Transition metal-mediated reductive coupling of diazoesters

Article abstract of DOI:10.1039/c9cc03771c

The first transition metal mediated reductive coupling of diazoesters through the terminal nitrogens is reported. The resulting tetrazene-bridged bis(diazenylacetate) serves as a novel dinucleating ligand to iron(III). DFT calculations suggest that the re

Full text of DOI:10.1039/c9cc03771c

View Article Online
View Journal
ChemComm
Chemical Communications
Accepted Manuscript
This article can be cited before page numbers have been issued, to do this please use: S. Groysman, A.
Grass, S. A. Stoian and R. L. Lord, Chem. Commun., 2019, DOI: 10.1039/C9CC03771C.
Volume 54
This is an Accepted Manuscript, which has been through the
Number
January 2018
Pages 1-112
1
4
Royal Society of Chemistry peer review process and has been
accepted for publication.
ChemComm
Chemical Communications
rsc.li/chemcomm
Accepted Manuscripts are published online shortly after acceptance,
before technical editing, formatting and proof reading. Using this free
service, authors can make their results available to the community, in
citable form, before we publish the edited article. We will replace this
Accepted Manuscript with the edited and formatted Advance Article as
soon as it is available.
You can find more information about Accepted Manuscripts in the
Information for Authors.
Please note that technical editing may introduce minor changes to the
text and/or graphics, which may alter content. The journal’s standard
Terms & Conditions and the Ethical guidelines still apply. In no event
shall the Royal Society of Chemistry be held responsible for any errors
or omissions in this Accepted Manuscript or any consequences arising
from the use of any information it contains.
ISSN 1359-7345
COMMUNICATION
S. J. Connon, M. O. Senge et al.
Conformational control of nonplanar free base porphyrins:
towards bifunctional catalysts of tunable basicity
rsc.li/chemcomm

Please do not adjust margins
Page 1 of 5
ChemComm
View Article Online
DOI: 10.1039/C9CC03771C
COMMUNICATION
Transition metal-mediated reductive coupling of diazoesters
Amanda Grass,a Sebastian A. Stoian,b Richard L. Lord,c*, and Stanislav Groysman*a
Received 00th January 20xx,
Accepted 00th January 20xx
DOI: 10.1039/x0xx00000x
Ad
The first transition metal mediated reductive coupling of
diazoesters through the terminal nitrogens is reported. The
resulting tetrazene-bridged bis(diazenylacetate) serves as a novel
dinucleating ligand to iron(III). DFT calculations suggest that the
reductive coupling takes place via a κ2 intermediate, which
induces significant radical character on the terminal nitrogen.
CPh2
N
N
N
N
N
2 Ph2CN2
MgII
2 N3Ad
MgII
]
[
MgI
[
]
[
]
MgI
[ ]
N
N
MgII
N
MgII
[
]
[
]
N
Mg
[
] = Mg-nacnac
N
CPh2
Ad
- N2
2009
ACIE
, 48, 2973.
CPh2
N
Diazoalkanes [NNCR1R2] are among the most important
nitrogen-containing reactive molecules employed in the
transition metal catalysis.1 The reactivity mode of the
coordinated diazoalkane is often determined by the
stereoelectronic nature of the transition metal complex.1 The
most common reactivity route exhibited by diazoalkane
[NNCR1R2] is the formation of carbene [CR1R2], concurrent with
N2 elimination.1,2 As a result, diazoalkanes are frequently used
as carbene precursors in cyclopropanation, carbene insertion
into C-H bonds, and other C-C bond forming reactions.3
However, coordinated diazoalkane can also follow other
reactivity routes, most involving diazoalkane carbon or R1/R2
groups, including nucleophilic addition, substitution, and
deprotonation.1 Reductive coupling of diazoalkanes through
carbons has been reported as well.4 In contrast, reductive
coupling of diazoalkanes through the terminal nitrogens has
not been reported in the transition metal realm, although
Stephan and coworkers have very recently described reductive
coupling of diphenyldiazomethane using a strongly reducing
main group synthon, Mg(I)-nacnac (Scheme 1, top).5, 6 The
initially formed product of the reductive coupling of
diphenyldiazomethane with Mg(I) synthon (featuring four-
O2
N
MgII
CPh2
[
]
MgII
[ ]
MgII
]
Ph2C
+ [
N
N
2018
, 24, 8589.
