Hydrothermal synthesis of chiral inorganic-organic CoII complex: Structural, thermal and catalytic evaluation

Article abstract of DOI:10.1016/j.molstruc.2018.04.002

By heating the cobalt chloride hexahydrate (CoCl₂·6H₂O) with the R form of the organic amine α-methylbenzylamine (C₈H₁₁N) under hydro(solvo)thermal conditions, we have successfully generated the corresponding non-centrosymmetric homochiral hybrid tris (α-methylbenzylammonium tetrachloridocobaltate chloride [R-(C₈H₁₂N)₃][CoCl₄]Cl abbreviated R(MBA)Co. We present the growth conditions together with a characterization of the single crystals by means of X-ray single-crystal diffraction, Fourier-transform infrared, TG/TDA thermal decomposition and catalytic properties. This inorganic–organic hybrid compound crystallizes in the chiral space group P2₁ and exhibits a supramolecular-layered organization wherein a double layer of (R)-methylbenzylammonium cations and the uncoordinated chloride anions are sandwiched between anionic layers, formed by isolated tetrachloridocobaltate tetrahedra. The crystal packing is governed by a three-dimensional network of N/C–H?Cl hydrogen bonds between the inorganic and organic moieties and C–H···π interactions between the aromatic rings of the organic moieties themselves. Thermal analysis discloses a phase transition at the temperature 130 °C. The Co complex was also employed as suitable catalyst activating the acetal formation reaction of aldehydes using MeOH as solvent and as the unique source of acetalization.

Full text of DOI:10.1016/j.molstruc.2018.04.002

Accepted Manuscript
II
Hydrothermal synthesis of Co chiral inorganic-organic complex: Structural,
thermal and catalytic evaluation
Assila Maatar Ben Salah, Raquel P. Herrera, Houcine Naïli
PII:
S0022-2860(18)30433-2
10.1016/j.molstruc.2018.04.002
MOLSTR 25075
DOI:
Reference:
To appear in:
Journal of Molecular Structure
Received Date:
Revised Date:
Accepted Date:
22 December 2017
29 March 2018
02 April 2018
Please cite this article as: Assila Maatar Ben Salah, Raquel P. Herrera, Houcine Naïli,
II
Hydrothermal synthesis of Co chiral inorganic-organic complex: Structural, thermal and catalytic
evaluation, Journal of Molecular Structure (2018), doi: 10.1016/j.molstruc.2018.04.002
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ACCEPTED MANUSCRIPT
Graphical abstract
Highlights
 New chiral and non-centrosymmetric single crystals of [R-(C8H12N)3][CoCl4]Cl have
been successfully synthesized and structurally characterized.
 C/N–H···Cl hydrogen bonds and C...H–π interactions are the driving forces in
generating a three-dimensional stable supramolecular network.
 Thermal analysis discloses a phase transition at the temperature 130°C.
 The Co complex is employed as suitable catalyst for the acetalization reaction of
aldehydes under mild conditions.

ACCEPTED MANUSCRIPT
Hydrothermal synthesis of CoII chiral inorganic-organic complex:
Structural, thermal and catalytic evaluation
Assila Maatar Ben Salaha, Raquel P. Herrerab and Houcine Naïlia*
a
Laboratoire Physicochimie de l’Etat Solide, Département de Chimie, Faculté des Sciences
de Sfax, BP 1171, 3000 Sfax, Université de Sfax, Tunisie.
b
Laboratorio de Organocatálisis Asimétrica, Departamento de Química Orgánica, Instituto
de Síntesis Química y Catálisis Homogénea (ISQCH), CSIC-Universidad de Zaragoza, C/
Pedro Cerbuna 12, E-50009 Zaragoza, Spain.
* Corresponding Author:
E-mail: houcine_naili@yahoo.com.
Tel: +216 98 660 026; Fax: +216 74 274 437.
