Nucleophilic versus Electrophilic Reactivity of Bioinspired Superoxido Nickel(II) Complexes

Article abstract of DOI:10.1002/anie.201808085

The formation and detailed spectroscopic characterization of the first biuret-containing monoanionic superoxido-Ni^II intermediate [LNiO₂]^? as the Li salt [2; L=MeN[C(=O)NAr)₂; Ar=2,6-iPr₂C₆H₃)] is reported. It results from oxidation of the corresponding [Li(thf)₃]₂[LNi^IIBr₂] complex M with excess H₂O₂ in the presence of Et₃N. The [LNiO₂]^? core of 2 shows an unprecedented nucleophilic reactivity in the oxidative deformylation of aldehydes, in stark contrast to the electrophilic character of the previously reported neutral Nacnac-containing superoxido-Ni^II complex 1, [L′NiO₂] (L′=CH(CMeNAr)₂). According to density-functional theory (DFT) calculations, the remarkably different behaviour of 1 versus 2 can be attributed to their different charges and a two-state reactivity, in which a doublet ground state and a nearby spin-polarized doublet excited-state both contribute in 1 but not in 2. The unexpected nucleophilicity of the superoxido-Ni^II core of 2 suggests that such a reactivity may also play a role in catalytic cycles of Ni-containing oxygenases and oxidases.

Full text of DOI:10.1002/anie.201808085

A Journal of the Gesellschaft Deutscher Chemiker
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Accepted Article
Title: Nucleophilic vs Electrophilic Reactivity of Bioinspired Super-oxido
Nickel(II) Complexes
Authors: Chakadola Panda, Anirban Chandra, Teresa Corona, Erik
Andris, Bhawana Pandey, Somenath Garai, Nils Lindenmaier,
Silvio Kuenstner, Erik R Farquhar, Jana Roithova, Gopalan
Rajaraman, Matthias Driess, and Kallol Ray
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To be cited as: Angew. Chem. Int. Ed. 10.1002/anie.201808085
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Angewandte Chemie International Edition
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COMMUNICATION
Nucleophilic versus Electrophilic Reactivity of Bioinspired Super-
oxido Nickel(II) Complexes
a‡
b‡
b
c
d
Chakadola Panda, Anirban Chandra, Teresa Corona, Erik Andris, Bhawana Pandey, Somenath
Garai, Nils Lindenmaier, Silvio Künstner, Erik R. Farquhar, Jana Roithová,* Gopalan Rajaraman,*d
a
a
e
f
c,g
a
b
Matthias Driess,* and Kallol Ray*
Dedicated to Helmut Schwarz on the occasion of his 75th birthday
Abstract: The formation and detailed spectroscopic characterization
peroxido-metal species, have been synthesized as chemical
II
of the first biuret-containing monoanionic superoxido-Ni intermediate
models of O
2
-M intermediates, and their reactivity has been
-
[2]
[
LNiO
2
]
as Li salt 2 [L = MeN[C(=O)NAr)
2
; Ar = 2,6-iPr
2
C
6
H
3
)] is
intensively investigated. Whereas, mononuclear peroxido-metal
species are generally associated with oxidative nucleophilic
N. reactions (e.g. aldehyde deformylation), superoxido-metal
complexes are typically considered as electrophilic oxidants
leading to hydrogen-atom abstraction (HAT) from a C-H bond and
oxygen-atom transfer (OAT) to alkenes, phosphines or sulfides.
reported. It results from oxidation of the corresponding
II
[Li(thf)
3
]
2
[LNi Br
2
] complex M with excess H
2
O
2
in the presence of Et
3
-
The [LNiO
2
] core of 2 shows an unprecedented nucleophilic reactivity
in oxidative deformylation of aldehydes, in stark contrast to the
electrophilic character of the previously reported neutral Nacnac-
II
containing superoxido-Ni complex 1, [L’NiO
2
] (L’ = CH(CMeNAr)
2
).
However, very recently nucleophilic reactivity of a superoxido-
iron[ complex with aldehydes has also been demonstrated,
which supports the ascribed roles of superoxido-iron species as
3]
According to Density Functional Theory (DFT) calculations, the
remarkably different behaviour of 1 vs 2 can be attributed to their
different charges and a two-state reactivity, in which a doublet ground
[
4]
[5]
both electrophilic and nucleophilic reactants in biology. A
copper-superoxido complex[ also exhibited both nucleophilic and
electrophilic properties in a related study.
