Catalytic disproportionation of hydrazine by thiolate-bridged diiron complexes

Article abstract of DOI:10.1016/j.inoche.2019.107735

Treatment of a thiolate-bridged diiron complex [N₂S₂FeClFe(MeCN)Cp*][PF₆] (1, Cp* = η⁵-C₅Me₅, N₂S₂ = N,N'-dimethyl-3,6-diazanonane-1,8-dithiolate) with CO or ^tBuNC resulted in ligand exchange to facilely generate [N₂S₂FeClFeLCp*][PF₆] (2, L = CO; 3, L = ^tBuNC). Further electrochemical studies indicate the co-ligand has an obvious influence on the redox properties of these complexes. Importantly, these complexes with different redox behaviors show distinct catalytic reactivity toward the disproportionation of hydrazine into ammonia.

Full text of DOI:10.1016/j.inoche.2019.107735

InorganicChemistryCommunications112(2020)107735
Contents lists available at ScienceDirect
Inorganic Chemistry Communications
journal homepage: www.elsevier.com/locate/inoche
Catalytic disproportionation of hydrazine by thiolate-bridged diiron
complexes
Linan Su, Dawei Yang⁎, Baomin Wang, Jingping Qu
State Key Laboratory of Fine Chemicals, Dalian University of Technology, Dalian 116024, PR China
G R A P H I C A L A B S T R A C T
A R T I C L E I N F O
A B S T R A C T
Keywords:
Treatment of
a
thiolate-bridged diiron complex [N2S2FeClFe(MeCN)Cp*][PF6] (1, Cp*
=
η5-C5Me5,
N2S2 = N,N'-dimethyl-3,6-diazanonane-1,8-dithiolate) with CO or tBuNC resulted in ligand exchange to facilely
Thiolate-bridged
Disproportionation of hydrazine
Redox properties
Diiron
t
generate [N2S2FeClFeLCp*][PF6] (2, L = CO; 3, L = BuNC). Further electrochemical studies indicate the co-
ligand has an obvious influence on the redox properties of these complexes. Importantly, these complexes with
different redox behaviors show distinct catalytic reactivity toward the disproportionation of hydrazine into
ammonia.
1. Introduction
Recently, crystallographic analysis clearly uncovered the structure of
the FeMo-cofactor in CO-inhibited state, in which CO is bridged be-
Nitrogenase assumes great importance in nature for catalyzing the
reduction of dinitrogen (N2) to ammonia (NH3) under ambient condi-
tions [1]. Although the active center has been unveiled as a complicated
[MoFe7S9C] cluster named FeMo-cofactor [2,3], the detailed me-
chanism of nitrogen fixation was still unclear. During the past two
decades, results of computational and experimental chemistry suggest
the diiron center in the “belt” region of the FeMo-cofactor is very likely
to be the binding and activation site of N2 and other substrates [4–8].
tween the two iron centers in the waist region of the FeMo-cofactor [9].
The coordination of a bridging CO leads the FeMo-cofactor to lose its
intrinsic three-fold symmetry and obtain a more asymmetrical struc-
ture, which is likely responsible for the change of catalytic properties of
nitrogenase [10]. As expected, further results of activity examination
reveals that CO-inhibited nitrogenase cannot reduce acetylene to
ethylene [9].
Because CO is an isoelectronic species of N2 and noncompetitive
⁎ Corresponding author.
E-mail address: yangdw@dlut.edu.cn (D. Yang).
https://doi.org/10.1016/j.inoche.2019.107735
Received 28 October 2019; Received in revised form 16 December 2019; Accepted 17 December 2019
Availableonline23December2019
1387-7003/©2019ElsevierB.V.Allrightsreserved.

L. Su, et al.
InorganicChemistryCommunications112(2020)107735
inhibitor, studies on interaction of diiron nitrogenase mimics with CO
are of significance to reveal potential nitrogen fixation mechanism. To
date, plenty of nitrogenase mimics were reported to be good promoters
for nitrogen fixation and functionalization [11–15], NeN bond clea-
vage of hydrazine [16–20], CO reduction [21–22] and so on. However,
there is no reaction system known to focus on how CO as inhibitor
affects the catalytic activity related to nitrogenase, especially with re-
spect to the transformation of hydrazine into NH3.
