Dinitrosyl Iron Complex [K-18-crown-6-ether][(NO)2Fe(MePyrCO2)]: Intermediate for Capture and Reduction of Carbon Dioxide

Article abstract of DOI:10.1002/anie.202002977

Continued efforts are made for the utilization of CO₂ as a C₁ feedstock for regeneration of valuable chemicals and fuels. Mechanistic study of molecular (electro-/photo-)catalysts disclosed that initial step for CO₂ activation involves either nucleophilic insertion or direct reduction of CO₂. In this study, nucleophilic activation of CO₂ by complex [(NO)₂Fe(μ-^MePyr)₂Fe(NO)₂]^2? (2, ^MePyr=3-methylpyrazolate) results in the formation of CO₂-captured complex [(NO)₂Fe(^MePyrCO₂)]^? (2-CO₂, ^MePyrCO₂=3-methyl-pyrazole-1-carboxylate). Single-crystal structure, spectroscopic, reactivity, and computational study unravels 2-CO₂ as a unique intermediate for reductive transformation of CO₂ promoted by Ca²⁺. Moreover, sequential reaction of 2 with CO₂, Ca(OTf)₂, and KC₈ established a synthetic cycle, 2 → 2-CO₂ → [(NO)₂Fe(μ-^MePyr)₂Fe(NO)₂] (1) → 2, for selective conversion of CO₂ into oxalate. Presumably, characterization of the unprecedented intermediate 2-CO₂ may open an avenue for systematic evaluation of the effects of alternative Lewis acids on reduction of CO₂.

Full text of DOI:10.1002/anie.202002977

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Accepted Article
Title: Dinitrosyl Iron Complex [K-18-crown-6-ether]
[(NO)2Fe(MePyrCO2)]: Intermediate for Capture and Reduction
of Carbon Dioxide
Authors: Tsai-Te Lu, Yu-Ting Tseng, Wei-Min Ching, and Wen-Feng
Liaw
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Me
Dinitrosyl Iron Complex [K-18-crown-6-ether][(NO)
2
Fe( PyrCO )]:
2
Intermediate for Capture and Reduction of Carbon Dioxide
Yu-Ting Tseng,[a],[b] Wei-Min Ching, Wen-Feng Liaw,* and Tsai-Te Lu,*
[c]
[b]
[a],[d]
[
a]
Mr. Yu-Ting Tseng, Prof. Tsai-Te Lu
Department of Chemistry, Chung Yuan Christian University, Taoyuan 32023, Taiwan.
Mr. Yu-Ting Tseng, Prof. Wen-Feng Liaw
[
b]
Department of Chemistry, National Tsing Hua University, Hsinchu 30013, Taiwan.
E-mail: wfliaw@mx.nthu.edu.tw
[
[
c]
d]
Dr. Wei-Min Ching
Institute of Chemistry, Academia Sinica, Taipei 10529, Taiwan.
Prof. Tsai-Te Lu
Institute of Biomedical Engineering, National Tsing Hua University, Hsinchu 30013, Taiwan.
E-mail: ttlu@mx.nthu.edu.tw
Supporting information for this article is given via a link at the end of the document.
2 1
Abstract: Continued efforts are made on utilization of CO as a C
feedstock for regeneration of valuable chemicals and fuels.
Mechanistic study of molecular (electro-/photo-)catalysts disclosed
that initial step for CO
2
activation involves either nucleophilic
insertion or direct reduction of CO
2
. In this study, nucleophilic
Me
2–
Me
activation of CO
2
2
by complex [(NO) Fe(- Pyr)
2
Fe(NO)
2
]
(2, Pyr
=
3-methylpyrazolate) results in the formation of CO
2
-captured
Me
–
Me
complex [(NO)
2
Fe( PyrCO
2
)] (2-CO
2
,
PyrCO
2
= 3-methyl-
pyrazole-1-carboxylate). Single-crystal structure, spectroscopic,
reactivity, and computational study unravels 2-CO as a unique
intermediate for reductive transformation of CO promoted by Ca .