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Abstract
By heating the cobalt chloride hexahydrate (CoCl2·6H2O) with the R form of the organic
amine α-methylbenzylamine (C8H11N) under hydro(solvo)thermal conditions, we have
successfully generated the corresponding non-centrosymmetric homochiral hybrid tris(α-
methylbenzylammonium
tetrachloridocobaltate
chloride
[R-(C8H12N)3][CoCl4]Cl
abbreviated R(MBA)Co. We present the growth conditions together with a characterization
of the single crystals by means of X-ray single-crystal diffraction, Fourier-transform infrared,
TG/TDA thermal decomposition and catalytic properties. This inorganic–organic hybrid
compound crystallizes in the chiral space group P21 and exhibits a supramolecular-layered
organization wherein a double layer of (R)-methylbenzylammonium cations and the
uncoordinated chloride anions are sandwiched between anionic layers, formed by isolated
tetrachloridocobaltate tetrahedra. The crystal packing is governed by a three-dimensional
network of N/C—H···Cl hydrogen bonds between the inorganic and organic moieties and C-
H···π interactions between the aromatic rings of the organic moieties themselves. Thermal
analysis discloses a phase transition at the temperature 130 °C. The Co complex was also
employed as suitable catalyst activating the acetal formation reaction of aldehydes using
MeOH as solvent and as the unique source of acetalisation.
KEYWORDS: Chiral; non-centrosymmetric; hybrid; hydrogen bonds; phase transition;
catalytic properties.
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1. Introduction
By combining the characteristic features of both organic and inorganic moieties, over the past
three decades, the design and synthesis of non-centrosymmetric inorganic-organic metal-
halide hybrid solids formed through self-organization under mild or solvothermal conditions,
have been one of the most fascinating and challenging areas due to their relevance to non-
linear optical (NLO) materials, in asymmetric catalysis and stereoselective recognition [1–5].
Among the numerous metal−organic non-centrosymmetric materials, the chiral coordination
compounds with non-centrosymmetric crystal structures are of special interest owing to their
distinctive physical properties, such as second-harmonic generation (SHG), ferroelectricity,
piezoelectricity, and pyroelectricity, which are potentially useful in electric-optical devices,
information storages, nonlinear optical (NLO) devices, and light modulators [6-8]. Hence,
inclusion of chirality in the molecule is a common strategy to ensure non-centrosymmetric
organization in the crystal lattice [9-10] and enantiomerically pure α-methylbenzylamine and
its derivatives have important applications as effective chiral adjuvants in the resolution of
racemates, and as ligands in asymmetric (or dissymmetric) catalysts [11]. Currently, this
amine is being used as a chiral auxiliary and as a chiral base. As an extension of our
systematic work on the organic–inorganic hybrid metal halides with the chiral α-
methylbenzylamine ligand under hydrothermal conditions [12], we report herein a new
inorganic–organic hybrid compound, [R-(C8H12N)3][CoCl4]Cl, possessing a zero-
dimensional structure. This salt crystallizes in a non-centrosymmetric space group and hence
could be a good candidate for non-linear optical applications. In addition, vibrational
spectrum, thermal analysis and the catalytic properties of the material have been investigated.
2. Experimental Section
2.1. Materials
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Cobalt(II) chloride hexahydrate (CoCl2·6H2O), hydrochloric acid (HCl; 37%) and (R)-(+)-α-
methylbenzylamine (C8H11N) were purchased from Sigma-Aldrich and used without further
purification.
2.2. Synthesis
The synthesis was carried out in home-built Teflon-lined stainless steel pressure autoclave of
120 mL maximum capacity. 1 mmol of CoCl2·6H2O and 3 mmol of (R)-α-methylbenzylamine
were dissolved together in 10 mL of water and hydrochloric acid (pH ≈ 3). The mixture was
placed in a Teflon-lined autoclave that was then sealed and heated to 120 °C for 4 days. It was
then allowed to cool to room temperature in a cold water bath. Blue plate crystals with
suitable dimensions for crystallographic study were collected. The crystals were washed
several times with distilled water and dried in open air. They are stable for months in normal
conditions of temperature and humidity.
2.3. Single-crystal data collection and structure determination
Suitable crystal was glued to a glass fiber on APEX II area detector 4-circles diffractometer.
Intensity data sets were collected using Mo Kα radiation (λ = 0.71073 Å) through the Bruker
AXS APEX2 Software Suite. The crystal structure was solved in the monoclinic symmetry,
space group P21, according to the automated search for space group available in Wingx [13].