Herein, we report the synthesis and characterization of two thiolate-
bridged diiron complexes with the coordination of CO or tBuNC.
t
Electrochemical measurements indicated CO and BuNC as strong do-
nors have a remarkable influence on the redox properties of diiron
complexes. Furthermore, these differences in electrochemical behaviors
determine their catalytic ability of the disproportionation of hydrazine
to release NH3.
Fig. 1. ORTEP (ellipsoids at 50% probability) diagram of complex 2. All hy-
2. Results and discussion
−
drogen atoms and the PF6 anion are omitted for clarity. Selected bond dis-
tances (Å) and bond angles (deg): Fe1eFe2 3.0676(5), Fe1eS1 2.3997(8),
Fe1eS2 2.3727(8), Fe2eS1 2.2526(7), Fe2eS2 2.2477(7), Fe1eCl1 2.2118(8),
Fe2eC1 1.766(3), C1eO1 1.137(3), Fe2eCp* 1.7608(3), Fe1eS1eFe2
82.44(2), Fe1eS2eFe2 83.15(2), S1eFe1eS2 93.35(3), S1eFe2eS2 100.97(3),
Fe2eC1eO1 176.6(3), S1eFe1eCl1 106.35(3), S2eFe1eCl1 111.19(3).
Given the lability of CH3CN as a ligand, we chose a reported com-
plex [N2S2FeClFe(MeCN)Cp*][PF6] (1, Cp* = η5-C5Me5, N2S2 = N,N'-
dimethyl-3,6-diazanonane-1,8-dithiolate) as reaction precursor [23]. As
shown in Scheme 1, treatment of 1 with 1 atmosphere of CO in CH2Cl2
from −78 °C to room temperature generated a thiolate-bridged diiron
complex [N2S2FeClFe(CO)Cp*][PF6] (2) as a green powder in 84%
yield. Complex 2 exhibits excellent solubility in CH2Cl2 and CH3CN, but
cannot dissolve in THF. This product was fully characterized by spec-
troscopy and X-ray crystallography. The electrospray ionization high-
resolution mass spectrum (ESI-HRMS) of complex 2 shows an expected
molecular peak of 516.0431 (calcd 516.0423) for [2–PF6]+, which
confirms the substitution of MeCN by CO. In the infrared (IR) spectrum
of 2, a diagnostic strong absorption band at 1975 cm−1 is observed,
which further confirms the existence of CO. In addition, this value in-
dicates the CO group is coordinated to the iron center in a terminal end-
on coordination mode, which is very close to that of nitrogenase in high
CO concentration (1973 cm−1) [24] and markedly higher than that of
nitrogenase in low CO concentration (1904 cm−1) [25]. Compared with
reported thiolate-bridged diiron [26,27] or iron-nickel [28–30] CO
complexes with similar coordination sphere, the CO vibration fre-
quency of 2 is significantly higher, which indicates the CO ligand is less
activated by the iron center. The formal oxidation states of the two iron
centers in 2 are +2 and +3, respectively, which indicates there is at
least one unpaired electron. Based on this understanding, we speculated
complex 2 should be a paramagnetic species. As we expected, the 1H
NMR spectrum of 2 shows a characteristic broad peak at −32.11 ppm
in the high field, which exhibits obvious paramagnetic shift. This re-
sonance may be assigned to the proton signals of the five methyl groups
in the Cp* ligand, however, further accurate assignments for other
signals are difficult. Furthermore, the magnetic susceptibility mea-
surement of complex 2 in CH2Cl2 solution was conducted at room
temperature by the Evans method. The value of effective magnetic
moment of complex 2 is 5.84 μB, which indicates complex 2 is in an
S = 5/2 ground state at room temperature.
{LFeCl} moiety resides above the N2S2 plane and capped with a
chloride group at apical position. The iron of the {Cp*Fe} moiety is
linked to the {LFeCl} moiety through two bridging thiolates of the N2S2
ligand. The {Cp*Fe} moiety of 2 possesses a terminal CO ligand with
the CeO distance of 1.137(3) Å, which is slightly shorter than those of
reported thiolate-bridged diiron [27,31] or iron-nickel [28] complexes.
The Fe1eFe2 distance decreases from 3.1152(8) Å in 1 to 3.0676(5) Å
in 2, which indicates that the two iron centers are more electron-defi-
cient upon the coordination of a better π-acceptor ligand (CO).
