A MnIIMnIII-Peroxide Complex Capable of Aldehyde Deformylation

Article abstract of DOI:10.1002/anie.201900717

Ribonucleotide reductases (RNRs) are essential enzymes required for DNA synthesis. In class Ib Mn₂ RNRs superoxide (O₂^.?) was postulated to react with the Mn^II₂ core to yield a Mn^IIMn^III-peroxide moiety. The reactivity of complex 1 ([Mn^II₂(O₂CCH₃)₂(BPMP)](ClO₄), where HBPMP=2,6-bis{[(bis(2-pyridylmethyl)amino]methyl}-4-methylphenol) towards O₂^.? was investigated at ?90 °C, generating a metastable species, 2. The electronic absorption spectrum of 2 displayed features (λ_max=440, 590 nm) characteristic of a Mn^IIMn^III-peroxide species, representing just the second example of such. Electron paramagnetic resonance and X-ray absorption spectroscopies, and mass spectrometry supported the formulation of 2 as a Mn^IIMn^III-peroxide complex. Unlike all other previously reported Mn₂-peroxides, which were unreactive, 2 proved to be a capable oxidant in aldehyde deformylation. Our studies provide insight into the mechanism of O₂-activation in Class Ib Mn₂ RNRs, and the highly reactive intermediates in their catalytic cycle.

Full text of DOI:10.1002/anie.201900717

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Accepted Article
Title: A MnIIMnIII-peroxide complex capable of aldehyde deformylation
Authors: Adriana M. Magherusan, Subhasree Kal, Daniel N. Nelis,
Lorna M. Doyle, Erik R. Farquhar, Lawrence Que, and Aidan
Richard McDonald
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To be cited as: Angew. Chem. Int. Ed. 10.1002/anie.201900717
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A MnIIMnIII-peroxide complex capable of aldehyde deformylation
Adriana M. Magherusan,a Subhasree Kal,b Daniel N. Nelis,a Lorna M. Doyle,a Erik R. Farquhar,c
Lawrence Que, Jr.,b Aidan R. McDonald*a
Abstract: Ribonucleotide reductases (RNRs) are essential enzymes
Supporting information for this article is given via a link at the end of the
document.
•–
required for DNA synthesis. In class Ib Mn2 RNRs superoxide (O2
)
was postulated to react with the MnII2 core to yield a MnIIMnIII-peroxide
Results and discussion. [MnII (O2CCH3)2(BPMP)](ClO4) (1,
2
moiety. The reactivity of complex 1 ([MnII (O2CCH3)2(BPMP)](ClO4) (1,
2
where HBPMP = 2,6-bis[(bis(2-pyridylmethyl)amino)methyl]-4-
methylphenol, Figure 1) was synthesised as previously
described.[7] To a solution of 1 at -90 °C was added KO2 and 18-
crown-6. An instantaneous reaction occurred (complete within 30
s), as evidenced by changes in the electronic absorption spectrum
(Figure 2), resulting in the formation of a new species (2).
where HBPMP
=
2,6-bis[(bis(2-pyridylmethyl)amino)methyl]-4-
•–
methylphenol))) towards O2 was investigated at -90 °C, generating
a metastable species, 2. The electronic absorption spectrum of 2
displayed features (λmax = 440, 590 nm) characteristic of a MnIIMnIII-
peroxide species, representing just the second example of such.
Electron paramagnetic resonance and X-ray absorption
spectroscopies, and mass spectrometry supported the formulation of
2 as a MnIIMnIII-peroxide complex. Unlike all other previously reported
Mn2-peroxides, which were unreactive, 2 proved to be a capable
oxidant in aldehyde deformylation. Our studies provide insight into the
mechanism of O2-activation in Class Ib Mn2 RNRs, and the highly
reactive intermediates in their catalytic cycle.
ClO4
N
N
N
N
N
N
N
N
O
N
N
N
N
O
MnII
MnII
N
MnII
MnIII N
N
N
O
O
O
O
O
O
[MnIIMnIII(O2)(N-Et-HPTB)]2+
1
Ribonucleotide reductases (RNRs) are essential enzymes that
play a pivotal role in the regulation of DNA synthesis.[1] Three
different RNR classes have been reported (I, II, and III).[2] Our
attention is focused on class Ib Mn2 RNRs, which use a Mn2
cofactor for catalytic activity.[3] Stubbe and co-workers have
proposed that superoxide anion (O2•–), rather than dioxygen,
Figure 1. [MnII2(O2CCH3)2(BPMP)](ClO4) (1) and [MnIIMnIII(O2)(N-Et-HPTB)]2+
.
