S. Hazra, A. Karmakar, M. Fátima C. Guedes da Silva et al.
Journal of Organometallic Chemistry 949 (2021) 121949
CoIIISnIV systems with three oxido bridges (one alkoxido and two
phenoxidos).
mixture resulted a red solution along with an unidentified brown
solid precipitate. After removing the solid product by filtration, the
obtained solution was kept at room temperature for slow evapora-
tion. Within 6 h, the formed red crystals, suitable for X-ray diffrac-
tion analysis, were collected by filtration and washed with cold
ethanol. Yield: 0.080 g (41%). C32H33Cl2N2O3CoSn (742.17): calcd.
C 51.79, H 4.48, N 3.77%; found. C 51.75, H 4.51, N 3.73%. IR data
(KBr, cm–1): ν(C=N), 1590s. ESI-MS: [Na(LCoPh)2]+ [calcd. 883.21
(100%), found 883.06]; [HLCoPh]+ [calcd. 431.12, found 431.10];
[Na(LCoPh)]+ [calcd. 453.01; found 453.10].
On the other hand, cyanosilylation is an important classic or-
ganic C–C bond forming reaction to synthesize α-silyloxy nitrile
species from aldehydes or ketones [21-23]. Such a nitrile can pro-
vide a useful protective group in organic synthesis or can be hy-
drolyzed to produce valuable functionalized organic derivatives
such as cyanohydrins, α-hydroxycarboxylic acids or β-amino al-
cohols which are important in synthetic chemistry and biological
ions were utilized to efficiently catalyze the reaction [32-34].
Therefore, the possibility of a heterometallic CoSn complex to act
as an effective catalyst can be anticipated. However, to our knowl-
edge, such a type of system has never been investigated in this
reaction. Hence, we have now tested the catalytic activity of the
above mentioned heteroorganometallic CoIIISnIV compounds in the
cyanosilylation reaction of benzaldehyde and substituted forms.
2.4. Crystal structure determination
X-ray quality crystals of 1 and 2 were immersed in cryo-oil and
mounted in a Nylon loop and measured at 298 K. Intensity data
were collected using a Bruker APEX II SMART CCD diffractometer
with graphite monochromated Mo-Kα (λ 0.71073) radiation. Cell
parameters were obtained with Bruker SMART [35] software and
refined with Bruker SAINT [35] on all the observed reflections. Ab-
sorption corrections were made by the multi-scan method (SAD-
ABS) [35]. Structures were solved by direct methods by using the
SHELXS-2014 package [36] and refined with SHELXL-2014/7 [36].
Calculations were performed using the WinGX System-Version
2014.1 [37]. Hydrogen atoms attached to carbon atoms were in-
serted at geometrically calculated positions and included in the re-
finement using the riding-model approximation. Uiso(H) were de-
fined as 1.2 Ueq of the parent carbon atoms. Solvent molecules
in the structure of 1 were highly disordered and could not be
2. Experimental section
2.1. Materials and physical methods
All the reagents and solvents were purchased from commercial
sources and used as received. The Schiff base H2L was synthesized
by condensing 2-hydroxyacetophenone with 1,2-ethylendiamine
following a similar procedure to that used for the synthesis of
salen [19]. NMR spectra of H2L were obtained on a Bruker 400
MHz spectrometer using tetramethylsilane [Si(CH3)4] as internal
reference. FT-IR spectra were recorded in the 400–4000 cm–1 re-
gion on a Bruker Vertex 70 spectrophotometer with samples as KBr
disks; abbreviations: s = strong, m = medium, and w = weak. El-
emental analyses were performed on a Perkin-Elmer 2400 II an-
alyzer. Mass spectra of sample solution in methanol (for 1) or
ethanol (for 2) were acquired on a Bruker HCT quadrupole ion trap
equipped with an electrospray ion source using the following typ-
ical instrumental parameters: solution flow rate, 2.5 μL/min; ESI
needle spray voltage, +4 kV; capillary exit voltage, −129 V; nebu-
lizer gas pressure, 8 psi; dry gas flow rate, 4 L/min; dry gas tem-
perature, 250°C; octopole RF amplitude, 187 Vpp. The spectra were
recorded in the range 100 – 1500 Da. Spectra typically correspond
to the average of 20–35 scans. Catalytic reactions were carried out
using a FISONS Instruments Anton Paar Monowave 300 microwave
synthesis reactor at 50°C.
