Synthesis, structures, and properties of Mn(II) and Cd(II) thiocyanato coordination compounds with 2,5-dimethylpyrazine as co-ligand

Article abstract of DOI:10.1515/znb-2015-0182

Reaction of manganese (II) thiocyanate with 2,5-dimethylpyrazine leads to the formation of three new coordination compounds of compositions Mn(NCS)₂ (2,5 dimethylpyrazine)₂ (H₂ O)₂ (1), Mn(NCS)₂ (H₂ O)₂ (MeOH)₂ -tris(2,5-dimethylpyrazine) solvate (2), and Mn(NCS)₂(H2 O)₄ -tetrakis(2,5-dimethylpyrazine) solvate (3) that were characterized by single crystal X-ray diffraction. In their crystal structures, the Mn(II) cations are sixfold coordinated by two terminally N-bonded thiocyanato anions and two water molecules as well as by two 2,5-dimethylpyrazine ligands (1), two ethanol (2), or two water molecules (3), within slightly distorted octahedra. In compounds 2 and 3, additional 2,5-dimethylpyrazine ligands are located in the cavities of the structures as solvate molecules. X-ray powder diffraction has shown that compounds 1 and 2 cannot be prepared as pure phases and that batches of compound 3 contain only minor traces of a contamination. Differential thermoanalysis and thermogravimetry have revealed that upon heating of compound 3, an intermediate of composition Mn(NCS)₂ (2,5-dimethylpyrazine) (4) is formed, which cannot be obtained from solution. To mimic the structure of 4, single crystals of a Cd compound of the same composition (5) were prepared from the liquid phase, and single crystal X-ray analysis has shown that it is isotypic to 4.

Full text of DOI:10.1515/znb-2015-0182

Z. Naturforsch. 2016; 71(5)b: 381–390
Stefan Suckert, Susanne Wöhlert and Christian Näther*
Synthesis, structures, and properties of Mn(II)
and Cd(II) thiocyanato coordination compounds
with 2,5-dimethylpyrazine as co-ligand
DOI 10.1515/znb-2015-0182
Received November 11, 2015; accepted December 1, 2015
1 Introduction
Abstract: Reaction of manganese (II) thiocyanate with Investigations on the synthesis, structures, and magnetic
2,5-dimethylpyrazine leads to the formation of three new properties of new coordination polymers are still a major
coordination compounds of compositions Mn(NCS)2(2,5- activity in coordination chemistry [1–11]. In this context,
dimethylpyrazine)2(H2O)2 (1), Mn(NCS)2(H2O)2(MeOH)2- compounds in which paramagnetic metal cations are
tris(2,5-dimethylpyrazine) solvate (2), and Mn(NCS)2 linked by “small-sized” anionic ligands that can mediate
(H2O)4-tetrakis(2,5-dimethylpyrazine) solvate (3) that were magnetic exchange are of special interest. Even if most
characterized by single crystal X-ray diffraction. In their of such compounds are based on, e.g. carboxylates or
crystal structures, the Mn(II) cations are sixfold coordi- azides, thio- or selenocyanato coordination compounds
nated by two terminally N-bonded thiocyanato anions and are also of interest because in dependence on the coordi-
two water molecules as well as by two 2,5-dimethylpyra- nation mode of the anionic ligand and the topology of the
zine ligands (1), two ethanol (2), or two water molecules coordination network and they can show a variety of dif-
(3), within slightly distorted octahedra. In compounds 2 ferent magnetic properties [12–32].
and 3, additional 2,5-dimethylpyrazine ligands are located
In our own investigations, we are especially interested
in the cavities of the structures as solvate molecules. X-ray in compounds in which the paramagnetic metal cations
powder diffraction has shown that compounds 1 and 2 are coordinated additionally by N-donor co-ligands and
cannot be prepared as pure phases and that batches of are linked by pairs of thiocyanato anions into chains
compound 3 contain only minor traces of a contamina- because, depending on the nature of the metal cation
tion. Differential thermoanalysis and thermogravimetry and the organic co-ligand, different magnetic proper-
have revealed that upon heating of compound 3, an inter- ties including a slow relaxation of the magnetization
mediate of composition Mn(NCS)2(2,5-dimethylpyrazine) are observed [33–40]. Because the terminal coordina-
(4) is formed, which cannot be obtained from solution. To tion of the anionic ligands is energetically favored, the
mimic the structure of 4, single crystals of a Cd compound compounds with bridging thiocyanato ligands are more
of the same composition (5) were prepared from the liquid difficult to prepare. In these cases, the compounds with
phase, and single crystal X-ray analysis has shown that it a bridging coordination can sometimes be obtained by
is isotypic to 4.