Furthermore, we also examined the reactivity of complex 1 with
tBuNC under similar conditions. After addition of 1 equiv. of tBuNC into
a CH2Cl2 solution of 1 at room temperature, the solution color changed
from dark green to brownish yellow. As shown in Scheme 2, the labile
t
MeCN was smoothly replaced by one BuNC group to afford a thiolate-
bridged diiron complex [N2S2FeClFe(tBuNC)Cp*][PF6] (3) in 73% yield
as a yellow powder. The product was also characterized by spectro-
scopy and X-ray crystallography.
The ESI-HRMS of complex 3 shows an anticipated molecular peak of
571.1213 (calcd. 571.1208) for [3–PF6]+, which confirms the cationic
composition of complex 3. In the IR spectrum of 3, a diagnostic strong
absorption band at 2137 cm−1 attributed to the N^C bond stretching
t
vibration was observed, which confirms the existence of BuNC in a
terminal end-on coordination fashion. This value is located at the
common range of the N^C bond stretching vibration frequency in
known thiolate-bridged diiron and diruthenium complexes [32–35].
The 1H NMR spectrum of 3 also shows a broad peak at −41.32 ppm.
The magnetic susceptibility measurement of complex 3 in CH2Cl2 so-
lution was conducted at room temperature by the Evans method. The
value of effective magnetic moment of complex 3 is 5.98 μB, which
suggests complex 3 is also in an S = 5/2 spin state.
Crystals suitable for X-ray diffraction of 2 were obtained by slow
diffusion of n-hexane into a dichloromethane solution of 2. As shown in
Fig. 1, crystallographic analysis of 2 reveals that the two iron centres
have completely different coordination geometry. The iron of the
Using the same method, crystals suitable for X-ray diffraction of 3
were also obtained. Crystallographic analysis of 3 (Fig. 2) reveals that
Scheme 1. Synthesis of complex 2.
2

L. Su, et al.
InorganicChemistryCommunications112(2020)107735
Scheme 2. Synthesis of complex 3.
Fig. 3. Cyclic voltammograms of complexes 1, 2 and 3, measured in 0.1 M
nBu4NPF6 in CH2Cl2 at 100 mV/s and internally referenced to Fc/Fc+
.
catalyzing redox reactions. Choosing the disproportionation of hy-
drazine as a model reaction, we examined the catalytic activity of these
complexes possessing different redox properties. Stirring the CH3CN
solution of complex 1 with 20 equiv. of hydrazine at room temperature
afforded ammonia in 56% yield (Eq. (1); Table 1, entry 1). When
changing the catalyst loading from 5 mol% to 2 mol% or 1 mol%, the
yield of ammonia remarkably reduced. However, there is no obvious
change in the turnover number (see Table S4). Reactions of complexes 2
and 3 with hydrazine were also performed under the same conditions,
and the yields of ammonia were 11% and 32%, respectively (Eq. (1);
Table 1, entries 2 and 3). The results show that complex 1 exhibits the
best reactivity toward disproportionation of hydrazine to generate
ammonia. In sharp contrast, complexes 2 and 3 have poor catalytic
activity. In previous studies [36], the highly oxidized Fe species was
proposed to be an important intermediate during the cleavage of the
NeN bond in hydrazine. Hence, since complex 1 has the lowest oxi-
dation potential among them, it is the most oxidizable to reach a high
oxidation state, which may be the rate-limiting step during the cata-
Fig. 2. ORTEP (ellipsoids at 50% probability) diagram of complex 3. All hy-
−
drogen atoms and the PF6 anion are omitted for clarity. Selected bond dis-
tances (Å) and bond angles (deg): Fe1eFe2 3.0830(14), Fe1eS1 2.3940(19),
Fe1eS2 2.4313(19), Fe2eS1 2.2426(19), Fe2eS2 2.2509(19), Fe1eCl1
2.236(2), Fe2eC1 1.848(7), C1eN1 1.145(8), N1eC2 1.467(9), Fe2eCp*
1.7587(10), Fe1eS1eFe2 83.28(6), Fe1eS2eFe2 82.27(6), S1eFe1eS2
92.56(6), S1eFe2eS2 101.80(7), Fe2eC1eN1 177.0(6), S1eFe1eCl1
114.58(9), S2eFe1eCl1 107.11(8).
the iron of the {Cp*Fe} moiety features a tBuNC ligand with the C1–N1
distance of 1.145(8) Å, which is close to those of thiolate-bridged diiron
tBuNC complexes [27,31,34] and some heteronuclear complexes with
{Cp*Fe(tBuNC)} fragment [32]. The Fe1eFe2 distance in
3 is
3.0830(14) Å, which suggests that tBuNC is a medium π-acceptor ligand
to this {Fe2S2} system compared with MeCN and CO.