6]
state and
a nearby spin-polarized doublet excited-state both
contribute in 1 but not in 2. The unexpected nucleophilicity of the
II
superoxido-Ni core of 2 suggests that such a reactivity may also play
Superoxido-nickel complexes (Table S1) are also attractive
targets for biomimetic synthetic studies. Evidence has been
a role in catalytic cycles of Ni-containing oxygenases and oxidases.
accumulating that
2
O -Ni species participate in biological
[
7]
oxidations; for example in quercetin-2,4-dioxygenase. Lessons
learned from synthetic models can be useful to uncover structure-
reactivity relationships of respective metalloproteins. Indeed,
recent synthetic advances have led to the isolation and
characterization of a few well-characterized superoxido-nickel
model complexes, and all of them are capable of performing
2
Mononuclear dioxygen-metal species (O -M) have been
implicated as key intermediates in biocatalytic cycles of dioxygen
activation with heme and non-heme metalloenzymes.[1] A number
2
of metal complexes binding an O unit, such as superoxido- and
electrophilic oxidation reactions.[ In particular, the isolable side-
8]
II
[
[
a]
b]
Dr. C. Panda, Dr. S. Garai, Dr. N. Lindenmaier, Prof. Dr. M. Driess
Department of Chemistry, Metalorganics and Inorganic Materials
Technische Universität Berlin
Strasse des 17. Juni 135, Sekr. C2, 10623 Berlin (Germany)
E-mail: matthias.driess@tu-berlin.de
M. Sc. A. Chandra, Dr. T. Corona, Prof. Dr. K. Ray
Department of Chemistry, Humboldt-Universität zu Berlin, Brook-
Taylor-Strasse 2 12489 Berlin, Germany
on superoxido-nickel(II) complex [L’Ni O
2
] 1(Scheme 1), involving
a monoanionic β-diketiminate ligand L’, exhibited a dioxygenase-
like reactivity when exposed to para-substituted di-tert-
butylphenols,[
8c][9]
affording an unprecedented oxidation product
2
incorporating both oxygen atoms from a single O -Ni subunit. The
mechanism of this transformation is proposed to involve the
III
mediation of a oxido-Ni species formed via O–O bond homolysis
E-mail: kallol.ray@chemie.hu-berlin.de
II
of an arylperoxido-Ni intermediate; this parallels the generally
[
[
c]
d]
M. Sc. E. Andris, Prof. Dr. J. Roithová
Department of Organic Chemistry, Faculty of Science, Charles
University Hlavova 2030/8, 128 43 Prague 2 (Czech Republic)
B. Pandey, Prof. G. Rajaraman
accepted mechanism for metal-mediated activation of dioxygen to
generate high-valent oxido-metal units by O–O bond homolysis or
heterolysis of (hydro)peroxido-metal cores in various oxygenase
and oxidase enzymes.[
Department of Chemistry, Indian Institute of Technology Bombay,
Powai, Mumbai, Maharashtra,400 076 (India)
E-mail: rajaraman@chem.iitb.ac.in
10]
Nucleophilic reactivity of superoxido-Ni complexes is,
however, unprecedented in the literature. The recently
demonstrated ability of superoxido-Cu and -Fe species to
undergo a nucleophilic attack of the electrophilic carbonyl carbon
atom in aldehydes[3,4] raised the question whether or not such
reactivity could be realized with other superoxido-metal
complexes as well. In our continuous effort to uncover structure–
reactivity relationships of mononuclear dioxygen-metal
intermediates, we now report the synthesis and reactivity of the
[
[
[
e]
f]
M. Sc. S. Künstner
Berlin Joint EPR lab, Institute Nanospectroscopy, Helmholtz-
Zentrum Berlin für Materialien und Energie, Berlin, Germany
Dr. E. R. Farquhar
CWRU Center for Synchrotron Biosciences, NSLS-II, Brookhaven
National Laboratory Upton, NY, 11973 USA.
Prof. Dr. J. Roithová
g]
Institute for Molecules and Materials, Radboud University,
Heyendaalseweg 135, 6525 AJ Nijmegen, The Netherlands.
Email: Jana.Roithova@ru.nl
[
‡]
These authors have contributed equaly to this work
II
II
-
novel superoxido-Ni complex monoanion [LNi O
the biuret ligand L (generated from LH , Scheme 1). We show that
although the electronic structures of the O –Ni cores in 1 and 2
2
] in 2 based on
Supporting information for this article is given via a link at the end of
the document.
