[Sc(OH)(H2O)5]2Cl8: Synthesis, structure, and solid-phase thermal transformation

Article abstract of DOI:10.1134/S0036023608010087

The reaction of [Sc(OH)(H₂O)₅]₂Cl ₄ ? 2H₂O in isopropanol with 4,4-Bipy in CHCl ₃ produced a crystalline compound, which was identified as [H ₄(4,4-Bipy)₃][Sc(OH)(H₂O)₅] ₂Cl₈ (I) by elemental analysis, IR spectra, and single-crystal X-ray diffraction. In the structure of compound I, the three protonated diimine molecules form a centrosymmetric trimer via N.N hydrogen bonds. The polyhedron around the Sc atom is an octahedron with one split vertex. The excursion of the Sc atom from the plane formed by the oxygen atoms (water molecules) toward the hydroxo bridges is 0.5 ?. The thermolysis of compound I generates ScCl₃, whereas the final decomposition product of the precursor dimer is ScOCl.

Full text of DOI:10.1134/S0036023608010087

ISSN 0036-0236, Russian Journal of Inorganic Chemistry, 2008, Vol. 53, No. 1, pp. 48–54. © Pleiades Publishing, Ltd., 2008.
Original Russian Text © A.B. Ilyukhin, Zh.V. Dobrokhotova, S.P. Petrosyants, 2008, published in Zhurnal Neorganicheskoi Khimii, 2008, Vol. 53, No. 1, pp. 53–59.
COORDINATION
COMPOUNDS
[
H (4,4'-Bipy) ][Sc(OH)(H O) ] Cl : Synthesis, Structure,
4
3
2
5 2
8
and Solid-Phase Thermal Transformation
A. B. Ilyukhin, Zh. V. Dobrokhotova, and S. P. Petrosyants
Kurnakov Institute of General and Inorganic Chemistry, Russian Academy of Sciences,
Leninskii pr. 31, Moscow, 119991 Russia
Received January 24, 2007
Abstract—The reaction of [Sc(OH)(H O) ] Cl · 2H O in isopropanol with 4,4'-Bipy in CHCl produced a
2
5 2
4
2
3
crystalline compound, which was identified as [H (4,4'-Bipy) ][Sc(OH)(H O) ] Cl (I) by elemental analysis,
4
3
2
5 2
8
IR spectra, and single-crystal X-ray diffraction. In the structure of compound I, the three protonated diimine
molecules form a centrosymmetric trimer via N…N hydrogen bonds. The polyhedron around the Sc atom is an
octahedron with one split vertex. The excursion of the Sc atom from the plane formed by the oxygen atoms
(water molecules) toward the hydroxo bridges is 0.5 Å. The thermolysis of compound I generates ScCl3,
whereas the final decomposition product of the precursor dimer is ScOCl.
DOI: 10.1134/S0036023608010087
Studies of coordination polymers of scandium sul- tored directly on a TG-50 unit; the weighing accuracy
–3
fates demonstrated the dependence of the supramolec- was ±2 × 10 mg. The accuracy of determination of
ular architecture on ditopic organic cations, such as anomalous points and peaks on the heat-flow-versus-
4
,4'-bipyridine (4,4'-Bipy) [1].
temperature curves was ±1 K and ±0.5%, respectively.
X-ray powder diffraction analysis of thermolysis prod-
ucts was carried out on an FR-552 monochromator
This work studies the influence of structure-forming
,4'-Bipy on the structural and thermal features of the
4
camera (CuK radiation) relative to an internal germa-
compound
synthesized
from
the
dimer
α1
[Sc(OH)(H O) ] Cl · 2H O (II) [2].
nium standard (X-ray diffraction patterns were digi-
tized on an IZA-2 comparator with the accuracy
2
5 2
4
2
±
0.01 mm) and on a STOE Powder Diffraction System.
