A sulfide-bridged diiron(II) complex with a N2H4 ligand

Article abstract of DOI:10.1002/zaac.201300163

A sulfide-bridged diiron(II) complex bearing a cis-N₂H ₄ (hydrazine) ligand has been prepared by reaction of LFe ^II(μ-S)Fe^IIL (1; L = sterically encumbered β-diketiminate ligand) with 2 molar equivalents of N₂H ₄. The metastable diiron(II) hydrazine complex LFe ^II(μ-S)(μ-H₂N-NH₂)Fe^IIL (3) is formed, as shown by crystallography, NMR, vibrational, and electronic absorption spectroscopy. Compound 3 has been crystallographically characterized as its DBU (1, 8-diazabicyclo[5.4.0]undec-7-ene) adduct, which exhibits weak N-H···DBU hydrogen bonding. The synthetic process evolves roughly 2 equivalents of NH₃. The cis-N₂H₄ bridge in 3 may be relevant to the structure and function of intermediates on the FeMoco of nitrogenase. Copyright

Full text of DOI:10.1002/zaac.201300163

SHORT COMMUNICATION
DOI: 10.1002/zaac.201300163
A Sulfide-Bridged Diiron(II) Complex with a N2H4 Ligand
Bryan D. Stubbert,[a] Javier Vela,[a] William W. Brennessel,[a] and Patrick L. Holland*[a]
Keywords: Nitrogenases; FeMoco; Hydrazine; Iron sulfide; Werner complex; Coordination chemistry
Abstract. A sulfide-bridged diiron(II) complex bearing a cis-N2H4
Compound 3 has been crystallographically characterized as its DBU
(hydrazine) ligand has been prepared by reaction of LFeII(μ-S)FeIIL (1,8-diazabicyclo[5.4.0]undec-7-ene) adduct, which exhibits weak
(1; L = sterically encumbered β-diketiminate ligand) with 2 molar N–H···DBU hydrogen bonding. The synthetic process evolves roughly
equivalents of N2H4. The metastable diiron(II) hydrazine complex 2 equivalents of NH3. The cis-N2H4 bridge in 3 may be relevant to the
LFeII(μ-S)(μ-H2N–NH2)FeIIL (3) is formed, as shown by crystallogra-
structure and function of intermediates on the FeMoco of nitrogenase.
phy, NMR, vibrational, and electronic absorption spectroscopy.
does not exchange during catalytic turnover.[8] This suggests
that the central carbide may function as a hemilabile ligand, in
which some bonds are reversibly broken upon reductive
activation of the cofactor.[6a,9] It is therefore reasonable to
hypothesize that substrate binding occurs at one or more low-
coordinate iron atoms bonded directly to a bridging sulfide
ligand. This idea could be supported by understanding of the
binding modes and behavior of N2Hx fragments on well-char-
acterized multi-iron sulfide complexes. Work by Sellmann
established the complexation of hydrazine and diazene in iron
complexes,[9a] and more recent progress has come from study
of additional mononuclear and dinuclear iron complexes with
parent N2H4 ligands.[10,11]
We previously reported the reactivity of a sulfide-bridged
diiron(II) complex (1) with ammonia and with substituted hy-
drazines.[12] Addition of H2NNR2 (R = alkyl) gave isolable
Lewis base adducts, while addition of phenylhydrazine af-
forded a mixed-valence FeIIFeIII complex (2).[12] Formation of
2 required two equivalents of 1 for every three PhNHNH2 con-
sumed, generating one equivalent each of NH3 and PhNH2
(Scheme 1). Herein, we report the reaction of 1 with the parent
N2H4, which releases NH3 and forms a DBU-stabilized di-
iron(II) complex of bridging hydrazine (3·DBU). To the best
Introduction
Coordination chemistry has its roots in the work of Werner,
which was recognized by a Nobel Prize 100 years ago in
1913.[1] Coordination chemistry relevant to biological systems
now represents a dynamic subdiscipline of coordination chem-
istry.[2] One challenge in bioinorganic chemistry is biological
dinitrogen reduction (Equation (1)),
N2 + 8 e– + 8 H+ Ǟ 2 NH3 + H2
(1)
which is best characterized at the iron-molybdenum cofactor
(FeMoco, Figure 1) of nitrogenase enzymes.[3] Likely interme-
diates include hydrazine (H2N–NH2) and its short-lived partner
diazene (HN=NH), which are also substrates for nitroge-
nase.[3,4] Recent studies have trapped adducts (or products)
from N2, HN=NCH3, and N2H4 on the FeMoco.[5]
Figure 1. Structural similarity between a portion of the FeMoco of
nitrogenase (left) and complex 1 (right).