Chem. Eur. J.
CPh2
CPh2
{Fe}
t
Fe
{
} = Fe(OC Bu2Ph)
N2CPh2
Ad
N
- N2
?
N
N
FeIII
{
}
2 Ph2CN2
2 N3Ad
FeII
N
N
CPh2
}
2 {
}
N
N
Ph2C
FeIII
{
}
N
FeII
-{
?
CPh2
N
Ad
CPh2
2013
Inorg. Chem.
, 52, 12335.
FeIII
N
{
- N2
{
}
N
FeIII
FeIII
}
{
}
N
FeIII
{
}
N
N
CPh2
CPh2
Scheme 1. Top: MgI-nacnac-promoted reductive coupling reactions of an organoazide
(right) and diphenyldiazoalkane (left). Bottom: Fe(OR)2-promoted reductive coupling of
AdN3 (right) and possible (two-electron and one-electron) mechanisms for the
formation of benzophenone azine (left).
membered
triazenido
chelates)
underwent
slow
decomposition at room temperature to give bridging imido
complex ([(nacnac)Mg(NCPh2)]2) and dinitrogen; subsequent
oxidation produced benzophenone azine Ph2CNNCPh2. We
have recently reported that cobalt(II) bis(alkoxide) complex
a. Department of Chemistry, Wayne State University, 5101 Cass Ave. Detroit MI
48202. E-mail: groysman@chem.wayne.edu
7
Co(OR)2(THF)2 (OR = OCtBu2Ph) formed isolable high-valent
cobalt-carbene
Co(OR)2(=CPh2)
upon
the
reaction
iron analogue
with
b. Department of Chemistry, University of Idaho, 875 Perimeter Dr, Moscow ID
83843.
diphenyldiazomethane,8
while
c.
Department of Chemistry, Grand Valley State University, 1 Campus Dr., Allendale,
9
Fe(OR)2(THF)2
yielded benzophenone azine and an
MI 49401. E-mail: lordri@gvsu.edu
unidentified metal product.8 Whereas formation of
benzophenone azine via a
Electronic Supplementary Information (ESI) available: Experimental procedures, X-
ray data collection/refinement details, NMR/IR/UV-is spectra, and computational
details. See DOI: 10.1039/x0xx00000x
Please do not adjust margins

Please do not adjust margins
ChemComm
Page 2 of 5
COMMUNICATION
Journal Name
Ar
C
View Article Online
DOI: 10.1039/C9CC03771C
R'O
RO
OR
FeIII
Ar
C
O
N
N
N2
C
THF
FeII
THF
CO2R'
N
N
O
FeIII
1/2
hexane, RT
RO
C
OR
OR
RO
OR'
C
1
2 4
-
2: Ar = Ph
R' = Me
Ar
3: Ar = Ph
R' = Et
4: Ar = p-Br-Ph
hexane
or C6D6,
RT
Ph
Ph
N2
C
R' = Et

- 1/2 N2
Ph
Ph
C(O)OR'
Ar
Ph
N
C
Ar
C
N
C
C
N
N
Ph
R'O(O)C
identified by GC-MS
Scheme 2. Reactions of Fe(OR)2(THF)2 with diphenyl diazomethane and aryl diazoesters
described in this manuscript.
