J. Nenwa et al. / Polyhedron 99 (2015) 26–33
27
With
propylenediammonium
cations,
stacks
of
filtered and left to stand in the hood at room temperature.
After two days, elongated crystals were isolated by filtration
bis(oxalato)cuprate(II) anions are obtained [20]. This flexibility
of the structural topology in (organic cation)-oxalatocuprate(II)
compounds bears testimony to the renewed interest in their
coordination chemistry.
In the present paper, we report on the structural characteriza-
tion of two novel copper(II) hybrid salts bis(guanidinium)
bis(oxalato)cuprate(II), (CN3H6)2[Cu(C2O4)2] (1), and bis(2-aminopy-
ridinium) bis(oxalato)cuprate(II) trihydrate, (C5H7N2)2[Cu(C2O4)2]Á
3H2O (2), the structures of which the common anionic
bis(oxalato)cuprate(II) entities exhibit different stacking patterns.
Low temperature magnetic studies reveal weak antiferromagnetic
behavior in both compounds.
and dried in air. Yield: 72%. Anal. Calc. for
C14H14CuN4O8
(429.88) which is the non-hydrated form of C14H20CuN4O11
(483.88): C, 39.08; H, 3.26, N, 13.03. Found: C, 39.16; H, 3.24,
N, 13.05%. IR (cmÀ1): 3310m, 3150m, 1710s, 1670s, 1630s,
1480w, 1400m, 1270m, 1000w, 802w, 763w, 552w.
2.3. X-ray crystallography
Appropriate single crystals of 1 and 2 were mounted in ran-
dom orientation on a glass fiber. Intensity data were collected
at 293 K on a Bruker APEX CCD area-dectector diffractometer
with
graphite-monochromatized
Mo
K
a
radiation
2. Experimental
(k = 0.71073 Å). The X-ray intensities were corrected for absorp-
tion using a semi-empirical procedure [23]. The structures were
solved by direct methods with SHELXS-97 [24] and refined by
full-matrix least squares method based on F2 with SHELXL-97
[24]. All non-hydrogen atoms were refined anisotropically. The
positions of hydrogen atoms were added in idealized geometrical
positions for the organic cations. The positions of hydrogen
atoms from the water molecules were assigned from the elec-
tronic density map generated by Fourier difference and they were
refined freely. The ORTEP-3 program [25] was used within the
winGX software package [26] to deal with the processed crystal-
lographic data and artwork representations. Crystal data and
2.1. Materials and physical measurements
Oxalic acid dihydrate, chromium(III) chloride hexahydrate, 2-
aminopyridine and copper(II) oxalate hemihydrate were pur-
chased from Riedel de Haën. The guanidinium carbonate salt was
obtained
from
Aldrich
and
the
starting
compound,
K2[Cu(C2O4)2(H2O)2], was prepared following the literature proce-
dure [21]. All the chemicals were used without further purification
and the chemical reactions were carried out in distilled water as
the solvent. Elemental analysis (C, H, N) was performed on a
Vario EL (Heraeus) CHNS analyzer. The infrared spectra were
recorded on a Perkin–Elmer (System 2000) FT-IR spectrometer
with a pressed KBr pellet in the scan range 4000–400 cmÀ1 and
the UV–Vis spectra on a Perkin–Elmer Lambda 900 spectropho-
tometer, in water solution, in the range 200–800 nm
(c = 5.571 Â 10À5 mol/L). Thermal analyses (TGA and TDA) were
performed with a Mettler Toledo TGA/SDTA 851 thermal analyzer.
The powdered sample (ca. 15 mg) was heated from 25 to 600 °C
structure refinement parameters for
Table 1, selected bond lengths and bond angles in Table 2.
1 and 2 are given in
Table 1
Crystal data and structure refinement for 1 and 2.
Compound
1
2
Empirical formula
Formula weight
T (K)
C6H12CuN6O8
359.76
293(2)
0.71073
monoclinic
P21/c
C14H20CuN4O11
483.88
293(2)
0.71073
triclinic
with
a rate of 10 °C/min in dry nitrogen gas flowing at
60 mL/min. Magnetic susceptibility data for the polycrystalline
complexes 1 and 2 were recorded using a Quantum Design
MPMS-5XL SQUID magnetometer in the temperature range
2–300 K at an applied magnetic field of 0.1 T. The diamagnetic
corrections of the constituent atoms were estimated from Pascal’s
constants [22]. The effective magnetic moment was calculated as
k (Å)
Crystal system
Space group
Unit cell parameters
a (Å)
b (Å)
c (Å)
ꢀ
P1
3.5821(4)
15.7044(17)
11.2936(12)
90
96.968(2)
90
630.63(12)
2
1.895
7.7104(17)
9.159(2)
14.853(3)
72.902(3)
88.896(3)
77.962(3)
979.5(4)
2
l
eff (T) = [(3k/NA
l
)
2B vT]1/2 ꢀ (8
v .
T)1/2
a
(°)
b (°)
2.2. Syntheses
c
(°)
V (Å3)
Z
2.2.1. Synthesis of (CN3H6)2[Cu(C2O4)2] (1)
Dcalc (g/cm3)
1.641
1.182
An aqueous solution (20 mL) of guanidinium carbonate
(180 mg, 1 mmol) was added dropwise to a blue solution of
K2[Cu(C2O4)2(H2O)2] (350 mg, 1 mmol) in 30 mL of warm water.
The mixture was stirred at 50 °C for 1 h. After cooling to room tem-
perature, the resulting solution was filtered, and the filtrate was
allowed to stand undisturbed at room temperature for about one
week. Blue-greenish single crystals were isolated by filtration
and dried in air. Yield: 80%. Anal. Calc. for C6H12CuN6O8 (359.76):
C, 20.03; H, 3.36, N, 23.36. Found: C, 20.02; H, 3.33, N, 23.56%. IR
(cmÀ1): 3470m, 1710m, 1660s, 1610m, 1410m, 1280m, 800w,
553w.
l
(mmÀ1
)
1.787
F(000)
366
498
Crystal size (mm)
h range for data collection
(°)
0.18 x 0.03 x 0.01
5.19 – 36.15
0.18 x 0.03 x 0.01
4.68 – 33.02
Index ranges
À5 < h < 5,
À11 < h < 9,
À12 < k < 14,
À22 < l < 22
9477
6919 (0.0419)
0.988 and 0.813
À25 < k < 23,
À18 < l < 12
6805
Total reflections
Unique reflections (Rint
Max. and min.
)
2765 (0.0257)
0.988 and 0.813
transmission
Refinement method
full-matrix least
full-matrix least
squares on F2
3456/9/348
0.990
R1 = 0.0686,
wR2 = 0.1201
R1 = 0.1515,
wR2 = 0.1569
2.679 and À1.947
squares on F2
Data/restraints/parameters 1987/0/121
2.2.2. Synthesis of (C5H7N2)2[Cu(C2O4)2]Á3H2O (2)
Goodness-of-fit (GOF) on F2 1.057
H2C2O4Á2H2O (126 mg, 1 mmol) and 2-aminopyridine (188 mg,
2 mmol) were dissolved in warm water (30 mL), giving a yellow-
ish solution. CuC2O4Á1/2H2O (72 mg, 0.5 mmol) was added in suc-
cessive small portions to the above solution and the mixture
stirred at 60 °C for 1 h and then cooled to room temperature
under ambient conditions. The resulting green solution was
R factor [I > 2
r
(I)]
R1 = 0.0397,
wR2 = 0.0944
R1 = 0.0634,
wR2 = 0.1122
0.521 and À0.365
R factor (all data)
Max and min residual
electron density (e/Å3)