Moreover, sequential reaction of 2 with CO , Ca(OTf) , and KC
2-CO [(NO) Fe(-
] (1) → 2, for selective conversion of CO into oxalate.
2
2+
2
2
2
8
established
a
synthetic cycle,
2
→
2
→
2
Me
2
Pyr) Fe(NO)
2
2
Presumably, characterization of the unprecedented intermediate 2-
CO may open an avenue for systematic evaluation of the effects of
alternative Lewis acids on reduction of CO
2
2
.
Continued efforts are made on utilization of CO
feedstock for regeneration of valuable chemicals and fuels.[1] As
opposed to reduced C product, formation of C -product oxalate
2 1
as a C
1
2
requires the thermodynamically disfavored reduction of CO
2
to
CO ●
–
(Eo ~ -1.9 V vs. SHE) and a kinetic pathway for C-C
2
●
–
(Scheme 1a).[2] Metal-mediated
coupling between two CO
reduction of CO was reported to assemble structure-
2
2
IV
III
1
●–
characterized [U /Ni : O-CO
magnetic coupling between CO
bulky (AdArOH) ligand (Scheme 1b).[3] Moreover,
tacn/PS
reductive coupling of CO promoted by low-valence
2
]
adduct, which features
and U /Ni center within
●
–
IV
III
2
3
3
2
I
II
II
I
I
Mg/Sc /Sm /Fe/Ni complex led to generation of oxalate-bridged
dinuclear complexes (Scheme 1c-1).[4] In particular, formation of
an oxalate-containing dinickel complex, derived from
tBu II
2
2
deprotonation of complex [L Ni ( -HCO )], was proposed to
occur via C-C coupling between two [Ni-CO
2
●–] intermediates
(
Scheme 1c-2).[ In addition to radical coupling between two
5]
CO
CO
2
●–, nucleophilic insertion of [(TiX
provides another possible mechanism for assembly of
3
)
2
2 2
( -CO )] into exogenous
2
oxalate (Scheme 1c-3).[6] In all aspects of catalytic conversion of
CO
development of dicopper complex for electrocatalytic reduction
of CO into lithium oxalate at an applied potential of -0.03 V vs.
2
into oxalate (Scheme 1d), Bouwman group pioneered in the
Scheme 1. Electrochemical/metal-mediated process, synthetic cycle, and
(electro)catalysis for CO -to-oxalate conversion.
2
2
NHE.[ Maverick group reported the chemical reduction of
7]
1
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pre-organized dicopper(II) complex by ascorbate, whereas the
respectively, demonstrates the capture of CO
CO
2
during the 2-to-2-
conversion. In comparison with complex 2, down-field H
to afford CuII-
-promoted
1
generated dicopper(I) complex reacts with CO
bound bridging oxalate. The subsequent HCl/HNO
release of oxalic acid completes the three-step process for CO
to-oxalate conversion.[8] Recently, Murray group explored a
process for reduction of CO into released oxalate catalyzed by
complex [Cu ( -S)]/[Cu (
2
2
3
NMR signals at  = 8.06, 6.27, and 1.90 ppm featured by
complex 2-CO reveal the nucleophilic activation of CO by the
(Figures S5
- and
2
-
2
2
pyrazolate ligand in the diamagnetic complex 2-CO
2
and S11). On the other hand, 3C NMR spectra of 12CO
1
2
2
1
3
2
-labeled 2-CO
2
indicate the 13C NMR signal of captured
at  = 153.0 ppm (Figures 2C and S12-13).
3
6
3
3
3
-Se)], which displays a pseudo-first-
CO
CO
[9]
order kobs 10 -fold larger than above-mentioned Cu complexes.
In comparison with direct CO
above, nucleophilic activation of CO
of CO -captured adduct into oxalate is scarce.