Progress in understanding the structure and reactive states
of FeMoco has been facilitated through spectroscopic studies
on model complexes and enzymes.[3–6] The FeMoco in its rest-
ing state has an intriguing six-coordinate carbide ion at its cen-
ter (Figure 1),[7] and 14C tracer studies indicate that the carbide
* Prof. Dr. P. Holland
E-Mail: holland@chem.rochester.edu
[a] Department of Chemistry
University of Rochester
Rochester, NY, 14627, USA
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/zaac.201300163 or from the au-
thor.
Scheme 1. Previously reported reactions of 1 with substituted hydraz-
ines, including the formation of complex 2.[12]
Z. Anorg. Allg. Chem. 2013, 639, (8-9), 1351–1355
© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
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B. D. Stubbert, J. Vela, W. W. Brennessel, P. L. Holland
SHORT COMMUNICATION
of our knowledge, 3 is the first sulfide-bridged diiron complex
of N2H4.[13] Because 3 has a low-coordinate iron-sulfide core
that resembles a part of the FeMoco, study of its structure
and spectroscopic features is an important step in defining the
possible geometries of iron-hydrazine adducts during N2 re-
duction.
Results and Discussion
In an improved synthesis, complex 1 was synthesized from
Me3P=S and 2 equiv. of a three-coordinate iron(II) β-diketim-
inate isobutyl complex in 89% yield (Ar = 2,6-diisoprop-
ylphenyl), as described in the Experimental Section.[14] When
1 is treated with at least 2 equiv. of hydrazine in [D8]THF at
1
0 to 30 °C, a red solution instantly forms with new H NMR
signals consistent with 3 (Scheme 2). Addition of excess N2H4
has no observable effect on product formation (leading only to
more rapid decomposition of 3), and addition of less than
2 equiv. of N2H4 to 1 gives partial conversion to 3. The life-
time of 3 in solution is relatively short (t1/2 ~ 30 min at 25 °C
Figure 2. Thermal-ellipsoid plot (50% probability) of cis-hydrazine
diiron(II) complex 3·DBU. Carbon-bound hydrogen atoms, isopropyl
groups of ligand, and DBU omitted for clarity. There is disorder in the
1
in C6D6, toluene, THF, or Et2O), with H NMR and UV/Vis
spectroscopic data showing decomposition to unidentified, in- bridging N2H4 ligand, and the major conformation is shown.
soluble products. This rapid decomposition prevented full
characterization of 3 by elemental analysis.
the literature for bridging hydrazines.[18] In the few known
diiron hydrazine adducts, a cis coordination geometry is par-
ticularly rare,[13,18,10b] and the solid-state structure of the
tris(phosphanyl)borate-supported low-spin diiron(II) complex
exhibits an N–Nhydrazine distance of 1.465(3) Å. The Fe–N–N
angles in 3·DBU are each roughly 112°, consistent with sp3
hybridization about N in the N2H4 ligand. Complex 3 also ex-
hibits UV/Vis (λmax 497 nm; ε = 3700 m–1 cm–1) and highly
1
symmetrical H NMR spectra at 25 °C, consistent with the as-
signed structure.
Scheme 2. Formation of 3, which is crystallized as 3·DBU. DBU
forms a hydrogen bond to 3 in the solid-state structure, but does not
bind strongly in solution.