thermal decomposition of simple discrete complexes of
compositions Mn(NCS)2(L1)4 or Mn(NCS)2(L1)2(L2)2 (L1 ꢀ=ꢀ
N-donor co-ligand; L2 ꢀ=ꢀ O-donor co-ligand as, e.g. H2O,
MeOH, EtOH), in which the metal cations are coordinated
by terminally N-bonded anionic ligands.
Keywords: cadmium;
crystal structure; manganese thiocyanates; synthesis;
thermochemistry.
coordination
compounds;
In this context, we became interested in 2,5-dimethyl-
pyrazine as a co-ligand, and we investigated if new Mn(II)
coordination polymers with μ-1,3-bridging thiocyanato
anions are directly available from solution or if simple
precursors can be obtained that might transform into the
desired compounds by simple heating. Only one structure
of a Mn coordination compound with this ligand has pre-
viously been reported, in which the co-ligand is located in
the cavities of the structure and thus does not participate
in metal coordination [41]. Here we report on the results of
our investigations.
Dedicated to: Professor Wolfgang Jeitschko on the occasion of his
80th birthday.
*Corresponding author: Christian Näther, Institut für Anorganische
Chemie, Christian-Albrechts-Universität zu Kiel, Max-Eyth-Straße 2,
24118 Kiel, Germany, Fax: +49-431-8801520,
E-mail: cnaether@ac.uni-kiel.de
Stefan Suckert and Susanne Wöhlert: Institut für Anorganische
Chemie, Christian-Albrechts-Universität zu Kiel, Max-Eyth-Straße 2,
24118 Kiel, Germany
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382ꢀ ꢀS. Suckert et al.: Mn(II) and Cd(II) thiocyanato coordination compounds with 2,5-dimethylpyrazine
2 Results and discussion
2.1 Crystal and molecular structures
If Co(NCS)2 is reacted with 2,5-dimethylpyrazine in
water, methanol, or ethanol, single crystals of three
new compounds of compositions Mn(NCS)2(2,5-
dimethylpyrazine)2(H2O)2 (1), Mn(NCS)2(H2O)2(MeOH)2-tris
(2,5-dimethylpyrazine) solvate (2), and Mn(NCS)2
(H2O)4-tris(2,5-dimethylpyrazine) solvate (3) are obtained.
2.1.1 Crystal and molecular structure of Mn(NCS)2
(2,5-dimethylpyrazine)2(H2O)2 (1)
Compound 1 crystallizes in the monoclinic space group
C2/c with four formula units in the unit cell. The asym-
metric unit consists of one manganese (II) cation located
on a twofold rotation axis and one thiocyanato anion, one
water molecule, and one 2,5-dimethylpyrazine ligand in
general positions (Fig. 1a). The manganese (II) cations are
coordinated by two N-bonded thiocyanato anions, two
water ligands, and two 2,5-dimethylpyrazine ligands in
a slightly distorted octahedral geometry forming discrete
complexes. The Mn–N distances range from 2.1382(12)
to 2.4000(10) Å, whereas the Mn–O distances amount to
2.2162(10) Å (Table 1). The bond angles range from 79.60(6)
to 102.98(4)° as well as from 165.42 to 166.56(5)°. In the
crystal structure, the discrete complexes are linked by
intermolecular O–H···N hydrogen bonding between the
water H atoms and the non-coordinating N atom of the
2,5-dimethylpyrazine ligand of a neighboring complex
into layers that are parallel to the bc plane (Fig. 1b and
Table 2).
Fig. 1:ꢀ(a) Ortep plot of 1 with a view of the coordination sphere
of the manganese (II) cation with atom labeling (symmetry code:
A ꢂ=ꢂ −x + 1, y, −z + 1/2) and displacement ellipsoids drawn at the
50 % probability level (top). (b) The crystal structure as viewed
along the crystallographic b axis (bottom). Hydrogen bonding is
shown by dashed lines.
