 11) the interconversion of these salts and
1
the coordination compounds by (de)hydrochlorination can-
not proceed cleanly. Although exposing 3, 5, 9, and 13 to
concentrated hydrochloric acid vapor or HCl gas produced
materials that contained (by inspection of their XRPD
patterns) 1, 4, 8, and 11 respectively, they were not and could
not have been pure phases because of the stoichiometry of the
reactions. Equally, converting the salts into the coordination
compounds would require reaction with both an external
base and some additional ligand.
a
A dotted line indicates a partial reaction.
Scheme 3. Outcomes of the Solid-State Manganese-Imidazole Re-
actions
a
Overall, we conclude that although the synthesis of known
coordination compounds or salts of cadmium and manga-
nese by solid-state routes is perfectly feasible, the controlled
synthesis of new phases is not reliable given that phases of
unexpected stoichiometry are formed in a number of cases
(
although this is of course also a problem in solution
a
The dotted line indicates a partial reaction.
chemistry). Of the compounds herein only 9 has not been
made in solution, and attempts to make unknown species
such as [H pz] [MnCl ] by solid-state reaction of appropriate
precursors in the correct stoichiometry were unsuccessful.
Similarly, while solid-state interconversion of salts and co-
ordination compounds can be achieved, it may be non-
quantitative because of differences in the stoichiometry of
the stable phases in the two series.
2
2
4
Scheme 4. Outcomes of the Solid-State Cadmium-Imidazole Reac-
tions
a
The isostructural nature of the cadmium and manganese
structures observed in the pairs 2 and 4, 3 and 5, and 8 and 11
implies that it should be possible to prepare solid solutions of
these compounds. We have recently shown how solid-state
methods such as those presented herein allow this to be
achieved with precise control over stoichiometry, in contrast
to the approximate stoichiometry afforded in samples pre-
a
The dotted line indicates a partial reaction.
ML Cl and MCl result from the elimination of the ligands
L from neighboring polymeric chloride-bridged chains and
subsequent chain linkage by chloro-bridging,
2
2
2
35
31,32
pared from solution.
so that (for
example) the MLCl phase corresponds to a double stranded
chain, as observed in the crystal structure of Cd(HIm)Cl2.
2
12
Experimental Section
These transformations are all apparently aided by the fact
that the compounds involved have parallel M-Cl chains
running throughout their structures, allowing condensation
to occur without major structural rearrangements. It has
been shown that such an arrangement is very common
Synthesis. Samples were ground by hand using an agate
mortar and pestle in air to give solids with the expected
elemental analysis and X-ray powder diffraction patterns. The
time required in grinding (typically 20-30 s) is only that
necessary to be sure that all the reagents have been thoroughly
mixed. All other reagents were purchased from Aldrich, Strem,
(
31) Masuda, Y.; Suzuki, T.; Yamada, T.; Sawada, K. Thermochim. Acta
988, 128, 225.
32) Pokhodnya, K. I.; Bonner, M.; DiPasquale, A. G.; Rheingold, A. L.;
(33) Hu, C.; Englert, U. CrystEngComm 2002, 4, 20.
(34) Adams, C. J.; Crawford, P. C.; Orpen, A. G.; Podesta, T. J.; Salt, B.
Chem. Commun. 2005, 2457.
(35) Adams, C. J.; Haddow, M. F.; Lusi, M.; Orpen, A. G. Proc. Natl.
Acad. Sci. 2010, 107, 16033.
1
(
Her, J.-H.; Stephens, P. W.; Park, J.-W.; Kennon, B. S.; Arif, A. M.; Miller,
J. S. Inorg. Chem. 2007, 46, 2471.

1
0484 Inorganic Chemistry, Vol. 49, No. 22, 2010
Adams et al.
or Lancaster and used without further purification. Prod-
uct samples were dried in vacuo or in the oven at 50 °C. No
attempts were made to control the atmosphere surrounding the
reaction.
of three compounds - [Cd(pz)
bles [CdCl (Hpz) ] 5. Several attempts to synthesize the title
2
]
n
, KCl, and another which resem-
2
2
compound by this route always ended up with starting material.