Figure 1. Structure of complex 2, [Fe2(μ-κ2:κ2-MeO2CC(Ph)NNNNC(Ph)CO2Me)(OR)4],
50% probability ellipsoids.19 H atoms and co-crystallized ether molecule are omitted for
clarity. Selected bond distances (Å) and angles (º): Fe – O1 1.785(1); Fe – O2 1.783(1),
Fe – O3 2.002(1), 2.034(1), O3 – C1 1.249(2), C1 – C2 1.436(2), C2 – N1 1.333(2), N1 –
N2 1.308(2), N2 – N2’ 1.394(2), O2 Fe O1 119.29(5), O2 – Fe – N1 114.71(5), O1 – Fe1 –
N1 123.36(5), O3 – Fe – N2 82.01, O3 – Fe – O2 102.90(5), O3 – Fe – O1 100.89(5).
metal-carbene intermediate is feasible (particularly given the
related Co chemistry), another route to the azine product can
also be envisioned, i.e. an FeII-promoted reductive coupling,
followed by an FeIII-promoted oxidation (Scheme 1, bottom).
This postulate would be consistent with the fact that
Fe(OR)2(THF)2 reductively couples azides to give an hexazene
complex,9a similarly to MgI(nacnac)6 (Scheme 1). We have also
described formation of reactive [Co(OR)2(CPh(CO2Me))]
intermediate via the reaction of Co(OR)2(THF)2 with diazoester
N2C(Ph)(CO2Me) (methyl phenyldiazoacetate).10 Herein we
demonstrate that changing the metal in M(OR)2(THF)2 to Fe
leads to a dramatic change in the reactivity of the coordinated
diazoester to the reductive coupling. Coupling of the iron-
ligated diazoesters through the terminal nitrogens affords a
new dinucleating tetrazenediacetate ligand, in which each iron
is ligated by the N,O-diazenylacetate chelate. Structural,
spectroscopic and computational studies are presented.
The reaction of Fe(OR)2(THF)2 (1) with one equivalent of
diphenyldiazomethane produced benzophenone azine in high
yield (Scheme 2). The reaction of sub-stoichiometric amounts
of Fe(OR)2(THF)2 with diphenyldiazomethane also led to its full
conversion to the corresponding azine (see SI for details),
suggestive of the catalytic process via an [FeII(OR)2]
intermediate, albeit we were not able to observe directly any
such intermediates. To shed light on the reactivity of iron
bis(alkoxide) with diazo compounds, we turned our attention
to diazoesters. Treatment of the pale yellow solution of 1 in
hexane with the yellow solution of methyl phenyldiazoacetate
N2C(Ph)(CO2Me) in hexane led to the immediate color change
to brown that transitioned to burgundy within 10 minutes; no
gas evolution was observed. Subsequent work-up and
recrystallization yielded purple crystals of 2, whose identity is
confirmed by X-ray crystallography. Similarly, treatment of 1
were too unstable to allow high-quality X-ray structure
determination, their identity is strongly supported by the
elemental analyses, as well as by the similarity of their IR, UV-
vis and Mössbauer spectra to the corresponding spectra of
complex 2 (see SI).
X-ray structure determination of 2 revealed a di-iron
complex bridged by a tetrazene-linked dinucleating ligand [μ-
κ2:κ2-MeO2CC(Ph)NNNNC(Ph)CO2Me] (Figure 1), that results
from the reductive coupling of diazoesters via terminal
nitrogens. The coordination environment around each iron is
distorted trigonal monopyramidal, featuring two monodentate
alkoxides, and the N,O-diazenylacetate chelate. The structure
is centrosymmetric, with half a molecule occupying the
asymmetric unit. Iron-oxygen bond distances suggest an
iron(III)
oxidation
state,
indicating
that
the
[MeO2CC(Ph)NNNNC(Ph)CO2Me] ligand is
a
dianion.