Within these layers pairs of 2,5-dimethylpyrazine,
ligands are stacked into dimers that are located around
centers of inversion, which is indicative of π···π interac-
tions. These layers are additionally linked by intermolecu-
lar O–H···S hydrogen bonds between the second water H
atoms and thiocyanato S atoms into a three-dimensional
network (Fig. 1b and Table 2).
Table 1:ꢀSelected bond lengths (Å) for compounds 1–3.
ꢁ
Mn–N (NCS) ꢁ
Mn–N ꢁ
(co-ligand)
Mn–O
1ꢂ
2.1382(12) ꢂ 2.4000(19)
ꢂ
ꢂ
2.2162(9)
2ꢂ 2.1541(15)–2.1940(14)
ꢂ
ꢂ
ꢂ
–
1409(12)–2.366(12)
2.1.2 Crystal and molecular structure of the
Mn(NCS)2(H2O)2(MeOH)2 tris(2,5-dimethylpyrazine)
solvate (2)
ꢂ
ꢂ 2.1792(13)–2.2191(12)
ꢂ 2.1740(11)–2.2246(11)
3ꢂ
2.2029(13)
–
Compound 2 crystallizes in the triclinic space group P1
̅
with two formula units in the unit cell. The asymmetric 2,5-dimethylpyrazine ligands in general positions. One
unit consists of one Mn(II) cation two water, two metha- additional 2,5-dimethylpyrazine ligand is located around
nol molecules and two thiocyanato anions as well as two a center of inversion (Fig. 2a).
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Table 2:ꢀHydrogen bonding parameters (Å and deg) for compounds
1–3.
Compoundꢁ Hydrogen bond
ꢁ
d(D···A) ꢁ d(H···A) ꢁ ꢁ<ꢁ(DHA)
1
1
2
2
2
3
3
3
3
3
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
O(1)–H(1O1)···N(11)ꢂ 2.8296(14)
O(1)–H(2O1)···S(1) ꢂ 3.3418(10)
O(1)–H(1O1)···N(10)ꢂ 2.7724(19)
O(4)–H(1O4)···N(20)ꢂ 2.8252(18)
O(4)–H(2O4)···S(1) ꢂ 3.4134(13)
O(1)–H(1O1)···N(2) ꢂ 2.8726(19)
O(2)–H(1O2)···N(1) ꢂ 2.8265(19)
O(1)–H(2O1)···N(22)ꢂ 2.8746(16)
O(2)–H(2O2)···N(12)ꢂ 2.8499(17)
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
2.02
2.57
1.93
1.99
2.57
2.04
2.00
2.06
2.01
3.02
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
168.2
158.2
178.3
175.6
177.0
168.3
168.7
163.8
174.7
170.7
C(5)–H(5B)···S(31)
ꢂ
3.993(2)
The Mn(II) cations are coordinated by two thiocy-
anato anions, two water, and two methanol molecules in
a slightly distorted octahedral geometry. The Mn–N dis-
tances are in the range of 2.1541(15) to 2.1940(14) Å and
the Mn–O distances ranges from 2.1409(12) to 2.2366(12) Å
(Table 1). The bond angles are between 83.18(5) and
99.89(6)° and between 170.46 and 170.99(5)°, respectively.
The discrete complexes are connected by intermolec-
ular O–H···S hydrogen bonds between one water H atom
and the thiocyanato S atom into chains that elongate in
the direction of the crystallographic a axis (Fig. 2b and
Table 2). There are cavities in the structure where unco-
ordinated 2,5-dimethylpyrazine ligands are located. These
molecules are involved in intermolecular O–H···N hydro-
gen bonding between the water and the methanol O–H H
atoms and the 2,5-dimethlypyrazine N atoms connecting
the discrete complexes into a three-dimensional hydro-
gen-bonded network (Fig. 2b and Table 2).
2.1.3 Crystal and molecular structure of the
Mn(NCS)2(H2O)4 tetrakis(2,5-dimethylpyrazine)
solvate (3)
Fig. 2:ꢀ(a) Ortep plot of 2 with a view of the coordination sphere
of the manganese (II) cation with atom labeling (symmetry code,
A ꢂ=ꢂ −x + 2, −y, −z + 3) and displacement ellipsoids drawn at the
50 % probability level (top). (b) Crystal structure as viewed along
the crystallographic b axis (bottom). Hydrogen bonding is shown by
dashed lines.