Transition metal and chloride atoms were located using the direct methods with the program
SIR97 [14]. C and N atoms from the amine were found from successive difference Fourier
calculations using SHELXL-97 [15]. Their positions were validated from geometrical
considerations as well as from the examination of possible hydrogen bonds. The absolute
structure given by the structure refinement is likely correct with a Flack parameter value of
0.00(19). H atoms were positioned geometrically and allowed to ride on their parent atoms,
with C–H = 0.98 Å and N–H = 0.89 Å. The figures were made with DIAMOND program
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[16]. Crystallographic data are given in Table 2. Bond distances and angles calculated from
the final atomic coordinates, as well as probable hydrogen bonds, are listed in Tables 3 and 4.
2.4. Infrared Spectroscopy
Infrared measurements were recording using a Perkin Elmer 1650 FT-IR Spectrophotometer.
The sample was diluted with spectroscopic grade KBr and pressed into a pellet. Scans were
collected over the range of 400–4000 cm-1 (Table 1).
2.5. Thermal analyses
TGA–DTA measurements were performed on raw powders with a TGA/DTA 'SETSYS
Evolution' (Pt crucibles, Al2O3 as a reference) from room temperature up to 600 °C at a
constant rate of 5 °C/min under flowing air (100 ml/min).
2.6. Powder X-ray diffraction
The temperature-dependent X-ray (TDXD) was performed with a D5005 powder
diffractometer (Bruker AXS) using CuKα1 radiation (λ = 1.5406 Å) selected with a
diffracted-beam graphite monochromator and equipped with an Anton Paar HTK1200 high-
temperature oven camera. The thermal decomposition of the compound was carried out in air
with a heating rate of 7 °C h-1 from ambient to 600 °C. Temperature calibration was carried
out with standard materials in the involved temperature range.
2.7. Catalytic study
R(MBA)Co complex (7.7 mg, 0.01292 mmol) and aldehydes 1a-l (0.323 mmol) were
dissolved in MeOH (0.25 ml) in a test tube. The resulting mixture was stirred at 40 °C during
24 h. The reactions were monitored by thin-layer chromatography. The yield of the reactions
is given by 1H NMR in Tables 6 and 7.
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3. Results and discussion
3.1. Infrared spectra
Table 1 represents the major selected absorptions in the IR spectra of R(MBA)Co (Figure 1)
with their respective assignments. The presence of α-methylbenzylammonium [17] was
+
evidenced by the appearance of the typical absorptions bands for bending of the NH3 group
at ~1600 cm−1, deformation of CH3 at 1375 cm−1, deformation of C−H at ~700 cm−1 and
stretching of the C−C ring at about 1460 cm−1.
3.2. Crystal structure
Chiral (R)-α-methylbenzylamine or (S)-α-methylbenzylamine have a chiral centre which has
shown tremendous scope in the synthesis of hybrid complexes [18-19]. At -173 °C, the cobalt
studied salt crystallizes in the chiral monoclinic space group P21 and all atoms are located in
general positions. The crystal of R(MBA)Co contained α-methylbenzylammonium molecules
with the R-configuration and the absolute structure parameter of 0.00(19) reflects the correct
choice for the single chiral centre. As shown in Figure 2, the asymmetric unit contains three
crystallographically independent chiral organic ammonium cations, a tetrahedral
tetrachloridocobaltate anion and one free chloride anion. The packing of the different
molecular entities is shown in Figure 3; the projection along the b axis reveals a
supramolecular layered structure made of an alternate stacking of inorganic layers, built of
discrete [CoCl4]2- anions, and organic chains of (C8H12N)+ cations, while the free Cl- anions
are intercalated between the organic and inorganic sheets, linked together through extensive
non-covalent interactions (Table 4). Within the inorganic layers, each [CoCl4]2- anion exhibits
a slightly distorted tetrahedral arrangement around Co with Co–Cl bonds in the range
2.2559(8)–2.2929(12) Å, giving a mean value of 2.744(8) Å (Table 3). The Cl–Co–Cl bond
angles in the range of 105.92(3)°–112.55(3)°. These values compare well with those found in,
for example, (C4H7N2)2[CoCl4] [20] and (C10H11N3)[CoCl4] [21]. The distortion tetrahedral
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coordination geometry around Co(II) atom is verified by the calculated (τ4) parameter for