In dinitrosyl iron complexes (DNICs), redox interconversion
between {Fe(NO)
}9 and {Fe(NO) }10 electronic states is tailored
by the non-innocent NO and supporting ligands. One-electron
redox capacity of [Fe(NO) ] unit entails the diverse reactivity
toward stabilization
radical/hydrosulfide/dithioformate,
2
2
-to-oxalate conversion described
followed by transformation
Single-crystal X-ray diffraction study of complex 2-CO
2
2
provides direct insight into the capture and activation of CO
shown in Figures 3 and S14, [Fe(NO) ]-bound pyrazolate ligand,
with a Fe–Nproximal bond distance of 2.051 Å, utilizes its distal N
2
. As
2
2
2
2
atom to achieve nucleophilic insertion into CO
2
for the buildup of
carbamate [MePyrCO
] . Chelation of this carbamate ligand, with
–
2
2
a longer Fe–O bond distance of 2.078 Å, completes the
coordination environment around the Fe center in a distorted
of
●NO/aminyl
of ●NO
2 2
} -{Fe(NO)
}10
1
0
activation
tetrahedral geometry. Similar to {Fe(NO)
complex 2, average Fe–NO and N–O bond distances of 1.634 Å
and 1.206 Å observed in complex 2-CO are comparable with
well-documented {Fe(NO)
}10 DNICs (Table S3).[10j] On the other
[
10]
/
nitrite/nitrate, and electrocatalysis for water splitting.
In
1
0
2
)]– and
particular, reaction of {Fe(NO)
2
}
DNIC [(NO)
2
Fe( -BH
4
2
CO
decomposition of {Fe(NO)
redox-active [Fe(NO) ] unit toward small-molecule activation,
herein, capture and reduction of CO
2
was reported to afford formate accompanied by the
2
}10 unit.[10j] Inspired by the reactivity of
hand, the C–Odistal/C–Oproximal/C–Npyr bond distance of
1.226/1.261/1.434 Å and O–C–O bond angle of 130.1 support
the nucleophilic/non-redox activation of CO in complex 2-CO .
2
2
2
o
2
1
0
10
2
by {Fe(NO)
Fe(-MePyr)
2
} -{Fe(NO)
2
}
complex [K-18-crown-6-ether]
Pyr = 3-methylpyrazolate) is investigated.
2
[(NO)
2
2
Fe(NO) ] (2,
2
Me
Regarding the two electrochemically reversible redox
+
couples at E1/2 = -0.87 and -1.18 V (vs. Fc/Fc ) displayed by
{
Fe(NO)
preparation of complex 2 was attempted through chemical
reduction of complex 1 by treatment of two equiv. of KC and 18-
crown-6-ether (or CoCp ) (Scheme 2a). Successful synthesis of
}9-{Fe(NO)
}9 DNIC [(NO)
Fe(-MePyr)
2 2
Fe(NO)
] (1),[11]
2
2
2
8
2
1
13
complex 2 was evidenced by solution/solid-state IR, H/ C NMR,
Fe K-edge XAS, single-crystal X-ray diffraction, and theoretical
calculation (Figures 1 and S1-S9). As shown in Figures 1 and
S3-S4, crystallographic study unravels the conformational
flexibility of [Fe(-MePyr)
Fe] core in complex 2 interconverting
2
between planar and butterfly geometry (see SI for detailed
discussion). In addition to the Fe1s→Fe3d pre-edge energy of
1
13
7
113.5 eV, sharp H/ C NMR signals and EPR silence exhibited
10
by complex
{
2
corroborate its diamagnetic {Fe(NO)
2
} -
[12]
Fe(NO)
2
}10 electronic configuration (Figures S5-S8).
Moreover, dominant contribution of Fe 3dz2 orbital to the LUMO
of complex 1 and HOMO of complex 2 demonstrates a metal-
based reduction process during the 1-to-2 conversion (Figure
S9).
2
Scheme 2. Synthetic cycle for CO -to-oxalate conversion promoted by DNIC.
When the THF solution of complex 2 is purged with CO2(g)
at
ether][(NO)
pyrazole-1-carboxylate) is identified by 13CO
35°C,
formation
of
complex
[K-18-crown-6-
3-methyl-
-/ NO-labeled IR,
H/ C NMR, Fe K-edge XAS, single-crystal X-ray diffraction,
and theoretical calculation (Scheme 2b, Figures 2-3, S8, and
S10-S14). Complex 2-CO displays the same Fe1s→Fe3d pre-
edge energy as complex 2 at 7113.5 eV, which characterizes its
Fe(NO)
}10 electronic structure (Figure S8).[12] As shown in
Fe(MePyrCO
)] (2-CO
,
MePyrCO
=
2
2
2
2
15
2
1
13
2
{
2
Figure 1. ORTEP drawing and labelling scheme of {Fe(NO)
complex [(NO)
geometry.
