Inorganic Chemistry
Article
Cat[SbBr ] (Cat = 1,1′-(1,2-ethanediyl)bis(pyridine) (PyC22+)
(Cu Kα radiation, Ni filter, linear One Sight detector, 5−50° 2θ range,
.0143° 2θ step, 2 s per step). Polycrystalline samples were gently
ground with hexane in an agate mortar, the resulting suspension was
deposited on the polished side of a standard quartz sample holder, and a
smooth thin layer was formed after drying. Experimentally obtained
for details.
5
0
(
1) and 1,1′-(1,2-ethanediyl)bis(3,5-dimethylpyridine) (3,5-
2
+
MePyC ) (2), respectively, featuring an unusual pentacoordi-
2
nated Sb and noncovalent Sb···Br contacts which, as described
below, are believed to be responsible for the appearance of the
unusual coloring. In the mother liquor, 1 transforms into
(
4
PyC ) [Sb Br ], which demonstrates polymorphism (3 and
), while 2 transforms into the single-phase polymeric (3,5-
2 2 2 10
MePyC ){[SbBr ]} (5).
2
4
2
RESULTS AND DISCUSSION
EXPERIMENTAL SECTION
■
■
For preparation of 1 and 2, we used the general approach which
Starting Materials. All reagents were obtained from commercial
sources and used as purchased. Solvents were purified according to the
standard procedures. C PyBr and (3,5-MePy)C Br were obtained by
4
2
2
2
2
reactions of 1,2-dibromoethane with pyridine or 3,5-dimethylpyridine,
1
respectively (1:2.1, reflux, CH CN, 12 h), and identified by H NMR
3
spectra and elemental analysis.
Synthesis of 1−5. A 60 mg portion (0.2 mmol) of Sb O was
2
3
dissolved in 3 mL of concentrated HBr, followed by addition of
C PyBr (70 mg, 0.2 mmol) or (3,5-MePy)C Br (70 mg, 0.2 mmol) in
2
2
2
2
3
mL of HBr. The mixtures were heated to 70 °C and slowly cooled to
Figure 1. Supramolecular associates formed by [SbBr5]2 anions in the
structures of 1 and 2. Color code and definition here and below: Sb,
−
rt, resulting in deep orange crystals of 1 or 2, respectively. After
approximately 12 h in mother liquor, 1 and 2 transform into 3 (4) and 5,
X-ray Diffractometry. Single-crystal XRD data for 1, 3, and 5 were
collected with an automated Agilent Xcalibur diffractometer equipped
0
.71073 Å) (Table S1 in the Supporting Information). Integration and
absorption correction were performed using the CrysAlisPro program
package (CrysAlisPro 1.171.38.46, Rigaku Oxford Diffraction, 2015).
Single-crystal XRD data for 2 were collected with a Bruker D8 Venture
diffractometer with a CMOS PHOTON III detector and IμS 3.0 source
4
−
n−
Figure 2. Structures of [Sb Br ] (left) and {[SbBr ] } (right)
2
10
4 n
anions in 3 and 5.
(λ(Mo Kα) = 0.71073 Å). Absorption corrections were applied with
the use of the SADABS program (Bruker Apex3 software suite: Apex3,
SADABS-2016/2 and SAINT, version 2018.7-2; Bruker AXS Inc.,
Madison, WI, 2017). Single-crystal XRD data for 4 were collected with
a Bruker Apex DUO diffractometer equipped with a 4K CCD area
detector (graphite monochromator, λ(Mo Kα) = 0.71073 Å).
Absorption corrections were applied with the use of the SADABS
program (2000−2012), APEX2 (Version 2.0), SAINT (Version 8.18c),
and SADABS (Version 2.11) (Bruker AXS Inc., Madison, WI). The
in order to generate bromoantimonate(III) species, followed by
2
̅
, a = 6.1343(3) Å, b =
.2857(4) Å, c = 17.2041(9) Å, α = 90.331(4)°, β =
00.259(4)°, γ = 99.912(4)°, Z = 2; 2, P2/n, a = 6.2898(4) Å,
9
1
39
b = 8.7454(7) Å, c = 20.4076(16) Å, β = 90.438(3)°, Z = 2). In
crystal structures were solved using SHELXT and were refined using
2−
40
41
both cases, there are mononuclear [SbBr5] anions with
pentacoordinated square-pyramidal Sb (examples of such
bromoantimonates(III) were reported earlier, but those are
SHELXL with the OLEX2 GUI. Atomic thermal displacement
parameters for non-hydrogen atoms were refined anisotropically. The
somewhat high R factor and high residual electron density for structure
3
2
is due to the presence of a diffuse scattering along the c* direction in
rather uncommon ). The main structural feature of these
structures is that, as follows from a comparison of Sb···Br
5
distances (3.686 and 3.736 Å in 1 and 2, respectively) with the
42,43
sum of the corresponding van der Waals radii (3.89 Å
), the
existence of the corresponding noncovalent interactions
2−
between the neighboring [SbBr5] anions, resulting in the
Differential Scanning Calorimetry (DSC). Thermal analysis was
performed with a NETZSCH DSC 204 F1 Phoenix differential
scanning calorimeter with a digital/discrete resolution of ∼0.01 μW.
DSC measurements were carried out by a heat flow measurement
formation of supramolecular linear chains (Figure 1), can be
assumed. In the case of 2, the axial bromide ligand is disordered
over two positions with 0.5/0.5 occupancy, arranging on either
−
1
−1
method at a 12−15 K min cooling/heating rate in 25 mL min Ar
flux in unsealed aluminum crucibles with lids. Powdered samples were
distributed uniformly over the bottom and carefully tamped. To
increase the sensitivity and reduce baseline noise, measurements were
side of the {SbBr } plane. The disorder can be rationalized as
4
2−
follows. The [SbBr5] chains spread along the a axis; they are
strictly ordered in this direction for stereochemical reasons.
Along the c axis, there is a low probability of chains ordering, as
reciprocal space reconstructions (Figure S1). Along the b axis,
the chains are either strictly ordered or randomly arranged: no
diffuse scattering is observed in the corresponding reconstruc-
tions.
−
1
taken at a heating rate of 12−15 K min without the supply of gas or
−
1
liquid nitrogen (self-heating rate of the calorimeter cell ∼10 K min at
1
30 K). The sensitivity of the sample carrier sensors and temperature
scale gradation were calibrated by melting and crystal to crystal
transition measurements of standard samples (cyclohexane, adaman-
tane, Hg, Ga, benzoic acid, KNO , In).
3
Powder X-ray Diffractometry (PXRD). XRD analysis of
polycrystals was performed on a Shimadzu XRD-7000 diffractometer
The ranges of Sb−Br distances in 1 and 2 are 2.547−2.838
and 2.580−2.813 Å, respectively. The shorter distances
2
798
Inorg. Chem. 2021, 60, 2797−2804
Usoltsev, Andrey N.