One step further, the redox behaviors of these two complexes were
investigated by the cyclic voltammetry for evaluating the effect of the
t
change of co-ligands (CO for 2 and BuNC for 3). The cyclic voltam-
t
lysis. For 2 and 3, affected by the co-ligands (CO and BuNC), their
mogram of complex 2 in CH2Cl2 solution (Fig. 3 red spectrum) shows
ox
oxidation potentials become more positive, resulting in the relatively
weak catalytic ability. Detailed mechanism of the catalyzed reactions
two reversible redox waves. The first redox event at E1/2 = 0.52 V
corresponds to an FeII/III (coordinated with Cp*) couple, which is sig-
ox
nificantly more positive than that of 1 (E1/2 = 0.13 V) [23]. We
speculated the potential shift of the redox wave is mainly caused by the
stronger π back-bonding interaction between the iron center and CO
donor. It helps to stabilize the electrons of the Fe center and thus in-
Table 1
Catalytic
disproportionation
of
hydrazine
(eq 1)
by
[FeFe]
complex-
TON
Cat: [FeFe]
es.a
3 N2H4
4 NH3 + N2
crease the redox potential. The second redox wave at E1/
CH3CN, rt, 12 h
red
= −0.49 V corresponds to an {LFeCl}III/II redox couple, which is
2
Entry [FeFe] complex
NH3/yield
N2/yield
(%)c
ca. 0.57 V less negative than that of 1 indicates that complex 2
(FeIIIFeII) is much easier to be reduced than 1 to generate “FeIIFeII”
speices. The cyclic voltammogram of complex 3 in CH2Cl2 solution
(Fig. 3 blue spectrum) also shows two reversible redox waves (E1/
(%)b
1
2
3
[N2S2FeClFe(MeCN)Cp*][PF6] (1) 56
61
24
40
11.2
2.2
[N2S2FeClFe(CO)Cp*][PF6] (2)
11
ox = 0.29 V, E1/2red = −0.95 V), which are closer to those of complex
[N2S2FeClFe(tBuNC)Cp*][PF6] (3) 32
6.4
2
1 and still much less positive than those of complex 2.
a
b
c
N2H4 (0.5 mmol), [FeFe] (25 μmol, 5 mol%), CH3CN (5 mL), rt, 12 h.
The yields of NH3 were determined by 1H NMR analysis
The yields of N2 were determined by GC.
In view of the basic understanding of the effect in redox properties
of the co-ligands, we next explored the differences of these complexes in
3

L. Su, et al.
InorganicChemistryCommunications112(2020)107735
promoted by these three complexes is still under investigation.
C19H33ClF6Fe2N2OPS2: C, 34.49; H, 5.03; N, 4.23. Found: C, 34.72; H,
5.39; N, 3.79.
3. Conclusions
4.5. Synthesis of [N2S2FeClFe(tBuNC)Cp*][PF6] (3)
In conclusion, two thiolate-bridged diiron CO and tBuNC complexes
were synthesized and characterized by spectroscopy and crystal-
lography. Due to the interaction between the iron centers and inhibitors
At room temperature, 1 equiv. of tBuNC (16 μL, 0.15 mmol) was added
to a stirred solution of [LFeClFe(MeCN)Cp*][PF6] (100 mg, 0.15 mmol) in
5 mL CH3CN. The solution was vigorously stirred for 2 h, whose color
immediately changed from initial dark green to yellow. Solvent was re-
moved in vacuo, and the crude product was washed with Et2O (3 × 3 mL)
to give a brown powder 3 (78.5 mg, 0.11 mmol, 73%). Crystals suitable for
X-ray diffraction were obtained from a CH2Cl2 solution layered with n-
hexane. Proton resonances in the 1H NMR spectrum of 3 are difficult to be
accurately assigned due to its paramagnetism. μeff (CD2Cl2, Evans method,
25 °C) = 5.98 μB. IR (KBr, cm−1): 2916, 2869, 2137(νNC), 1465, 1376,
1190, 840, 557. ESI-HRMS: Calcd. for [3–PF6]+ 571.1208; Found
571.1213. Anal. Calcd for C23H42ClF6Fe2N3PS2: C, 38.54; H, 5.91; N, 5.86.
Found: C, 38.57; H, 6.11; N, 6.36.
t
(CO and BuNC), electrochemical properties of these complexes were
obviously affected, which is evidenced by cyclic voltammetry. Further
investigation on the catalytic activity demonstrates the thiolate-bridged
diiron complex possessing the higher oxidation potential can serve as a
relatively poor promoter for the disproportionation of hydrazine, which
t
is in good agreement with the inhabitation effect of CO or BuNC.