Synthesis of [H (4,4'-Bipy) ][Sc(OH)(H O) ] Cl
8
EXPERIMENTAL
4
3
2
5 2
Solvents (i-PrOH and CHCl ) and 4,4'-Bipy were (I). A solution of 4,4'-Bipy (0.04 g, 0.26 mmol) in
3
commercially available products and used as received CHCl (5 mL) was overlaid with a solution of
without being purified or dried. A solution of [Sc(OH)(H O) ] Cl · 2H O (II) in i-PrOH (0.13 mmol
3
2
5 2
4
2
[
Sc(OH)(H O) ] Cl · 2H O in i-PrOH, with a scandium Sc) diluted with i-PrOH (3 mL). The lower layer
2
5 2
4
2
concentration of 2.2%, was used in the synthesis. All clouded; after stirring, the solution became homoge-
operations were performed in air.
neous. The next day, druses of large crystals appeared
in the clear solution. Samples for X-ray structure exper-
iments were chosen from these crystals. The other crys-
tals were separated from the mother solution on a glass
Elemental analysis for C, H, and N was carried out
using standard procedures on a Carlo Erba analyzer at
the Shared Facilities Center, Kurnakov Institute of Gen-
eral and Inorganic Chemistry.
IR spectra were recorded as Nujol mulls (KBr cells)
on a Nexus Nicolet spectrometer in the range 400–
filter, washed with CHCl , and dried to constant weight
3
over silica gel in a desiccator. Yield: 0.03 g (40% for
Sc).
–1
For C H O N Cl Sc (FW = 1060.3) anal. calcd., %:
30 50 12 6 8 2
C, 33.98; H, 4.75; N, 7.93.
4
000 cm at the Shared Facilities Center, Kurnakov
Institute of General and Inorganic Chemistry.
The thermolysis of complexes I and II was studied
by differential scanning calorimetry (DSC) and ther-
mogravimetric analysis (TGA) on a Mettler TA-3000
thermal analyzer using DSC-20 and TG-50 units. All
experiments were carried out at a constant heating rate
Found, %: C, 33.63; H, 4.90; N, 7.55.
–1
IR spectrum (cm ): ν(H O) 3320, ν(NH) 3197,
2
σ(H O) 1634, σ(ScOH) 909, ν(ScO) 535, 440.
2
Compound I was structurally studied (Enraf-Nonius
of 5 K/min in air. In DSC experiments, test samples CAD4 diffractometer, MoK radiation, graphite mono-
α
were heated in aluminum containers; in TGA experi- chromator, ω scans). The structure was solved by a
ments, in alundum crucibles. Sample sizes did not direct method. The hydrogen atoms of water molecules
exceed 10 mg. Weight change upon heating was moni- were found from Fourier electron-difference synthesis.
4
8

[
H (4,4'-Bipy) ][Sc(OH)(H O) ] Cl : SYNTHESIS, STRUCTURE, AND SOLID-PHASE
49
4
3
2
5 2
8
The Bipy hydrogen atoms (at the carbon atoms and one Table 1. Selected crystal data and the results of structure re-
finement for compound I
NH atom) were generated geometrically. The structure
was refined by the full-matrix least-squares technique
in the anisotropic approximation with the fixed hydro-
gen atoms of water molecules; the Bipy hydrogen
atoms were included in the rider model. All calcula-
tions were performed using the SHELXS97 [3] and
SHELXL97 [4] program packages.
Parameter
Value
Formula unit
Temperature, K
Radiation
C H Cl N O Sc
3
0
50
8
6
12
2
295
CuKα
Selected crystal data and the results of structure Crystal system
Triclinic
refinement are listed in Table 1.
Space group
P1
The structure data were deposited with the Cam-
bridge Structural Database (CCDC no. 631981).
a, Å
9.2757(12)
10.924(2)
12.5492(13)
84.12(2)
b, Å
c, Å
RESULTS AND DISCUSSION
α, deg
Compound I was prepared with the ratio 4,4'-Bipy :
Sc = 2 (mol/mol). When this ratio decreased to one β, deg
77.61(2)
(
with all other synthesis parameters being the same), a
γ, deg
V, Å3
Z
70.63(2)
crystal phase was not isolated. Moreover, an attempt to
1171.0(3)
1
use interdiffusion with a 2.5 mL CHCl + 2.5 mL
3
i-PrOH interlayer (in the ratio 4,4'-Bipy : Sc =
2
(mol/mol)) yielded crystals that were identified as the ρcalc, g/cm3
1.504
7.202
salt H (4,4'-Bipy)Cl using single-crystal X-ray diffrac-
µ, mm–1
2
2
tion [5].
