Cleavage and Formation of Molecular Dinitrogen in a Single System Assisted by Molybdenum Complexes Bearing Ferrocenyldiphosphine

Article abstract of DOI:10.1002/anie.201405673

The Ni≡N bond of molecular dinitrogen bridging two molybdenum atoms in the pentamethylcyclopentadienyl molybdenum complexes that bear ferrocenyldiphosphine as an auxiliary ligand is homolytically cleaved under visible light irradiation at room temperature to afford two molar molybdenum nitride complexes. Conversely, the bridging molecular dinitrogen is reformed by the oxidation of the molybdenum nitride complex at room temperature. This result provides a successful example of the cleavage and formation of molecular dinitrogen induced by a pair of two different external stimuli using a single system assisted by molybdenum complexes bearing ferrocenyldiphosphine under ambient conditions.

Full text of DOI:10.1002/anie.201405673

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DOI: 10.1002/anie.201405673
N2 Cleavage and Formation
Cleavage and Formation of Molecular Dinitrogen in a Single System
Assisted by Molybdenum Complexes Bearing
Ferrocenyldiphosphine**
Takamasa Miyazaki, Hiromasa Tanaka, Yoshiaki Tanabe, Masahiro Yuki, Kazunari Nakajima,
Kazunari Yoshizawa,* and Yoshiaki Nishibayashi*
ꢀ
Abstract: The N N bond of molecular dinitrogen bridging two
molybdenum atoms in the pentamethylcyclopentadienyl
molybdenum complexes that bear ferrocenyldiphosphine as
an auxiliary ligand is homolytically cleaved under visible light
irradiation at room temperature to afford two molar molyb-
denum nitride complexes. Conversely, the bridging molecular
dinitrogen is reformed by the oxidation of the molybdenum
nitride complex at room temperature. This result provides
a successful example of the cleavage and formation of
molecular dinitrogen induced by a pair of two different
external stimuli using a single system assisted by molybdenum
complexes bearing ferrocenyldiphosphine under ambient con-
ditions.
reversibly, it is still quite difficult to understand the hetero-
geneous reaction in detail on the atomic and molecular levels.
Since the first discovery of a transition-metal–dinitrogen
complex,[2] various stoichiometric and catalytic transforma-
tions using transition-metal–dinitrogen complexes have been
well investigated toward the development of the next
generation nitrogen fixation system.[3,4] During our study on
the development of novel nitrogen fixation system under mild
reaction conditions,[4b,5] we have focused on use of ferroce-
nyldiphosphine as an auxiliary ligand chelating to molybde-
num atom to capture and activate molecular dinitrogen.[6] We
have now found that molecular dinitrogen is cleaved and
reformed on the pentamethylcyclopentadienyl molybdenum
complexes in medium oxidation states bearing ferrocenyldi-
phosphine as an auxiliary ligand. In this reaction system,
molecular dinitrogen bridging two molybdenum moieties is
cleaved under visible light irradiation at room temperature to
afford the corresponding molybdenum nitride complex.
Conversely, the bridging molecular dinitrogen is reformed
by oxidation of the molybdenum nitride complex at room
temperature. This result provides a successful example of the
cleavage and formation of molecular dinitrogen induced by
a pair of two different external stimuli (both photochemically
and oxidatively) using a single system under ambient
conditions.
N
itrogen fixation, the production of ammonia from molec-
ular dinitrogen, is one of the most important chemical
processes on earth because ammonia is widely used as an
essential source of nitrogen fertilizers. Industrially, ammonia
is produced from molecular dinitrogen and molecular dihy-
drogen using iron-based heterogeneous catalysts under harsh
reaction conditions, such as quite high temperatures and
pressures.[1] In the Haber–Bosch process, the rate-determin-
ing step is the dissociative chemisorption of dinitrogen on the
surface of the iron catalyst, which includes adsorption of
ꢀ
dinitrogen, cleavage of the N N triple bond, and the bonding
of two nitrogen atoms to the iron surface as nitride species.[1]
Although all these elementary steps are known to occur
When the monocationic dinitrogen-bridged dimolybde-
num complex chelated by 1,1’-bis(diethylphosphino)ferro-
cene (depf)[6a] (1), which was prepared by the reaction of
molybdenum(II)-dinitrogen hydride complex (2)[6c] with the
trityl cation, was reduced with KC8 in dark or oxidized with
FcBArF (Fc = Fe(h5-C5H5)2, ArF = 3,5-(CF3)2C6H3), the neu-
[*] Dr. T. Miyazaki, Dr. Y. Tanabe, Dr. M. Yuki, Dr. K. Nakajima,
Prof. Dr. Y. Nishibayashi
4
tral dinitrogen-bridged dimolybdenum complex (3) or the
dicationic dinitrogen-bridged dimolybdenum complex (4) was
obtained in 34% or 96% yield, respectively (Scheme 1). A
cyclic voltammetric study of 4 has revealed two consecutive
one-electron reversible processes, leading us to examine the
direct back-and-forth transformations between 3 and 4. Thus,
treatment of 4 with KC8 afforded 3 in 94% yield (determined
by the UV/Vis spectrum), while that of 3 with FcBArF4 gave 4
in 53% yield (Scheme 1).