Infrared spectra of 3 showed a νN–H band at 3361 cm–1 that
is shifted to 2490 cm–1 in 3-d4 (formed in an analogous fashion
from 1 and N2D4). This N–H stretching frequency is shifted
A single crystal of 3·DBU was obtained by allowing an from that in free N2H4, which exhibits a single band centered
Et2O solution of 1, hydrazine, and DBU (1,8-diazabicycloun- at approx. 3300 cm–1. Related hydrazine complexes (and their
dec-7-ene) to stand at –38 °C (Scheme 2). The major con- isotopomers) display similar IR absorptions between 3398 and
former in the X-ray crystallographic structure is shown in Fig- 3139 cm–1.[10]
ure 2. Complex 3·DBU is a rare example of a crystallographi-
It is important to note that formation of the characteristic 1H
cally characterized sulfide-bridged N2H4 complex,[15] and the NMR resonances of 3 was independent of the presence or ab-
only such diiron complex.[16] The solid-state structure displays sence of DBU. These experiments suggest that this base does
an Fe···Fe distance of 3.5960(7) Å, and the Fe–S–Fe angle of not play a significant role in forming 3, and does not bind
105.68(4)° is similar to those in other sulfide-bridged diiron strongly to 3 in solution. However, a hydrogen bond between
complexes.[12,17] Previous diiron hydrazine complexes exhibit hydrazine and DBU is clearly present in crystalline 3·DBU,
Fe–Nhydrazine distances of 2.02–2.25 Å and N–N distances of with an N···N distance of 2.91(2) Å. Thus, we surmise that its
1.42–1.44 Å. In 3·DBU the Fe–Nhydrazine distances of role is limited to enabling the packing of 3·DBU into single
2.231(13) and 2.163(6) Å are similar. The asymmetry in the crystals.
Fe–Nhydrazine bond lengths is also similar to literature hydraz-
ine complexes.[14]
The requirement for more than 1 equiv. of hydrazine during
the formation of 3 suggested that some of the hydrazine might
The X-ray structural data for 3·DBU fit well to a superposi- be reduced to ammonia, as previously observed during the for-
tion of two conformers, which could be modeled adequately. mation of 2.[12] Thus, a toluene solution of 1 was treated with
In order to model this disorder, the N–N distances in each Ն 2 equivalents of N2H4 (with or without DBU) at 25 °C in a
conformer were restrained to be similar and therefore should sealed vessel, followed by vacuum distillation of volatile mate-
be viewed with some caution, though the average refined rials onto a degassed solution of 1.0 m HCl in Et2O at –78 or
N–N bond length of 1.434(13) Å is similar to those in –196 °C. The NH4Cl formed was weighed to determine the
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A Sulfide-Bridged Diiron(II) Complex with a N2H4 Ligand
1
cooling in a 0 °C bath, then allowing the solution to warm to
yield of NH3. In smaller scale reactions, H NMR spectra of
20 °C overnight.[20] LMeFeiBu,[21] HLMe [22]
,
[LMeFe(μ-Cl)]2,[23]
NH4Cl solutions in [D6]DMSO were used to integrate the
amount of recovered ammonia vs. an internal mesitylene inte-
gration standard.[19] Each method indicated the presence of
1.7 Ϯ 0.3 equiv. of NH4Cl per mole of 1. Because we were
unable to isolate significant quantities of 3 or 3·DBU in pure
form, we were unable to determine whether the approx.
2 equiv. of ammonia arose during the formation of 3 or from
subsequent degradation of 3. Therefore, the full stoichiometry
of the formation of 3 (Scheme 2), its decomposition pathway,
and the source of electrons for the hydrazine reduction remain
unknown.
The poor solubility of hydrazine in suitable solvents and
extremely rapid formation of 3 hindered studies to determine
the mechanism through which complex 3 is formed. However,
we note that neither 1,4-cyclohexadiene (up to 1 m) nor BHT
(up to 50 mM) has a discernible effect on the formation of 2
or 3, suggesting the absence of free radicals. Also, the presence
or absence of DBU gave no appreciable differences in the life-
[24]
FeCl2(THF)1.5
were prepared according to literature procedures.
LMe refers to the 2,4-bis(2,6-diisopropylphenylimido)pentyl anion.
LMeFe(μ-S)FeLMe (1): A 100 mL resealable flask was charged with a
magnetic stir bar, LMeFeiBu (480 mg, 0.905 mmol), and toluene
(15 mL). To this solution was slowly added a toluene solution (15 mL)
of Me3PS (213 mg, 1.97 mmol) over 2–3 min while stirring at 25 °C.
The dark red-brown solution was heated in a 100 °C oil bath for 24 h.
Volatile materials were removed in vacuo at 25 °C, leaving a brown
residue. The solids were taken up in pentane (20 mL), and the resulting
brown solution was filtered through a Celite pad and evacuated to
dryness. Crystallization from pentane or 4:1 pentane:(Me3Si)2O mix-
ture (ca. 15 mL) affords 1 as a crystalline burgundy solid in 89.2%
yield (395 g, 0.403 mmol). The spectroscopic properties agree with
literature values.[12]
LMeFe(μ-S)(μ-N2H4)FeLMe (3): This complex was prepared in situ or
immediately prior to spectroscopic studies because of its decomposi-
tion within minutes at room temperature. In NMR scale experiments,
the purity of up to 1.0 mL of a 5–20 mM solution of 3 in [D6]benzene,
[D8]toluene, or [D8]THF was verified by 1H NMR spectroscopy in a J.