Compound 3 crystallizes in the triclinic space group P1
with one formula unit in the unit cell. In the crystal struc-
ture, two thiocyanato ligands and four water molecules are
̅
coordinated to the Mn(II) cations, forming a slightly dis- molecules, of which two are located around centers of
torted octahedron (Fig. 3a). The Mn–N distances amount inversion (Fig. 3a).
to 2.2029(13) Å, and the Mn–O distances are 2.1740(11)
In contrast to compounds 1 and 2, no intermolecu-
and 2.2246(11) Å, with bond angles ranging from 87.67(4) lar O–H···S hydrogen bonds are observed. As in com-
to 92.33(4)° as well as 180° (Table 1). The asymmetric unit pound 1, there are O–H···N hydrogen bonds between the
consists of a Mn(II) cation that is located on a center of water H atoms and the 2,5-dimethylpyrazine N atoms
inversion and two water ligands as well as two thiocy- to give chains in the direction of the crystallographic
anato anions that occupy general positions. There are b axis (Fig. 3b). Within these chains, centrosymmetric
three additional and uncoordinated 2,5-dimethylpyrazine 2,5-dimethylpyrazine dimers are observed with parallel
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384ꢀ ꢀS. Suckert et al.: Mn(II) and Cd(II) thiocyanato coordination compounds with 2,5-dimethylpyrazine
experimental patterns. Despite much effort to obtain pure
phases, results show that none of the compounds obtained
were pure phases. Additional solvates containing differ-
ent amounts of solvate molecules formed. However, one
batch of compound 3 was obtained that contains only a
very small amount of an additional crystalline phase that
cannot be identified, and this batch was used for further
investigations (Fig. 4).
2.2 Thermoanalytical measurements
In all of our investigations, we have found no hints of the
formation of a compound in which the metal cations are
linked by the anionic ligands into chains. Therefore, we
have investigated compound 3 by simultaneous differen-
tial thermoanalysis and thermogravimetry (DTA-TG). It is
to be expected that not all of the water molecules and the
2,5-dimethylpyrazine ligands are removed in one step and
that intermediates will form, which might correspond to
the desired compounds. In this context, it must be kept in
mind that even if compound 3 contains a small amount of
a contamination, it can be assumed that this phase also
consists of a solvate that will lose the solvate molecules
on heating and that presumably transforms into the same
co-ligand-deficient compound.
DTA-TG of compound 3 shows three mass steps in the
TG curve that are accompanied with endothermic events
in the DTA curve (Fig. 5). The experimental mass loss of
56.3 % in the first step is in reasonable agreement with
that calculated for the removal of all of the water mole-
cules and three of the 2,5-dimethylpyrazine ligands
Fig. 3:ꢀ(a) Ortep plot of 3 with a view of the coordination sphere
of the manganese (II) cation with atom labeling (symmetry codes:
A ꢂ=ꢂ −x, −y + 2, −z + 1; B ꢂ=ꢂ −x + 1, −y + 2, −z; C ꢂ=ꢂ −x, −y + 2, −z) and
displacement ellipsoids drawn at the 50 % probability level (top).
(b) Crystal structure as viewed along the crystallographic a axis
(bottom). Hydrogen bonding is shown by dashed lines.
orientation, indicative of π···π interactions (Fig. 3b). These
chains are linked by additional O–H···N hydrogen bonds
of 2,5-dimethylpyrazine molecules into a three-dimen-
sional network. The 2,5-dimethylpyrazine ligands that are
involved in this interaction form columns that elongate in
the direction of the crystallographic a axis (Fig. 3b).
It is noteworthy that in two of the three structures,
the 2,5-dimethylpyrazine ligands do not participate in
the metal coordination and that they only act as solvate
molecules to form a dense packing. A similar situation is
found in the Mn coordination compound mentioned in
the introduction, which indicates that 2,5-dimethylpyra-
zine is a weakly coordinating ligand [41]. Coordination to
the N atoms is hindered because of the neighboring bulky
methyl groups.
Based on single crystal data, X-ray powder diffraction
Fig. 4:ꢀExperimental (top) and calculated (bottom) XRPD pattern
(XRPD) patterns have been calculated and compared with of 3.
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Fig. 6:ꢀIR spectra of compound 3 (top), the intermediate obtained
by thermal decomposition 4 (middle), and of the Cd compound 5
(bottom).