2
}10-{Fe(NO)
2-
2 2 2
Fe(- Pyr) Fe(NO) ] featuring a (A) planar and (B) butterfly
2
}10
Figures 2A-2B, IR CO2 and NO absorption peaks at 1723 and
Me
1686, 1636) cm- are exhibited by complex 2-CO
1
. When
(
1
2
3CO2(g) and 15NO-labeled complex 2 are used, shift of these IR
-1

CO2 and NO absorption peaks to 1699 and (1655, 1603) cm ,
2
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COMMUNICATION
Figure 2. IR spectra of (A) 12CO
-/13CO -labeled (blue/red) and (B) 14NO-/15NO-labeled (blue/pink) 2-CO in THF. (C) 13C NMR spectra of 12CO - and 13CO
-
2 2 2 2
2
8
labeled 2-CO
2
(blue/red) in d -THF.
promotes the dissociation of Fe–Npyr bond and the cleavage of
Fe(-MePyr)
Fe] core. Subsequent chelation of generated
carbamate ligand stabilizes the {Fe(NO)
}10 core through the
assembly of 2-CO . Regarding the one-electron reduction
power of {Fe(NO) and the reported inductive
}10 core in 2-CO
effect of redox-inactive Lewis acids, effects of cationic additives
[
2
2
2
2
2
and protic solvent on conversion of activated CO
further elucidated.[
2
in 2-CO
2
are
3, 14]
As shown in Scheme 2c and Figure S18, [FeCp
the 2-CO -to-1 conversion accompanied by the release of CO
Of interest, treatment of one (or half) equiv. of redox-inactive
Ca(OTf) to complex 2-CO leads to the similar formation of
2
]+ triggers
2
2
.
2
2
complex 1 (yield = 81%, Scheme 2d and Figure S19).
Accompanied generation of precipitated calcium oxalate was
characterized by the distinctive IR CO absorption peak at 1657
-1
-1
13
2
cm , which shifts to 1633 cm when 2- CO is used (Figure
S20).[9] After protonation of insoluble calcium oxalate, 13C NMR
and indole-based colorimetric assay identify and quantify the
formation of oxalic acid ( = 162.0 ppm, yield = 74.8±1.5%,
1
Figures S21-S22). According to the GC and H NMR analysis,
2
Figure 3. ORTEP drawing and labelling scheme of 2-CO .
formation of other gaseous/soluble CO
not detected (Figure S21B). Using the complex 1 recovered
from reaction of 2-CO and Ca(OTf) , three consecutive “1 → 2
2-CO → 1” synthetic cycles were further conducted to
2
-reduced product was
2 2
Inspired by CO -activation reactivity of 2, reactions of CO
with alternative DNICs were further investigated (Scheme S1).
2
2
→
2
1
0
}10
9
produce calcium oxalate with a yield of 72.3±5.0% (Figure S23).
Unlike {Fe(NO)
Fe(NO)
}9 complex
(NO) Fe(TMEDA)]/[(NO)
Figures S15-17). Recently, nucleophilic insertion of anionic
2
} -{Fe(NO)
2
complex 2, {Fe(NO)
}10 complex
] are all inert toward CO
2
} -
Based on the kinetic study in the presence of excess Ca(OTf)2,
{
[
(
{
2
1
and neutral {Fe(NO)
Fe(PPh
2
reaction between 2-CO
order condition relative to the concentration of 2-CO
S24-S26). In the reaction of pyrazolate, CO , and KC (or Na
2
and Ca(OTf)
2
follows a pseudo-first-
2
2
3
)
2
2
2
(Figures
2
)]– into CO
Fe(NO)
2
}10 complex [(NO)
2
Fe( -BH
4
2
yielding
2
8
2
and Ca(OTf) ) under a similar condition, absence of generated
released formate was reported to induce the degradation of
10
unit in Ca2+-
10j]
oxalate supports the critical role of {Fe(NO)2}
[
[
Fe(NO)
2
C
]
unit.[
Transformation
into [(Triphos )Fe (CO)
of
complex
II
C
0
assisted transformation of CO /carbamate into oxalate (Figures
(Triphos )Fe (H)(BH
4
)]
2
],
in
[13]
2
o
S27-S31). As opposed to the conversion of 2-CO
2
into 1 and
comparison, occurs under 7 bar CO2(g) atmosphere at 70 C.