Detailed molecular structures of 1, 3, and 4 were
determined by X-ray crystallographic analyses (Figure 1a).[7]
In all these complexes, two {Cp*Mo(depf)} moieties are
bridged by one dinitrogen ligand in an end-on fashion with an
almost linear Mo-N-N-Mo backbone. However, other metric
features around the Mo-N-N-Mo backbone depend on the
oxidation states of molybdenum atoms in 1, 3, and 4. In fact,
Institute of Engineering Innovation, School of Engineering
The University of Tokyo, Yayoi, Bunkyo-ku, Tokyo 113-8656 (Japan)
E-mail: ynishiba@sogo.t.u-tokyo.ac.jp
Dr. H. Tanaka, Prof. Dr. K. Yoshizawa
Institute for Materials Chemistry and Engineering and
International Research Center for Molecular System
Kyushu University, Nishi-ku, Fukuoka 819-0395 (Japan)
E-mail: kazunari@ms.ifoc.kyushu-u.ac.jp
[**] K.Y. thanks Grants-in-Aid for Scientific Research (No. 24109014)
from the Japan Society for the Promotion of Science (JSPS) and the
Ministry of Education, Culture, Sports, Science and Technology of
Japan (MEXT) and the MEXT Projects of “Integrated Research on
Chemical Synthesis” and “Elements Strategy Initiative to Form Core
Research Center”. Y.N. thanks the Toyota Motor Corporation and
the NEOS Hydrogen Trust Fund.
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/anie.201405673.
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ꢁ
N and Mo N bonds of 1’, 3, and 4’, where 1’ and 4’ are the
cationic part of 1 and 4, respectively. Results of the BP86
ꢁ
ꢁ
functionals satisfactorily reproduce both the N N and Mo N
distances in all the complexes. Two-electron reduction of 4
ꢁ
causes an increase in the N N bond order (1.40 (4’)!1.60
ꢁ
(1’)!1.80(3)) with a decrease in the Mo N bond order (1.22
(4’)!1.03 (1’)!0.84 (3) in average), implying that the
bridging dinitrogen ligand in the dimolybdenum complexes
is reductively activated by at least two electrons, although the
Mo-N-N-Mo backbone is close to linear in all the complexes.
The structural differences in the Mo-N-N-Mo backbone can
be understood from the singly-occupied molecular orbitals
(SOMOs) of 3 (Figure 1b). Two SOMOs of 3, which are
occupied by two electrons added to the dicationic complex 4’,
have a bonding character between two nitrogen atoms, while
they have an antibonding character between the molybdenum
and nitrogen atoms.
Scheme 1. Redox interconversions between dinitrogen-bridged dimo-
lybdenum complexes chelated by depf.
When a benzene solution of 3 was irradiated by visible
light (l > 400 nm), cleavage of the bridging dinitrogen ligand
occurred to give the corresponding molybdenum(IV) nitride
complex (5) in 33% NMR yield (Scheme 2).[8,10,11] In contrast,
Scheme 2. Photoinduced conversion of 3 into 5 and the X-ray crystallo-
graphic structure of 5.
