Aerobic Oxidation Catalysis by a Molecular Barium Vanadium Oxide

Article abstract of DOI:10.1002/chem.201706046

Aerobic catalytic oxidations are promising routes to replace environmentally harmful oxidants with O₂ in organic syntheses. Here, we report a molecular barium vanadium oxide, [Ba₄(dmso)₁₄V₁₄O₃₈(NO₃)] (={Ba₄V₁₄}) as viable homogeneous catalyst for a series of oxidation reactions in N,N-dimethyl formamide solution under oxygen (8 bar). Starting from the model compound 9,10-dihydroanthracene, we report initial dehydrogenation/ aromatization leading to anthracene formation; this intermediate is subsequently oxidized by stepwise oxygen transfer, first giving the mono-oxygenated anthrone and then the di-oxygenated target product, anthraquinone. Comparative reaction analyses using the Neumann catalyst [PV₂Mo₁₀O₄₀]^5? as reference show that oxygen diffusion into the reaction mixture is the rate-limiting step, resulting in accumulation of the reduced catalyst species. This allows us to propose improved reactor designs to overcome this fundamental challenge for aerobic oxidation catalysis.

Full text of DOI:10.1002/chem.201706046

A Journal of
Accepted Article
Title: Aerobic Oxidation Catalysis by a Molecular Barium Vanadium
Oxide
Authors: Manuel Lechner, Katharina Kastner, Chee Jian Chan, Robert
Güttel, and Carsten Streb
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To be cited as: Chem. Eur. J. 10.1002/chem.201706046
Link to VoR: http://dx.doi.org/10.1002/chem.201706046
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COMMUNICATION
Aerobic Oxidation Catalysis by a Molecular Barium Vanadium
Oxide
Manuel Lechner,[a] Katharina Kastner,[a] Chee Jian Chan,[c] Robert Güttel[c]* and Carsten Streb[a,b]
*
Dedicated to Professor Achim Müller (Bielefeld) on the occasion of his 80th birthday
Abstract: Aerobic catalytic oxidations are promising routes to replace
petrochemicals (alkanes, aromatics)[5] and biogenic feedstocks[6–
to value-added products. Their versatility is illustrated by a
8]
environmentally harmful oxidants with O2 in organic syntheses. Here,
we
report
a
molecular
barium
vanadium
oxide,
variety of catalytic oxidations most notably C-H-activations,[9]
epoxidations,[10] hydroxylations and more recently, water
oxidation.[11,12]
[Ba4(dmso)14V14O38(NO3)] (= {Ba4V14}) as viable homogeneous
catalyst for a series of oxidation reactions in N,N-dimethyl formamide
solution under oxygen (8 bar). Starting from the model compound
To-date, aerobic POM oxidation catalysis is mainly focused on
Keggin-type vanadomolybdate clusters of the type [PVxMo12-xO40]
(x = 2, 3, 4) with a particular focus on the heteropolyacid
H5[PV2Mo10O40] = {V2Mo10}. Using this compound,[13] Neumann et
al. have performed pioneering catalytic and mechanistic studies
and reported catalytic activity for C-H activation,[14] aromatic
oxidation,[15] epoxidation,[16] oxidative dimerization and
aromatization[17] reactions.[13] Notably, the authors proposed that
the oxidative catalytic activity is based on a Mars-van-Krevelen
mechanism[14,18] where the oxygen atom transferred to the
substrate originates from the cluster oxo ligands, not from
molecular oxygen.[13] This is a critical observation, as it could
enable the de-coupling of substrate oxidation and catalyst re-
oxidation, thereby eliminating uncontrolled O2-based autoxidation
reactions.[19] In a recent landmark paper, Neumann et al.
demonstrated that {V2Mo10} can be used for the liquid phase
9,10-dihydroanthracene, we report initial dehydrogenation
/
aromatization leading to anthracene formation; this intermediate is
subsequently oxidized by stepwise oxygen transfer, first giving the
mono-oxygenated anthrone and then the di-oxygenated target
product, anthraquinone. Comparative reaction analyses using the
Neumann catalyst [PV2Mo10O40]5- as reference show that oxygen
diffusion into the reaction mixture is the rate-limiting step, resulting in
accumulation of the reduced catalyst species. This allows us to
propose improved reactor designs to overcome this fundamental
challenge for aerobic oxidation catalysis.
Introduction
The selective catalytic oxidation of organic substrates is one of
the most important reaction classes in chemistry as it gives
access to a wide range of (partially) oxidized compounds ranging
from bulk to fine chemicals.[1,2] Often, solid-state metal oxides (e.g.