Young NMR tube containing a sealed capillary tube holding an internal
standard solution (typically LtBuFeCl in [D8]toluene). In the glovebox,
neat N2H4 (ca. 1–100 μL) was added by microsyringe to the wall of
the NMR tube, taking care to prevent mixing with the solution of 3.
1
time of 3, as measured by UV/Vis and H NMR spectroscopy.
Conclusions
A sulfide-bridged hydrazine complex 3 has been generated
by addition of N2H4 to a low-coordinate, sulfide-bridged di-
iron(II) complex and characterized by X-ray crystallography,
1
The sample was then shaken immediately before freezing or H NMR
1
spectroscopic observations. H NMR spectra at 25 °C were similar in
C6D6 (Figure S1) and [D8]THF (Figure S2), and are most consistently
assigned as δ = 10 (6 H, backbone CH3), 7.2 (4 H, isopropyl
CH(CH3)2 or m-Ar), –1.4 (2 H, p-Ar), –2.3 (12 H, isopropyl
CH(CH3)2), –7 (4 H, isopropyl CH(CH3)2 or m-Ar), –14 (1 H, back-
bone CH), –24 (12 H, isopropyl CH(CH3)2) ppm (all broad singlets).
The assignments are not definitive, due to overlap with peaks from
decomposition products (identified in Figures S1 and S2). FT-IR (thin
film on NaCl plates): νN–H 3361 cm–1; νN–D 2490 cm–1; see Figure S3.
UV/Vis (toluene): λmax 497 nm; ε 3700 m–1 cm–1. Elemental analysis
was not feasible due to instability. Single crystals suitable for X-ray
diffraction were obtained using a similar procedure, quickly combining
Et2O solutions of 1, DBU, and N2H4 in a 1:2:2 molar ratio and imme-
diately cooling to –40 °C.
1
as well as by H NMR and FT-IR spectroscopy. This is rel-
evant to biological N2 reduction, by showing that N2H4 can be
cooperatively bound by two nearby Fe atoms with a sulfide
bridge, and providing metrical and spectroscopic details on this
type of compound.
Experimental Section
General Considerations: All manipulations were performed under N2
or Ar atmosphere via standard Schlenk techniques or in an inert atmo-
sphere glovebox maintained at Ͻ 2 ppm O2 and Ͻ 2 ppm H2O. Unless
otherwise noted, NMR spectra were recorded on a 500 MHz Bruker
Avance spectrometer at 20 °C, and are referenced to residual solvent
peaks. Infrared data were recorded using a Shimadzu FT-IR 8400S
spectrometer. Electronic absorption spectra were recorded using a Cary
50 UV/Vis spectrophotometer using quartz cuvettes with a screw cap.
Low-temperature (T Ն –60 °C) and in situ-added N2H4 experiments
were conducted in quartz cuvettes fused to a resealable glass extension
bearing a sidearm valve and a ground glass joint sealed with a rubber
septum or glass stopper. Excess N2H4 was added via cannula syringe
(loaded in the glovebox) as a neat reagent. FT-IR spectroscopic studies
were conducted using thin films cast onto NaCl plates from concen-
trated Et2O solutions (or the aforementioned reaction media) immedi-
ately prior to data collection. Anhydrous hydrazine (Aldrich) was de-
X-ray Crystallography: A crystal was placed onto the tip of a 0.1 mm
diameter glass fiber and mounted on a Siemens SMART CCD platform
diffractometer for data collection at 193(2) K.[25] The full data collec-
tion was carried out using Mo-Kα radiation (graphite monochromator)
with a frame time of 10 seconds and a detector distance of 5.09 cm.