Crystal size, mm
θ, deg
0.25 × 0.20 × 0.15
3.61–64.94
4170
The structure of compound I is built of
4
+
[
Sc(OH)(H O) ] dimeric cations (Fig. 1a), proto-
2
5
2
Reflections collected
Unique reflections
Refined parameters
nated 4,4'-Bipy cations, and chloride ions. The sur-
rounding of a scandium atom in the cation is irregular;
the polyhedron can be described as a pentagonal bipyr-
3927
262
amid with a strongly nonplane base, but we believe it GOOF (F2)
1.024
more reasonable to consider it as an octahedron with
R1, wR2 (I > 2σ)
R1, wR2 (All reflections)
0.0482, 0.1719
0.0699, 0.1762
one split vertex (hydroxo bridges). Naturally, the
scandium atom departs by 0.5 Å from the O(3)–O(6)
atomic plane (Fig. 1a) toward the hydroxo bridges.
The highest intrinsic symmetry of the complex dimers
is mmm. This crystallographic symmetry is not crys-
tallographic one in any compound hitherto studied by
single-crystal X-ray diffraction. In the precursor salt
Projection in the Sc…Sc direction highlights what
happens with the cation when its intrinsic symmetry
changes (for clarity, the hydrogen atoms in the fig-
ures are omitted, and the oxygen atoms of the
hydroxo bridges are numbered). In transfer from
symmetry 2/m to –1, the hydroxo bridges are rotated
relative to water molecules (Figs. 1b, 1c); the sym-
metry of the cations dictates their eclipsed conforma-
tion. In [Sc(OH)(H O) ] (PhSO ) · 2H O, the cation
[
Sc(OH)(H O) ] Cl · 2H O, its bromine analogue [2],
2 5 2 4 2
and [Sc(OH)(H O) ] {Na (H O) [calix[4]arene(SO ) ] } ·
2
5 2
4
2
8
3 4 2
1
3H O [6], the crystallographic symmetry of the cation
2
is 2/m (in all cases, the scandium atoms and the oxygen
atoms of hydroxo bridges lie in plane m). In compound I,
the crystallographic symmetry of the cation is –1. Mat-
sumoto et al. [7] determined the structure of the salt
2
5 2
3 4
2
has a trans-conformation [8]. Different conforma-
tions are reflected in different Sc–O bond lengths. In
the [Sc(OH)(H O) ] X · 2H O (X = Cl or Br) com-
[
Sc(OH)(H O) ] (PhSO ) · 2H O (space group P1 ), in
2 5 2 3 4 2
2
5 2
4
2
which the cation symmetry is 1. Ng Seikweng and Hu
Shengzhi [8], using the data of Matsumoto et al. [7],
heightened the crystal symmetry to C2/c, with the crys-
tallographic symmetry of the cation being 2 (axis 2 is
normal to the fragment {{Sc(OH)}2).
pounds
[2],
compound
I,
and
[
Sc(OH)(H O) ] {Na (H O) [calix[4]arene(SO ) ] ·
3H O [16], the bond lengths are as follows: Sc–O
.03–2.08 Å, Sc−Ow trans to hydroxo bridges,
.21−2.28 Å; and Sc–Ow 2.17–2.19 Å. In
2 5 2 4 2 8 3 4 2
1
2
2
2
O
H
In crystals, the intrinsic and crystallographic sym-
[
Sc(OH)(H O) ] (PhSO ) · 2H O [8], the bond lengths
4
2
+
2 5 2 3 4 2
metries of Sc(OH)(H O) ]
cations coincide.
2
5
are as follows: Sc–OOH 2.07 Å, Sc–O trans to hydroxo
w
Figures 1b–1d show the configuration of cations in bridges, 2.25 Å; and four Sc–O bonds, which the most
clustered bonds in the above four compounds, are
Sc(OH)(H O) ] (PhSO ) · 2H O [8], respectively. grouped in pairs (2.14, 2.15, and 2.23 × 2 Å). There are
w
[
[
Sc(OH)(H O) ] Cl · 2H O [2], compound I, and
2
5 2
4
2
2
5 2
3 4
2
RUSSIAN JOURNAL OF INORGANIC CHEMISTRY Vol. 53 No. 1 2008

5
0
ILYUKHIN et al.
