Zinc 2-: N -methyl N-confused porphyrin: An efficient catalyst for the conversion of CO2 into cyclic carbonates

Article abstract of DOI:10.1039/c9cy00739c

A zinc 2-N-methyl N-confused porphyrin (Zn(NCP)Cl) catalyst was developed for the solvent-free synthesis of cyclic carbonates from epoxides and CO₂. Zn(NCP)Cl exhibited very high catalytic activity. Using this catalyst, a series of epoxides have been converted into the corresponding cyclic carbonates in high yields and selectivity (>99%). The turnover frequency (TOF) value reached 266667 h^-1 for the conversion of CO₂ with epichlorohydrin into cyclic carbonate at 120 °C and an initial CO₂ pressure of 1.7 MPa within 3 h. Furthermore, an almost quantitative cyclic carbonate product was achieved under atmospheric CO₂ within 24 h. X-ray structural analysis of Zn(NCP)Cl reveals that the Zn²⁺ ion is four-coordinate, surrounded by three nitrogen atoms from the N-confused porphyrin and a chlorine atom. Due to the strong electron-withdrawing ability of chloride, zinc shows strong acidity, thereby enhancing its ability to activate epoxide. Density functional theory calculations (DFT) suggest that the ring-opening of epoxide is the rate-determining step of the catalytic cycle.

Full text of DOI:10.1039/c9cy00739c

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DOI: 10.1039/C9CY00739C
ARTICLE
Zinc 2-N-Methyl N-confused porphyrin: An Efficient Catalyst
for the Conversion of CO2 into Cyclic Carbonates
Received 00th January 20xx,
Accepted 00th January 20xx
Yuansheng Ge,a Guoe Cheng*,a Nanfeng Xu,a Weizhou Wang*,b and Hanzhong Ke*a
DOI: 10.1039/x0xx00000x
A zinc 2-N-Methyl N-confused porphyrin (Zn(NCP)Cl) catalyst was developed for the solvent-free synthesis of cyclic
carbonates from epoxides and CO2. Zn(NCP)Cl exhibited very high catalytic activity. Using this catalyst, a series of epoxides
have been converted into the corresponding cyclic carbonates in high yields and selectivity (>99%). The turnover
o
frequency (TOF) value reached 266667 h-1 for the conversion of CO2 with epichlorohydrin into cyclic carbonate at 120 C
and an initial CO2 pressure of 1.7 MPa within 3 h. Furthermore, almost quantitative cyclic carbonate product was achieved
under atmospheric CO2 within 24 h. X-ray structural analysis of Zn(NCP)Cl reveals that the Zn2+ ion is four-coordinate,
surrounded by three nitrogen atoms from the N-confused porphyrin and a chlorine atom. Due to the strong electron-
withdrawing ability of chloride, zinc shows strong acidity, thereby enhance its ability to activate epoxide. Density
functional theory calculations (DFT) suggest that the ring-opening of epoxide is the rate-determine step of the catalytic
cycle.
nonflammable. Furthermore, the synthesis of cyclic
carbonate from CO2 and epoxide exhibits 100% atom
Introduction
efficiency.12 However, the CO2/epoxide coupling
reaction is hindered due to the thermodynamic and
kinetic stability of CO2. In recent decades, much effort
has been devoted to develop highly efficient and
practical catalysts for this reaction, such as metal-based
catalysts (for example, metal salen complexes,13-19
Carbon dioxide (CO2) is a waste product of many
processes. The excessive emission of CO2 into the
atmosphere has result in serious global climate change.