R(MBA)Co which corresponds to 0.96 [22]. The free Cl- anions play an important role in the
cohesion of the structure so they are located in the gaps between the [CoCl4]2- moiety and
protonated organic cations. In fact, the presence of those anions as a part of an anionic
sublattice together with [CoCl4]2- leads to a total negative charge of (-3) on the framework
which is balanced by the presence of three independent fully protonated (C8H12N)+ molecules
situated in the space delimited by the anionic sublattice (CoCl4 tetrahedra). Interestingly, the
crystal structure exhibits a layered inorganic-organic structure although the 0-dimension of
the inorganic backbone (isolated CoCl4 tetrahedra as shown in Figure 3. In fact, the distance
between the mean planes of two adjacent inorganic layers is remarkably high, indeed, it
corresponds to the value of the c unit cell parameter, i.e. , 14.42 Å (see Table 2). With regard
to the organic cation arrangement, the organization of methylbenzylammonium groups, not in
opposition, is favourable to a non-centrosymmetric arrangement [23]. The benzene rings are
nearly planar with the maximum deviation being 0.0077(19) Å for C8 in ring 1 (C8/C3–C7),
0.0098(19) Å for C12 in ring 2 (C12/C11–C13) and 0.0118(19) Å for C24 in ring 3
(C24/C19–C23). The bond lengths and angles within the organic cations are close to the usual
values observed in others (R)-α-methylbenzylammonium salts [12,19]. To predict and control
the crystal structure of such compound, one of the strategies that have been adopted in the
field of crystal engineering is the identification of specific intermolecular interactions that
control aggregation of molecular species, and the field of crystal supramolecularity seeks to
understand intermolecular interactions by analysis of crystal packing. The compound has an
extensive network of hydrogen bonding due to numerous acceptor and donor atoms. Indeed,
the different organic and inorganic sublattices are stabilized and governed significantly
through C/N–H∙∙∙Cl hydrogen bonding between the inorganic and organic moieties and C-
H···π stacking interactions between the aromatic rings of the amine molecules themselves
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(Tables 4 and 5). An interesting aspect of the directional effect of the H-bonding interactions
is that each organic chain has the (R)-α-methylbenzylammonium cations arranged radially
around it with the ammonium heads pointing inwards to engage in N–H···Cl hydrogen
bonding interactions, as shown in Figure 4. Due to the hydrogen bonds, the Co–Cl bond
lengths increase, resulting in slightly deformed CoCl4 tetrahedra. Moreover, it is worthwhile
to mention that within the organic section, the protonated amines are linked together through
the aromatic-aromatic C-H···π interactions between the benzene rings in a perpendicular
arrangement to form a T-shaped configuration [24]. Indeed, the centroid to centroid distance
is of 4,940(1) Å which is close enough to enable a C(7)–H(7)…Cg interaction to occur with a
distance of 2.755(1) Å from C7. Hence, both C/N–H···Cl and C-H···π stacking interactions
are the driving forces in generating a three-dimensional stable supramolecular network, as
shown in Figure 5.
3.3. Thermal analyses
The simultaneous (TG-DTA) curves of R(MBA)Co, carried out with a heating rate of 5
°C/min from 25 to 600 °C, are depicted in Figure 6. Figure 7 shows the successive powder
patterns obtained during the thermal decomposition. According to the TG curve, this
compound seems to be stable up to about 200 °C; however, the TDA curve depicts a strong
endothermic peak at 130 °C which is assigned to a phase transition confirmed by the
significant modification of the powder patterns shown on the TDXD plot at ~ 130 °C. The
only weight loss observed between 200 and 350 °C, is due to the loss of the organic moiety,
Cl2 molecule and the free Cl- anion, thus leading to the formation of CoCl2 moiety . While the
experimental weight loss as observed in the TG curve is 78.26%, the theoretical weight loss as
the suggested pattern is 79.25%. This decomposition process is accompanied by two
endothermic peaks on the DTA curve at 262 and 273 °C. The final transformation
corresponds to the formation of Cobalt oxide, Co3O4, which crystallises immediately after
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CoCl2 starts to decompose between 300 and 550 °C as shown on the TDXD plot (PDF N° 00-
042-1467).