Of interest, coordination of CH
calcium oxalate triggered by Ca2+ in THF, spontaneous
II
3
CN solvent to the Fe center in
transformation of 2-CO
to afford [HCO2] and [CH OCO ] without formation of other
gaseous products (Figure S32).
DFT calculation was further employed to probe different
effect of [K-18-crown-6-ether] /[K(THF) ] /[Ca(THF) ] (n = 3 or
2
into 1 in THF/CH
3
OH (v/v = 5:1) occurs
this neutral complex is proposed to enhance the hydricity and
promote the CO -to-formate conversion in CH
CN.[13]
Accordingly, mechanism for capture and activation of CO by
complex 2 is rationalized and proposed below. Reduction of 1
into 2 enriches the electron density around the [Fe(-MePyr)
Fe]
–
–
3
2
2
3
2
+
+
2+
n
n
2
Me
–
2
) on complex [(NO)
compounds [MePyrCO
(NO)
Fe(MePyrCO
S8. As shown in Figures 4 and S34-S35, Fe 3dz2 and [MePyr-
CO ]  orbitals dominate the contribution to HOMO and LUMO,
2
Fe( PyrCO
2
)] . Bonding analyses on
core and the nucleophilic reactivity of pyrazolate ligands as
evidenced by increased Fe…Fe and Fe–NPyr bond distances
–
Fe(MePyrCO
–
2
] , [(NO)
2
2
)] , 2-CO
2
, and
+
[
2
2 3
)Ca(THF) ] are summarized in Tables S4-
(
[
Table
(NO) Fe(TMEDA)]/[(NO)
anionic pyrazolate ligands in complex 2 into exogenous CO
S1).
In
contrast
to
neutral
complex
2
2
Fe(PPh
3 2
) ], nucleophilic insertion of
2
2
3
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Angewandte Chemie International Edition
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COMMUNICATION
respectively. In addition, these DNICs feature covalent Fe-to-
NO -backbonding interactions. According to the Fe-carbamate
Based on the reactivity, kinetic, and computational study
described above, proposed mechanism for alternative

-bonding MOs, predominant Fe-Npyr bonding interaction
conversion of 2-CO
with [FeCp
]+, Fe-based oxidation of 2-CO
acidity of Fe center and triggers the heterolytic cleavage of N-C
2
is depicted in Scheme S2. In the reaction
imposes the docking of {Fe(NO)
carbamate ligand. Compared to complex [(NO)
with/without the binding of [K-18-crown-6-ether] , binding of
2
}10 unit at the chelating site of
2
2
enhances the Lewis
Fe(MePyrCO
+
)]–
2
2
2
bond within carbamate to afford released CO and 1. Upon
2
+
2+
Ca
(NO)
CO
at the carboxylate site of carbamate in complex
treatment of Ca to complex 2-CO
2
, rate-determining binding of
Fe(MePyrCO )]– in a 1:1
stoichiometry promotes the intramolecular electron transfer
Me
)]– induces the enhanced contribution of
Ca2+ toward anionic complex [(NO)
[
2
Fe( PyrCO
2
2
2
*in to the Fe-Npyr -bonding orbital and reduces the
2
HOMO-LUMO gap (Figures 4 and S34-S35). With the support
from Mülliken and NPA charge analysis (Tables S9-S12), this
from [(NO)
2
Fe(MePyr)] unit to [CO
this Ca -induced reduction of CO
2
:Ca] fragment. Presumably,
2
+
10
2
by {Fe(NO)
2
}
core, a one-
Fe(MePyrCO
implicates
)] , 2-CO
–
, and
electron reductant, triggers the heterolytic cleavage of N-C
comparison of complexes [(NO)
(NO) )Ca(THF)
Fe(MePyrCO ]+
2
2
2
[
2
2
3
the
potential
bond within [Fe(NO)
proposed intermediate [(NO)
2
]-bound carbamate and affords the
2
+
Fe(MePyr)(CO
●–
–
2+
mechanism for Ca -induced charge transfer within the pre-
organized complex [(NO)
2
2
)] :[Ca(THF)
2+
n
] .