(‡)
O(5A)
O(4A)
O(3)
Sc(1A)
O(1)
O(6)
O(2)
O(2A)
O(1A)
Sc(1)
O(6A)
O(3A)
O(4)
O(5)
(
b)
(c)
(d)
O(1A)
O(2)
O(2A)
O(1)
O(6)
O(6A)
4
5
2
+
Fig. 1. Panel (a): the configuration of the complex cation [Sc(OH)(H O) ] in the structure of compound I. Panels (b–d): the
2
4
2
+
conformation of complex cations Sc(OH)(H O) ] in the structure of (b) [Sc(OH)(H O) ] Cl · 2H O, (c) compound I, and
2
5
2
5 2
4
2
(
d) [Sc(OH)(H O) ] (PhSO ) · 2H O [8].
2 5 2 3 4 2
C(2)
C(12)
C(7)
C(11)
C(1)
C(5)
N(1)
C(8)
N(2)
C(13)
C(14)
C(6)
N(3)
C(15)
C(13A)
C(3)
N(3A)
C(4)
C(9)
C(10)
Cl(4A)
4
+
Fig. 2. Configuration of a fragment [H (4,4'-Bipy) ] in the structure of compound I.
4
3
no steric hindrances in the cation, and the different confor- H-bonds (Table 2). The hydrogen atom at the nitrogen
mations are due to stacking factors.
atom in this H-bond has not been located; most likely,
There are 22 hydrogen atoms (20 water molecules all possible forms of the trimer are in equilibrium at
and two hydroxo bridges) in the complex cation. All room temperature. The terminal hydrogen atoms are
hydrogen atoms of the water molecules are H-bonded:
O–H…Cl (Table 2). The hydroxo hydrogen atom is not
located; there are two O(1)…Cl contacts (Table 2) that
can be regarded as H-bonds.
H-bonded: N–H…Cl.
The crystal structure can be derived from a primitive
cubic structure: complex cations reside at lattice sites,
The protonated diimine molecules are linked into protonated diimines are in cubic interstices, and chlo-
centrosymmetric trimers (Fig. 2) through two N–H…N ride ions, so to speak, flow around complex cations
RUSSIAN JOURNAL OF INORGANIC CHEMISTRY Vol. 53 No. 1 2008

[
H (4,4'-Bipy) ][Sc(OH)(H O) ] Cl : SYNTHESIS, STRUCTURE, AND SOLID-PHASE
51
4
3
2
5 2
8
Table 2. Hydrogen-bond geometry in the structure of compound I
Distance, Å
H…A
Contact D--H···A
D–H
Angle DNA, deg
D…A
O(1)…Cl(1) (–x + 1, –y + 1, –z + 1)
O(1)…Cl(3) (–x + 1, –y, –z + 1)
3.269(4)
3.355(4)
3.146(3)
3.168(3)
3.064(3)
3.165(3)
3.106(4)
3.014(4)
3.088(3)
3.103(4)
3.055(4)
3.000(4)
2.760(5)
3.072(5)
O(2)–H(2)…Cl(2) (–x + 1, –y, –z + 1)
O(2)–H(3)…Cl(2)
0.84
0.87
0.96
0.60
1.00
0.86
0.92
0.50
1.05
0.90
2.32
2.32
2.20
2.60
2.19
2.31
2.19
2.62
2.00
2.11
171
166
149
160
151
139
165
163
174
168
O(3)–H(4)…Cl(3)
O(3)–H(5)…Cl(3) (–x, –y + 1, –z + 1)
O(4)–H(6)…Cl(2)
O(4)–H(7)…Cl(1) (–x + 1, –y + 1, –z + 1)
O(5)–H(8)…Cl(3) (x + 1, y, –z)
O(5)–H(9)…Cl(2) (–x + 1, –y, –z + 1)
O(6)–H(10)…Cl(1)
O(6)–H(l1)…Cl(4)
N(1)…N(3)
N(2)–H(2)B…Cl(4) (x, y + 1, –z)
0.86
2.38
138
(
Fig. 3). Cationic and anionic layers are distinguished
The study of the behavior of aquascandium species
in water and crystals [9] showed that the cation
in the structure.
a
b
c
0
Fig. 3. Projection of the structure of compound I along axis x.