V2O5) are used as catalysts due to their high activity and long-
term stability. However, over the last decade, liquid phase
operations have led to a renewed interest in soluble molecular
metal oxides, so-called polyoxometalates (POMs) as
homogenous oxidation catalysts, particularly when low-
temperature aerobic oxidations (using molecular O2 as oxidant)
are targeted.[3] POMs are polynuclear metal oxide anions typically
based on early transition metals in their highest oxidation states
(e.g. MoVI, WVI, VV), see Fig. 1.
The presence of several redox-active metal centers together with
oxo ligands on the cluster surface makes POMs ideally suited for
proton-coupled multi-electron transfer reactions.[3,4] Their high
activity, stability and catalytic selectivity together with the use of
environmental friendly O2 as re-oxidant have led to an increased
interest in POM catalysts for the conversion of base
chemical/electrochemical
conversion
of
cellulose
or
hemicellulose to carbon monoxide and hydrogen, i.e. syngas,
showing the potential use of the catalyst in the field of non-fossil
chemical feedstocks.[20] Related studies by Albert, Wasserscheid
et al. have led to the industrial OxFA process where {V2Mo10} is
used as catalyst for the aerobic oxidative conversion of wet
biomass to formic acid.[6–8]
These seminal works show that POM-catalyzed aerobic
oxidations are critical reactions for the sustainable chemical
oxidations with industrial relevance. However, the use of O2 as
benign oxidant[21] results in new challenges, as the biphasic
reaction systems require not only the development of high
performance catalysts, but at the same time, novel reactor design
paradigms are required to prevent mass transfer limitations due
to the slow diffusion of O2 into the liquid reaction mixtures.[22]
We have recently started to investigate metal-functionalized
polyoxovanadates[23–25] as potential catalysts for chemical or
photochemical oxidations.[26–31] To enable a targeted metal-
functionalization of vanadate clusters, we developed a chloride-
templated vanadate “host” cluster (Me2NH2)2[V12O32Cl]3- (= {V12})
[a]
M. Sc. M. Lechner, Dr. K. Kastner, Prof. Dr. C. Streb
Institute of Inorganic Chemistry I
Ulm University
+
featuring two Me2NH2 -blocked metal binding sites.[26,27,32–34]
Incorporation of one or two reactive 3d metal “guests” is possible,
leading to metal-functionalized vanadates as multi-electron
transfer sites,[27,32] e.g. in battery electrodes[34] or as catalysts for
C-H-activation[27] and alcohol oxidation.[33] Based on these studies,
we became interested in expanding this “host-guest” assembly
strategy by developing a vanadate “host” capable of binding larger
metals, e.g. large alkali or alkali earth cations. A specific focus
was set on the incorporation of barium centers, as solid-state
Albert-Einstein-Allee 11, 89081 Ulm (Germany)
E-mail: carsten.streb@uni-ulm.de
Prof. Dr. C. Streb
Helmholtz Institute Ulm for Electrochemical Energy Storage, 89081
Ulm, Germany and Karlsruhe Institute of Technology, P.O. Box
3640, 76021 Karlsruhe, Germany
PgDipSc. A. Chan, Prof. Dr.-Ing. R. Güttel
Institute of Chemical Engineering
[b]
[c]
Ulm University
Albert-Einstein-Allee 11, 89081 Ulm (Germany)
Email: robert.guettel@uni-ulm.de
Supporting information for this article is given via a link at the end of
the document.
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barium vanadates are well-known oxidation catalysts, e.g. for
alkane dehydrogenation[35] or selective methanol oxidation.[36]
Here, we report the synthesis of a novel vanadate “host” featuring
an enlarged binding site suitable for binding four Ba2+ centers.
Enlargement of the binding site was possible by using nitrate as
an internal template, while in {V12}, a smaller chloride template
was used. The new cluster is fully characterized in the solid-state
and in solution. Initial aerobic oxidation studies show the high
reactivity of the catalyst and emphasize that future aerobic
catalytic studies need to focus on optimizing the oxygen transfer
into the liquid phase to improve catalytic efficiency.
barium centers are bridged by two 2-DMSO ligands and feature
five additional, terminal DMSO ligands for stabilization. Each Ba
center therefore is nine-coordinate in a distorted coordination
polyhedron, see SI. All V-O and Ba-O distances are in line with
the expected values reported in the literature.[37,38] Initial
electrochemical studies by cyclic voltammetry (in N,N-dimethyl
formamide containing 0.1 M nBu4NPF6) show that {Ba4V14}
features one reversible redox-wave at E1/2 = 0.64 V (vs Fc/Fc+),
see SI.