The conversion of CO2 into valuable chemicals is a most
worthwhile area due to the economic and
environmental benefits in light of the problem of
greenhouse effect and the renewable carbon
resource.1-4 One of the most important products of CO2
transforming is cyclic carbonates (Scheme 1)5 which
have been widely used as organic synthetic
intermediates,6 polar aprotic solvents,7 electrolytes in
lithium ion batteries,8 precursors for biomedical
applications,9-10 and as raw materials for engineering
plastics.11 As an attractive C1 feedstock in organic
synthesis, CO2 is abundant, inexpensive, nontoxic, and
metal
porphyrins,20-28
aluminum
triphenolate
complex,29 alkali metal salts,30 metal oxides,31 Metal–
Organic Frameworks32) and metal-free catalysts (for
example, quaternary ammonium salts,33-38 imidazolium
salts,39-45 phosphonium salts,46-48 phenolic catalysts,49-51
and ionic liquids52-54). Among these catalysts, the Lewis
acidity of zinc compounds shows outstanding catalytic
performance for the cycloaddition of CO2 to epoxides.
Maeda and co-workers reported that a zinc (II)
porphyrin with quaternary ammonium bromides
(nucleophiles) at the meta positions showed very high
catalytic activity.55 The TOF value of this catalyst
reached 31500 h-1, which is among the highest
reported for monometallic complexes for the
cycloaddition of CO2 and epoxides to cyclic carbonates.
a. Faculty of Materials Science and Chemistry, China University of Geosciences
(Wuhan), Wuhan 430074, People’s Republic of China.
E-mail：chengge@cug.edu.cn; kehanz@163.com
b. College of Chemistry and Chemical Engineering, and Henan Key Laboratory of
Function-Oriented Porous Materials, Luoyang Normal University, Luoyang
471934, People’s Republic of China.
E-mail： wzw@lynu.edu.cn
Electronic Supplementary Information (ESI) available: 1H and 13C NMR, FT-IR, HRMS
spectra of Zn(NCP)Cl, typical procedure for the synthesis of cyclic carbonates, 1H According to the mechanism reported by the
NMR spectra of cyclic carbonates, details of crystal data, DFT calculations.
literatures,56-58 activation of epoxides via coordination

Catalysis Science & Technology
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ARTICLE
Journal Name
with metal center is critical in these metal catalytic
reactions. It is well understood that the reactivity of
such metal catalysts is strongly dependent on their
View Article Online
DOI: 10.1039/C9CY00739C
CH3
CH3
N
N
HC
N
HC
N
N
N
ZnCl2
Lewis acidity.
CH3CN
O
NH
NH
O
O
O
Catalyst
CO2
+
Cl
Cl
Zn(NCP)Cl
NCP
Scheme 1. The Cycloaddition of epichlorohydrin and CO2
Scheme 2 Synthesis of Zn(NCP)Cl
N-confused porphyrin is a porphyrin isomer with an
inverted pyrrole ring. Different from the N4
coordinated sites of porphyrin, such an exotic
porphyrin provide N3 or N3C coordinated sites to form
two kinds of metal complexes.59-61 Zinc 2-N-Methyl N-
confused porphyrin (Zn(NCP)Cl) (see Scheme 2) has a
zinc-chlorine bond as well as three zinc-nitrogen bonds
(see figure 1). The strong electron-withdrawing ability
of chloride can enhance the acidity of zinc.62 We
reasoned that Zn(NCP)Cl with a more Lewis acidic
metal center is a new powerful catalyst. In this context,
we reported the catalytic activity of Zn(NCP)Cl as the
first example of metal N-confused porphyrin for the
conversion of CO2 into cyclic carbonates.