Microanalytical data (%), Calculated for [(C H N ) Cd] þ 2KCl:
3
3
2 2
[
1 mmol) of MnCl
(
H pz][MnCl (H O)] (1). Mechanochemical synthesis: 198 mg
2
C, 18.21; H, 1.53; N, 14.16. Found C, 18.69; H, 1.77; N, 14.18.
2
3
(
2
4H
1 mmol) of pyrazolium chloride to form a pinkish paste,
2
O was forcefully ground with 105 mg
[H
previously reported.
[H im] [MnCl ][MnCl ] (8). Mechanochemical synthesis: 198 mg
2 3 2
im][MnCl (H O)] (7). Single crystals of 7 were obtained as
3
1
6
which dries into a pink powder which was further dried in
vacuo. Microanalytical data (%) for [C H N ][MnCl (H O)],
2
6
6
4
3
5
2
3
2
(1 mmol) of MnCl 4H O and 209 mg (2 mmol) of imidazolium
2
2
3
Calculated: C, 14.51; H, 2.84; N, 11.28. Found C, 14.92; H, 3.01;
N, 11.62. Vapor Absorption: A vial containing 63 mg of an
off-white powder of 3 was placed in a jar containing concen-
trated HCl. The powder changes to a pinkish color after 8 h.
chloride were ground in an agate mortar, forming 8 as a white paste
which dries into a white crystalline powder, which was dried in
vacuo. Microanalytical data (%), Calculated for [C H N ] -
3
5
2 6
[MnCl ][MnCl ] þ 2[(C H N ) MnCl ] þ 2[C H N ]Cl: C, 21.52;
6
4
3
4
2 2
2
3
5
2
Microanalytical data (%) for [C
3
H N
5 2
][MnCl
3
(H
2
O)], Calcu-
H, 3.01; N, 16.73. Found C, 21.64; H, 3.53; N, 16.94. Vapor
Absorption: A vial containing 20 mg of solid 9 was placed in a jar
containing concentrated HCl. In about 2 h the white powder
became pinkish as 8 was formed. Microanalytical data (%) Cal-
lated: C, 14.51; H, 2.84; N, 11.28. Found C, 14.85; H, 3.26;
N, 11.63.
[
MnCl
H pz][MnCl ] (2). Solution synthesis: 198 mg (1 mmol) of
3
2
4H
2
O and 136 mg (2 mmol) of pyrazole were dissolved
culated for [C
2[C ]Cl: C, 21.52; H, 3.01; N, 16.73. Found C, 21.28; H, 3.20;
N, 16.66.
[MnCl (Him) ] (9). Mechanochemical synthesis: 198 mg
3
H
5
N
2
]
6
[MnCl
6
][MnCl
4
] þ 2[(C
3
H
4
N
2
)
2
MnCl
2
] þ
2
3
in concentrated HCl solution, which was then allowed to
evaporate slowly at room temperature. After a few days color-
less needle-like crystals were obtained.
3 5 2
H N
2
2
[MnCl (Hpz) ] (3). Mechanochemical synthesis: 198 mg
1 mmol) of MnCl
were forcefully ground in an agate mortar, resulting in the
formation of an off-white polycrystalline powder. This was
dried in vacuo to remove excess water. Microanalytical data
(1 mmol) of MnCl 4H O and 136 mg (2 mmol) of imidazole
2 2
2
2
3
(
2
4H O and 136 mg (2 mmol) of pyrazole
2
were forcefully ground in an agate mortar, resulting in the
formation of a white polycrystalline powder of 9. This was dried
in vacuo to remove excess water. Microanalytical data (%) for
3
[(C
Found C, 27.40; H, 3.76; N, 21.35. Reaction of imidazolium
chloride with MnCO : 115 mg (1 mmol) of MnCO and 209 mg
H N ) MnCl ], Calculated: C, 27.51; H, 3.08; N, 21.38.