Aerobic catalytic studies
To assess the general utility of {Ba4V14} as homogeneous aerobic
(i.e. O2-dependent) oxidation catalyst, we examined the well-
understood aerobic oxidation of 9,10-dihydroanthracene (DHA) to
anthraquinone as a model reaction (Fig. 2). This reaction was
pioneered by Neumann et al. using {V2Mo10} as homogeneous
catalyst.[13] To compare the performance of {Ba4V14}, we therefore
used the Neumann-catalyst {V2Mo10} as reference. For {V2Mo10},
it was shown that the oxidation is a three-step process where
oxidative dehydrogenation of DHA to anthracene is followed by
two oxygenation steps to give anthraquinone (Fig. 2).[22]
Figure 1: (a) structural representation of {Ba4V14}, Ba4(dmso)14[V14O38(NO3)].
-
(b) {V14} cluster framework showing the template NO3 . (c), (d) Comparison of
the metal binding sites in the literature-known, chloride-templated {V12}
[26,27] and
the nitrate-templated {Ba4V14}. Colour scheme: Ba: orange, V: teal, O: red, Cl:
green, N: blue, S: yellow, C: grey.
Results
Synthesis and characterization of {Ba4V14}
(nBu4N)4[V4O12] • 4 H2O (= {V4}) and Ba(NO3)2 were reacted in
dimethyl sulfoxide (DMSO) in the presence of aqueous nitric acid.
Diffusion of acetone into the deep red solution gave red block
crystals suitable for single-crystal X-ray diffraction (yield: 7.13 g,
2.35 mmol, 98% based on V). Single-crystal X-ray diffraction gave
the formula [Ba4(dmso)14V14O38(NO3)] (= {Ba4V14}), see Fig. 1.
Chemical composition and bulk purity were verified by elemental
analyses, FT-IR-, UV-Vis spectroscopies and ESI mass
spectrometry and cyclic voltammetry, see SI. {Ba4V14} is
composed of 14 square pyramidal [VO5] units arranged around a
central nitrate template, giving a C2v-symmetric vanadium oxide
shell. Long-range electrostatic interactions between the nitrate
Figure 2: Reaction scheme for the two-step oxidation of DHA to anthraquinone
catalyzed by {Ba4V14}.
The catalytic test reaction was carried out in N,N-dimethyl
o
formamide (DMF) at T = 80 C and p(O2) = 4-8 bar in a 50 mL
discontinuous magnetically stirred glass pressure reactor. The
initial concentration of the substrate DHA was 46 mM and the
respective catalyst concentration was 0.9 mM (2 mol-% with
respect to DHA). The formation of the intermediates anthracene,
anthrone and the product anthraquinone was quantified using
high-pressure liquid chromatography (HPLC). Note that the initial
“induction phase” observed between t = 0-1 h (Fig. 3) is most likely
due to the heating up of the reactor, as the starting point of the
reaction (t = 0 h) was defined as switch-on of the reactor heating.
This was experimentally the most consistent approach for full data
collection.
oxygen atoms and the
V
centers are indicated by the
corresponding V…O separations (d(V…O(NO3 )) ~2.90 – 3.14 Å).
Notably, the belt-shaped vanadium oxide arrangement results in
the formation of two binding sites on top and bottom of the cluster
-
shell where formally, seven bridging oxo ligands form
a
As shown in Figure 3, catalytic conversion of DHA to anthracene,
anthrone and anthraquinone is observed for {Ba4V14} and
{V2Mo10}. Under identical conditions, the rates of anthraquinone
formation are comparable for both catalysts. However, an earlier
onset of anthraquinone formation is observed for {Ba4V14} so that
at the defined end of the reaction (t = 7 h), higher yields of
heptadentate binding site with approximate dimensions of 0.7 x
0.5 nm (Fig. 1).
In {Ba4V14}, one Ba2+ ion is bound at each binding site through
five Ba-O coordination bonds (d(Ba-O) = 2.82 – 3.02 Å). In
addition, a second Ba2+ center is linked to the vanadium oxide
through one Ba-O coordination bond (d(Ba-O) = 2.78 Å). The two
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anthraquinone are observed for {Ba4V14} (40 %) compared with
{V2Mo10} (28 %). To understand this diverging behavior, we
investigated the formation of the reaction intermediates
anthracene and anthrone by both catalysts (Fig. 3). It was noted
that for {Ba4V14}, very little accumulation of the intermediate
anthracene (less than 2 % over the whole course of the reaction)
is observed while significant amounts of anthrone are formed (up
to ~15 % at t = 3 h). For {V2Mo10}, we note a higher amount of
anthracene accumulation (maximum ~8 % at t = 3 h) while
anthrone accumulation is only noted in later reaction phases
(maximum ~11 % at t = 7 h). This suggests that for {Ba4V14}, the
anthracene to anthraquinone reaction steps proceed faster than
for {V2Mo10}. These findings also explain the observed difference
in anthraquinone yield after t = 7 h: while for {Ba4V14}, we observe
a fast conversion of anthracene to the oxidized products,
{V2Mo10} leads to an accumulation of anthracene, which results
in a later onset of anthraquinone formation. Based on literature
reports[13] as well as the structural similarities between {V2Mo10}
and {Ba4V14} and the known redox-activity of vanadium, we
suggest that the V centres are the catalytically active sites, while
the role of the Ba centers is currently not fully understood.