ascertained by X ray crystallography. The compound
crystallized in the I 2/a space group. A perspective view
of Zn(NCP)Cl is depicted in Figure 1. The geometry
about Zn is distorted tetrahedral. The Zn atom in the
core were tetracoordinated with three pyrrolic
nitrogens, N(2), N(3), and N(4), and an axial Cl anionic
ligand. The bond length between Zn and N(2), N(3) and
N(4) atoms are 2.105(4), 2.011(4) and 2.107(4) Å, and
the Cl-Zn bond length is 2.2575(15) Å. The strong
electron-withdrawing ability of chloride can enhance
the acidity of zinc. The Zn⋯C(3) distance is 2.506(5) Å,
This value is much longer than the normal Zn-C bond
distance found, hence, there is no direct interaction
between Zn and C(3).63 The Zn center is displaced by
0.592 Å out of the 3N mean plane formed by N((2)-
N(3)-N(4) toward the axial chloride. The chloride ligand
occupies the equatorial position with a N(3)-Zn-Cl angle
of 119.33(13)°. The larger N(3)-Zn-Cl angle indicates
that the axial ligand leans more toward the inverted
pyrrole ring in Zn(NCP)Cl, which gives a more
tetrahedral-like metal center rather than square-
pyramidal, as found in tetracoordinated Zn porphyrin
complexes. The confused pyrrole ring sharply tilted
away from the plane defined by the tri-pyrrole unit and
the dihedral angle between the confused pyrrole plane
and the 3N plane is 49.55° (for details of crystal data,
Result and discussion
Scheme 2 shows the chemical structure and the
strategy for the synthesis of Zn(NCP)Cl discussed in the
present study. The complex Zn(NCP)Cl can be easily
synthesized in 49% yield by reacting NCP with excess
ZnCl2 in CH3CN. The newly synthesized compound
1
Zn(NCP)Cl was characterized by H NMR and 13C NMR.
The 1H NMR spectrum (in CDCl3) of Zn(NCP)Cl showed a
singlet at δ = –0.59 ppm for the H(3) proton. This
confirms that there is no coordinated bond between Zn
and C(3) in Zn(NCP)Cl. The MALDI-TOF high resolution
mass spectra (HRMS) of Zn(NCP)Cl exhibits [M-Cl]+ peak
at 691.1808, which deviate by 3.7617 ppm from the
theoretical value of 691.1834. The solid-state structure
see
the
Supporting
Information).
of
Zn(NCP)Cl
was
2 | J. Name., 2019, 00, 1-3
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Page 3 of 9
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1083
13
14
15
16e
17f
0.004
0.004
0.004
0.004
0.0001
-
3
3
3
3
3
120 1.7
13
View Article Online
120 D1O.I7: 10.106399/C9CY507057309C
TBAC
TBAI
TBAB
120 1.7
120 1.7
120 1.7
74
79
6167
6583
81 270000
TBAB
a
Reaction conditions: Epichlorohydrin (3.13 mL, 40 mmol),
cocatalyst (0.016 mol %), 100 mL autoclave. bDetermined by
1H NMR using mesitylene as an internal standard.
cSelectivity for the cyclic carbonate product >99%. dThe
reaction was carried out in a 100 mL three-neck flask under
CO2 atmosphere. eUsing Zn(TPP) instead of Zn(NCP)Cl as
catalyst. fUsing Phenyl glycidyl ether as a substrate.
Figure 1. X-Ray structure of Zn(NCP)Cl. Hydrogen atoms are
omitted for clarity. Selected bond lengths [Å] and bond
angles [°]: Zn(1)-N(2), 2.105(4); Zn(1)-N(3), 2.011(4); Zn(1)-
N(4), 2.107(4); Zn(1)-Cl(1), 2.2575(15); Zn(1)⋯C(3), 2.506(5);
N(2)-Zn(1)-N(3), 89.24(15); N(3)-Zn(1)-N(4), 89.76(16); N(2)-
Zn(1)-N(4), 146.07(16); N(2)-Zn(1)-Cl(1), 105.98(12); N(3)-
Zn(1)-Cl(1), 119.33(13); N(4)-Zn(1)-Cl(1), 103.99(12).