Figure 1. Molecular structures of dinitrogen-bridged dinitrogen com-
plexes. a) Crystallographic structures of the main parts of 4, 1, and 3.
b) Optimized structure of 3 in the triplet spin state and spatial
distribution of the SOMOs (HOMOꢁ1 (left) and HOMO (right)).
irradiation of visible light (l > 580 nm) to 3 at room temper-
ature or heating of 3 at 708C in dark did not give 5, indicating
that the cleavage of the dinitrogen ligand in 3 proceeds
specifically under the photochemical conditions (400 nm <
l < 580 nm). Separately, we confirmed that irradiation of
visible light to 1 and 4 did not give the corresponding
molybdenum nitride complexes, where release of free depf
was only observed by NMR spectra after reactions.
The molecular structure of 5 was characterized by 1H and
31P{1H} NMR spectra. The IR spectrum of 5 exhibits
a moderate nMoN absorption at 1024 cmꢁ1 that is assignable
to the terminal nitride ligand. More detailed molecular
structure of 5 was unequivocally characterized by an X-ray
analysis (Scheme 2).[7]
ꢁ
the N N bond lengths of 4 (1.256(9) ꢀ), 1 (1.226(4) ꢀ) and 3
(1.182(5) ꢀ) correspond to the bonding modes of the bridging
dinitrogen ligand as [N2]4ꢁ, [N2]3ꢁ, and [N2]2ꢁ, respectively.[8]
Characteristics of the Mo-N-N-Mo backbone of 1, 3, and 4
have been investigated by using density-functional-theory
(DFT) calculations at the BP86 level of theory. Table 1
summarizes the distances and Mayer bond orders[9] of the N
ꢁ
ꢁ
Table 1: Distances (d) and the Mayer bond orders (b.o.) of the N N and
To obtain more information on the reaction pathway of
the photo-induced cleavage of the coordinated dinitrogen, we
investigated the time-course change of the absorption spec-
trum of 3 under irradiation (l > 400 nm). As a typical
absorbance at 748 nm derived from 3 decreased, shoulder
peaks at 292 nm and 332 nm derived from 5 newly appeared
(Figure 2a).
ꢁ
Mo N bonds of the dimolybdenum complexes 1’, 3, and 4’.
Complex
ꢁ
ꢁ
(total charge)
N N
dcalc
Mo N
dcalc
dexp
b.o. dexp
b.o.
4’ (+2)
1’ (+1)
3 (0)
1.256(9) 1.254 1.40 1.835(6) 1.853 1.22
1.824(6) 1.852 1.22
1.226(4) 1.228 1.60 1.888(3) 1.907 1.02
1.874(3) 1.904 1.04
1.182(5) 1.208 1.80 1.955(4) 1.971 0.83
1.955(4) 1.969 0.85
For the assignment of the absorption band responsible for
ꢀ
the N N bond cleavage, electronic transition energies of 3
were obtained with a time-dependent DFT calculation using
the BP86 functional. Use of the BP86 functional was
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Scheme 3. Reactivity of 5. a) Dimerization of 5 into 4. b) Formation of
4 and 6 by the reaction with additives. c) A proposed reaction pathway
for 4 and 6.
Figure 2. Time-dependent and simulated UV/Vis spectra of 3. a) Time-
dependent UV/Vis spectra of the conversion of 3 into 5 recorded every
3 min for 51 min under visible-light irradiation. b) UV/Vis spectrum of
3 simulated with the time-dependent BP86 method. Two inserts are
electron density difference maps (EDDMs) showing isosurface plots of
loss (light blue) and gain (purple) of electron density for the calculated
electronic transitions.
sponding nitridyl complexes are proposed to work as key
reactive intermediates.[13j,k]
To investigate the reaction pathway for the oxidation-
triggered dimerization of 5, we next examined the effect of
addition of a hydrogen source. When the oxidation of 5 with
1 equiv of FcBArF was carried out in the presence of 1,4-
4
cyclohexadiene as a hydrogen source, formation of 4 was
observed in 16% NMR yield together with the cationic
molybdenum(IV) imide complex (6) and benzene in 21% and
8% NMR yields, respectively (Scheme 3b). We also con-
firmed that no direct dimerization of 6 into 4 occurred under
the similar reaction conditions, and thus 6 was revealed to be
not a reaction intermediate for the dimerization of 5. Rather
validated by comparing UV/Vis spectra simulated with
various functionals.[12] As shown in Figure 2b, the calculated
electronic transitions (200 transitions, l > ca. 400 nm) rea-
sonably reproduced the shape of the measured UV/Vis
spectrum of 3. Three distinguished electronic transitions
were found at 383, 495, and 657 nm in the simulated spectrum.