0.8
reacts with the MnII core, to form a mixed valent MnIIMnIII-
2
0.6
0.4
(hydro)peroxide adduct.[3d] Mn-peroxide species have often been
implicated as precursors to high-valent oxidants,[4] and the
MnIIMnIII-(hydro)peroxide was postulated to be a precursor to the
active oxidant, a µ-O-MnIIIMnIV moiety. We expect a MnIIMnIII-
(hydro)peroxide to be highly reactive, however, no insight into any
Mn2-peroxide reactivity is currently available. Exploring the
reactivity of the peroxide core will provide information on how
external stimuli (i.e. H+, electrophilies) activate the peroxide core
in RNRs.
768
770
776
778
780
772m7/7z4
0.2
0.0
We recently reported the first example of a MnIIMnIII-
•–
peroxide complex formed from the reaction of O2
with
400
500
600
700
800
[MnII (O2CCH3)(N-Et-HPTB)](ClO4)2 (N-Et-HPTB
= N,N,N’,N’-
2
tetrakis(2-(1-ethylbenzimidazolyl))-2-hydroxy-1,3-
Wavelength (nm)
diaminopropane, Figure 1).[5] However, that complex proved to be
unreactive as either an electrophilic or nucleophilic oxidant.[5] All
other reported Mn2-peroxide complexes (one MnIII2- and one
MnIV2-peroxide)[6] also displayed no reactivity towards external
substrates. Herein, we report the preparation of the second
example of a MnIIMnIII-peroxide complex and demonstrate it to be
(to the best of our knowledge) the first example of a reactive Mn2-
peroxide.
Figure 2. Electronic absorption spectra of 1 (black trace, 1.5 mM) and 2 (purple
trace, from the reaction of 1 (1.5 mM) with KO2 (1.25 equiv.) at -90 °C in 1:9
CH3CN/THF). Inset: The ESI-MS spectrum showing the molecular ion for 2
({[Mn2(O2)(BPMP)](ClO4)}+).
The electronic absorption spectrum of 1 displayed no absorbance
bands above 400 nm, whereas 2 displayed two low intensity
features at λmax = 440 and 590 nm (Figure 2). The electronic
absorption features of 2 were remarkably similar to those of
[Mn2(O2)(N-Et-HPTB)]2+ that we recently reported (λmax = 460, 610
nm, Figure S1).[5] Furthermore, such features are also
characteristic of mononuclear MnIII-peroxide complexes, which
have been reported to display absorption bands at λmax = 400 -
500 nm and 550 – 650 nm.[8] This led us to conclude that species
2 was the second example of a MnIIMnIII-peroxide complex.
Cold injection electrospray ionisation mass spectrometry
(ESI-MS) on a just-thawed solution of 2 revealed a peak at m/z =
a]
Adriana M. Magherusan, Daniel N. Nelis, Lorna M. Doyle, Dr. Aidan R.
McDonald, School of Chemistry, Trinity College Dublin, The University
of Dublin, College Green, Dublin 2, Ireland
E-mail: aidan.mcdonald@tcd.ie
[b]
[c]
Subhasree Kal, Prof. Lawrence Que, Jr., Department of Chemistry and
Centre for Metals in Biocatalysis, University of Minnesota, 207 Pleasant
St. SE, Minneapolis, MN 55455, USA
Dr. Erik R. Farquhar, Case Western Reserve University Centre for
Synchrotron Biosciences, National Synchrotron Light Source II,
Brookhaven National Laboratory, Upton, NY 11973, USA.
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10.1002/anie.201900717
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770.2933 with the appropriate isotope distribution pattern to be
consistent with its formulation as the mono-cation
{[Mn2(O2)(BPMP)](ClO4)}+ [6a, 4a] (Figures 2, S2). In this cation both
acetate ligands from the precursor complex 1 were absent. This
mirrors our observations made with [Mn2(O2)(N-Et-HPTB)]2+
where the starting material contained an acetate ligand, but by
ESI-MS we identified only the [Mn2(O2)(N-Et-HPTB)]2+ dication.[5]
At 2 K complex 2 displays a 22-line electron paramagnetic
2 and [MnIIMnIII(O2CCH3)2(BPMP)]2+ are different species, leading
us to define complex 2 as [MnIIMnIII(O2)(BPMP)]2+.