Comparison of the intraligand [ONNNNO] bond distances (see
Figure 1) with the corresponding bond distances in free
diazoalkane11 points to significant electron delocalization
within the chelate rings. Whereas the central N-N bond
distance (1.394(2) Å) appears close to a single bond, the
planarity of the ligand suggests electron delocalization
between the O,N-chelates. We also note that while the overall
ligand structure, resulting from the reductive coupling of the
diazoester, is new,12 it is related to the dinucleating hexazene
ligand, which results from the reductive coupling of
organoazides.6, 9, 13, 14
The IR spectra of the compounds 2-4 are similar,
demonstrating prominent signals around 1555, 1260, 1150 and
1005 cm-1, suggestive of the C=O ester, tetrazene N-C/N-N,
and alkoxide C-O stretching vibrations (Figure S1-S4). This
with
ethyl
phenyldiazoacetate
or
ethyl
(4-
bromophenyl)diazoacetate yields purple crystals of
compounds 3 and 4. While the crystals of compounds 3 and 4
2 | J. Name., 2012, 00, 1-3
This journal is © The Royal Society of Chemistry 20xx
Please do not adjust margins

Page 3 of 5
ChemComm
Please do not adjust margins
Journal Name
COMMUNICATION
assignment relies on previously reported IR spectra of the diazoester is significantly slower due to the chelating
View Article Online
tetrazene complexes,15 and the recent combined spectroscopic nature of the intermediate.
DOI: 10.1039/C9CC03771C
and computational investigation of the IR spectra of related
N2
Ph
hexazene complexes.16 DFT calculations17 support these
MeO
MeO
assignments, with calculated stretches at 1570, 1335, 1224,
and 1060 cm–1 for these motions that have significant intensity
Ph
N
O
O
N
(Figure S21). The UV-vis spectra for 2-4 (see SI) all
demonstrate a peak at 516 nm.
HSMII
RO
HSMIII
OR
OR
RO
Inspection of the zero-field 57Fe Mössbauer spectrum
recorded at 80 K of a neat powder sample of 2 reveals a well-
defined quadrupole doublet that accounts for ~97% of the iron
present in the sample. This doublet has parameters, δ =
0.55(1) mm/s and EQ = 2.52(3) mm/s, that are very similar to
those observed for Fe(OR’)(ArNNNNAr), δ = 0.49 mm/s and
EQ = 2.20 mm/s (where R’ = CtBu2(3,5-Ph2Ph) and Ar =
MeOPh, 3,5-Me2Ph).18 The latter values were shown to
originate from high-spin iron(III) ions of complexes for which
the S = 5/2 iron spin is antiferromagnetically coupled to the S =
1/2 of an anionic tetrazene ligand. Thus, this similarity clearly
indicates that the two iron sites of 2 also adopt a high-spin
ferric configuration. However, the resonances observed for 2
are considerably broader than those of Fe(OR’)(ArNNNNAr)
(L/R = 0.68/0.75 mm/s vs  = 0.33 mm/s). The spectra of 3 and
4 (SI) exhibit very similar spectral parameters to the spectrum
of 2 (Table S8). While the increased linewidth might be
indicative of structural heterogeneities, it might also originate
from unresolved magnetic hyperfine splitting. Further studies
are being undertaken to delineate these effects.
1.43
0.00
Fe
Co
0.00
5.30
G‡ = 29.33
G‡ = 37.02


– N2
Ph
OR
O
RO
MeO
O
N
HSMIII
Ph
O
N
MeO
1/2
N
N
HSMIII
M
OR
RO
OMe
RO
OR
Ph
–11.35
–3.54
–12.93
–0.73
Figure 3. Summary of Gibbs free energies (kcal/mol) for N2 loss vs. reductive coupling
pathways for iron (red) and cobalt (blue). The energy for the reductively coupled
product is presented per metal equivalent.