3
4 2 2 2
(
%) for [(C
1.38. Found C, 13.46; H, 3.12; N, 21.47. Reaction of pyrazolium
chloride with MnCO : 115 mg (1 mmol) of MnCO and 209 mg
3 4 2 2 2
H N ) MnCl ], Calculated: C, 13.51; H, 3.08; N,
2
3
3
(2 mmol) of imidazolium chloride were forcefully ground in an
agate mortar, resulting in the formation of light-brown poly-
crystalline powder of 9. This was dried in vacuo to remove excess
3
3
(
2 mmol) of pyrazolium chloride were forcefully ground in an
agate mortar, resulting in the formation of a light-brown poly-
crystalline powder. This was dried in vacuo to remove excess
water. Microanalytical data (%) for [(C H N ) MnCl ], Calcu-
3 4 2 2 2
water. Microanalytical data (%) for [(C H N ) MnCl ], Calcu-
lated: C, 27.51; H, 3.08; N, 21.38. Found C, 27.51; H, 3.77; N, 21.19.
[Mn Cl (Him) ] 1.234EtOH (10). Solution synthesis: To a
3
4
2 2
2
lated: C, 13.51; H, 3.08; N, 21.38. Found C, 13.13; H, 3.46; N,
4
8
8
3
21.19. Mechanochemical elimination: 248 mg (1 mmol) of 1,
68 mg (1 mmol) of pyrazole and 56 mg (1 mmol) of KOH were
solution of imidazole 136 mg (2 mmol) in absolute alcohol
(5 mL) was added 198 mg (1 mmol) of MnCl2 4H O. On
3
2
forcefully ground in an agate mortar, resulting in the formation
of an off-white polycrystalline powder, which was dried in
evaporation at room temperature, white crystals were obtained
after a few weeks.
[H im] [CdCl ][CdCl ] (11). Mechanochemical synthesis:
vacuo. Microanalytical data (%) for [(C
KCl, Calculated: C, 21.41; H, 2.40; N, 16.65. Found C, 21.01;
H, 2.85; N, 16.28.
3
H
4
N
2
)
2
MnCl
2
] þ
2
6
6
4
1
2
83 mg (1 mmol) of CdCl and 314 mg (3 mmol) of imidazolium
chloride were ground in an agate mortar, forming 11 as a white
crystalline powder. Microanalytical data (%), Calculated for
[C H N ] [CdCl ][CdCl ]: C, 21.75; H, 3.04; N, 16.91. Found C,
[
H pz][CdCl ] (4). Solution synthesis: To a solution of 136 mg
2 3
(
(
2 mmol) of pyrazole in conc. HCl (5 mL) was added 183 mg
1 mmol) of CdCl . On slow evaporation at room temperature,
3
5
2 6
4
6
2
21.79; H, 3.25; N, 16.82. Solution synthesis: A small amount of
11 was dissolved in acetonitrile. The solution was allowed to
evaporate slowly at room temperature and colorless needle-like
crystals were obtained after a few weeks.
white crystals were obtained after a few weeks. Microanalytical
data (%) for [C H N ] [CdCl ], Calculated: C, 18.37; H, 2.57;
N, 14.28. Found C, 18.13; H, 2.55; N, 14.48.
3
5
2 2
4
[
CdCl (Hpz) ] (5). Mechanochemical synthesis: 183 mg
2
[H
solution of imidazole 136 mg (2 mmol) in concentrated HCl
(5 mL) was added 183 mg (1 mmol) of CdCl . On evaporation at
2 2 2 6 2 2
im] [Cd Cl (OH) ] 2H O (12). Solution synthesis: To a
2
3
(
2
1 mmol) of CdCl and 136 mg (2 mmol) of pyrazole were
forcefully ground in an agate mortar, resulting in the formation
of a white polycrystalline powder of [{CdCl (Hpz) } ]. Micro-
analytical data (%) for [(C H N ) CdCl ], Calculated: C, 22.56;
2
room temperature, colorless needle-like crystals were obtained
after a few days.