avoid any substrate effects (such as high volatility), the
cycloaddition of CO2 and Phenyl glycidyl ether (Boiling
o
point: 245-247 C) was also investigated at the same
conditions. The yield and TOF reached 81% and 270000
h-1 (Table 1, Entry 17), respectively. At a catalyst
loading of 0.004 mol% and a TBAB loading of 0.016 mol
%, almost quantitative cyclic carbonate product (98%)
of this was achieved within 3 h (Table 1, Entry 3). When
the reaction time was shortened to 1 h, the yield was
still up to 89% (Table 1, Entry 5). Ema reported that
metalloporphyrins have excellent catalytic activity for
the cycloaddition of CO2 to epoxide.25 For comparison,
The catalytic activities of this catalyst were initially
investigated for the cycloaddition of CO2 to
epichlorohydrin under solvent-free conditions in
combination with tetrabutylammonium bromide
(TBAB) as a cocatalyst. The results are summarized in
Table 1. It could be found that Zn(NCP)Cl was an
efficient catalyst with high selectivity (>99%) for the
coupling reaction of CO2 and epichlorohydrin to
chloropropene carbonate. When the catalyst and TBAB
amounts were 0.0001 mol % and 0.016 mol %,
respectively, 80% yield was obtained with a TOF of
266667 h-1 (Table 1, Entry 1). In order to
a
catalytic system composed of (5,10,15,20-
tetraphenylporphyrinato)Zinc (Zn(TPP)) and TBAB was
evaluated under the same conditions. Only 79%
product of cyclic carbonate was obtained with a TOF of
6583 h-1 (Table 1, Entry 16).
The effect of reaction temperature on the
cycloaddition of CO2 and epichlorohydrin to
chloropropene carbonate was investigated in the
temperature range of 65-120°C (Table 1, entries 3, 6-
8). under the identical conditions (catalyst loading,
0.004 mol%; TBAB loading, 0.016 mol%; CO2 pressure,
1.7 MPa; 3 h), the yield of chloropropene carbonate
increased with the elevation of temperature from 65 °C
to 120 °C. The yields at 65°C, 80°C, 100°C and 120°C
were 24%, 51%, 90% and 98%, respectively.
The effect of CO2 pressure on the catalytic
performance was also examined under the identical
conditions (catalyst loading, 0.004 mol%; TBAB loading,
0.016 mol%; 120 °C; 3 h) (Table 1, entries 3,9-10). The
yields retained nearly constant (>92%) at initial CO2
pressure in the range of 0.1-1.7 MPa, suggesting that
Table 1. Catalytic data for Zn(NCP)Cl catalyzed reactions of
CO2 with epichlorohydrina
Entry Zn(NCP)Cl cocat.
(mol %)
t
T
P
yield.b,c TOF
(h) (oC) (MPa) (%) (h -1)
1
0.0001
TBAB
3
120 1.7
80 266667
92 15333
2
3
4
5
6
7
8
9
0.002
0.004
0.004
0.004
0.004
0.004
0.004
0.004
0.004
0.004
-
TBAB
TBAB
TBAB
TBAB
TBAB
TBAB
TBAB
TBAB
TBAB
3
3
2
1
3
3
3
3
3
120 1.7
120 1.7
120 1.7
120 1.7
100 1.7
98
8167
92 11500
89 22250
7500
4250
2000
8000
7667
1010
90
51
24
96
92
97
19
80
65
1.7
1.7
120 1.0
120 0.5
10
11d
12
TBAB 24 120 0.1
TBAB 120 1.7
3
This journal is © The Royal Society of Chemistry 20xx
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CO2 was not the rate-determining step in this pressure catalyzed reaction are shown in Figure 3. At the first
View Article Online
DOI: 10.1039/C9CY00739C
range. To our excitement, almost quantitative yield step of the catalytic cycle, lewis acidic Zn center
(97%) of cyclic carbonate was obtained under activated the epichlorohydrin and the nucleophilic Br−
atmospheric CO2 within 24 h (Table 1, entry11).