To gain better insight into the oxidation state of 2, Mn K-edge
X-ray absorption near edge spectroscopy (XANES) was carried
out on frozen samples of 1 and 2. The edge energy of 1 was found
to be 6548.4 eV, while that of 2 was 6548.9 eV, an increase of 0.5
eV (Table S1, Figures 4, S5). Systematic studies of Mn
coordination compounds have shown that each integer change in
formal oxidation state elicits a blue-shift of 2-4 eV in K-edge
inflection energy.[11] For a mixed valent Mn2 species, a shift of 1
eV would therefore be expected upon quantitative oxidation of a
MnIIMnII precursor (1) to a MnIIMnIII-peroxide (2) adduct. Here, the
yield of 2 was only ~50%, according to EPR analysis, consistent
with the observed blue-shift of 0.5 eV. For the previously reported
peroxide complex [Mn2(O2)(N-Et-HPTB)]2+ we observed an ~1 eV
shift upon conversion of the MnII2 starting material to the MnIIMnIII
species [Mn2(O2)(N-Et-HPTB)]2+ (obtained in 80% yield, Figure
resonance (EPR) signal centered at g ~ 1.96 (Figure 3), which
can be attributed to an S = ½ MnIIMnIII species.[9] A 36-line
spectrum would be expected assuming an isotropic g-tensor,
however, the number of lines is expected to increase with
anisotropy, but at the same time there is overlap, resulting in a
22-line spectrum for 2. The yield of 2 was determined by EPR
integration to be ~50% (Figure S3).The EPR signal of 2 has a
wide spectral width and is well-resolved below 10 K. Above 10 K
the signal broadens, obscuring its characteristic 22-line pattern.
Similar behavior was reported for the EPR signals of previously
reported MnIIMnIII complexes, which exhibit well-resolved 24-29-
line signals but only at temperatures below 15 K.[10a, 10b, 9, 10c, 10d]
Furthermore, [Mn2(O2)(N-Et-HPTB)]2+, the only other MnIIMnIII-
peroxide reported to date, also displayed a well-resolved 29-line
EPR signal centered at g ~ 1.96 with a wide spectral width but
was only well resolved below 10 K (Figures 3, S4).[5] This
temperature dependence is indicative of
interaction between the Mn ions.[10c]
a weak coupling
S6).[5]
Figure 4. Normalised XANES spectra of 1 (solid trace) and 2 (dashed trace).
The inset shows an expansion of the pre-edge region.
Notably, there was a significant increase in the pre-edge area
from 5.8 to 9.4 units upon conversion of 1 to 2, respectively
(Figure 4, S7, Table S1). The increased pre-edge area is
indicative of a decrease in symmetry from octahedral Mn sites in
1000
2000
3000
4000
5000
1 to a lower degree of symmetry (possibly 5-coordinate Mn site(s))
12]
in 2.[11b,
The pre-edge peak of 1 can be constructed as a
Field˚(G)
combination of two independent peaks at 6540.0 eV and 6540.8
eV (Figures S7-S9). The weighted average of these two
transitions give a pre-edge energy of approximately 6540.3 eV,
which is identical to that of 2 (also 6540.3 eV, Table S1). This is
not unexpected, as appreciable changes in pre-edge energy are
generally not found until the MnIV state is achieved.[11c] It has been
shown that octahedral MnII complexes exhibit two 1s → 3d
transitions of similar energy (1s → 3d(eg) and 1s → 3d(t2g)),
separated by ~ 0.8 – 1 eV.[13, 11b] We assume that the two features
observed derive from the octahedral nature of the Mn sites in 1.
The observation of a loss of symmetry in the pre-edge feature for
2, upon conversion of 1 to 2, indicates a change in coordination
environment at the metals. The loss of an electron, through Mn
oxidation, could lead to an increase in the number of vacant
valence d-orbitals present, thus affecting the 1s → 3d transitions.
This would in turn increase the area of the pre-edge feature, as is
observed.[11b, 12] A change comparable to this was reported by
Kovacs, DeBeer, and co-workers, wherein a 5-coordinate starting
Figure 3. Perpendicular mode X-band EPR spectrum of 2 at 2 K (purple trace,
obtained from the reaction of 1 (1.5 mM) and KO2 in 1:9 CH3CN/THF, 9.64 GHz,
0.2 mW microwave power) and [Mn2(O2)(N-Et-HPTB)]2 (red trace, for
comparison).