[CdCl (Him) ] (13). Mechanochemical synthesis: 183 mg
2
2 n
3
4
2 2
2
H, 2.52; N, 17.54. Found C, 22.58; H, 2.58; N, 17.74. Reaction of
pyrazolium chloride with (i) Cd(OH) : 209 mg (2 mmol) of
pyrazolium chloride was ground with 146 mg (1 mmol) of
Cd(OH) , forming a white polycrystalline powder of [{CdCl
pz) ], which was dried in vacuo. Microanalytical data (%),
Calculated for [(C CdCl ]: C, 22.56; H, 2.52; N, 17.54.
2
2
2
(1 mmol) of CdCl and 136 mg (2 mmol) of imidazole were
2
forcefully ground in an agate mortar, resulting in the formation
of a white polycrystalline powder of 13 which was dried in
2
2
-
(
H
2
2
}
n
vacuo. Microanalytical data (%), Calculated for [(C H N ) -
2 2
3
4
H
3 4
2
N )
2
2
CdCl ]: C, 22.56; H, 2.52; N, 17.54. Found C, 22.42; H, 2.58; N,
2
Found C, 22.83; H, 2.60; N, 17.99. (ii) CdCO : 209 mg (2 mmol)
3
17.63. Reaction of imidazolium chloride with (i) CdCO : 209 mg
3
of pyrazolium chloride was ground with 172 mg (1 mmol) of
(2 mmol) of imidazolium chloride was ground with 172 mg
(1 mmol) of CdCO forming a white polycrystalline powder,
CdCO , forming a white polycrystalline powder of [{CdCl
(
Calculated for [(C H N ) CdCl ]: C, 22.56; H, 2.52; N, 17.54.
3
2
-
H pz) } ], which was dried in vacuo. Microanalytical data (%),
3
2
2 n
which was dried in vacuo. Microanalytical data (%), Calculated
for [(C H N ) CdCl ]: C, 22.56; H, 2.52; N, 17.54. Found C,
22.54; H, 2.50; N, 17.51. (ii) Cd(OH) : 209 mg (2 mmol) of
3
4
2 2
2
3
4
2 2
2
Found C, 22.99; H, 2.58; N, 17.83.
Cd(pz) (6). Mechanochemical elimination: 320 mg
1 mmol) of [CdCl (Hpz) ] 5 was forcefully ground with 112
2
[
2
]
n
imidazolium chloride was ground with 146 mg (1 mmol) of
(
2
2
Cd(OH)
dried in vacuo. Microanalytical data (%), Calculated for
[(C CdCl ]: C, 22.56; H, 2.52; N, 17.54. Found C,
22.63; H, 2.59; N, 17.48.