Electron density differential maps (EDDMs) present isosur-
face plots of loss (light blue) and gain (purple) of electron
density for the transitions at 495 and 657 nm. The loss of
electron density between the two nitrogen atoms observed for
the transition at 495 nm could be responsible for the cleavage
of the bridging dinitrogen ligand induced by irradiation (l >
400 nm).
surprisingly, treatment of 5 with [LutH][BArF ] (LutH = 2,6-
4
lutidinium) as a protic acid also afforded a mixture of 6 and 4
in 39% and 37% NMR yields, respectively, together with
molecular dihydrogen (H2) in 9% GC yield (Scheme 3b), as
we had expected that only protonation of 5 took place to
afford 6 as the sole product. These results demonstrate that
the one-electron oxidation of 5 rather preferentially takes
place to afford an oxidized cationic nitride species (A), which
further dimerizes into 4 via the homocoupling reaction or
transfers a hydrogen atom from 1,4-cyclohexadiene to afford
6 and benzene (Scheme 3c). Furthermore, treatment of 5 with
an excess amount of CoCp*2 as a reductant and an excess
Oxidation of the nitride complex 5 with 1 equiv of
FcBArF led to its dimerization to generate the dinitrogen-
4
bridged dimolybdenum complex 4 in 36% NMR yield
(Scheme 3a). This result is in sharp contrast to the previously
reported dimerization of electrophilic late-transition-metal–
nitride complexes, where coupling of nitrides is not induced
by oxidation.[13] In fact, Schneider, de Bruin, and their co-
workers have recently found that dimerization of iridium and
rhodium nitride complexes bearing PNP-type pincer ligand is
induced by reduction or photoirradiation, where the corre-
amount of [LutH][BArF ] as a proton source under an
4
atmospheric pressure of argon in toluene at room temper-
ature for 20 h in dark gave 0.37 equiv of ammonia based on
5.[12] This result provides a successful example of the
formation of ammonia derived from the metal nitride
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resulting 6’ and benzene in the singlet state is 37.4 kcalmolꢁ1
more stable than the reactant complex (Supporting Informa-
tion, Figure S8).[12] The DFT calculations demonstrate that
the intermediate A is able to transfer hydrogen atoms from
1,4-cyclohexadiene at room temperature, despite no spin
density at the nitride N atom, and therefore A is a possible
candidate for the reactive species in the dimerization of 5.
In summary, we have prepared a series of molybdenum–
dinitrogen complexes bearing ferrocenyldiphosphine and
have revealed their interconversions by redox and light-
induced processes. We believe that our findings provide a new
aspect in molybdenum–dinitrogen complexes in medium
oxidation states.
Received: May 27, 2014
Revised: July 28, 2014
Published online: September 11, 2014
Keywords: dinitrogen complexes · Haber–Bosch process · iron ·
.
molybdenum · nitrogen fixation
Figure 3. DFT study on the hydrogen transfer by 5. a) Optimized
structures of the intermediate A and the cationic part of imide complex
6 (6’). b) Spatial distribution of the SOMO of 6’. c) Energy profile and
optimized structures for hydrogen transfer from 1,4-cyclohexadiene by
A to afford 6’. RC and PC represent the reactant complex involving A
and cyclohexadiene, and the product complex involving 6’ and the
corresponding cyclohexadiene radical. Energies and interatomic dis-
tances are given in kcalmolꢁ1 and ꢀ, respectively.
[1] R. Schlçgl in Handbook of Heterogeneous Catalysis, Vol. 5,
2ednd ed(Eds.: G. Ertl, H. Knçzinger, F. Schꢁth, J. Weitkamp),
Wiley-VCH, Weinheim, 2008, pp. 2501 – 2575.
[2] A. D. Allen, C. V. Senoff, Chem. Commun. 1965, 621.
[3] a) J. Ballmann, R. F. Munhꢂ, M. D. Fryzuk, Chem. Commun.
2010, 46, 1013; b) Y. Shibata, H. Seino, Y. Mizobe, M. Hidai in
Encyclopedia of Catalysis (Ed.: I. T. Horvath), Wiley-VCH,
Weinheim, 2010, DOI: 10.1002/0471227617.eoc016.pub2; c) J. L.