4. Experimental section
4.1. General procedures
All manipulations were routinely carried out under an argon at-
mosphere, using standard Schlenk-line techniques. All solvents were
dried and distilled over an appropriate drying agent under argon.
Complex [N2S2FeClFe(MeCN)Cp*][PF6] (1) was prepared according to
4.6. General procedure for catalytic reduction of hydrazine
A CH3CN (5 mL) solution of 1 (16.8 mg, 0.025 mmol) was placed to
a 25 mL Schlenk flask. Then N2H4 (16 μL, 0.50 mmol) was introduced
into the stirred solution. After being stirred for 12 h at room tem-
perature, the reaction volatiles were transferred under reduced pressure
into a frozen ethereal solution of HCl (4 M, 2 mL) in a 25 mL Schlenk
flask. After thawing, the solution was stirred at room temperature for
15 min. All solvents and excess HCl were removed in vacuo to yield
colorless solids. 1H NMR analysis (DMSO‑d6) of the resulting colorless
solids indicated the presence of NH4Cl. The NH4Cl was quantified by
integration of the NH4+ resonance with respect to an internal reference
of ferrocene. The yields of N2 were determined by GC.
t
the literature [23]. BuNC (Energy Chemical), CO (Junfeng Gas) and
hydrazine (Aldrich) were used without further purification.
4.2. Spectroscopic measurements
The 1H NMR spectra were recorded on a Bruker 400 Ultra Shield
spectrometer. Infrared spectra IR spectra were recorded with
a
NEXVSTM FTIR spectrometer. ESI-HRMS were recorded on an HPLC/Q-
Tof microspectrometer. Elemental analyses were performed on a Vario
EL analyzer. Solution phase magnetic measurements were performed by
the Evans method [37]. Cyclic voltammetry experiments were carried
out with a three-electrode cell under argon at room temperature. The
working electrode was a glassy carbon disk (diameter 3 mm), the re-
ference electrode was a nonaqueous Ag/Ag+ electrode, the auxiliary
electrode was a platinum wire, and the supporting electrolyte was
0.1 M nBu4NPF6 in CH2Cl2. All potentials reported herein are quoted
CRediT authorship contribution statement
Linan Su: Methodology, Validation, Formal analysis, Investigation,
Writing - original draft. Dawei Yang: Conceptualization, Formal ana-
lysis, Investigation, Writing - review & editing. Baomin Wang: Writing
- review & editing. Jingping Qu: Conceptualization, Formal analysis,
Supervision, Project administration.
+
relative to the FeCp2/FeCp2 couple. Gas chromatography was per-
formed with a Techcomp GC7900 gas chromatography instrument with
argon as the carrier gas and a thermal conductivity detector.
Declaration of Competing Interest
4.3. X-ray crystallography procedures
The authors declare that they have no known competing financial
interests or personal relationships that could have appeared to influ-
ence the work reported in this paper.
Single-crystal X-ray diffraction studies were carried out on a Bruker
SMART APEX CCD diffractometer with graphite-monochromated Mo
Kα radiation (λ = 0.71073 Å). Empirical absorption corrections were
performed using the SADABS program [38]. All of the structures were
solved by direct methods and refined by full-matrix least-squares based
on all data using F2 using SHELXTL 2014 [39,40]. All of the non-hy-
drogen atoms were refined anisotropically. All of the hydrogen atoms
were generated and refined in ideal positions.
Acknowledgements
This work was supported by the National Natural Science
Foundation of China (Nos. 21231003, 21571026, 21690064), the
Program for Changjiang Scholars and Innovative Research Team in
University (No. IRT13008) and the “111” project of the Ministry of
Education of China and the Fundamental Research Funds for the
Central Universities (DUT19RC(3)013).