2
2
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Angewandte Chemie International Edition
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COMMUNICATION
II
can both be described in terms of the presence of a low-spin Ni
excess H
2
O
2
and Et
3
N in acetonitrile at 25°C to form a metastable
(
d8; SNi=0) ion bound to a S=1/2 superoxide (O
2
-•) anion radical,
yellowish-orange species 2 with a half-life (t1/2) of 30 min at 25°C.
they exhibit different reactivity patterns. Whereas, the neutral
superoxido-Ni complex 1 exhibits electrophilic HAT reactions with
substrates containing weak N-H/O-H bonds,[ monoanionic 2
performs nucleophilic attack to carbonyl carbons leading to
deformylation of aldehydes. In addition to the different charges of
The yellowish-orange color is associated with an UV-Vis
−
1
−1
absorption band at 455 nm (ε = 5900ꢀM ꢀcm ) with a shoulder
near 300 nm (Fig. 1). The nature of the yellow-orange species can
be established by a variety of spectroscopic techniques. ESI-MS
(Fig. S4) of 2 showed the existence of an intense peak at a mass-
9]
1
and 2, a two-state reactivity (TSR) model, in which a doublet
to-charge ratio (m/z) value at 539.3 whose mass and isotope
+
ground state and a nearby doublet excited-state both contribute,
provides a useful model for interpreting the reactivity trends of 1
vs 2.
distribution patterns correspond to {Li
introduction of 18O into 2 using H 18O
543.3 (Fig. S5), thereby demonstrating that two oxygen atoms
2
[LNiO
2
]} . Upon
2
2
, mass shifts from 539.3 to
The 2,6-diisopropylphenyl-substituted biuret LH
2
(Scheme 1
from H
2
18O
2
are incorporated into 2.
II
]2-, which is EPR silent, the X-band
and Scheme S1) was prepared by coupling of the dichloroformyl-
methylamine with two molar equivs. of 2,6-diisopropylaniline in
the presence of triethylamine (Et
amounts of the deprotonated biuret ligand L and NiBr
tetrahydrofuran (thf) afforded the blue [LNi Br
obtained as the dilithium salt [Li(thf)
CCDC 1832378). Complex M is paramagnetic with S = 1 (μeff
3
In contrast to [LNi Br
2
EPR spectrum of 2 at 10 K shows a slightly rhombic signal at
=2.21, g =2.17, and g =2.06 (Fig.1, inset). Spin quantification of
3
N). Reactions of equimolar
g
x
y
z
2-
2
(thf)1.5 in
the EPR signal can account for > 85ꢀ% of the total nickel spins
present in solution, thereby showing that 2 represents the major
II
]2- dianion, which is
2
II
II
]2- with H
−g
]
3 2
[LNi Br
2
] M (Scheme 1;
product of the reaction of [LNi Br
2
2
O
2
at 25°C. The
=
observed g-anisotropy (Δg = g
closely the Δg value of 0.12 determined for “free” O in water with
2
g = [2.10, 2.00, 1.98]. A larger Δg of 0.23 has, however, been
z
x
) of 0.15 resembles quite
-
•
.1 Bohr magnetons) in the electronic ground state, in accordance
8
II
[11]
with the presence of a tetrahedral (Td) coordinate d -Ni ion
(
Scheme 1). The starting materials LH
2
and M were characterized
previously noted for a superoxido-Ni(II) complex with the unpaired
1
2
[12]
by a number of spectroscopic techniques, including H-NMR
spectroscopy, electrospray ionization mass spectrometry (ESI-
MS), elemental analyses, UV-Vis and IR spectroscopy (Figs. S1-
S3).
electron located in the dz orbital of the Ni center. We therefore
conclude that the electronic structure of 2, like 1, is consistent with
a predominantly superoxide-centered radical (S = 1/2) coupled to
8
II
a square planar (SqP) low-spin d -Ni center. Notably, 1 exhibited
a lower Δg of 0.06.[ This could be correlated to the nature of
8c]

-
spin distribution at the ground state, with 1 exhibiting larger O
2
II
radical character with polarization of spins at Ni center (negative
-
spin density), while 2 exhibiting relatively less O
2
radical
II
character with delocalization of spin density at Ni as revealed by
density functional theoretical (DFT) calculations (see below).