Fig. 5:ꢀDTA, TG, and DTG curves of 3.
paramagnetic counterparts and their structures can be
determined by XRPD.
(Δmcalcd. ꢀ=ꢀ 58.7 %). Therefore, it can be expected that in the
Crystals of a compound of the composition
first TG step, a compound of composition Mn(NCS)2(2,5- Cd(NCS)2(2,5-dimethylpyrazine) (5) can easily be obtained
dimethylpyrazine) (4) is formed, in which the metal by the reaction of Cd(NCS)2 and 2,5-dimethylpyrazine.
cations must be linked by bridging anionic ligands. In Its structure has been determined by single crystal X-ray
the second TG step, the remaining 2,5-dimethylpyrazine diffraction.
molecules are removed, and on further heating, decompo-
sition of Mn(NCS)2 is observed (Fig. 5). A closer look onto
the DTG curve indicates that the first TG step consists of 2.2.1 Crystal and molecular structure of Cd(NCS)2
additional steps, but heating rate-dependent TG measure-
ments have shown that these events cannot be resolved.
(2,5-dimethylpyrazine) (5)
To investigate the compound formed in the first step, The Cd compound 5 crystallizes in the monoclinic space
a second TG run was performed in which this intermedi- group P21/c with two formula units in the cell. The Cd(II)
ate was isolated and investigated by infrared (IR) spec- cations are coordinated by four thiocyanato anions as
troscopy (Fig. 6). For this compound, the asymmetric CN well as two 2,5-dimethylpyrazine ligands forming an octa-
stretching vibration is observed at 2095 cm−1 and is there- hedron with a slightly distorted geometry (Fig. 7a). The
fore shifted to significantly higher values compared with bond lengths around the cadmium center are in range of
the precursor. In compound 3, this vibration is observed at 2.299(3) to 2.508(2) Å for the Cd–N and 2.6696(11) Å for the
2063 cm−1, which is exactly in the range expected for termi- Cd–S. The bond angles are between 85.45(9) and 94.55(9)°
nally N-bonded thiocyanato anions [42–44]. In contrast, a and at 180°.
value of 2095 cm−1 is a clear indication that μ-1,3-bridging
thiocyanato anions are present [42–44].
The asymmetric unit consists of a Cd(II) cation and a
2,5-dimethylpyrazine ligand that are located on centers of
However, because the structure of compound inversion and a thiocyanato anion in a general position.
4 is unknown, we used an alternative procedure to The Cd(II) cations are linked by μ-1,3-bridging thiocyanato
extract structural information. In a previous work, we anions to four different Cd cations forming layers that are
have shown that corresponding compounds based on located in the bc plane (Fig. 7b). These layers are further
cadmium(II) can be prepared [45]. Because this cation linked by μ-1,4-bridging 2,5-dimethylpyrazine ligands
is much more chalcophilic, the compounds with bridg- forming
a three-dimensional coordination network
ing thiocyanato anions are more stable and can easily (Fig. 7c). In contrast to the structure of compounds 1–3,
be crystallized from solution, even if an excess of the co- neighboring 2,5-dimethylpyrazine ligands are oriented
ligand is used. In several cases, they are isotypic to their perpendicularly to another. It is noted that a compound
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386ꢀ ꢀS. Suckert et al.: Mn(II) and Cd(II) thiocyanato coordination compounds with 2,5-dimethylpyrazine
previously investigated in our group also shows a similar
thiocyanato coordination network [14].
Based on the structural data of compound 5, the XRPD
pattern was calculated and compared with that measured
for compound 4, which clearly shows that both compounds
are isotypic (Fig. 8, top). To additionally prove the identity
of compound 4, a Pawley fit was made, from which the unit
cell parameters were extracted. Like the Cd compound 5,
the Mn compound 4 crystallizes in space group P21/c with
a ꢀ=ꢀ 7.6179(3), b ꢀ=ꢀ 9.6011(5), c ꢀ=ꢀ 7.8762(3) Å, β ꢀ=ꢀ 112.101(3)°,
and V ꢀ=ꢀ 533.76(4) Å3. From the difference curve, it is indi-
cated that a pure material might have been obtained.
Finally, in the IR spectra of compound 5, the asymmetric
CN stretching vibration is observed at 2104 cm−1, which is in
the range observed for the Mn intermediate 4 (Fig. 6).