4.4. Synthesis of [N2S2FeClFe(CO)Cp*][PF6] (2)
Under CO, a solution of [N2S2FeClFe(MeCN)Cp*][PF6] (1) (100 mg,
0.15 mmol) in 5 mL CH2Cl2 was stirred from −78 °C to room tem-
perature for 6 h, the solution color gradually changed from initial dark
green to light green. After removal of the solvent, the residue was
washed with Et2O (3 × 3 mL) to give a green powder 2 (82.4 mg,
0.12 mmol, 84%). Crystals suitable for X-ray diffraction were obtained
from a CH2Cl2 solution layered with n-hexane. Proton resonances in the
1H NMR spectrum of 2 are difficult to be accurately assigned due to the
paramagnetism. μeff (CD2Cl2, Evans method, 25 °C) = 5.84 μB. IR (KBr,
cm−1): 2918, 2873, 1975(νCO), 1466, 1431, 1381, 876, 841. ESI-HRMS:
Calcd. for [2–PF6]+ 516.0431; Found 516.0423. Anal. Calcd for
Appendix A. Supplementary material
CCDC 1449150, 1955005 contain the supplementary crystal-
lographic data in CIF format for the structure reported. This data can be
obtained free of charge via http://www.ccdc.cam.ac.uk/conts/
retrieving.html, or from the Cambridge Crystallographic Data Centre,
12 Union Road, Cambridge CB2 1E, UK; fax: (+44) 1223-336-033; or e-
mail: deposit@ccdc.cam.ac.uk.
Supplementary data to this article can be found online at https://
doi.org/10.1016/j.inoche.2019.107735.
4

L. Su, et al.
InorganicChemistryCommunications112(2020)107735
References
Chem. Commun. 83 (2017) 66–69.
[21] K. Tanifuji, N. Sickerman, C.C. Lee, T. Nagasawa, K. Miyazaki, Y. Ohki, K. Tatsumi,
Y. Hu, M.W. Ribbe, Structure and reactivity of an asymmetric synthetic mimic of
nitrogenase cofactor, Angew. Chem. Int. Ed. 55 (2016) 15633–15636.
[22] N.S. Sickerman, K. Tanifuji, C.C. Lee, Y. Ohki, K. Tatsumi, M.W. Ribbe, Y. Hu,
Reduction of C1 substrates to hydrocarbons by the homometallic precursor and
synthetic mimic of the nitrogenase cofactor, J. Am. Chem. Soc. 139 (2017)
603–606.
[1] B.K. Burgess, D.J. Lowe, Mechanism of molybdenum nitrogenase, Chem. Rev. 96
(1996) 2983–3012.
[2] K.M. Lancaster, M. Roemelt, P. Ettenhuber, Y. Hu, M.W. Ribbe, F. Neese,
U. Bergmann, S. DeBeer, X-ray emission spectroscopy evidences a central carbon in
the nitrogenase iron-molybdenum cofactor, Science 334 (2011) 974–977.
[3] T. Spatzal, M. Aksoyoglu, L.M. Zhang, S.L.A. Andrade, E. Schleicher, S. Weber,
D.C. Rees, O. Einsle, Evidence for interstitial carbon in nitrogenase FeMo cofactor,
Science 334 (2011) 940.
[23] L. Su, D. Yang, Y. Zhang, B. Wang, J. Qu, Methylene insertion into an Fe2S2 cluster:
formation of a thiolate-bridged diiron complex containing an Fe-CH2-S moiety,
Chem. Commun. 54 (2018) 13119–13122.
[4] B.M. Hoffman, D. Lukoyanov, Z.-Y. Yang, D.R. Dean, L.C. Seefeldt, Mechanism of
nitrogen fixation by nitrogenase: the next stage, Chem. Rev. 114 (2014)
4041–4062.
[24] L. Yan, C.H. Dapper, S.J. George, H. Wang, D. Mitra, W. Dong, W.E. Newton,
S.P. Cramer, Photolysis of Hi-CO nitrogenase – observation of a plethora of distinct
CO species using infrared spectroscopy, Eur. J. Inorg. Chem. 2011 (2011)
2064–2074.
[5] D. Sippel, M. Rohde, J. Netzer, C. Trncik, J. Gies, K. Grunau, I. Djurdjevic,
L. Decamps, S.L.A. Andrade, O. Einsle, A bound reaction intermediate sheds light on
the mechanism of nitrogenase, Science 359 (2018) 1484–1489.