RUSSIAN JOURNAL OF INORGANIC CHEMISTRY Vol. 53 No. 1 2008

5
2
ILYUKHIN et al.
m, mg
Heat flow, mW
∆
(‡)
(b)
–
5
1
4
1
8
5
–
–
–
15
25
35
1
–
45
0
200
400
0
200
400 T, °C
Fig. 4. (a) Heat flow and (b) weight change vs. temperature upon heating of [Sc(OH)(H O) ] Cl · 2H O.
2
5 2
4
2
4
2
+
[
Sc(OH)(H O) ] is one of the most stable species. The phase composition of the solid product was deter-
2
5
mined by X-ray powder diffraction (Table 3); scandium
oxochloride was the only compound detected in the
final solid product to the error of X-ray powder diffrac-
tion (3.0 wt %). The final product weight is (39.7 ±
The same should hold for water–alcohol solutions,
which is verified by the synthesis of compound I and
the salts [Sc(OH)(H O) ] X · 2H O (X = Cl or Br) [2].
2
5 2
4
2
1
.5)% of the weight of the starting salt sample (the cal-
We studied the solid-phase thermolysis of
Sc(OH)(H O) ] Cl · 2H O. The thermolysis occurs in
culated ScOCl percentage in the salt is 40.04%).
[
2
5 2
4
2
stages. Before 78°ë, the sample loses 2.0% of its
weight with energy absorption (a shoulder at the first
endotherm; Fig. 4). At 78.5 ± 1.0°ë, melting occurs
with further degradation. The weight loss at the first
stage (67–100°ë) is 7.7 ± 1.0%, which corresponds to
the percentage of outer-sphere water (calcd., 7.47%).
Thus, the first stage is dehydration with attendant melt-
When compound I is heated, processes associated
with energy evolution, but not with weight change, are
observed in the range 45–75°ë. Evidently, we are deal-
ing with the dissociation of multiple hydrogen bonds
(
the first exotherm; Fig. 5a).
The first thermolysis stage in the range 75–105°ë
ing. The second stage (107–200°ë) occurs in two well- occurs with energy absorption (the second endotherm)
defined steps. The first step is at 107–152°ë and the sec- and a weight loss of (6.3 ± 1.0)%. This stage, likely,
ond one at 159 –200°ë, both with energy absorption and involves the deprotonation of the terminal diimine mol-
the weight loss at each step equal to 18.75%. The total ecules of the trimer and the elimination of the resulting
weight loss at the second stage is 37.5 ± 1.0% (the cal- two hydrogen chloride molecules (calcd., 6.89% HCl).
culated percentage of coordinated water is 37.34%); The product is thermally stable up to 132.0 ± 2.0°ë.
this means that the second stage can be considered as Above this temperature, in the range 132–253°ë (the
deaquation. The third stage occurs at 201–220°ë. The second stage), a multistep process occurs with atten-
weight loss at this stage is (15.1 ± 1.0)%. Probably, the dant complex energy changes (the third endotherm,
relevant process is the final destruction of the dimeric which is the superposition of three peaks, and the fourth
complex cation, accompanied by the elimination of two endotherm). The weight loss during the second stage is
hydrogen chloride moles (the calculated 2HCl percent- (20.9 ± 2.0)%. Presumably, this stage involves the fol-
age is 15.10%). The overall weight loss in the range 67– lowing processes: the deaquation and full degradation
2
20°ë is (60.3 ± 1.5)%. Above 220°ë, processes with a of the complex cation (this process occurs here at
change in energy occur, with the weight remaining vir- higher temperatures than for salt II and by another
tually constant; these processes are usually associated mechanism), the deprotonation of the central diimine
with the structure formation of the final solid product. molecule of the trimer, and the generation of two water
RUSSIAN JOURNAL OF INORGANIC CHEMISTRY Vol. 53 No. 1 2008

[
H (4,4'-Bipy) ][Sc(OH)(H O) ] Cl : SYNTHESIS, STRUCTURE, AND SOLID-PHASE
53
4
3
2
5 2
8
Table 3. Phase analysis of the solid decomposition product Table 4. Phase analysis of the solid decomposition product
of [Sc(OH)(H O) ] Cl · 2H O
of [H (4,4'-Bipy) ][Sc(OH)(H O) ] Cl
2
5 2
4
2
4
3
2
5 2
8
ScOCl*
Decomposition product
ScCl3*
Decomposition product
d, Å
I, %
d, Å
I, %
d, Å
I, %
d, Å
I, %
8
.21
100
2
8.205
3.580
2.645
2.470
1.985
1.865
1.582
100
20
20
10
15
10
5
5.9481
2.8142
2.1750
2.0771
1.893
60
100
60
6.005
2.835
2.165
2.070
1.885
1.855
1.552
50
100
40
3
2
2
1
1
1
.573
.649
.491
.982
.885
.586
3
1
20
30
1
20
15
1
1.8438
1.542
80
60
1
60
40
*
JCPDS Powder Diffraction File, card no. 36-1020.