The new Mn compound was also investigated by
magnetic susceptibility measurements. The susceptibility
Fig. 7:ꢀ(a) Ortep plot of 5 with a view of the coordination sphere of
the cadmium (II) cation with atom labeling (symmetry codes, A ꢂ=ꢂ −x,
−y, −z, B ꢂ=ꢂ −x + 1, −y, −z, C ꢂ=ꢂ x, −y − 1/2, z − 1/2, D ꢂ=ꢂ −x, y + 1/2, −z
+ 1/2, E ꢂ=ꢂ −x, y − 1/2, −z + 1/2) and displacement ellipsoids drawn
at the 50 % probability level. (b) Crystal structure as viewed along
the crystallographic a axis (2,5-dimethylpyrazine ligands omitted
for clarity) and (c) along the b axis.
Fig. 8:ꢀTop: Experimental x-ray powder pattern of the residue 4
obtained by thermal decomposition of compound 3 (top) and calcu-
lated pattern for the Cd compound 5 (bottom). Bottom: Pawley-Fit of
compound 4.
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continuously increases with decreasing temperature, filtrate was concentrated to complete dryness, resulting
showing only paramagnetic behavior. The χT versus T in a white residue of Mn(NCS)2. Cd(NCS)2 was prepared by
curve decreases, indicating dominating antiferromagnetic the reaction of equimolar amounts of CdSO4·8/3H2O and
interactions. Several batches were measured, and accord- Ba(NCS)2·3H2O in water. The resulting white precipitate of
ing to our measurements, some of them are contaminated BaSO4 was filtered off, and the filtrate was concentrated to
with a very small amount of an additional crystalline complete dryness, resulting in a white residue of Cd(NCS)2.
phase that also shows paramagnetic behavior. However, The purity was proven by XRPD and elemental analysis.
the occurrence of only paramagnetism is not surprising
because other Mn thiocyanato coordination polymers
with μ-1,3-bridging anionic ligands show either paramag- 4.1.1 Preparation of Mn(NCS)2(2,5-dimethylpyrazine)2
netic behavior or antiferromagnetic ordering [24].
(H2O)2 (1)
Single crystals suitable for X-ray diffraction were obtained
by the reaction of Mn(NCS)2 (25 mg, 0.15 mmol) and
2,5-dimethylpyrazine (33 μL, 0.30 mmol) in 1 mL acetoni-
trile. Block-shaped single crystals were obtained after a
few weeks, but XRPD showed that no pure sample was
obtained.
3 Conclusions
In the present work, new manganese (II) thiocyanato
coordination compounds with 2,5-dimethylpyrazine were
prepared with the major goal of obtaining compounds in
which the Mn cations are linked by the anionic ligands
into Mn(NCS)2 chains. Independent of molar stoichiom-
etry and the solvent used, compounds with terminally
N-bonded co-ligands were constantly obtained, and in
most, the 2,5-dimethylpyrazine molecules do not partici-
pate in metal coordination. The N coordination is hindered
because of the methyl groups next to the N atom. However,
if one of these compounds is heated, a transformation into
a new compound of composition Mn(NCS)2(2,5-dimethyl-
pyrazine) is obtained, which is isotypic to the correspond-
ing Cd compound prepared in this work. This shows the
importance of the diamagnetic analogues to retrieve struc-
tural information on their paramagnetic counterparts. In
the crystal structure of the new Mn compound, the metal
cations are linked by μ-1,3 bridging thiocyanato anions,
and therefore, this coordination corresponds to the desired
one. Even if this new phase cannot be obtained in pure
form, it demonstrates the potential of thermal decomposi-
tion reactions for the synthesis of new coordination poly-
mers that cannot be obtained from the solution phase.
4.1.2 Preparation of Mn(NCS)2(H2O)2(MeOH)2-tris
(2,5-dimethylpyrazine) solvate (2)
Single crystals suitable for X-ray diffraction were obtained
by the reaction of Mn(NCS)2 (25 mg, 0.15 mmol) and
2,5-dimethylpyrazine (66 μL, 0.60 mmol) in 1 mL methanol.
Block-shaped single crystals were obtained after a few
weeks, but XRPD showed that no pure sample was obtained.