attacking to the least substituted carbon atom of
The role of co-catalyst TBAB was found to be quite epichlorohydrin leads to the formation of the metal
important.64 When TBAB and Zn(NCP)Cl were used alkoxide intermediate Int1 with an energy barrier of
alone as catalysts for the coupling reaction of CO2 and 15.6 kcal mol-1. And the release of the chloride anion
epichlorohydrin, the yields were only 19% (Table 1, via transition state TS2, with an energy barrier of 4.9
entry 12) and 13% (Table 1, entry 13), respectively. kcal mol-1. The relative free energy of Int2 is 3.4 kcal
However, when Zn(NCP)Cl/TBAB was used as catalyst, a mol-1 below the reference energy of Int1. This energy
quantitative cyclic carbonate product was achieved. stabilization is caused by strong interaction between
These results indicated that the presence of both the negatively charged oxygen atom and the positive
Zn(NCP)Cl and TBAB was necessary for high efficiency. Zinc center. The addition of the CO2 molecule leads to
The metal center and Br- anion acted as a Lewis acid the formation of the intermediate int3. Subsequently,
and a Lewis base or nucleophile, and Both worked CO2 insertion and intramolecular ring closure leads to
cooperatively to open the epoxide ring. The effect of the formation of the product-coordinated intermediate
the X- anion on the catalytic activity was examined by Int4. This step proceeds via transition state TS4 by
using TBAB, tetrabutylammonium chloride (TBAC), and surmounting an energy barrier of 15.1 kcal mol-1. The
tetrabutylammonium iodide (TBAI) as the cocatalyst relative free energy of transition state TS4 is 22.2
(Table 1, entries 3, 14-15). The order of catalytic kcal/mol, which is reasonably in line with the kinetic
activity is TBAB (98%) > TBAI (74%) >TBAC (69%). TBAB data presented in Table 1, entry 8 (slow reaction at 65
showed much higher catalytic activity than TBAI and oC). Finally, the dissociation of cyclic carbonate from
TBAC.
Int4 and regeneration of the Zn(NCP)Cl complex allows
On the basis of our experimental results and the further ECH turnover. The overall reaction was
mechanism reported by the literatures,65-67 we propose calculated to be exergonic by 9.7 kcal mol-1.
the catalytic cycle shown in Scheme 3. In the catalytic
cycle, the epoxide is first activated via coordination
with Lewis acidic Zn center. The Lewis acidic Zn center
can activate the C–O bond of the epoxide to facilitate
ring-opening. Then, nucleophilic attack by Br- ion on
the less hindered side of the epoxide produces the
metal alkoxide intermediate via
a ring-opening
reaction, which is followed by CO2 insertion and
intramolecular ring closure to produce the cyclic
carbonate and the catalyst is regenerated.
To gain deeper insight into the reaction mechanism,
we performed DFT calculations along the proposed
reaction pathway (Scheme 3). The assistance of the
quaternary ammonium salt was simulated by including
only the bromine anion, and epichlorohydrin was used
as a substrate. The free energy profile calculated for
the reaction catalyzed by Zn(NCP)Cl/TBAB is shown in
Figure 2. The optimized structures for the reactant,
intermediates, transition states and product in the
Scheme 3. A Proposed mechanism for the coupling of
epoxide and CO2 catalyzed by Zn(NCP)Cl/TBAB
4 | J. Name., 2019, 00, 1-3
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Our catalyst system showed high-activity towards
View Article Online
DOI: 10.1039/C9CY00739C
terminal epoxides. Propylene oxide (Table 2, entry 1),
epichlorohydrin (Table 2, entry 2) and isobutylene
oxide (Table 2, entry 4) were quantitatively converted
into corresponding cyclic carbonates within 3 h, while
ethylene oxide (Table 2, entry 3) and styrene oxide
(Table 2, entry 5) within 6 h. To achieve 99 % yield,
ethylethylene oxide took longer time than propylene
oxide, which could be attributed to the electron-
donating effect of the ethyl group and its steric
hindrance that obstructed the approach of
ethylethylene oxide towards the catalytic site. For
internal cyclohexene oxide, 92% yield was achieved
after a reaction time of 12 h (Table 2, entry 6). For 1,2-
dimethylethylene oxide, it also showed the presentable
catalytic performance (Table 2, entry 7).