[25] Z.-Y. Yang, L.C. Seefeldt, D.R. Dean, S.P. Cramer, S.J. George, Steric control of the
Hi-CO MoFe nitrogenase complex revealed by stopped-flow infrared spectroscopy,
Angew. Chem. Int. Ed. 50 (2011) 272–275.
[6] J. Kästner, P.E. Blöchl, Ammonia production at the FeMo cofactor of nitrogenase:
results from density functional theory, J. Am. Chem. Soc. 129 (2007) 2998–3006.
[7] Y. Luo, Y. Li, H. Yu, J. Zhao, Y. Chen, Z. Hou, J. Qu, DFT studies on the reduction of
dinitrogen to ammonia by a thiolate-bridged diiron complex as a nitrogenase
mimic, Organometallics 31 (2012) 335–344.
[26] R. Büchner, J.S. Field, R.J. Haines, Electron-transfer salts derived from N, N′-di-
cyano-p-benzoquinone diimines and the novel dinuclear organometallic donor
[Fe2(η-C5Me5)2(µ-SEt)2(CO)2], J. Chem. Soc., Dalton Trans (1996) 3533–3538.
[27] Y. Chen, Y. Zhou, J. Qu, Synthesis and Reactions of Novel Triply Thiolate-Bridged
Diiron Complexes [Cp*Fe(μ2-SR)3FeCp*] (Cp* = η5-C5Me5; R = Et, Ph),
Organometallics 27 (2008) 666–671.
[8] Y. Li, Y. Li, B. Wang, Y. Luo, D. Yang, P. Tong, J. Zhao, L. Luo, Y. Zhou, S. Chen,
F. Cheng, J. Qu, Ammonia formation by a thiolate-bridged diiron amide complex as
a nitrogenase mimic, Nat. Chem. 5 (2013) 320–326.
[28] D. Yang, Y. Li, L. Su, B. Wang, J. Qu, Versatile reactivity of CH3CN-coordinated
nickel-iron heterodimetallic complexes with Cp* ligand on diazadithiolate (N2S2) or
dithiadithiolate (S4) platforms, Eur. J. Inorg. Chem. 2015 (2015) 2965–2973.
[29] S. Ding, P. Ghosh, A.M. Lunsford, N. Wang, N. Bhuvanesh, M.B. Hall,
M.Y. Darensbourg, Hemilabile bridging thiolates as proton shuttles in bioinspired
H2 production electrocatalysts, J. Am. Chem. Soc. 138 (2016) 12920–12927.
[30] P. Ghosh, M. Quiroz, N. Wang, N. Bhuvanesh, M.Y. Darensbourg, Complexes of
MN2S2·Fe(η5-C5R5)(CO) as platform for exploring cooperative heterobimetallic ef-
fects in HER electrocatalysis, Dalton Trans. 46 (2017) 5617–5624.
[31] Y. Li, Y. Zhang, D. Yang, Y. Li, P. Sun, B. Wang, J. Qu, Synthesis and reactivity of
thioether-dithiolate-bridged multi-iron complexes, Organometallics 34 (2015)
1661–1667.
[9] T. Spatzal, K.A. Perez, O. Einsle, J.B. Howard, D.C. Rees, Ligand binding to the
FeMo-cofactor: Structures of CO-bound and reactivated nitrogenase, Science 345
(2014) 1620–1623.
[10] A.D. Scott, V. Pelmenschikov, Y. Guo, L. Yan, H. Wang, S.J. George, C.H. Dapper,
W.E. Newton, Y. Yoda, Y. Tanaka, S.P. Cramer, Structural characterization of CO-
inhibited mo-nitrogenase by combined application of nuclear resonance vibrational
spectroscopy, extended X-ray absorption fine structure, and density functional
theory: new insights into the effects of CO binding and the role of the interstitial
atom, J. Am. Chem. Soc. 136 (2014) 15942–15954.
[11] I. Čorić, P.L. Holland, Insight into the iron-molybdenum cofactor of nitrogenase
from synthetic iron complexes with sulfur, carbon, and hydride ligands, J. Am.
Chem. Soc. 138 (2016) 7200–7211.
[32] P. Chen, Y. Peng, C. Jia, J. Qu, Synthesis of a new family of heteronuclear thiolate
iron complexes that contain isocyanide ligands, Eur. J. Inorg. Chem. 2010 (2010)
5239–5246.