2
forming a white polycrystalline powder, which was
mg (2 mmol) of KOH. The reaction proceeded with no signifi-
cant color change, forming a white polycrystalline powder
which was dried in vacuo. XRPD pattern reveals the presence
H
N )
2
3
4
2
2

Article
Inorganic Chemistry, Vol. 49, No. 22, 2010 10485
Table 1. Summary Crystallographic Data
crystal data
T/K
formula
1
2
4
11
12
100(2)
[C
100(2)
O)] [C
230.38
100(2)
[C
287.86
173(2)
[C
993.86
173(2)
[C
647.74
3
H
5
N
2
][MnCl
3
(H
2
3
H
5
N
2
][MnCl
3
]
3
H
5
N
2
][CdCl
3
]
3
H
5
N
2
]
6
[CdCl
4
][CdCl
6
]
3
H
5
N
2
]
2
[Cd
2
Cl
6
(H
2
O)
2
] 2H
3
2
O
formula weight 248.41
color
morphology
colorless
needle
1.891
colorless
needle
2.036
colorless
needle
2.436
colorless
needle
1.867
colorless
needle
2.124
-
3
Dcalc/ Mg m
crystal system
space group
orthorhombic
Pbca
7.2477(14)
14.614(3)
16.473(3)
90
1744.7(6)
0.71073
8
monoclinic
C2/c
monoclinic
C2/c
tetragonal
I4 /a
12.1221(12)
12.1221(12)
24.730(24)
90
3633.9(7)
0.71073
4
monoclinic
P2 /c
1
1
˚
a/A
22.561(5)
3.7413(7)
20.895(4)
121.54(3)
1503.2(7)
0.71073
8
22.886(6)
3.8529(10)
20.990(6)
121.99(4)
1569.7(7)
0.71073
8
7.5463(17)
21.385(5)
12.531(3)
95.505(7)
2012(8)
0.71073
4
˚
b/A
˚
c/A
β/deg
3
˚
V/A
λ/A
˚
Z
data collected
unique data
R(int)
18480
2006
0.0375
1.89, 4.58
7613
1721
0.0324
3.00, 7.81
7374
1778
0.0283
1.82, 5.01
19245
2091
0.0346
2.03, 4.37
6014
4125
0.0188
2.53, 6.46
R1, wR2(%)
X-ray Single Crystal Analysis. Single crystal X-ray data (see
Table 1) were collected at 100 K on a Bruker APEX diffrac-
on a Bruker D8 diffractometer using Cu-K X-radiation. In all
R
the cases the experimental pattern matched that calculated on
the basis of the single crystal structure determination at room
temperature, indicating phase purity except when the powder
patterns of the products of mechanochemical eliminations
R
tometer using Mo-K X-radiation Data were corrected for
3
6
absorption using empirical methods (SADABS) based upon
symmetry-equivalent reflections combined with measurements
at different azimuthal angles. Crystal structures were solved and
(reactions with KOH or K
2 3
CO ) show an extra peak at 2θ =
2
refined against all F values using the SHELXTL suite of
28° due to the presence of KCl.
Thermogravimetric Analysis. Thermal analysis of the samples
37
programs. Non-hydrogen atoms were refined anisotropically
and hydrogen atoms were generally placed in calculated posi-
tions refined using idealized geometries (riding model) and
assigned fixed isotropic displacement parameters, except for
the hydrogen atoms of the water molecules in 1 and 12, which
were located in the difference map and refined freely (though
was carried out on a TA Q500 V6.4 build 193 instrument under
N flow over the temperature range 20-700 °C at variable (high
2
resolution mode) heating rate and analyzed by TA Universal
analysis 2000 software.
˚
with the O-H distance restrained to 0.84 A in 12). In the
Acknowledgment. We thank the Universities of Bristol and
Bayero for support (M.A.K.) and Professor Dario Braga of the
Institute of Advanced Studies, University of Bologna, for
hospitality (to A.G.O.).
structure of 11, one of the imidazolium cations is disordered
about a crystallographic 2-fold rotational axis. In the structure
of 12 one of the imidazolium cations also shows some disorder,
which was modeled by refining two alternative orientations with
the sum of their occupancies constrained to 1, with the dis-
ordered carbon and nitrogen atoms sharing the same position
and the same anisotropic displacement parameters.
Supporting Information Available: Details of the crystal
structures of 1, 2, 4, 11, and 12 as cif files, thermal ellipsoid
plots, tables of hydrogen bond lengths and angles, complete
powder patterns for all syntheses, and TGA traces. This ma-
terial is available free of charge via the Internet at http://pubs.
acs.org.
X-ray Powder Diffraction Analysis. All crystalline phases
were analyzed at room temperature by powder X-ray diffraction
(
36) Sheldrick, G. M. SADABS: Empirical absorption correction program;
University of G €o ttingen: G €o ttingen, Germany, 1995.
(37) Sheldrick, G. M. Acta Crystallogr. 2008, A64, 112.