Figure 2. B3LYP-D3 free energy profile for the cycloaddition
of CO2 with epichlorohydrin catalyst by Zn(NCP)Cl/TBAB. The
relative energies are given in kcal mol-1 and relative to the
R1. TBAB is simulated by including only the bromine anion.
To investigate the general applicability of Zn(NCP)Cl,
terminal epoxides (propylene oxide, epichlorohydrin,
ethylethylene oxide, isobutylene oxide, styrene oxide)
and internal epoxides (1,2-dimethylethylene oxide,
cyclohexene epoxide) were used as substrates at the
identical conditions (catalyst loading, 0.02 mol%; TBAB
loading, 0.08 mol%; CO2 pressure, 1.7 MPa; 120 °C) and
the results are summarized in Table 2. At a low catalyst
Conclusions
In summary, Zn(NCP)Cl/TBAB was proved to be an
excellent catalyst system for the coupling of CO2 with
epoxides to conversion cyclic carbonates selectively
under solvent-free conditions. The TOF value of
this
Figure 3. Optimized structures for the reactant, intermediates, transition states and product. Interatomic distances are in Å.
Grey=carbon, white=hydrogen, blue=nitrogen, red=oxygen, yellow=zinc, green=chloride, brown=bromine.
Table 2. Cycloaddition of CO2 with Various Epoxides
loading (0.02 mol %), these epoxides could be
converted into the corresponding cyclic carbonates
with high selectivities (>99%) and excellent yields,
indicating the high versatility of this catalyst system.
Entry
Epoxide Product
t(h)
Yield (%)
O
O
O
1
3
99
O
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distilled, and deaerated prior to use. VieNw CArPticle Ownlainse
O
DOI: 10.1039/C9CY00739C
O
Cl
synthesized by following the literature procedure.68
O
2
3
3
99
99
O
Cl
NMR spectra were recorded with a Bruker Avance III
O
1
HD 400 MHz spectrometer. H NMR chemical shifts are
O
6
reported relative to TMS (δ=0.00 ppm) and 13C NMR
chemical shifts are reported relative to CDCl3 (δ=77.16
ppm). High-resolution mass spectra, reported as m/z,
were obtained with a Bruker Autoflex MALDI-TOF mass
spectrometer. FT-IR spectra were recorded with a
Bruker Vertex 70 FT-IR spectrometer.
O
O
O
O
4
5
3
6
99
O
O
O
99
O
O
Synthesis of Zn(NCP)Cl
O
O
A mixture of NCP (315 mg, 0.5 mmol) and ZnCl2 (680
mg, 5 mmol) were refluxed in CH3CN (50 mL) for 12 h.
After removing the solvent, the residue was purified by
column chromatography on silica gel using
CHCl3/MeOH (v/v, 50:1) as the eluent. The yield was
180 mg (49 %). MALDI-TOF HRMS: calcd. for [M-Cl]+
691.1834, found 691.1808. 1H NMR (400 MHz, CDCl3): δ
= – 0.59 (s, 1H), 3.23 (s, 3H), 6.24 (s, 1H), 7.59 (s, 6H), 7.
68–7.85 (m, 14H), 8.11–8.14 (m, 4H), 8.27-8.28 (d, J = 4
Hz, 2H), 8.33-8.34 (d, J = 4 Hz, 2H). 13C NMR (400 MHz,
O
6
7
12
12
92
68
O
O
O
Reaction conditions: Epoxide (40.0 mmol), catalyst (0.02
mol %, 5.83 mg, 0.008 mmol), TBAB (0.08 mol %, 10.32 mg,
0.032 mmol), CO2 (1.7 MPa), 120 oC. The yield was
determined by 1H NMR using mesitylene as an internal
standard. The selectivity for the cyclic carbonate
product >99%.