modelled; therefore, they were removed by using PLATON SQUEEZE
3
˚
routine [38]. A total void of 122 A containing 58 electrons per unit
cell was found and fits well for one methanol (18 electrons) and
one water molecule (10 electrons) per asymmetric unit, being con-
sistent with the elemental analysis. Disordered phenyl (C26-C28)
and ethoxido (C31 and C32) carbons in 2 were modelled by means
of PART 1 and PART 2 instructions, leading to the occupancies of
57.5 and 42.5%. Least square refinements with anisotropic thermal
motion parameters for all the non-hydrogen atoms were employed.
Crystallographic data are summarized in Table S1 (Supplementary
information, SI).
2.5. Cyanosilylation of benzaldehyde catalyzed by
heteroorganometallic CoIIISnIV complexes
A mixture of benzaldehyde (0.50 mmol), trimethylsilyl cyanide
(1.0 mmol) and 1 mol% catalyst (7.8 or 7.4 mg for 1 or 2, respec-
tively) was placed in a Pyrex tube covered with a teflon cap and
stirred at 50°C under microwave irradiation (10 W) for 90 min
without any solvent. The final product was identified by 1H NMR
spectroscopy and the product yield was calculated using the same
procedure as reported in the literature [23].
2.2. Synthesis of [{SnPhCl2}(1κO2N2,2κO2-μ-L)(μ-OMe){CoPh}] (1)
To a methanol suspension (15 mL) of H2L (0.074 g, 0.25 mmol)
was added a methanol solution (2 mL) of CoCl2·6H2O (0.060 g,
0.25 mmol) to obtain an orange solution. Subsequent addition of
a methanol solution (3 mL) of [SnPh2Cl2] (0.086 g, 0.25 mmol)
to that reaction mixture produced a dark red solution which was
kept at room temperature for slow evaporation. Within 1 d, the
formed red crystals, suitable for X-ray diffraction analysis, were
collected by filtration and washed with cold methanol. Yield: 0.148
g (76%). C32H37Cl2N2O5CoSn (778.20): calcd. C 49.39, H 4.79, N
3.60%; found. C 49.51, H 4.83, N 3.59%. IR data (KBr, cm–1): ν(C=N),
1581s. ESI-MS: [Na·1·MeOH]+ [calcd. 783.02 (100%); found 782.96];
[HLCoPh]+ [calcd. 431.12; found 431.10].
3. Results and discussion
3.1. Synthesis and characterization
The single compartmental Schiff base N,N’-ethylenebis(2-
hydroxyacetophenoneimine) (H2L) (Scheme 1) was syn-
thesized by condensing 2-hydroxyacetophenoneimine with
1,2-ethylenediamine (2:1) in methanol following the re-
ported procedure used for the synthesis of salen [N,N’-
ethylenebis(salicylaldimine)] [19]. The reaction of H2L with
CoCl2·6H2O and [SnPh2Cl2] in MeOH, under open atmosphere
and at room temperature, produces the heteroorganobimetal-
2.3. Synthesis of [{SnPhCl2}(1κO2N2,2κO2-μ-L)(μ-OEt){CoPh}] (2)
To an ethanol suspension (15 mL) of H2L (0.074 g, 0.25 mmol)
was added an ethanol solution (2 mL) of CoCl2·6H2O (0.060 g, 0.25
mmol) to obtain an orange solution. Addition of an ethanol solu-
tion (3 mL) of [SnPh2Cl2] (0.086 g, 0.25 mmol) to that reaction
lic
CoIIISnIV
compound
[{SnPhCl2}(1κO2:2κO2N2-μ-L)(μ-
OMe){CoPh}]·CH3OH·H2O (1). We have also successfully isolated
2