Hendrickson and co-workers previously reported a mixed valent
form of complex
1
([MnIIMnIII(O2CCH3)2(BPMP)]2+) which
displayed a 29-line signal centred at g ~ 2 at 7.5 K[10a] and differs
from the 22-line EPR spectrum exhibited by 2 at 2 K. Thus, we
conclude that complex 2 represented a unique MnIIMnIII complex
supported by the BPMP ligand. Furthermore, while the electronic
absorption spectrum of 2 exhibited two weak absorption bands at
λmax = 440 and 590 nm, the Hendrickson complex displayed three
absorption bands at λmax = 427, 478 and 620 nm which were
markedly more intense as well.[7a] The different EPR and
electronic absorption spectra support our postulate that complex
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MnII complex was oxidised to a 6-coordinate MnIII2-peroxide
complex, leading to a decrease in the pre-edge area, providing
support for our interpretation.[14] The shift of the edge energy by
0.5 eV as well as the changes to pre-edge area and decreased
site symmetry support our assignment of 2 as a MnIIMnIII species.
Extended X-ray absorption fine structure (EXAFS) analysis on 2
was not carried out due to the low yield obtained (~ 50%). Based
on the spectroscopic results along with the mass spectrometric
evidence, we concluded that 2 was a MnIIMnIII-peroxide complex.
CH3-C6H4C(H)O (~3000 equiv.). k2 values were determined for
the substrates that did react. Importantly, exponential changes to
kobs were not observed for the benzaldehyde substrates (to the
limits of [substrate] before precipitation of the substrate). This
suggests that for the p-X-C6H4C(H)O substrates the kinetic results
provide insight into the initial nucleophilic attack, while the
subsequent Criegee rearrangement does not influence the
kinetics. This observation is consistent with Criegee
rearrangement being slower for the electron-poor a-C atom
(relative to the aldehyde ketone) benzaldehydes than for the
electron-rich a-C PPA and CCA. Overall, this indicates that at low
[PPA] or low [CCA], and for all [p-X-C6H4C(H)O], nucleophilic
attack is rate limiting. While at high [PPA] or [CCA] Criegee
rearrangement is rate limiting.
At -90 °C, 2 displayed a t1/2 = 2 h, but decayed fully within 180
s upon warming to room temperature. The electronic absorption
spectrum of 2 at -90 °C remained unchanged upon the addition of
triphenylphosphine (PPh3), cyclohexene, or substrates containing
weak X–H bonds (all added in 100-fold excess, including 1-
methyl-1,4-cyclohexadiene, 9,10-dihydroanthracene, and 2,4-di-
tert-butylphenol). Hence,
2 was determined to be a poor
electrophilic oxidant. This observation was consistent with our
observations for [Mn2(O2)(N-Et-HPTB)]2+,[5] which was also
unreactive towards such substrates.
In contrast, at -90 °C in 1:9 CH3CN/THF 2 reacted readily with
aldehyde substrates including 2-phenylpropionaldehyde (PPA),
cyclohexanecarboxaldehyde (CCA), and para-substituted
benzaldehydes (p-X-C6H4C(H)O). The reactions with PPA and
CCA (Figures S10-S17) afforded acetophenone and
cyclohexanone,
respectively,
as
evidenced
by
gas
chromatography mass spectrometry. By plotting the change in the
absorbance of the λmax = 440 nm feature of 2 against time and
fitting the resulting curve, first order rate constants (kobs) for the
reaction with PPA or CCA were determined (Figures S10, S14).
To calculate a second order rate constant (k2) we plotted kobs
against [substrate] for a series of [substrate] (Figures S12, S16).
At low [substrate] the relationship appeared to be linear allowing
for an estimation of k2 values (Table 1). However, and surprisingly,
at higher [substrate] the rate at which 2 reacted increased
exponentially.[21]
Figure 5. Hammett plot for the reaction between 2 and p-X-C6H4C(H)O (X = H,
Cl, CF3, CN, NO2).
A Hammett plot of the log(Rk2/Hk2) versus the para-substituent (σp)
was linear and resulted in a positive ρ value of 0.64 (Figure 5).
Previous reports showed that the nucleophilic character of the
{MIIIO2} unit (M = Mn, Ni, Co) could be confirmed by using p-X-
PhC(O)H. For these metal-peroxides a Hammett plot was always
linear with a positive ρ value in the range of 1.7-2.5.[17] The slightly
higher ρ values were obtained for mononuclear complexes and
when compared to the ρ value of 0.64 obtained for 2 indicate that
the electronic influence of the substrate on the rate of nucleophilic
attack may be diminished for 2. Nonetheless, these results
confirm that the rate limiting step in the reaction of 2 and p-X-
C6H4C(H)O was nucleophilic attack. 2 was thus a capable
aldehyde deformylating oxidant, and the first Mn2-peroxide to
display reactivity towards external substrates.