catalyst reached 266667 h-1 for the conversion of CO2 CDCl3): δ = 163.46, 162.91, 154.55, 153.69, 143.53,
o
with epichlorohydrin into cyclic carbonate at 120 C 143.09, 141.72, 141.30, 140.72, 136.29, 134.99, 134.85,
and an initial CO2 pressure of 1.7 MPa within 3 h. We 134.70, 133.58, 133.45, 131.70, 130.88, 130.48, 129.30,
demonstrated that almost quantitative cyclic carbonate 129.06, 128.33, 127.90, 127.76, 127.20, 126.71, 124.05,
product was achieved under atmospheric CO2 within 24 115.81, 115.27, 106.21, 38.83. FT-IR (KBr, cm-1): 2922,
h. Furthermore, this catalyst also displays a wide 2852, 1596, 1546, 1502, 1259, 1070, 997, 796, 709.
substrate scope. X-ray structural analysis of Zn(NCP)Cl General procedure for the synthesis of cyclic
reveals that the Zn2+ ion is four-coordinate with three carbonates
nitrogen atoms and one chlorine atom. Due to the The respective epoxide (40.0 mmol), Zn(NCP)Cl and
strong electron-withdrawing ability of chloride, zinc TBAB were charged into a 100 mL stainless steel
shows strong acidity, thereby enhance its ability to autoclave equipped with a magnetic stir bar. The
activate epoxide. A possible mechanism was proposed autoclave was subjected to three cycles of
and supported by the results of DFT calculations. DFT pressurization and depressurization with carbon
calculations reveal that the ring-opening of epoxide by dioxide, and then pressurized to the required carbon
zinc is the rate-determine step of the catalytic cycle.
Experimental
General
dioxide pressure. The reaction mixture was heated with
stirring to the required temperature. At the end of the
reaction, the reactor was cooled down to room
All epoxide substrates and reagents were purchased temperature with an ice bath before the excess CO2
from Energy Chemical (China) and used as received was released. The yield was determined by means of 1H
unless stated otherwise. Carbon dioxide (99.999%) was NMR using mesitylene as an internal standard. The
purchased from Wuhan Iron and Steel Group Gas products were purified using column chromatography
Company and used without further purification. with ethyl acetate/n-hexane (v/v, 1:4) as the eluent (for
Solvents were dried according to standard procedures, typical procedure, see the Supporting Information).
6 | J. Name., 2019, 00, 1-3
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Single crystals of Zn(NCP)Cl suitable for X-ray diffraction
study were grown by slow diffusion of hexanes into a
CH2Cl2 solution of Zn(NCP)Cl at room temperature. The
XRD crystal X-ray data were collected at 273 K using a
Bruker SMART APEX diffractometer with MoKα
2
3
4
radiation (λ= 0.71073 Å) and
a
graphite
monochromator operating in multi-scan mode. Using
Olex2,69 the structure was solved with the SIR200470
structure solution program using Direct Methods and
refined with the ShelXL71 refinement package using
Least Squares minimization. All non-hydrogen atoms
were refined with anisotropic displacement
parameters. Hydrogen atoms were placed in their
idealized positions and allowed to ride on the
respective carbon atoms. The single-crystal data are
listed in Table S1.
5
6
7
8
9
CCDC-1902277
contains
the
supplementary
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crystallographic data for compound Zn(NCP)Cl. These
data can be obtained free of charge from The
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www.ccdc.cam.ac.uk/data_request/cif.
Computational methods
All the DFT calculations were carried out with the
Gaussian 09 quantum chemistry package in the
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D3/6-31G(d) method can be found elsewhere.74
Frequency calculations at the same level of theory
were also performed to identify all stationary points as
minima (zero imaginary frequencies) or transition
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Acknowledgements
This work was supported financially by the National
Science Foundation of China (Grant no. 21777149).
Computer time was provided by National
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