Computational studies were conducted to understand the
origins of the divergent reactivity between Fe (reductive
coupling) and Co (carbene formation); key results are
presented in Figure 3. DFT calculations on the methyl
phenyldiazoacetate adduct suggest the quintet state is lowest
0
in energy and corresponds to
a
high-spin FeIII ion
10
antiferromagnetically coupled to a diazoester anion radical
(Figure S18); the κ2-adduct is slightly more stable than the κ1-
adduct for Fe. Reduction of the diazoester, which occupies an
N–N * orbital, and formation of the six-membered
metallacycle stabilizes this species toward N2 expulsion. The
barrier to N2 expulsion is calculated to be 29.3 kcal/mol and
the reaction to form the quintet iron carbene is exergonic by
11.4 kcal/mol. Reductive coupling to form 2 from two of these
adducts is exergonic by –25.9 kcal/mol. This species is
calculated to be a ferromagnetically coupled S = 5 state with
two high-spin FeIII ions (see Table S4 for alternative spin
states). Coupling of the diazoester radicals is predicted to have
no enthalpic barrier on both surfaces (Figure S19). Using the
entropy loss for formation of 2 from two diazo adducts places
an upper limit on the entropic barrier of ~17 kcal/mol, much
lower than the calculated barrier for N2 loss. A comparison to
cobalt (Figure 3) illuminates why we did not observe this
coupled product for that metal.10 Formation of the 2 product,
which has reduced diazoester and HSCoIII is disfavored, as
compared to Fe, due to the lower reducing potential of
Co(OR)2.7 We hypothesize that this unfavorable equilibrium,
which must be overcome for two equivalents before reductive
coupling can occur, makes N2 loss and carbene formation
-4
-2
0
2
4
velocity [mm/s]
Figure 2. 57Fe Mössbauer spectrum recorded in zero field at 80 K for 2 and simulation
(red trace).
The stability of complex 2 was investigated. A stirred
solution of 2 (0.178 mM) slowly decayed at room temperature,
demonstrating a color change from purple to dark-brown.
Monitoring the decomposition reaction by UV-vis showed
gradual disappearance of the peak at 516 nm (2), while a new
peak at 378 nm grows in (see SI for details); approximately
20% of 2 remains after 5 days. The decomposition reaction
followed first order, with k = 4×10-6 s-1. Heating the solution of
2 to 50 °C overnight led to full decomposition, producing a
yellow-brown solution. Whereas 1H NMR of the resulting
solution contains only broad resonances, the GC-MS spectrum
contains the corresponding azine, free diazoalkane, and the
alkoxide ligand. No olefin was observed in GC, suggesting,
albeit indirectly, that no carbene forms in the reaction.10 These
results are consistent with the eventual decomposition of the
tetrazene-bridged bis(diazenylacetate) species to produce
azine, as could be proposed by the Fe(OR)2-catalyzed reaction
with diphenyldiazoalkane; we hypothesize that the reaction of
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 3
Please do not adjust margins

Please do not adjust margins
ChemComm
Page 4 of 5
COMMUNICATION
Journal Name
Doyle), John Wiley & Sons, 2013, Chapter 15, 491–525. (d) C.
competitive as compared to iron. Unlike iron, cobalt is also
predicted to favor carbene formation over reductive coupling.
In conclusion, we have demonstrated that iron(II)
bis(alkoxide) complex Fe(OR)2(THF)2 reductively couples
methyl phenyldiazoacetate through the terminal nitrogens to
afford a dinuclear product featuring dinucleating tetrazene-
bridged bis(diazenylacetate) ligand. Spectroscopic, structural,
and computational studies indicate two high-spin iron(III)
centers coordinated by a monoanionic 2-diazenylacetate
chelate each. DFT suggests that reductive coupling takes place
via a κ2-bound diazoester that develops significant radical
character at the terminal nitrogen. This behavior stands in
contrast to the related cobalt complex that undergoes N2
expulsion and carbene formation, in part due to the preferred
κ1-bound diazoester. This work provides insight into the
reactivity of Fe(OR)2(THF)2 with diazoalkanes, and gives
another example of the unique “metalloradical” nature of
[Fe(OR)2]. Our future studies will focus on the exploration of
the reductive coupling of additional substrates using uniquely
mild yet powerful one-electron reagent Fe(OR)2(THF)2.
te Grotenhuis and B de Bruin, Synlett, 2018, 29,V2ie2w3A8rt–ic2le2O5n0li;ne
DOI: 10.1039/C9CC03771C
(e) N. M. G. Franssen, A. J. C. Walters, J. N. H. Reek and B. de
Bruin, Catal. Sci. Technol., 2011, 1, 153-165.