A randomly oriented region of reciprocal space was surveyed: four
major sections of frames were collected with 0.25° steps in ω at four
different φ settings and a detector position of –28° in 2θ. The intensity
data were corrected for absorption.[26] Final cell constants were calcu-
lated from the xyz centroids of 4012 strong reflections from the actual
data collection after integration.[27]
gassed using three freeze-pump-thaw cycles, and then dried by passage The two independent iron-diketiminate moieties are related by a
through a plug of activated alumina in the glove box. Solvents were pseudo-inversion center located at the midpoint of the iron atoms. The
dried with Na/benzophenone and/or by passage through a column
(Glass Contour Co., Laguna Beach, CA) or plug of activated alumina center, nor are there any significant unassigned electron density peaks
under N2 atmosphere and stored in the glovebox. Celite was dried to suggest disorder. Likewise the cocrystallized DBU molecule does
bridging sulfide and hydrazine ligands, however, are not related by the
at 200 °C under vacuum overnight. Trimethylphosphine sulfide was not possess inversion symmetry and no electron density peaks sug-
prepared in quantitative yield by adding a slight excess of a 1.0 m gested disorder. Initially, space group P1 was selected because the
toluene solution of trimethylphosphine to a rapidly stirred solution of E2–1 value was 0.754. Afterwards the Flack parameter refined to
elemental sulfur dissolved in toluene under an N2 atmosphere while 0.227(14), which confirmed the choice of the chiral space group. As
Z. Anorg. Allg. Chem. 2013, 1351–1355
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1353

B. D. Stubbert, J. Vela, W. W. Brennessel, P. L. Holland
SHORT COMMUNICATION
¯
Ribbe, Acc. Chem. Res. 2009, 43, 475; c) B. M. Hoffman, D. R.
Dean, L. C. Seefeldt, Acc. Chem. Res. 2009, 42, 609; d) B. M.
Hoffman, D. Lukoyanov, D. R. Dean, L. C. Seefeldt, Acc. Chem.
Res. 2013, 46, 587.
a further test, the structure was also refined in space group P1 with
the bridging ligands modeled as disordered with each other over a
crystallographic inversion center and with the DBU molecule modeled
as disordered over another center: the R1 value increased by over 3%.
Thus the structure is best represented in chiral space group P1 as an
inversion twin with a component mass ratio of 73:27.
[7] a) O. Einsle, F. A. Tezcan, S. L. A. Andrade, B. Schmid, M. Yosh-
ida, J. B. Howard, D. C. Rees, Science 2002, 297, 1696; b) K. M.
Lancaster, M. Roemelt, P. Ettenhuber, Y. Hu, M. W. Ribbe,
F. Neese, U. Bergmann, S. DeBeer, Science 2011, 334, 974;
c) T. Spatzal, M. Aksoyoglu, L. Zhang, S. L. A. Andrade, E.
Schleicher, S. Weber, D. C. Rees, O. Einsle, Science 2011, 334,
940; d) J. A. Wiig, Y. Hu, C. C. Lee, M. W. Ribbe, Science 2012,
337, 1672.
Although one cocrystallized pentane solvent molecule was identified
and located in the difference Fourier map, it was disordered over mul-
tiple positions. Reflection contributions from this solvent molecule
were removed using the Squeeze function of program Platon,[28] which
determined there to be 44 electrons in 182 Å3 removed per unit cell.
Because the amount and identity of the solvent were known, the sol-
vent was included in the molecular formula. The bridging hydrazine
ligand is modeled as disordered over two positions (53:47). Due to the
proximity of atom N2’ to atom N1 (atoms from different orientations
of the hydrazine ligand disorder), the two N–N bond lengths (N1–N2
and N1Ј–N2’) were restrained to be similar. Additionally, the aniso-
tropic displacement parameters for atoms N1 and N2’ were constrained
to be equivalent. There is one cocrystallized DBU molecule per di-
iron molecule that is hydrogen-bonded via the hydrazine ligand. A full
ORTEP diagram including the DBU is in Figure S4.
[8] J. A. Wiig, C. C. Lee, Y. Hu, M. W. Ribbe, J. Am. Chem. Soc.
2013, 135, 4982.
[9] a) D. Sellmann, A. Fursattel, J. Sutter, Coord. Chem. Rev. 2000,
200–202, 545; b) P. L. Holland, Can. J. Chem. 2005, 83, 296.
[10] a) M. J. Zdilla, A. K. Verma, S. C. Lee, Inorg. Chem. 2008, 47,
11382; b) C. T. Saouma, P. Muller, J. C. Peters, J. Am. Chem. Soc.
2009, 131, 10358; c) Y. Lee, N. P. Mankad, J. C. Peters, Nat.