Me
–
2
Fe( PyrCO
2
)] .
In addition to inductive effect, the dicationic Ca may further
bridge the bimolecular interaction between two anionic
[
(NO)
2
Fe(MePyrCO
2
)]– for C-C/radical coupling of activated
●
–
CO /[Fe(NO)
2
2
]-bound CO
2
yielding precipitated calcium
oxalate (Scheme S2B). In THF/CH
interaction between complex [(NO)
3
OH, hydrogen-bonding
Fe(MePyrCO
)] and CH
–
OH
2
2
3
may promote a similar formation of transient intermediate
●–
–
[
(NO)
atom abstraction of adjacent CH
yields [HCO
generated CH
leads to the formation of [CH
2
Fe(MePyr)(CO
2
)] :[(CH
3
OH)
n
]. In this intermediate, H-
●
–
3
2 2
OH by [Fe(NO) ]-bound CO
]– and 1, whereas subsequent reaction of
O with another complex [(NO)
OCO
]– and 1 (Scheme S2C).
2
Fe(MePyrCO )]–
3
2 2
3
2
Utilization of radical-trapping reagent DMPO as well as freeze-
quench-EPR experiments were attempted but failed to
●
–
characterize the formation of transient (Fe-bound) CO
species during the 2-CO
-to-1 conversion (Figure S36). [3-9]
In this study, we demonstrate a “2 → 2-CO → 1 → 2”
synthetic cycle for selective reduction of CO into oxalate. In
2
2
2
2
complex 2, nucleophilic pyrazolate ligand, neutral {Fe(NO)
unit, and [K-18-crown-6-ether] countercation work in concert to
2
}10
+
2
2
capture and activate CO via the assembly of 2-CO . Based on
the spectroscopic, crystallographic, and computational study, 2-
2
CO is best described as a diamagnetic {Fe (NO )
2
}10 DNIC,
II
–
whereas investigation on electronic structure of DNICs by
Mössbauer spectroscopy will be pursued in the near future.
Relying on one-electron reduction power of {Fe(NO)
complex 2-CO
, addition of dicationic Ca2+ further initiates the
C-C coupling between activated/reduced CO and yields
2
}10 core in
2
2
precipitated calcium oxalate. Bridging nature of pyrazolate
ligand, moreover, promotes the re-assembly of complex 1,
which holds the potential to recover complex 2 for continued
capture and activation of CO
2
at a low reduction potential of -
as a
+
1.18 V (vs. Fc/Fc ). Discovery of carbamate-bound 2-CO
2
critical intermediate may open an avenue for systematic
evaluation of the effect of redox-inactive/redox-active/boron-
based Lewis acid on the transformation of CO .
2
Acknowledgements
We gratefully acknowledge the financial support from the
Ministry of Science and Technology (Taiwan) (MOST 102-
2
113-M-033-009-MY2,
MOST 104-2113-M-033-005-MY2, MOST 106-2113-M-007-
28-MY2, MOST 108-2113-M-007-011). We thank Dr. Ting-
MOST
103-2632-M-033-001-MY3,
0
Figure 4. (A) Energy level diagram and contour plots of selected MOs for
Me
–
complex [(NO)
2
Fe( PyrCO
2
)] . Contour plots of Fe-Npyr -bonding orbitals for
Shen Kuo and Ms. Kai-Jieah Hsing (National Taiwan Normal
University) for the single-crystal X-ray structural determinations;
Me
+
complexes (B) 2-CO
2
, and (C) [(NO) Fe( PyrCO )Ca(THF) ] .