We believe that, as typical for Baeyer-Villiger oxidations
(Scheme 1),[15] the reaction between 2 and aldehyde involves
initial reversible nucleophilic attack of the peroxide on the
electrophilic aldehyde C-atom, followed by Criegee-
rearrangement (where the C-atom a to the aldehyde C-atom
attacks the distal O-atom resulting in O–O bond scission, which is
irreversible, Scheme 1).[16] The latter is normally ascribed as the
rate-limiting step in such reactions. We postulate that at low
[substrate] the kinetic results provide insight into the reversible
nucleophilic attack, and at high [substrate] the kinetic results are
likely associated with the Criegee rearrangement.
Previously reported mononuclear MnIII-peroxide complexes also
R
R
R
proved to be competent PPA and CCA deformylating oxidants
O
H
R
R
H
H
17b, 8d]
(both TMC- (tetramethylcyclam)[18,
and polypyridine-[19]
O
R
O
O
R
O
R
O
supported complexes, Table 1). For PPA, at -90 °C 2 displayed a
relatively low estimated k2 compared to k2 values determined for
those MnIII-peroxide complexes. It is important, however, to
consider the different temperatures these measurements were
performed at: -90 °C for 2; 0 °C for [MnIII(O2)(Pro3Py)]+; +20 °C
for TMC-supported complexes. In contrast, 2 oxidised CCA at -
90 °C at rates comparable to those determined for TMC-
supported complexes at significantly higher temperatures (+10 °C,
Table 1), while still displaying lower reactivity than polypyridine-
supported complexes (-40 °C). Overall, 2 proved to be an effective
deformylating oxidant considering the low temperature the
O
O
O
R
MnIII
MnIII
MnII
MnIII
MnII
MnII
Scheme 1. Nucleophilic attack of 2 on aldehyde substrates followed by
irreversible Criegee rearrangement.
2 also reacted with electron-poor p-X-C6H4C(H)O (X = H, Cl,
CF3, CN, NO2, Figures S15-S20). The products of the oxidation of
these substrates were the respective benzoic acids. No reaction
was observed when 2 was reacted with p-OCH3-C6H4C(H)O or p-
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10.1002/anie.201900717
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COMMUNICATION
reactivity was performed under.[18, 17b, 8d] The reactivity properties
of previously reported Mn2-peroxide complexes were not
addressed.[6] The lower metal oxidation state in 2 with respect to
the other examples (MnIII2- and MnIV2-peroxide complexes) could
enhance its nucleophilic reactivity.[6] We believe that 2 was more
reactive than [Mn2(O2)(N-Et-HPTB)]2+ due to the presence of less
steric bulk in 2 allowing for more facile access to the peroxide core.
That aldehydes reacted with 2 demonstrates that an electrophile
is required to activate the MnIIMnIII-peroxide core, as in the RNRs
where H+ is postulated to activate the core.
and Environmental Research and the National Institutes of Health
(P41-GM-103393). E.R.F. is supported by NIH grant P30-EB-
009998.
Keywords: ribonucleotide reductases
•
MnIIMnIII-peroxide
•
superoxide activation
•
nucleophilic reactivity
•
aldehyde
deformylation
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Table 1. Rate constants for deformylation by Mn-peroxide complexes.
PPA
k2 [M-1s-1]
CCA
k2 [M-1s-1]
Ref
Ref
(T [°C])
(T [°C])
2
0.0006 (-90)
0.014 (-90)
0.3 (0)
[MnIII(O2)(12-TMC)]+
[MnIII(O2)(13-TMC)]+
[MnIII(O2)(14-TMC)]+
[MnIII(O2)(Pro3Py)]+
[MnIII(O2)(L7py26-Me)]+
[MnIII(O2)(L7py24-Me)]+
[MnIII(O2)(L8py2H)]+
0.04 (20)
[8d]
[8d]
[8d]
[19]
[18]
[17b]
[17b]
0.03 (20)
0.02 (10)
0.04 (10)
-
0.04 (20)
0.003 (0)
-
[20]
-
-
-
0.32 (-40)
0.40 (-40)
0.19 (-40)
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[20]
[20]
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B. Epel, L. V. Kulik, L. Rapatskiy, F. Neese, J. Messinger, K.