II
II
2-
2
Scheme 1. Synthesis of the nickel(II) precursor complex [Li(thf)
3
]
2
[LNi Br
2
] (M)
Figure 1. UV-Vis spectral changes associated with the reaction of [LNi Br ]
2-
supported by a dianionic bidentate biuret ligand L and its reaction with
2 2 3 3
with excess H O and Et N to form 2 in CH CN at 25°C. In the inset is shown
the experimental (bold) and simulated (dotted) X-band EPR spectrum of a 2 mM
i
hydrogen peroxide and Et
3
N to yield 2; Ar = 2,6-Pr
2 6
C H
3
(top); the inset shows
the structure of 1. The molecular structure of M (bottom) determined by X-ray
solution of 2 in CH CN at 10K.
3
diffraction analysis.
The infrared photodissociation (IRPD) spectrum[ of the
13]
The typical synthesis of superoxido-nickel(II) intermediates
-
D
2
-tagged [LNiO
2
] anion (Fig. 2 left and Fig. S6) contains an
I
[8a,c,d]
involves the activation of dioxygen (O
2
) at Ni centers
or
−1
−1
oxygen sensitive band at 980 cm , which shifts to 932 cm upon
O labelling. The isotope shift of 48 cm agrees well with the
calculated (57 cm ) shift for a diatomic O-O bond stretching
reaction of NiII complexes with excess of hydrogen peroxide
18
−1
II
(H
2
O
2
) and Et
3
N.[8b] Consistent with its Ni assignment, complex
−1
2
M did not react with O , but was readily oxidized in presence of
-1
vibrational mode. Furthermore, the O-O vibration in 2 (980 cm )
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Angewandte Chemie International Edition
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COMMUNICATION
appears at similar energy to the side-on superoxido nickel
electrophiles. Thus, although 1 oxidised O–H and N–H groups
from various exogenous organic substrates, addition of
benzaldehyde to 1 did not result in any change in its UV-Vis
spectra.[ In contrast, 2 did not demonstrate any electrophilic HAT
reactivity towards the weak C-H bonds of dihydroanthracene or
O-H bonds of para-substituted di-tert-butylphenols. However, a
pseudo-first order decay of the absorption feature at 455 nm (Fig.
3) and the subsequent formation of acetophenone (75% yield; Fig.
S8A) and Ni(II) products (based on EPR (silent) and ESI-Mass
spectroscopic methods; Figure S8B) were observed upon
addition of 2-phenylpropionaldehyde (2-PPA) to a preformed
solution of 2 at 25°C. The rate constant increases proportionally
-
1
complex 1 (971 cm ). This, together with the similar EPR spectra
of 1 and 2, may also point to a side-on superoxido nature of 2.
Ni K-edge X-ray absorption spectroscopic studies were
performed to directly probe the Ni oxidation state and geometry in
9]
2
. Figure 2 (right) shows a comparison of the Ni K-edge spectrum
of 2 with its precursor M, as well as 1. Notably, both 1 and 2 show
an intense 1s-to-4p+ shakedown transition along the edge at
~
8338.5 eV that is not seen in M. Furthermore, the 1s-to-3d pre-
edges in 1 and 2, found at 8333.2 eV, are significantly weaker
than that of M (Epre-edge = 8333.25 eV). Both observations can be
attributed to a SqP coordination geometry of Ni in 1 and 2 vs the
Td symmetry of M.[ In addition, the absence of any pre-edge
14]
with the substrate concentration (Fig. S9), affording a second‐
II
−1 −1
shift in 1 and 2 compared with M is consistent with a Ni
2
order rate constant, k , of 0.00012ꢀM ꢀs at 25°C. Additional
assignment for both complexes, corroborating our EPR analysis.
Extended X-ray absorption fine structure (EXAFS) analysis of M
reveals retention of the 4-coordinate XRD structure in solution
mechanistic studies with para-substituted benzaldehydes (para‐
Y‐C
7
H
5
O; Y = tBu, Me, H, Cl,) reveal a good linear correlation of
+
the rate to the σ
P
values of the para substituents (Fig. S10). A
(
Fig. S7, Table S2a) with two Ni-N/O scatterers @ 1.93 Å and two
positive Hammett ρ value of +0.44 is obtained, which supports the
nucleophilic character of the [Ni O ] core in 2 in the oxidation of
2
II
-• -
Ni-Br scatterers @ 2.40 Å. The Fourier transform of the EXAFS
of 2 shows loss of the dominant Ni-Br scattering seen in M at r =
benzaldehydes. To our knowledge, 2 is the only example of a
superoxido-metal complex that shows any reactivity with para-
substituted benzaldehydes. The nucleophilicity of 2 is also
demonstrated by its ability to undergo reaction with cyclohexane-
carboxaldehyde (CCA) to afford cyclohexane-carboxylic acid in
76% yields (Fig. S11).