4
(a) T. Aoshima, T. Tanase, Y. Mizobe, Y. Yamamoto and M.
Hidai, J. Chem. Soc., Chem. Commun., 1992, 586-588; b) C. J.
Pickett, J. E. ToIhurst, A. Copenhaver, T. A. George and R. K.
Lester, J. Chem. Soc., Chem. Commun., 1982, 1071-1072; c) J.
J. Curley, T. Murahashi and C. C. Cummins, Inorg. Chem.,
2009, 48, 7181–7193.
5
6
7
J. Zhou, L. L. Liu, L. L. Cao and D. W. Stephan, Chem. Eur. J.,
2018, 24, 8589-8595.
S. J. Bonyhady, S. P. Green, C. Jones, S. Nembenna and A.
Stasch, Angew. Chem. Int. Ed., 2009, 48, 2973-2977.
(a) J. A. Bellow, D. Fang, N. Kovacevic, P. D. Martin, J.
Shearer, G. A. Cisneros and S. Groysman, Chem. Eur. J., 2013,
19, 12225-12228; b) J. A. Bellow, M. Yousif, D. Fang, E. G.
Kratz, G. A. Cisneros and S. Groysman, Inorg. Chem., 2015,
54, 5624-5633.
J. A. Bellow, S. A. Stoian, J. Van Tol, A. Ozarowski, R. L. Lord
and S. Groysman, J. Am. Chem. Soc., 2016, 138, 5531-5534.
(a) J. A. Bellow, P. D. Martin, R. L. Lord and S. Groysman,
Inorg. Chem., 2013, 52, 12335 -12337. (b) J. A. Bellow, M.
Yousif, A. C. Cabelof, R. L. Lord and S. Groysman,
Organometallics., 2015, 34, 2917-2923.
8
9
10 A. Grass, N. S. Dewey, R. L. Lord and S. Groysman,
Organometallics, 2019, 38, 962-972.
11 I. V. Shishkov, F. Rominger and P. Hofmann, Organometallics,
2009, 28, 1049-1059.
Acknowledgements
12 Based on Cambridge Structural Database search, accessed on
April 10, 2019.
S.A.S acknowledges partial support from the University of
Idaho. We thank Dr. Andrew Ozarowski at NHMFL and Prof.
Yisong Guo at CMU for recording the Mössbauer data. NHMFL
is supported by the NSF Cooperative Agreement No. DMR-
1157490 and the State of Florida. S.G. and R.L.L. are grateful to
the National Science Foundation (NSF) for current support
under grant number CHE-1855681. A.G. is a Rumble fellow.
13 (a) R. E. Cowley, J. Elhaïk, N. A. Eckert, W. W. Brennessel, E.
Bill and P. L. Holland, J. Am. Chem. Soc., 2008, 130, 6074-
6075; (b) R. E. Cowley, N. J. DeYonker, N. A. Eckert, T. R.
Cundari, S. DeBeer, E. Bill, X. Ottenwaelder, C. Flaschenriem
and P. L. Holland, Inorg. Chem., 2010, 49, 6172-6187.
14 S. Gondzik, S. Schulz, D. Bläser, C. Wölper, R. Haack and G.
Jansen, Chem. Commun., 2014, 50, 927-929.
15 (a) W. H. Monillas, G. P. A. Yap and K. H. Theopold, Inorg.
Chim. Acta, 2011, 369, 103-119; (b) G. R. Elpitiya, B. J.
Malbrecht and D. M. Jenkins, Inorg. Chem., 2017, 56, 14101-
14110; c) S. Vanicek, M. Jochriem, C. Hassenrück, S. Roy, H.
Kopacka, K. Wurst, T. Müller, R. F. Winter, E. Reisner and B.
Bildstein, Organometallics, 2019, 38, 1361–1371; (d) P.