Chem. 2010, 2, 558; d) C. T. Saouma, C. E. Moore, A. L.
Rheingold, J. C. Peters, Inorg. Chem. 2011, 50, 11285.
[11] a) S. P. Rath, M. M. Olmstead, A. L. Balch, Inorg. Chem. 2004,
43, 6357; b) Y. Yu, W. W. Brennessel, P. L. Holland, Organome-
tallics 2007, 26, 3217; c) J. L. Crossland, L. N. Zakharov, D. R.
Tyler, Inorg. Chem. 2007, 46, 10476; d) L. D. Field, H. L. Li,
A. M. Magill, Inorg. Chem. 2009, 48, 5; e) J. L. Crossland, C. G.
Balesdent, D. R. Tyler, Dalton Trans. 2009, 4420; f) L. D. Field,
H. L. Li, S. J. Dalgarno, P. Jensen, R. D. McIntosh, Inorg. Chem.
2011, 50, 5468; g) J. L. Crossland, C. G. Balesdent, D. R. Tyler,
Inorg. Chem. 2012, 51, 439; h) C. T. Saouma, C. C. Lu, J. C.
Peters, Inorg. Chem. 2012, 51, 10043.
Supporting Information (see footnote on the first page of this article):
NMR spectra of 3; details on X-ray crystal structure of 3·DBU.
Acknowledgments
[12] J. Vela, S. Stoian, C. J. Flaschenriem, E. Münck, P. L. Holland, J.
Am. Chem. Soc. 2004, 126, 4522.
The authors thank the NIH (GM-065313) for funding, and Christine
Flaschenriem for crystallographic contributions.
[13] Thiolate-bridged iron complexes have been reported with diazene
ligands: a) Y. Chen, Y. Zhou, P. Chen, Y. Tao, Y. Li, J. Qu, J.
Am. Chem. Soc. 2008, 130, 15250; b) M. Yuki, Y. Miyake, Y.
Nishibayashi, Organometallics 2012, 31, 2953; c) Y. Chen, L.
Liu, Y. Peng, P. Chen, Y. Luo, J. Qu, J. Am. Chem. Soc. 2011,
133, 1147;d) D. Sellmann, D. C. F. Blum, F. W. Heinemann, In-
org. Chim. Acta 2002, 337, 1; e) D. Sellmann, W. Soglowek, F.
Knoch, M. Moll, Angew. Chem. Int. Ed. Engl. 1989, 28, 1271..
[14] This approach was recently reported for a similar family of diiron
sulfide complexes: M. M. Rodriguez, B. D. Stubbert, C. C. Scar-
borough, W. W. Brennessel, E. Bill, P. L. Holland, Angew. Chem.
Int. Ed. 2012, 51, 8247.
References
[1] a) F. Basolo, From Coello to Inorganic Chemistry: A Lifetime of
Reactions. Kluwer Academic/Plenum Publishers, 2002; b) E. C.
Constable, C. E. Housecroft, Chem. Soc. Rev. 2013, 42, 1429 and
references cited therein.
[2] I. Bertini, H. B. Gray, E. I. Stiefel, J. S. Valentine, Biological In-
organic Chemistry: Structure and Reactivity. University Science
Books: Sausalito, CA, 2006.
[3] a) J. B. Howard, D. C. Rees, Chem. Rev. 1996, 96, 2965; b) B. K.
Burgess, D. J. Lowe, Chem. Rev. 1996, 96, 2983; c) P. L. Holland,
in Comprehensive Coordination Chemistry II, Vol. 8 (Eds.: J.
McCleverty, T. J. Meyer), Elsevier, Oxford, 2004, pp. 569; d)
B. M. Barney, H.-I. Lee, P. C. Dos Santos, B. M. Hoffman, D. R.
Dean, L. C. Seefeldt, Dalton Trans. 2006, 2277.
[4] a) B. M. Barney, M. Laryukhin, R. Y. Igarashi, H.-I. Lee, P. C.