3.4. Catalytic properties
The acetalisation process is one of the most straightforward strategies for protecting carbonyl
groups [25]. Proof of that is the huge amount of bibliography treating this organic process
[26-33], which in spite of their wide development still presents some disadvantages.
Therefore, the design of new effective and simple catalyst is of interest in this area of research
as demonstrated by the recent publications [34-37]. It is worth mention that despite the great
number of reports concerning this synthetic protocol, to the best of our knowledge the use of
Co-based catalysts to perform this reaction has been almost disregarded in the literature so far
[38,39]. Hence, the development of new Co catalysed examples using mild reaction
conditions is still interesting in this field.
As a part of our ongoing project to discover new catalysts and based on our previous
experience in the acetalisation reaction [40,41], we explored the effectiveness of R(MBA)Co
in this model process.
The catalytic activity of R(MBA)Co was initially tested in the acetalisation reaction described
in Table 6 between aldehyde 1a and MeOH as the unique source of acetalisation, and in sharp
contract with the commonly used CH(OMe)3.
Based on the results reported in Table 6, the best values were achieved at 40 ºC, using only 4
mol% of catalyst and 0.25 mL of MeOH (entry 5). Interestingly, the reaction also worked
with only 2 mol% (entry 1) although with lower yield. The dilution (entry 4) or the
concentration (entry 6) of the reaction mixture had a slight negative effect over the reactivity
of the process. It is interesting that the reaction worked well using MeOH as solvent and as
the unique source of acetalisation without the necessity of an additional source. Moreover, the
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use of MeOH as a source of acetalisation, in the absence of the commonly used trimethyl
orthoformate, is highly desirable due to its major availability.
With the best reaction conditions in hand, different substituted aldehydes 1 were explored in
order to show the scope of our reaction (Table 7).
The reaction crudes are very clean and the desired products 2 are obtained in all cases from
moderate to excellent yields. Therefore, this straightforward method was successfully applied
to all aldehydes examined 1a–l. It is remarkable that no special conditions to carry out the
reactions were needed, such as inert atmosphere or dry conditions. Interestingly, the process
does not have background since the reactions did not work in the absence of catalyst, which
support the role played by our catalyst promoting the process. In general, it seems that the
activated aldehydes, bearing electron-withdrawing groups in their structure, afforded better
yields in comparison with non-activated ones (compare entries 1-5 with entries 6-8). The
protocol also worked with aliphatic aldehydes, although in the case of aldehyde 1l the steric
effect could be the responsible of the lowest reactivity observed in comparison with 1j and
1k. The mechanism of this process could be envisioned as that proposed previously by us
[40,41], where the Cobalt would act as a Lewis acid promoting the activation of the carbonyl
group. Interestingly, during the exploration of the screening of the reaction (Table 6) we
observed by NMR the hemiacetal intermediate of this process (<5%), which supports our
mechanism. It is also expected that in the course of the reaction the intermediate was
consumed giving rise to the final acetal 2.
4. Conclusions
In summary, promising non-centrosymmetric optical single crystals of [R-
(C8H12N)3][CoCl4]Cl have been successfully synthesized and structurally characterized.
Crystallographic studies have illustrated that the studied compound crystallizes in the chiral
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non-centrosymmetric space group P21, confirmed by the absolute structure parameter. Despite
the 0-inorganic backbone dimensionality, this hybrid material exhibits a layered inorganic-
organic structure stabilized and governed significantly through extensive C/N–H∙∙∙Cl
hydrogen bonding between the inorganic and organic moieties and C-H···π interactions
between the aromatic rings of the amine molecules themselves. Furthermore, thermal analyses
reveal that the title compound undergoes one phase transition around 130 °C, confirmed by
the three-dimensional representation of the powder diffraction patterns (TDXD). Moreover,
we disclosed the study of R(MBA)Co complex as catalyst in the acetalisation reaction of
different aldehydes under very mild conditions in the presence of MeOH, as the solvent of the
process and, more interesting, as the unique source of acetalisation.