2 2 3
4
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[
[
12]
13]
S.-W. Yeh, C.-W. Lin, B.-H. Liu, C.-C. Tsou, M.-L. Tsai,
W.-F. Liaw, Chem. Eur. J. 2015, 21, 16035-16046.
L. Iffland, A. Khedkar, A. Petuker, M. Lieb, F. Wittkamp,
M. van Gastel, M. Roemelt, U.-P. Apfel, Organometallics
2019, 38, 289-299.
Prof. I-Jui Hsu (National Taipei University of Technology) and
National Synchrotron Radiation Research Center (Taiwan) for
the support on XAS measurements; Mr. Sheng Chuang
(
National Chiao Tung University) and Ms. Hui-Chi Tan (National
[
14]
a) W. Nam, Acc. Chem. Res. 2015, 48, 2415-2423; b) W.
H. Bernskoetter, N. Hazari, Acc. Chem. Res. 2017, 50,
Tsing Hua University) for their help on NMR measurements,
and National Center for High-Performance Computing for their
support on the software applied in this work.
1049-1058; c) J. B. Geri, J. P. Shanahan, N. K.
Szymczak, J. Am. Chem. Soc. 2017, 139, 5952-5956; d)
E. G. Abucayon, R. L. Khade, D. R. Powell, Y. Zhang, G.
B. Richter-Addo, J. Am. Chem. Soc. 2018, 140, 4204-
4207; e) M. M. Deegan, J. C. Peters, J. Am. Chem. Soc.
Keywords: Carbon dioxide fixation • Reduction • Iron •Lewis
2
017, 139, 2561-2564; f) J. A. Buss, D. G. VanderVelde,
acids
T. Agapie, J. Am. Chem. Soc. 2018, 140, 10121-10125;
g) L. T. Elrod, E. Kim, Inorg. Chem. 2018, 57, 2594-2602.
[
[
1]
2]
B. Mondal, J. Song, F. Neese, S. Ye, Curr. Opin. Chem.
Biol. 2015, 25, 103-109.
a) A. Gennaro, A. A. Isse, M.-G. Severin, E. Vianello, I.
Bhugunb, J.-M. Savéant, J. Chem. Soc., Faraday Trans.
1996, 92, 3963-3968; b) C. Costentin, M. Robert, J. M.
Saveant, Chem. Soc. Rev. 2013, 42, 2423-2436.
a) I. Castro-Rodriguez, H. Nakai, L. N. Zakharov, A. L.
Rheingold, K. Meyer, Science 2004, 305, 1757-1759; b)
T.-W. Chiou, Y.-M. Tseng, T.-T. Lu, T.-C. Weng, D.
Sokaras, W.-C. Ho, T.-S. Kuo, L.-Y. Jang, J.-F. Lee, W.-F.
Liaw, Chem . Sci. 2016, 7, 3640-3644.
[
[
3]
4]
a) D. H. Woen, G. P. Chen, J. W. Ziller, T. J. Boyle, F.
Furche, W. J. Evans, Angew. Chem. Int. Ed. 2017, 56,
2050-2053; b) C. C. Lu, C. T. Saouma, M. W. Day, J. C.
Peters, J. Am. Chem. Soc. 2007, 129, 4-5; c) C. T.
Saouma, C. C. Lu, M. W. Day, J. C. Peters, Chem . Sci.
2013, 4, 4042-4051; d) B. Horn, C. Limberg, C. Herwig, B.
Braun, Chem. Comm. 2013, 49, 10923-10925; e) William
J. Evans, Christopher A. Seibel, J. W. Ziller, Inorg. Chem.
1998, 37, 770-776; f) A. J. Boutland, I. Pernik, A. Stasch,
C. Jones, Chem. Eur. J. 2015, 21, 15749-15758.
[
[
5]
6]
P. Zimmermann, S. Hoof, B. Braun-Cula, C. Herwig, C.
Limberg, Angew. Chem. Int. Ed. 2018, 57, 7230-7233.
A. Paparo, J. S. Silvia, C. E. Kefalidis, T. P. Spaniol, L.
Maron, J. Okuda, C. C. Cummins, Angew. Chem. Int. Ed.