* JCPDS Powder Diffraction File, card no. 45-0975.
molecules with the participation of hydroxo bridges, temperature range (T (4,4'-Bipy) = 305.2°ë [10]), we
b
which is made possible by the existence of é(1)…Cl can infer that Bipy elimination occurs at this stage. The
contacts. Thus, we can believe that, in the range 132– overall weight loss in the range 75–370°ë is (73.3 ±
2
53°ë, the gaseous thermolysis products are 12 water 2.5)%; the percentage of the solid decomposition prod-
molecules per molecule of compound I (the calculated uct is (26.7 ± 2.5)% against the calculated ScCl per-
3
water percentage is 20.37%). Above 253 and up to
70°ë, systematic weight loss is observed; the resulting
weight loss at this stage is (46.1 ± 2.5)%. This process
centage in compound I equal to 28.58%. The phase
composition of the solid product was determined by
X-ray powder diffraction (Table 4); within the X-ray
3
is accompanied by energy absorption (the fifth endot- powder diffraction accuracy, poorly crystallized scan-
herm; ƍ = 353.0 kJ/mol). From the values of the dium trichloride is the only compound in the final ther-
weight loss (the theoretical 4,4'-Bipy percentage in molysis product. The variations in the heat flow
compound I is 44.15%), the heat of the process (Fig. 5a) and sample weight (Fig. 5b) at temperatures
∆subH°(4,4'-Bipy) = 106.3 ± 2.8 kJ/mol [10]), and the above 370°ë, likely, correspond to the structure forma-
Heat flow, mW
∆m, mg
1
5
0
5
0
5
(
‡)
(b)
1
1
1
0
.8
.4
.0
.6
1
–
–
–
10
15
0.2
0
200
400
0
200
400
T, °C
Fig. 5. (a) Heat flow and (b) weight change vs. temperature upon heating of [H (4,4'-Bipy) ][Sc(OH)(H O) ] Cl .
4
3
2
5 2
8
RUSSIAN JOURNAL OF INORGANIC CHEMISTRY Vol. 53 No. 1 2008

5
4
ILYUKHIN et al.
tion of the final thermolysis product with simultaneous
sublimation.
3. G. M. Sheldrick, SHELXS97. Program for the Solution
of Crystal Structures (Univ. of Göttingen, Göttingen,
1
997).
4
. G. M. Sheldrick, SHELXL97. Program for the Refine-
ment of Crystal Structures (Univ. of Göttingen, Göttin-
gen, 1997).
ACKNOWLEDGMENTS
This work was supported by the Russian Foundation
for Basic Research (project no. 06-03-32460) and the
Fundamental Research Program of the Presidium of the
Russian Academy of Sciences (grant no. 8P31).
5. P. A. Iyere, W. Y. Boadi, D. Atwood, and S. Parkin, Acta
Crystallogr., Sect. B: 59 (5), 664 (2003).
6. H. R. Webb, M. J. Hardie, and C. L. Raston, Chem. Eur.
J. 7 (16), 3616 (2001).
7
. F. Matsumoto, Y. Ohki, Y. Suzuki, and A. Ouchi, Bull.
Chem. Soc. Jpn. 62 (6), 2081 (1989).
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