Supplementary materials
Crystallographic data (excluding structure factors) for the structure reported in this article
have been deposited with the Cambridge Crystallographic Data Center as supplementary
publication No CCDC-1478232 via www.ccdc.cam.ac.uk/data_request/cif.
Acknowledgments
The authors would like to gratefully thank Mr. Thierry Bataille from the CDIFX (Centre de
Diffractometrie X) – Sciences Chimiques de Rennes (UMR CNRS 6226), Groupe Matériaux
Inorganiques: Chimie Douce et Réactivité, Université de Rennes I, France, for supplying
single-crystal data collection. The authors are grateful, likewise, to Prof. Abdelmottaleb
Ouederni for his assistance in TGA/DTA measurements of this study (The Unit of Joint
Service of Researche National School of Engineers of Gabes, University of Gabes, Tunisia).
R.P.H. thanks Ministerio de Economía, Industria y Competitividad MINECO-FEDER
CTQ2017-88091-P and Diputación General de Aragón (DGA) (Research Group E07-17R) for
financial support of her research.
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Table 1. Assignments of the Bands of the Infrared Absorption Spectrum for [R-
(C8H12N)3][CoCl4]Cl
[R-(C8H12N)3][CoCl4]Cl
vibrational mode assignement
C−H out of plane deformation
mode
691.11
761.11
917
975
CH2 rocking mode
C−C stretching mode
1096
1166
in plan C−H deformation mode
1228
1350
CH3 deformation mode
NH3 rocking mode
+
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1375
1455
1507
CH3 symmetric deformation mode
C−C ring stretching
+
1612
2923
3040
3417
NH3 symmetric bending mode
antisymmetric CH2 stretch
aromatic CH
Table 2. Crystal data and structure refinement details for [R-(C8H12N)3][CoCl4]Cl
Chemical formula
Compound weight (g mol-1)
Temperature (K)
Crystal system
Space group
a(Å)
[R-(C8H12N)3][CoCl4]Cl
602.74
100 (2)
Monoclinic
P21
13.9553(4)
b (Å)
7.5120(2)
c (Å)
14.4210(4)
β (°)
V (Å3)
98.4830(10)
1495.25(7)
Z
2
ρcal (g cm-3)
Crystal dimension, mm3
Habit- colour
μ (mm−1)
1.339
0.37×0.3×0.25
Prismatic blue
1.04
θ range (deg)
index ranges
θmin = 2.9 θmax = 27.5
-18≤ h≤17
-9≤ k≤9
-18≤ l ≤18
Unique data
5905
Observed data [I > 2σ(I)]
4979
F(000)
626
R1
0.041
wR2
0.132
GooF
0.91
No. param
299
Transmission factors
Largest difference map hole (e Å-3)
Tmin= 0.688, Tmax= 0.995
Δρmin =-0.63 Δρmax = 0.53
Table 3. Selected bond distances (Å) and angles ( ) for [R-(C8H12N)3][CoCl4]Cl
Within the [CoCl4]2- tetrahedra
Within the (C8H12N)+ cation
Co—Cl1
Co—Cl3
Co—Cl2
Co—Cl4
2.2559 (8)
2.2694 (10)
2.2923 (10)
2.2929 (12)
110.90 (5)
N2—C10
N1—C2
N3—C18
C3—C8
C3—C4
1.491 (6)
1.508 (5)
1.513 (5)
1.389 (6)
1.392 (6)
Cl1—Co—Cl3
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Cl1—Co—Cl2