4.1.3 Preparation of Mn(NCS)2(H2O)4 tetrakis
(2,5-dimethylpyrazine) solvate (3)
Single crystals suitable for X-ray diffraction were obtained
by the reaction of Mn(NCS)2·4H2O (60 mg, 0.25 mmol) and
2,5-dimethylpyrazine (108 μL, 1.00 mmol) in 1 mL water.
Block-shaped single crystals were obtained after a few
weeks. A beige crystalline powder was obtained by react-
ing Mn(NCS)2·4H2O (159 mg, 0.5 mmol) and 2,5-dimethyl-
pyrazine (216 μL, 2.00 mmol) in 1 mL water. XRPD showed
that this compound is nearly phase-pure and contains
only a very small amount of a different crystalline phase
that does not correspond to compounds 1 or 2. – C26H40Mn-
N10O4S2: calcd. C 46.21, H 5.97, N 20.73, S 9.49; found C 47.47,
H 6.44, N 21.81, S 11.07 %.
4 Experimental section
4.1 Syntheses of Mn(NCS)2 and Cd(NCS)2
MnSO4·H2O, Cd(SO)4·8/3H2O, and 2,5-dimethylpyra-
zine were obtained from Merck and Ba(NCS)2 ·3H2O
was obtained from Alfa Aesar. Mn(NCS)2 and Cd(NCS)2 4.1.4 Preparation Cd(NCS)2(2,5-dimethylpyrazine) (5)
were prepared by the reaction of equimolar amounts
of MnSO4·H2O and Ba(NCS)2·3H2O in water. The result- Single crystals suitable for X-ray diffraction were obtained
ing white precipitate of BaSO4 was filtered off, and the by the reaction of Cd(NCS)2 (34 mg, 0.15 mmol) and
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ꢀꢀꢀꢁ
388ꢀ ꢀS. Suckert et al.: Mn(II) and Cd(II) thiocyanato coordination compounds with 2,5-dimethylpyrazine
2,5-dimethylpyrazine (65 μL, 0.60 mmol) in 1 mL water. 75 mL/min and were corrected for buoyancy and current
Block-shaped single crystals were obtained after a few effects. The instrument was calibrated using standard ref-
weeks. A white crystalline powder was obtained by react- erence materials.
ing CdCl2 (159 mg, 0.5 mmol) with KNCS (87 mg, 0.9 mmol)
and 2,5-dimethylpyrazine (192 μL, 1.75 mmol) in 1 mL
water. – C8H8CdN4S2: calcd. C 28.54, H 2.39, N 16.64, S 4.4 Single-crystal structure determinations
19.05; found C 28.65, H 2.28, N 16.60, S 19.37 %.
Data collections were carried out on an imaging plate dif-
fraction system: Stoe IPDS-1 and Stoe IPDS-2 with MoKα
4.2 Elemental analysis
radiation. The structures were solved with Direct Methods
using Shelxs-97, and structure refinements were per-
CHNS analysis was performed using a Euro EA elemental formed against F2 using Shelxl-97 [46]. Numerical absorp-
analyzer manufactured by Euro Vector Instruments and tion correction was applied using the programs X-Red and
Software.
X-Shape of the program package X-Area [47–49]. All non-
hydrogen atoms were refined with anisotropic displace-
ment parameters. All hydrogen atoms were positioned
with idealized geometry and were refined isotropically
with Uiso(H) ꢀ=ꢀ −1.2 Ueq(C) (−1.5 for methyl H atoms) using
a riding model with C–H ꢀ=ꢀ 0.95 Å for 2 and 3 and C–H ꢀ=ꢀ
4.3 Differential thermal analysis and
thermogravimetry
The heating-rate-dependent DTA-TG measurements were 0.93 Å for 1 and 5 for aromatic and C–H ꢀ=ꢀ 0.98 Å for 2 and
performed in a nitrogen atmosphere (purity, 5.0) in Al2O3 3 and C–H ꢀ=ꢀ 0.96 Å for 1 and 5 for methyl H atoms. The
crucibles using an STA-409CD instrument from Netzsch. methyl H atoms were allowed to rotate but not to tip. The
All measurements were performed with a flow rate of O–H hydrogen atoms were located in a difference map,
Table 3:ꢀSelected crystal data and details of the structure refinements for compounds 1, 2, 3, and 5.