Dos Santos, T.-C. Yang, B. M. Hoffman, D. R. Dean, L. C. See-
feldt, Biochemistry 2005, 44, 8030; b) J. Kästner, P. E. C. Blöchl,
J. Am. Chem. Soc. 2007, 129, 2998; c) B. M. Barney, J. McClead,
D. Lukoyanov, M. Laryukhin, T.-C. Yang, D. R. Dean, B. M.
Hoffman, L. C. Seefeldt, Biochemistry 2007, 46, 6784; d) K. Dan-
yal, B. S. Inglet, K. A. Vincent, B. M. Barney, B. M. Hoffman,
F. A. Armstrong, D. R. Dean, L. C. Seefeldt, J. Am. Chem. Soc.
2010, 132, 13197; e) D. Lukoyanov, Z.-Y. Yang, B. M. Barney,
D. R. Dean, L. C. Seefeldt, B. M. Hoffman, Proc. Natl. Acad. Sci.
USA 2012, 109, 5583.
[15] a) K. Matsumoto, T. Koyama, Y. Koide, J. Am. Chem. Soc. 1999,
121, 10913; b) Y. Liu, P. D. Kanhere, C. L. Wong, Y. Tian, Y.
Feng, F. Boey, T. Wu, H. Chen, T. J. White, Z. Chen, Q. Zhang,
J. Solid State Chem. 2010, 183, 2644.
[16] Cambridge Structural Database, Version 5.34, update 2, February
2013.
[17] See, for example: a) R. N. Mukherjee, T. D. P. Stack, R. H. Holm,
J. Am. Chem. Soc. 1988, 110, 1850; b) F. Corazza, C. Floriani,
M. Zehnder, J. Chem. Soc., Dalton Trans. 1987, 709; c) J. R.
Dorfman, J. J. Girerd, E. D. Simhon, T. D. P. Stack, R. H. Holm,
Inorg. Chem. 1984, 23, 4407.
[18] D. Sellmann, P. Kreutzer, G. Huttner, A. Frank, Z. Naturforsch.
1978, 33b, 1341.
[19] a) S. D. Brown, J. C. Peters, J. Am. Chem. Soc. 2005, 127, 1913;
b) T. A. Betley, J. C. Peters, J. Am. Chem. Soc. 2004, 126, 6252;
c) D. V. Yandulov, R. R. Schrock, J. Am. Chem. Soc. 2002, 124,
6252.
[20] W. D. Jones, A. D. Selmeczy, Organometallics 1992, 11, 889.
[21] J. Vela, S. Vaddadi, T. R. Cundari, J. M. Smith, E. A. Gregory,
R. J. Lachicotte, C. J. Flaschenriem, P. L. Holland, Organometal-
lics 2004, 23, 5226.
[5] a) B. M. Barney, T.-C. Yang, R. Y. Igarashi, P. C. Dos Santos, M.
Laryukhin, H.-I. Lee, B. M. Hoffman, D. R. Dean, L. C. Seefeldt,
J. Am. Chem. Soc. 2005, 127, 14960; b) D. Lukoyanov, S. A.
Dikanov, Z.-Y. Yang, B. M. Barney, R. I. Samoilova, K. V.
Narasimhulu, D. R. Dean, L. C. Seefeldt, B. M. Hoffman, J. Am.
Chem. Soc. 2011, 133, 11655.
[22] D. Adhikari, B. A. L. Tran, F. J. Zuno-Cruz, G. S. Cabrera, D. J.
Mindiola, K. P. Chiang, R. E. Cowley, T. R. Dugan, P. L. Holland,
Inorg. Synth. 2010, 35, 8.
[6] a) J. C. Peters, M. P. Mehn, in Activation of Small Molecules (Ed.:
W. B. Tolman), VCH, Weinheim, 2006, pp. 81; b) Y. Hu, M. W.
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www.zaac.wiley-vch.de
© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Z. Anorg. Allg. Chem. 2013, 1351–1355

A Sulfide-Bridged Diiron(II) Complex with a N2H4 Ligand
[23] B. D. Stubbert, P. L. Holland, D. Adhikari, D. J. Mindiola, Inorg.
Synth. 2010, 35, 38.
[24] G. Winter, Inorg. Synth. 1973, 14, 101.
[27] SAINT, version 7.06A, Bruker AXS, Madison, WI, 2003.
[28] A. L. Spek, Acta Crystallogr., Sect. D 2009, 65, 148.
[25] SMART, V5.629, Bruker AXS, Madison, WI, 2003.
[26] G. M. Sheldrick, SADABS, version 2008/1, University of
Göttingen, Göttingen, Germany, 2008.
Received: March 19, 2013
Published Online: May 24, 2013
Z. Anorg. Allg. Chem. 2013, 1351–1355
© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
www.zaac.wiley-vch.de
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