Crossland, D. R. Tyler, Coord. Chem. Rev. 2010, 254, 1883; d) N.
Hazari, Chem. Soc. Rev. 2010, 39, 4044; e) J. Sgrignani, D.
Franco, A. Magistrato, Molecules 2011, 16, 442; f) Y. Nishibaya-
shi, Dalton Trans. 2012, 41, 7447; g) S. Hinrichsen, H. Broda, C.
Gradert, L. Sçncksen, F. Tuczek, Annu. Rep. Prog. Chem. Sect. A
2012, 108, 17; h) Y. Tanabe, Y. Nishibayashi, Coord. Chem. Rev.
2013, 257, 2551; i) K. C. MacLeod, P. L. Holland, Nat. Chem.
2013, 5, 559; j) H.-P. Jia, E. A. Quadrelli, Chem. Soc. Rev. 2014,
43, 547.
[4] a) D. V. Yandulov, R. R. Schrock, Science 2003, 301, 76; b) K.
Arashiba, Y. Miyake, Y. Nishibayashi, Nat. Chem. 2011, 3, 120;
c) J. S. Anderson, J. Rittle, J. C. Peters, Nature 2013, 501, 84.
[5] a) H. Tanaka, K. Arashiba, S. Kuriyama, A. Sasada, K.
Nakajima, K. Yoshizawa, Y. Nishibayashi, Nat. Commun. 2014,
5, 3737; b) S. Kuriyama, K. Arashiba, K. Nakajima, H. Tanaka,
N. Kamaru, K. Yoshizawa, Y. Nishibayashi, J. Am. Chem. Soc.
2014, 136, 9719.
complex formed via the light-induced cleavage of the nitro-
gen–nitrogen bond of molecular dinitrogen.[14]
Herein we theoretically discuss the electronic structure
and reactivity of the proposed intermediate A. Optimized
structures of A and the cationic part of imide complex 6 (6’)
ꢁ
are presented in Figure 3a. The Mo N bond distance (Mayer
bond order) of A is elongated from 1.689 ꢀ (2.59) to 1.754 ꢀ
ꢁ
(1.91) after hydrogen transfer. Although the calculated Mo
N distance of 6’ is slightly longer than the experimental value
(1.718(4) ꢀ),[7] the N H stretching frequency of the imide
ꢁ
moiety is reasonably reproduced (3444 cmꢁ1). The spin
density of 6’ is localized at the molybdenum atom (0.91),
while a negligibly small amount of the spin density is assigned
to the nitrogen atom (ꢁ0.06). This spin localization reflects
spatial distribution of the SOMO of 6’ (Figure 3b). These
results are completely different from the iridium and rhodium
nitride complexes reported by Schneider, de Bruin, and their
co-workers.[13j,k] Their metal nitride complexes possess
[6] a) M. Yuki, Y. Miyake, Y. Nishibayashi, I. Wakiji, M. Hidai,
Organometallics 2008, 27, 3947; b) H. Tanaka, A. Sasada, T.
Kouno, M. Yuki, Y. Miyake, H. Nakanishi, Y. Nishibayashi, K.
Yoshizawa, J. Am. Chem. Soc. 2011, 133, 3498; c) T. Miyazaki, Y.
Tanabe, M. Yuki, Y. Miyake, K. Nakajima, Y. Nishibayashi,
Chem. Eur. J. 2013, 19, 11874.
=
a nitridyl M NC radical character, where the spin density is
almost equally distributed on both the metal and nitrogen
atoms. Figure 3c shows an energy profile calculated for
hydrogen transfer from 1,4-cyclohexadiene by intermediate A
to afford 6’. The calculated activation energy (17.4 kcalmolꢁ1)
indicates that A is capable of picking a hydrogen atom up
from cyclohexadiene at room temperature. Although this
process is endothermic by 7.1 kcalmolꢁ1, the generated
cyclohexadiene radical is readily converted into benzene by
the following hydrogen transfer by A. Hydrogen transfer
from the cyclohexadiene radical by A requires a lower
activation energy of 10.7 kcalmolꢁ1 in the triplet state, and the
[7] CCDC 976705 (1), 976706 (3), 976707 (4·C4H10O·C6H14), 976708
(5), and 976709 (6·C4H8O) contain the supplementary crystallo-
graphic data for this paper. These data can be obtained free of
charge from The Cambridge Crystallographic Data Centre via
www.ccdc.cam.ac.uk/data_request/cif.