Compound
ꢁ
1
ꢁ
2
ꢁ
3
ꢁ
5
Formula
Mw, g/mol
Crystal system
Space group
a, Å
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
C14H20MnN6O2S2ꢂ
C19H32MnN7O4S2ꢂ
C26H40MnN10O4S2 ꢂ
C8H8CdN4S2
336.70
Monoclinic
P21/c
7.7389
9.780
7.8893
90
423.42
Monoclinic
C2/c
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
541.57
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
675.74
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
Triclinic
Triclinic
P1
̅
P1̅
16.1856(7)
8.1509(3)
14.2615(6)
90
9.1476(7)
12.2779(7)
12.7508(10)
76.810(10)
84.669(9)
86.529(10)
1387.13(18)
200
9.7846(9)
10.3411(9)
10.8683(10)
84.311(11)
66.043(10)
63.678(10)
896.35
170
b, Å
c, Å
α, deg
β, deg
γ, deg
V, Å3
92.930(3)
90
113.43
90
1879.12(13)
293
547.9
293
T, K
Z
4
2
1
2
D
calcd., mg/cm3
1.50
1.30
1.25
2.04
μ, mm−1
θmax, deg
0.9
0.7
0.5
2.3
28.00
27.01
28.06
26.00
5168
Measured refl.
Unique refl./Rint
Refl. with Fo ꢂ>ꢂ 4 σ(Fo)ꢂ
15,599
2257/0.0236
2165
15,111
9406
5881/0.0553
5092
4163/0.0361
3386
1077/0.0394
967
71
0.0240
0.0503
1.171
0.45/−0.35
Refl. parameters
R1a [Fo ꢂ>ꢂ 4 σ(Fo)]
wR2b (all data)
GOFc
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
116
314
201
0.0258
0.0691
1.082
0.0369
0.0353
0.0896
1.028
0.0963
1.035
Δρmax/min, e/Å3
0.19/−0.36
0.32/−0.51
0.23/−0.52
2
2
2
2
aR1 ꢂ=ꢂ Σ||Fo| − |Fc||/Σ|Fo|; bwR2 ꢂ=ꢂ [Σw(Fo2 − Fc2)2/Σw(Fo )2]1/2, w ꢂ=ꢂ [σ2(Fo ) + (AP)2 + BP]−1, where P ꢂ=ꢂ (max(Fo , 0) + 2Fc2)/3; c GoF ꢂ=ꢂ S ꢂ=ꢂ [Σw(Fo
−
Fc2)2/(nobs − nparam)]1/2
.
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ꢁꢀꢀꢀ
S. Suckert et al.: Mn(II) and Cd(II) thiocyanato coordination compounds with 2,5-dimethylpyrazineꢃ
ꢃ389
[12] B. Machura, A. Świtlicka, J. Mroziński, B. Kalińska,
their bond lengths were set to ideal values, and finally,
they were refined isotropically with Uiso(H) ꢀ=ꢀ −1.5 Ueq(O)
using a riding model. Details of the structure determina-
tion are given in Table 3.
CCDC 1433519 (5), 1433520 (1), 1433521 (2), and 1433522
(3) contain the supplementary crystallographic data for
this paper. These data can be obtained free of charge from
the Cambridge Crystallographic Data Centre via http://
www.ccdc.cam.ac.uk/data_request/cif.
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R. Kruszynski, J. Solid State Chem. 2013, 197, 218.
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Chem. 2015, 3066.
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S. S. Massoud, Polyhedron 2015, 85, 20.
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4.5 Spectroscopy
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The IR spectra were measured using an ATI Mattson
Genesis Series FTIR Spectrometer with Winfirst software
from ATI Mattson.
[21] J. G. Małecki, T. Groń, H. Duda, Polyhedron 2012, 36, 56.
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4.6 X-ray powder diffraction
The measurements were performed using (1) a PANalytical
X’Pert Pro MPD Reflection Powder Diffraction System with
CuKα radiation (λ ꢀ=ꢀ 154.0598 pm) equipped with a PIXcel
semiconductor detector from PANanlytical and (2) a STOE
Transmission Powder Diffraction System (Stadi P) with
CuK radiation that was equipped with a Mythen K1000
deteαctor from STOE & Cie.
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Acknowledgments: This work was supported by the state
of Schleswig-Holstein. We also thank Prof. Dr. Wolfgang
Bensch for access to his experimental facilities.
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