Cl3—Co—Cl2
Cl1—Co—Cl4
Cl3—Co—Cl4
Cl2—Co—Cl4
106.22 (5)
C3—C2
C10—C11
C10—C9
C19—C20
C19—C24
C19—C18
C11—C12
C11—C16
C2—C1
C4—C5
C24—C23
C6—C5
C6—C7
C12—C13
C23—C22
C22—C21
1.500 (6)
1.508 (5)
1.523 (5)
1.383 (7)
1.397 (6)
1.508 (6)
1.384 (7)
1.384 (7)
1.513 (7)
1.385 (7)
1.391 (7)
1.371 (7)
1.384 (7)
1.415 (7)
1.378 (7)
1.374 (7)
1.364 (9)
1.379 (10)
1.391 (7)
1.386 (7)
1.520 (7)
1.396 (7)
117.9 (4)
121.6 (4)
119.8 (4)
119.9 (5)
118.9 (5)
121.2 (4)
118.7 (5)
120.6 (4)
112.0 (4)
108.0 (3)
112.9 (3)
120.1 (4)
120.0 (4)
118.6 (4)
120.8 (4)
120.6 (4)
119.7 (4)
122.9 (4)
117.3 (4)
109.5 (4)
113.8 (3)
108.2 (3)
120.0 (4)
121.6 (4)
109.7 (3)
111.14 (4)
112.55 (5)
109.96 (4)
105.92 (4)
C13—C14
C15—C14
C16—C15
C20—C21
C18—C17
C8—C7
C8—C3—C4
C8—C3—C2
C23—C24—C19
C5—C6—C7
C11—C12—C13
C22—C23—C24
C21—C22—C23
C4—C3—C2
N2—C10—C11
N2—C10—C9
C11—C10—C9
C6—C7—C8
C6—C5—C4
C20—C19—C24
C20—C19—C18
C24—C19—C18
C12—C11—C16
C12—C11—C10
C16—C11—C10
C3—C2—N1
C3—C2—C1
N1—C2—C1
C6—C5—C4
C5—C4—C3
C19—C18—N3
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C19—C18—C17
N3—C18—C17
C14—C13—C12
C19—C20—C21
C11—C16—C15
C14—C15—C16
C22—C21—C20
C3—C8—C7
114.0 (4)
108.8 (4)
121.0 (6)
120.6 (4)
120.5 (6)
120.1 (6)
121.1 (5)
120.6 (4)
119.7 (4)
C13—C14—C15
Table 4. Hydrogen-bonding geometry (Å, ) for [R-(C8H12N)3][CoCl4]Cl
D—H···A (Å)
d (D—H) (Å)
0.89
0.89
0.89
0.89
0.89
0.89
0.89
0.89
0.89
0.89
0.98
0.96
0.89
0.89
0.89
0.89
0.89
0.89
0.89
0.89
0.89
0.89
0.96
0.89
0.89
0.89
0.89
0.89
0.89
0.96
d (H···A) (Å)
2.30
2.26
2.30
2.47
2.36
2.39
2.45
2.32
2.56
2.71
2.97
2.80
2.30
2.26
2.30
2.47
2.36
2.39
2.45
2.32
2.56
2.71
2.80
2.36
2.39
2.45
2.32
2.56
2.71
2.80
d (D···A) (Å)
3.096 (3)
3.131 (4)
3.176 (3)
3.299 (4)
3.195 (4)
3.234 (4)
3.270 (4)
3.183 (3)
3.319 (4)
3.319 (4)
3.815 (4)
3.741 (5)
3.096 (3)
3.131 (4)
3.176 (3)
3.299 (4)
3.195 (4)
3.234 (4)
3.270 (4)
3.183 (3)
3.319 (4)
3.319 (4)
3.741 (5)
3.195 (4)
3.234 (4)
3.270 (4)
3.183 (3)
3.319 (4)
3.319 (4)
3.741 (5)
D—H···A (°)
149
167
168
155
156
160
154
162
144
126
145
168
149
167
168
155
156
160
154
162
144
126
168
156
160
154
162
144
126
168
N2—HN2B···Cl5i
N2—HN2A···Cl5
N2—HN2C···Cl4ii
N1—HN1A···Cl4iii
N1—HN1B···Cl5
N1—HN1C···Cl2iv
N3—HN3A···Cl4ii
N3—HN3B···Cl2v
N3—HN3C···Cl3
N3—HN3C···Cl1
C10—H10···Cl1
C1—H1B···Cl2iii
N2—HN2B···Cl5i
N2—HN2A···Cl5
N2—HN2C···Cl4ii
N1—HN1A···Cl4iii
N1—HN1B···Cl5
N1—HN1C···Cl2iv
N3—HN3A···Cl4ii
N3—HN3B···Cl2v
N3—HN3C···Cl3
N3—HN3C···Cl1
C1—H1B···Cl2iii
N1—HN1B···Cl5
N1—HN1C···Cl2iv
N3—HN3A···Cl4ii
N3—HN3B···Cl2v
N3—HN3C···Cl3
N3—HN3C···Cl1
C1—H1B···Cl2iii
Symmetry codes: (i) −x+2, y+1/2, −z+2; (ii) x, y−1, z; (iii) −x+2, y−3/2, −z+2; (iv) −x+2, y−1/2, −z+2;
(v) −x+1, y−1/2, −z+2.