Wieghardt, W. Lubitz, Inorg. Chem. 2011, 50, 8238-8251; d) Y. Sano,
A. C. Weitz, J. W. Ziller, M. P. Hendrich, A. S. Borovik, Inorg. Chem.
2013, 52, 10229-10231.
12-TMC
=
1,4,7,10-tetramethyl-1,4,7,10-tetraazacyclododecane; 13-TMC
=
1,4,7,10-tetramethyl-1,4,7,10-tetraazacyclotridecane; 14-TMC
tetramethyl-1,4,8,11-tetraazacyclotetradecane. L7py2
pyridylmethyl)-1,4-diazepane; L7py24-Me = 1,4-bis(4-methyl-2-pyridylmethyl)-1,4-
diazepane; L8py2H = 1,5-bis(2-pyridylmethyl)-1,5-diazacyclooctane.
=
1,4,8,11-
6-Me
= 1,4-bis(6-methyl-2-
Conclusions. We prepared and characterized a meta-stable
MnIIMnIII-peroxide complex from the reaction between a Mn2
II
complex and superoxide anion, mimicking the postulated
biochemistry of the class Ib Mn2 RNRs. The complex displayed
features typical of a MnIIMnIII-peroxide complex by electronic
absorption, EPR, and XAS spectroscopies, and mass
spectrometry. Interestingly, 2 was found to be an efficient
nucleophilic aldehyde deformylation reagent, exhibiting
comparable reaction rates to previously reported mononuclear
Mn-peroxide complexes. To the best of our knowledge this is the
first example of a reactive Mn2-peroxide entity, and furthermore
demonstrates that an electropositive species (H+ for RNRs,
electrophilic aldehyde for 2) is required to activate the peroxide
core in RNRs.
[11] a) T. C. Weng, W. Y. Hsieh, E. S. Uffelman, S. W. Gordon-Wylie, T. J.
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126, 8070-8071; b) F. Farges, Phys. Rev. B 2005, 71; c) R. E.
Schreiber, H. Cohen, G. Leitus, S. G. Wolf, A. Zhou, L. Que, Jr., R.
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Ackowledgments: This publication has emanated from research
supported by the Irish Research Council (IRC) under Grant
Chem. 2015, 54, 6410-6422.
Numbers
GOIPG/2014/942
to
A.
Magherusan
and
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M. Kubo, T. Ogura, E. I. Solomon, W. Nam, Nat. Chem. 2009, 1, 568;
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GOIPG/2017/525 to D. Nelis. Research in the McDonald lab is
supported in part by the European Union (ERC-2015-STG-
678202) and research grants Science Foundation Ireland
(SFI/15/RS-URF/3307, SFI/17/RS-EA/3470). Support for this
research in the Que lab has been provided by the US National
Institutes of Health (GM38767). XAS measurements benefited
from support of SSRL by the U.S. Department of Energy, Office
of Science, Office of Basic Energy Sciences under Contract No.
DE-AC02-76SF00515, as well as support of the SSRL Structural
Molecular Biology Program through the DOE Office of Biological
[19] J. Du, D. Xu, C. Zhang, C. Xia, Y. Wang, W. Sun, Dalton. Trans. 2016,
45, 10131-10135.
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10.1002/anie.201900717
Angewandte Chemie International Edition
COMMUNICATION
[20] R. A. Geiger, S. Chattopadhyay, V. W. Day, T. A. Jackson, Dalton
Trans. 2011, 40, 1707-1715.
[21] kobs measurements at very high [substrate] were too fast to perfrom
accurate kinetic analysis.
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10.1002/anie.201900717
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COMMUNICATION
Entry for the Table of Contents:
COMMUNICATION
Nucleophilic reactivity:
Adriana M. Magherusan,a
Subhasree Kal,b Daniel N.
Nelis,a Lorna Doyle,a Erik
R. Farquhar,c Lawrence
Que, Jr.,b Aidan R.
The reaction of a MnII
O
2
complex with superoxide
H
O
MnIIMnIII-
N
N
yielded
a
O
N
N
MnII MnIII
KO2
O
MnII MnII
peroxide complex which
mimics intermediates in
N
O
O
N
O
O
O
O
+ HCO2
class
Ib
Mn2
McDonald*a
ribonucleotide
reductases.
The
MnIIMnIII-peroxide
Page No. – Page No.
species displayed an
unexpected nucleophilic
character in aldehyde
deformylation.
A MnIIMnIII-peroxide
complex capable of
aldehyde deformylation
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