2
.1 Å along with a shift to lower r for the putative Ni-N/O shell
around r = 1.5 Å (Fig. S7). This is consistent with the near-
stoichiometric conversion of M to 2 upon reaction with H
O .
2 2
Analysis of the EXAFS data of 2 (Fig. S7; Table S2b) shows a
best fit of four N/O scatterers at 1.85 Å, which is comparable to
the average Ni-N/O distance of 1.838 (2) Å of 1.[8c]
DFT calculations were performed in order to understand the
contrasting reactivity patterns of neutral 1 and monoanionic 2 (see
Supporting Information) complexes. 1 has two low lying S = 1/2
2
II
states (Fig. 4). The ground state (GS), 1als, has low-spin ls-Ni
and the unpaired electron is mostly localized on the O
2
ligand. The
2
first excited state (ES), 1ahs, arises from an antiferromagnetic
II
-
coupling between the S = 1 high-spin hs-Ni and the S = 1/2 O
2
II
centers. In addition, a ferromagnetic coupling between the hs-Ni

-
4
and the S = 1/2 O
4
2
centers results in an S = 3/2 ( 1ahs) ES (Fig.
). The 1ahs (21ahs) states lie at 25.1 (36.3) kJ mol higher in
4
-1
2
2
energy relative to the 1als GS. The 1als state features short Ni-
O (1.89 Å) and Ni-N (1.87 Å) distances, in good agreement with
the experiment (Fig. 4, Table S3). In contrast, the presence of
II
]- complex anion (m/z 525,
Figure 2. Left: D
grey trace) and 18O-labeled [LNi O
with the ISORI instrument; right) Ni K-edge XANES spectra of 1 (solid line), 2
dash-dotted line) and M (dotted line) in frozen CH CN solutions at 4K.
2
-tagging IRPD spectra of [LNi O
2
II
-
2
] complex (m/z 529, black trace) recorded
2
2
2
II
x z
unpaired electrons in the d -y and d orbitals of the S = 1 Ni ion
(
3
makes the O
2
binding unfavorable, resulting in relatively longer
2
Ni-O distances in the 1ahs state (Fig. 4, Table S3). As expected,
II
2
the geometry around the Ni center is SqP in 1als but Td in the
2
2
1ahs state. Thus, although 1als is assigned as the ground state,
the calculated low energy of the 2,41ahs states would suggest that
both of these spin-states are accessible for reactivity. Notably, the
21
ahs state is associated with a large negative spin-density at the
oxygen atoms; furthermore, it involves greater charges both at the
oxygen and the NiII sites compared to the 21als state. As
demonstrated previously by one of us,[ such a spin-polarized
electronic structure in superoxido-metal species may lead to
electrophilic reactivity. Thus, a two-state mechanism is proposed
15]
2
in 1, with the excited 1ahs state being responsible for the
electrophilic reactivity.
2
For monoanionic 2, the calculated ground state is also 2als
,
Figure 3. Absorption spectral changes associated with the reaction of a 1 mM
solution of 2 in CH CN with PPA (25 mM) at 25°C. In the inset is shown the time
trace of the decay of the 455 nm band (black squares) corresponding to 2 and
with the Ni-O (1.88 Å) and Ni-N (1.86 Å) distances in good
agreement with the EXAFS data (Fig. 4, Table S3). However, the
stronger electron donation from the dianionic biuret ligand L
3
the pseudo-first order fitting (solid line).
II
destabilizes the dx2-y2 and dz2 orbitals of the S = 1 Ni ion, which
makes the spin-polarized 22ahs state extremely high-lying in
energy (+63.2 kJ mol-1 relative to 2als) and hence is unlikely to
2
Usually, the superoxido-nickel(II) cores act as strong
electrophiles and are typically unreactive towards other
4
be relevant for the reactivity of 2. In addition, the 2ahs state is also
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Angewandte Chemie International Edition
10.1002/anie.201808085
COMMUNICATION
very high in energy (see Fig. 4). Thus in the absence of any low
established for oxido-metal complexes,[17] may also provide a
framework for understanding the reactivity of superoxido-metal
species.
lying excited states, the reactivity of 2 likely occurs solely at the
2
2
ground 2als state. Furthermore, the oxygen atoms in the 2als
2
state carry higher negative charge than in the 1als state, as
evident from the Natural Population Analysis (Fig. S13). This
explains the higher nucleophilicity of 2 relative to 1 in presence of
added electrophiles.