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Table 5. Details of C–H···Cg interactions for R(MBA)Co
D–H···Cg
D–H (Å) H···Cg (Å) Cg···Cg (Å)
Symmetry
transformations
-1+x, y, z
 D–H···Cg (°)
C7–H7···Cg1
C14–H14···Cg2
0.93(1)
0.93(1)
2.755(1)
3.5483(1)
4.9409(1)
5.015(1)
154.819(3)
119.296(2)
1-x, 1/2+y, 1-z
Table 6. Screening of the acetalisation reaction using R(MBA)Co as catalyst.
O
OMe
OMe
R(MBA)Co
H
MeOH, 24 h
NO2
NO2
1a
2a
Entry
1
R(MBA)Co
(mol %)
2
MeOH (mL)
0.25 mL
Temp (°C)
r.t.
Yield (%)a
60
2
3
4
5
6
4
6
4
4
4
0.25 mL
0.25 mL
0.50 mL
0.25 mL
0.10 mL
r.t.
r.t.
r.t.
40
40
72
64
62
89
77
a Yields of 2a [42] determined by 1H-NMR spectroscopy.
Table 7. Scope of the acetalisation reaction using R(MBA)Co as catalyst.
OMe
OMe
O
R(MBA)Co
(4 mol%)
R
R
H
MeOH 0.25 mL
40 ºC, 24 h
1b-l
2b-l
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Entry
R
Product
Yield (%)a
1
4-ClPh, 1b
3-ClPh, 1c
2b [43]
2c [43]
2d [43]
2e [43]
2f [44]
2g [45]
2h [43]
2i [43]
2j [43]
2k [46]
2l [47]
87
2
80
3
4-BrPh, 1d
4-NO2Ph, 1e
4-CNPh, 1f
4-PhPh, 1g
Ph, 1h
80
4
82
5
92
6
49
7
55
8
1-Naphthyl, 1i
PhCH2CH2, 1j
CH(CH3)CH2CH2, 1k
tBu, 1l
70
9
>95
>95
75
10
11
a Yields determined by 1H-NMR spectroscopy.
Figures
19

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Fig.1
Fig. 2
20

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Fig. 3
Fig. 4
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Fig. 5
Fig. 6
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Fig. 7
Figures captions
Figure 1: The infrared absorption spectra of R(MBA)Co, dispersed in a KBr pellet.
Figure 2: A view of the asymmetric unit cell of R(MBA)Co. Displacement ellipsoids for
non–H atoms are presented at the 50 % probability level.
Figure 3: Packing diagram of R(MBA)Co, showing the lamellar character and the stacking
along the c axis.
Figure 4: Packing diagram view along the b axis, showing hydrogen bonding interactions
between the chloride atoms and the hydrogen atoms on the organic cation in R(MBA)Co.
Figure 5: Crystal packing arrangement showing the C/N–H···Cl hydrogen bonding between
the inorganic and organic moieties (dashed purple lines) and the C...H–π interaction between
the cations (dashed blue lines)
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Figure 6: Simultaneous TG-DTA curves for the decomposition of R(MBA)Co, under
flowing nitrogen (5 °C/min from 25 to 600 °C).
Figure 7: TDXD plot for the decomposition of R(MBA)Co in air (7 °C h-1 from 20 to 600
°C).
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Highlights
 New chiral and non-centrosymmetric single crystals of [R-(C8H12N)3][CoCl4]Cl have
been successfully synthesized and structurally characterized.
 C/N–H···Cl hydrogen bonds and C...H–π interactions are the driving forces in
generating a three-dimensional stable supramolecular network.
 Thermal analysis discloses a phase transition at the temperature 130°C.
 The Co complex is employed as suitable catalyst for the acetalization reaction of
aldehydes under mild conditions.