[12] N. Hazari, Homogeneous iron complexes for the conversion of dinitrogen into
ammonia and hydrazine, Chem. Soc. Rev. 39 (2010) 4044–4056.
[13] Y. Tanabe, Y. Nishibayashi, Recent advances in catalytic silylation of dinitrogen
using transition metal complexes, Coord. Chem. Rev. 389 (2019) 73–93.
[14] R.J. Burford, M.D. Fryzuk, Examining the relationship between coordination mode
and reactivity of dinitrogen, Nat. Rev. Chem. 1 (2017) 0026.
[33] F. Xu, S. Du, Y. Liu, J. Hassan, J. Zhang, A.M. Bond, Synthesis and characterization
of diiron dithiolate complexes containing a quinoxaline bridge, Dalton Trans. 40
(2011) 10907–10917.
[34] D. Yang, S. Xu, Y. Zhang, Y. Li, Y. Li, B. Wang, J. Qu, Reactivity toward unsaturated
small molecules of thiolate-bridged diiron hydride complexes, Inorg. Chem. 57
(2018) 15198–15204.
[15] J. Li, J. Yin, C. Yu, W. Zhang, Z. Xi, Direct transformation of N2 to N-containing
organic compounds, Acta Chim. Sinica 75 (2017) 733–743.
[16] D. Coucouvanis, P.E. Mosier, K.D. Demadis, S. Patton, S.M. Malinak, C.G. Kim,
M.A. Tyson, The catalytic reduction of hydrazine to ammonia by the MoFe3S4 cu-
banes and implications regarding the function of nitrogenase. Evidence for direct
involvement of the molybdenum atom in substrate reduction, J. Am. Chem. Soc.
115 (1993) 12193–12194.
[35] Q. You, D. Yang, S. Xu, B. Wang, J. Qu, Synthesis, characterization and structure of
thiolate-bridged diruthenium and iron-ruthenium complexes with isocyanide li-
gands, Inorg. Chem. Commun. 106 (2019) 27–33.
[36] K. Umehara, S. Kuwata, T. Ikariya, N-N bond cleavage of hydrazines with a mul-
tiproton-responsive pincer-type iron complex, J. Am. Chem. Soc. 135 (2013)
6754–6757.
[17] S. Kuwata, Y. Mizobe, M. Hidai, Catalytic N-N bond cleavage of hydrazines at the
coordinatively unsaturated diruthenium center in [Cp*Ru(μ-SR)2RuCp*] (Cp* =η5-
[37] S. Venkataramani, U. Jana, M. Dommaschk, F.D. Sönnichsen, F. Tuczek, R. Herges,
Magnetic bistability of molecules in homogeneous solution at room temperature,
Science 331 (2011) 445–448.
i
C5Me5 R = Pr, 2,6-Me2C6H3) and isolation of μ-phenyldiazene complexes [Cp*Ru
(μ-PhN=NH)(μ-SR)2RuCp*], Inorg. Chem. 33 (1994) 3619–3620.
[18] S.E. Creutz, J.C. Peters, Diiron bridged-thiolate complexes that bind N2 at the
FeIIFeII, FeIIFeI, and FeIFeI redox states, J. Am. Chem. Soc. 137 (2015) 7310–7313.
[19] Y. Chen, Y. Zhou, P. Chen, Y. Tao, Y. Li, J. Qu, Nitrogenase model complexes [Cp*Fe
(μ-SR1)2(μ-η2-R2N=NH)FeCp*] (R1 = Me, Et; R2 = Me, Ph; Cp* = η5-C5Me5):
synthesis, structure, and catalytic N−N bond cleavage of hydrazines on diiron
centers, J. Am. Chem. Soc. 130 (2008) 15250–15251.
[38] G.M. Sheldrick, SADABS, Program for Area Detector Adsorption Correction,Institute
for Inorganic Chemistry, Institute for Inorganic Chemistry, University of Göttingen,
Germany, 1996.
[39] G.M. Sheldrick, SHELXL-2014, Program for Refinement of Crystal Structures,
University of Göttingen, Germany, 2014.
[40] G.M. Sheldrick, SHELXS-2014, Program for Solution of Crystal Structures,
University of Göttingen, Germany, 2014.
[20] Y. Zhang, J. Zhao, D. Yang, Y. Zhang, B. Wang, J. Qu, Catalytic N−N bond cleavage
of hydrazine by thiolate-bridged iron-ruthenium heteronuclear complexes, Inorg.
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