Overbosch, G. Van Koten, A. L. Spek, G. Roelofsen and A. J.
M. Duisenberg, Inorg. Chem., 1982, 21, 3908-3913; (e) R. E.
Cowley, E. Bill, F. Neese, W. W. Brennessel and P. L. Holland,
Inorg. Chem., 2009, 48, 4828–4836; f) T. Gehrmann, J. L.
Fillol, H. Wadepohl and L. H. Gade, Organometallics, 2012,
31, 4504−4515.
16 C. Stienen, S. Gondzik, A. Gehlhaar, R. Haack, C. Wölper, G.
Jansen and S. Schulz, Organometallics, 2016, 35, 1022-1029.
17 BP86-D3/def2-SVP optimized structures with harmonic
frequencies. See SI for a full description of the computational
details.
Conflicts of interest
There are no conflicts to declare.
Notes and references
1
2
(a) W. A. Herrmann, Angew. Chem. Int. Ed. Engl., 1978, 17,
800; (b) Y. Mizobe, Y. Ishii and M. Hidai, Coord. Chem. Rev.,
1995, 139, 281-311; (c) M. Dartiguenave, M. J. Menu, E.
Deydier, Y. Dartiguenave and H. Siebald, Coord. Chem. Rev.,
1998, 178-180, 623-663. (d) P. de Frémont, N. Marion and S.
P. Nolan, Coord. Chem. Rev., 2009, 253, 862−892.
For selected recent examples, see: (a) R. Cohen, B.
Rybtchinski, M. Gandelman, H. Rozenberg, J. M. L. Martin
and D. Milstein, J. Am. Chem. Soc., 2003, 125, 6532-6546; (b)
S. C. Bart, A. C. Bowman, E. Lobkovsky and P. J. Chirik, J. Am.
Chem. Soc., 2007, 129, 7212-7213; (c) M. E. Reesbeck, K.
Grubel, D. Kim, W. W. Brennessel, B. Q. Mercado and P. L.
Holland, Inorg. Chem., 2017, 56, 1019-1022; (d) A. Pereira, Y.
Champouret, C. Martin, E. Alvarez, M. Etienne, T. R.
Belderrain and P. J. Perez, Chem. Eur. J., 2015, 21, 9769-
9775; (e) B. J. Barret and V. M. Iluc, Organometallics, 2017,
36, 730-741.
18 M. Yousif, D. Wannipurage, C. D. Huizenga, E. Washnock-
Schmid, N. J. Peraino, A. Ozarowski, S. A. Stoian, R. L. Lord
and S. Groysman, Inorg. Chem., 2018, 57, 9425-9438.
19 CCDC 1915378 contains the supplementary crystallographic
data for this paper. These data are provided free of charge
by The Cambridge Crystallographic Data Centre.
3
(a) M. P. Doyle, R. Duffy, M. Ratnikov and L. Zhou, Chem.
Rev., 2010, 110, 704–724; (b) Y. Xia, D. Qiu and J. Wang,
Chem. Rev. 2017, 117, 13810–13889; (c) X. Cui and X. P.
Zhang, “Cobalt-Mediated Carbene Transfer Reactions”, in
Contemporary Carbene Chemistry (Eds.: R. A. Moss, M. P.
4 | J. Name., 2012, 00, 1-3
This journal is © The Royal Society of Chemistry 20xx
Please do not adjust margins

Page 5 of 5
ChemComm
View Article Online
DOI: 10.1039/C9CC03771C
TOC graphic and abstract
Ph
Ph
C
MeO
C
RO
OR
FeIII
MeO
C
O
N
N
CO2Me
Ph
N
N
C
O
THF
FeII
THF
N2
C
N
O
FeIII
FeIII
RO
OR
N
C
RO
OR
OMe
RO
OR
C
Ph
The first transition-metal mediated reductive coupling of diazoesters is reported. The reaction proceeds
via a κ2-coordinated intermediate, featuring significant radical character on the terminal nitrogen.