2015, 54, 9115-9119.
[
[
[
[
7]
R. Angamuthu, P. Byers, M. Lutz, A. L. Spek, E.
Bouwman, Science 2010, 327, 313-315.
8]
U. R. Pokharel, F. R. Fronczek, A. W. Maverick, Nat.
Comm. 2014, 5, 5883 doi: 5810.1038/ncomms6883
B. J. Cook, G. N. Di Francesco, K. A. Abboud, L. J.
Murray, J. Am. Chem. Soc. 2018, 140, 5696-5700.
a) C.-H. Ke, C.-H. Chen, M.-L. Tsai, H.-C. Wang, F.-T.
Tsai, Y.-W. Chiang, W.-C. Shih, D. S. Bohle, W.-F. Liaw,
J. Am. Chem. Soc. 2017, 139, 67-70; b) C.-C. Tsou, F.-T.
Tsai, H.-Y. Chen, I.-J. Hsu, W.-F. Liaw, Inorg. Chem.
9]
10]
2013, 52, 1631-1639; c) C.-C. Tsou, W.-C. Chiu, C.-H.
Ke, J.-C. Tsai, Y.-M. Wang, M.-H. Chiang, W.-F. Liaw, J.
Am. Chem. Soc. 2014, 136, 9424-9433; d) F.-T. Tsai, T.-
S. Kuo, W.-F. Liaw, J. Am. Chem. Soc. 2009, 131, 3426-
3427; e) F.-T. Tsai, P.-L. Chen, W.-F. Liaw, J. Am. Chem.
Soc. 2010, 132, 5290-5299; f) F.-T. Tsai, Y.-C. Lee, M.-H.
Chiang, W.-F. Liaw, Inorg. Chem. 2013, 52, 464-473; g)
C.-H. Hsieh, S. Ding, Ö . F. Erdem, D. J. Crouthers, T. Liu,
C. C. McCrory, W. Lubitz, C. V. Popescu, J. H.
Reibenspies, M. B. Hall, M. Y. Darensbourg, Nat. Comm.
2014, 5, 3684 doi: 3610.1038/ncomms4684; h) P. Ghosh,
S. Ding, R. B. Chupik, M. Quiroz, C.-H. Hsieh, N.
Bhuvanesh, M. B. Hall, M. Y. Darensbourg, Chem . Sci.
2
017, 8, 8291-8300; i) T.-W. Chiou, T.-T. Lu, Y.-H. Wu,
Y.-J. Yu, L.-K. Chu, W.-F. Liaw, Angew. Chem. Int. Ed.
015, 54, 14824 –14829; j) H.-C. Huang, W.-M. Ching,
Y.-T. Tseng, C.-H. Chen, T.-T. Lu, Dalton Trans. 2019,
8, 5897-5902; k) W. Y. Wu, C. N. Hsu, C. H. Hsieh, T.
2
4
W. Chiou, M. L. Tsai, M. H. Chiang, W. F. Liaw, Inorg
Chem 2019, 58, 9586-9591.
[
11]
Y.-T. Tseng, C.-H. Chen, J.-Y. Lin, B.-H. Li, Y.-H. Lu, C.-
H. Lin, H.-T. Chen, T.-C. Weng, D. Sokaras, H.-Y. Chen,
Y.-L. Soo, T.-T. Lu, Chem. Eur. J. 2015, 21, 17570-17573.
5
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Angewandte Chemie International Edition
10.1002/anie.202002977
COMMUNICATION
Entry for the Table of Contents
In anionic 2, nucleophilic pyrazolate ligand, neutral {Fe(NO)
unit, and [K-18-crown-6-ether] countercation work in concert to
2
}10
+
promote the capture and nucleophilic activation of CO
2
via the
assembly of stable 2-CO . Relying on one-electron reduction
2
power
(NO)
of
{Fe(NO)
2
}10
core
in
anionic
complex
Me
–
2+
[
2
Fe( PyrCO
2
)] , addition of dicationic Ca further initiates
the C-C coupling of activated/reduced CO
precipitated calcium oxalate.
2
and yields
6
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