Acknowledgements
We thank the Deutsche Forschungsgemeinschaft (UniCat;
EXC 314-2 and Heisenberg Professorship to KR) and
European Research Council (ERC CoG No. 682275) for
financial support. CP and TC gratefully acknowledge the
Alexander von Humboldt Foundation for postdoctoral
fellowships. XAS experiments were performed at SSRL
beamline 4-1 (SLAC National Accelerator Laboratory,
USA) benefited from support of the US DOE Office of
Science (DE ‐ AC02 ‐ 76SF00515) and the US NIH
(
P30‐EB‐009998 and P41‐GM‐103393). TC also
thanks the COST Action CM1305 (ECOSTBio) for a STSM
grant (COST-STSM-CM1305-39979).
Keywords: β-diketiminate • biuret • oxido-metal species
•nucleophilic oxidation • two state reactivity
[
[
1] a) K. Ray, F. F. Pfaff, B. Wang, W. Nam, J. Am. Chem. Soc. 2014, 136,
3942-13958; b) W. Nam, Acc. Chem. Res. 2007, 40, 465-465 (and
1
references therein).
-
1
Figure 4. Relative energies (kJ mol ) of the DFT-derived ground- and excited-
states of 1 and 2, respectively, along with the optimized geometries and spin-
2] a) S. Yao, M. Driess, Acc. Chem. Res. 2012, 45, 276-287; b) A. Bakac,
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Shearer, R. C. Scarrow, J. A. Kovacs, J. Am. Chem. Soc. 2002, 124,
density (positive: black, negative: grey) plots of 21als ( 1ahs) and 2als ( 2ahs
2
2
2
)
states (see also Fig. S12).
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E. I. Solomon, W. Nam, Nat. Commun. 2014, 5, 5440; g) J. Cho, J. Woo,
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In conclusion, the contrasting reactivity of putative
superoxido-nickel(II) intermediates in bio-relevant oxidation
reactions is strongly dependent on subtle electronic changes as
shown for 1 and 2. The unexpected nucleophilicity of the
II
superoxido-Ni core in 2 suggests that such a reactivity may also
[3] S. Kundu, E. Matito, S. Walleck, F. F. Pfaff, F. Heims, B. Rábay, J. M. Luis,
A. Company, B. Braun, T. Glaser, K. Ray, Chem. Eur. J. 2012, 18, 2787-
play a role in catalytic cycles of Ni-containing oxygenases and
oxidases. Furthermore, the contrasting reactivity of 1 and 2 can
be explained by results of DFT calculations. Notably, an identical
GS has been predicted for both 1 and 2 in spite of their different
charges; this is also reflected in the experimentally determined
comparable O-O vibrational energies, Ni-N/O bond distances,
EPR g-tensors, and Ni K-edge/pre-edge energies for 1 and 2.
However, the nature of the ES differs in the two cases. The
observed electrophilic reactivity of 1 is most probably due to the
2791.
[
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[
[
[
[
2
2
availability of two closely lying spin states, 1als GS and 1ahs ES,
2
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d
reactivity on the 2als surface. The higher availability of the T Ni -
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8
II
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5
[
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Angewandte Chemie International Edition
10.1002/anie.201808085
COMMUNICATION
[
17] a) D. Usharani, D. Janardanan, C. Li, S. Shaik, Acc. Chem. Res. 2013, 46,
4
1
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39-145.
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Angewandte Chemie International Edition
10.1002/anie.201808085
COMMUNICATION
COMMUNICATION
Chakadola Panda, Anirban Chandra,
Teresa Corona, Erik Andris, Bhawana
Pandey, Somenath Garai, Nils
Lindenmaier, Silvio Künstner, Erik R.
Farquhar, Jana Roithová,* Gopalan
Rajaraman,* Matthias Driess,* and Kallol
Ray*
Page No. – Page No.
Nucleophilic vs Electrophilic
Reactivity of Bioinspired Super-oxido
Nickel(II) Complexes
Switching Reactivity of Superoxo: A two state reactivity (TSR) rationalizes the
contrasting reactivity patterns of two superoxido-nickel(II) complexes involving the
monoanionic β-diketiminate and dianionic biuret ligands. This study underlines the
importance of subtle electronic differences, which change the reactivity of
2
biologically relevant O -M intermediates.
This article is protected by copyright. All rights reserved.