[8] a) C. E. Laplaza, M. J. A. Johnson, J. C. Peters, A. L. Odom, E.
Kim, C. C. Cummins, G. N. George, I. J. Pickering, J. Am. Chem.
Soc. 1996, 118, 8623; b) J. J. Curley, T. R. Cook, S. Y. Reece, P.
Mꢁller, C. C. Cummins, J. Am. Chem. Soc. 2008, 130, 9394;
c) P. P. Fontaine, B. L. Yonke, P. Y. Zavalij, L. R. Sita, J. Am.
Chem. Soc. 2010, 132, 12273.
[9] I. Mayer, Chem. Phys. Lett. 1983, 97, 270.
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.
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[10] For photochemical cleavage of dinitrogen under ambient
reaction conditions, see also: a) E. Solari, C. Da Silva, B.
Iacono, J. Hesschenbrouck, C. Rizzoli, R. Scopelliti, C. Floriani,
Angew. Chem. Int. Ed. 2001, 40, 3907; Angew. Chem. 2001, 113,
4025; b) H. Kunkely, A. Vogler, Angew. Chem. Int. Ed. 2010, 49,
1591; Angew. Chem. 2010, 122, 1636; c) A. S. Huss, H. J. Curley,
C. C. Cummins, D. A. Blank, J. Phys. Chem. B. 2013, 117, 1429.
[11] For thermal or reductive cleavage of dinitrogen at ambient
reaction conditions, see also: a) C. E. Laplaza, C. C. Cummins,
Science 1995, 268, 861; b) J. S. Figueroa, N. A. Piro, C. R. Clough,
C. C. Cummins, J. Am. Chem. Soc. 2006, 128, 940; c) F. Akagi, T.
Matsuo, H. Kawaguchi, Angew. Chem. Int. Ed. 2007, 46, 8778;
Angew. Chem. 2007, 119, 8934; d) I. Klopsch, M. Finger, C.
Wꢁrtele, B. Milde, D. B. Werz, S. Schneider, J. Am. Chem. Soc.
2014, 136, 6881 and references therein.
1997, 36, 5678; d) K. D. Demadis, E.-S. El-Samanody, G. M.
Coia, T. J. Meyer, J. Am. Chem. Soc. 1999, 121, 535; e) C.
Newton, K. D. Edwards, J. W. Ziller, N. M. Doherty, Inorg.
Chem. 1999, 38, 4032; f) S. B. Seymore, S. N. Brown, Inorg.
Chem. 2002, 41, 462; g) W.-L. Man, T.-M. Tang, T.-W. Wong, T.-
C. Lau, S.-M. Peng, W.-T. Wong, J. Am. Chem. Soc. 2004, 126,
478; h) T. A. Betley, J. C. Peters, J. Am. Chem. Soc. 2004, 126,
6252; i) W.-L. Man, G. Chen, S.-M. Yiu, L. Shek, W.-Y. Wong, W.-
T. Wong, T.-C. Lau, Dalton Trans. 2010, 39, 11163; j) M. G.
Scheibel, B. Askevold, F. W. Heinemann, E. J. Reijerse, B.
de Bruin, S. Schneider, Nat. Chem. 2012, 4, 552; k) M. G.
Scheibel, Y. Wu, A. C. Stꢁckl, L. Krause, E. Carl, D. Stalke, B.
de Bruin, S. Schneider, J. Am. Chem. Soc. 2013, 135, 17719.
[14] Formation of ammonia derived from the nitride complexes
formed via reductive cleavage of dinitrogen has been reported:
a) M. M. Rodriguez, E. Bill, W. W. Brennessel, P. L. Holland,
Science 2011, 334, 780; b) T. J. Hebden, R. R. Schrock, M. K.
Takase, P. Mꢁller, Chem. Commun. 2012, 48, 1851.
[12] See the Supporting Information for details.
[13] a) D. C. Ware, H. Taube, Inorg. Chem. 1991, 30, 4605; b) H.-W.
Lam, C.-M. Che, K.-Y. Wong, J. Chem. Soc. Dalton Trans. 1992,
1411; c) K. D. Demadis, T. J. Meyer, P. S. White, Inorg. Chem.
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