reduced {Ba4V14} is accumulated (as identified by the formation
of a characteristic intervalence charge-transfer band at  ~ 600-
900 nm, see SI). This supports the suggestion that catalyst re-
oxidation by dissolved O2 is limiting the overall reaction. In sum,
our findings are in line with previous studies by Neumann et al.
who observed that re-oxidation of {V2Mo10} is rate-limiting for the
anthracene-to-anthraquinone oxidation.[17]
Next, we assessed whether {Ba4V14} can be recovered from
solution and can be recycled. To this end, the catalyst was
precipitated from the reaction solution by addition of diethyl ether,
centrifuged off, air-dried and re-dissolved in a fresh reaction
mixture to perform our standard aerobic DHA oxidation. The
results showed that recycling is possible and only minor changes
in the initial product formation rates was observed (run 1: 8.9 %/h;
run 2: 11.2 %/h; run 3: 7.8 %/h, see SI). UV-Vis spectroscopy of
the recycled catalyst shows similar characteristic absorption
features than the native catalyst, see SI. Intriguingly, we noted an
increase of the “induction period” described earlier. This might be
related to an initial re-oxidation step required for catalyst
activation and is still under investigation. Further mechanistic
studies will explore the detailed changes of {Ba4V14} structure and
reactivity during recycling.
Figure 4: Similar anthraquinone formation rates observed for the catalytic
aerobic oxidation of DHA at different {Ba4V14} concentrations, indicating that
catalytic turnover is not rate-limiting. Conditions: p(O2)= 8 bar, T = 80 oC,
solvent: DMF, [cat] = 0.45 mM (1 mol%), 0.9 M (2 mol%), 1.8 mM (4 mol%),
[DHA]= 46 mM.
Table 1: Catalytic DHA conversion by POM catalysts[a]
Catalyst
[Cat] /
mM
Reaction
time / h conversion / %
DHA
Initial anthraquinone
formation rate / %h-1
{Ba4V14
}
0.90
0.90
7
16
7
59.5
71.3
46.3
71.5
9.4
9.5
-
Figure 3: Aerobic oxidation of DHA using (a) {Ba4V14} and (b) {V2Mo10} as
catalyst. Conditions: p(O2)= 8 bar, T = 80 oC, solvent: DMF, [cat] = 0.9 mM,
[DHA]= 46 mM.
{Ba4V14
}
{V2Mo10
{V2Mo10
{V4}
}
0.90
7.4
-
}
0.90
16
7
The similar rates of anthraquinone formation observed for both
catalysts led us to suggest that the reaction is mass transfer
limited due to the slow diffusion of O2 from the gas phase into the
liquid reaction mixture.[22] To verify this hypothesis, we performed
the catalytic reaction at varying concentrations of the catalyst
([{Ba4V14}] = 0.45 – 1.8 mM). The results show that within
experimental error (±3 %) the rate of anthraquinone formation is
independent of the catalyst concentration in the concentration
range investigated (0.45 mM: 8.9 %/h; 0.9 mM: 9.5 %/h; 1.8 mM:
7.1 %/h), see Fig. 4 and SI. In situ UV-vis spectrometry of the
reaction solution indicated that with progressing reaction time,
3.16[b]
3.16[b]
1.9
3.3
{V4} +
7
15.7
Ba(NO3)2
(nBu4N)3
1.27[b]
7
31.4
3.2
[H3V10O28
]
[a] conditions: solvent: DMF, p = 8 bar O2, T = 80 °C; [b] the cluster concentration
was chosen to give identical vanadium concentrations in solution as for {Ba4V14
(i.e. 14 x 0.9 mM = 12.6 mM).
}
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Finally, we compared the catalytic performance of {Ba4V14} and
{V2Mo10} with the iso-polyoxovanadates {V4}, [H3V10O28]3- and a
mixture of {V4} and Ba2+ (i.e. the components used to form
{Ba4V14} to establish the importance of the cluster structure and
to verify that the presence of a vanadate moiety is not sufficient
for effective DHA oxidation catalysis. As shown in Table 1, under
identical experimental conditions (and identical vanadium
concentrations), we note significantly higher rates of
anthraquinone formation for {Ba4V14} and {V2Mo10} compared
with the reference components. While this initial result does not
provide deep mechanistic insight into the role of the cluster
structure, it nevertheless emphasizes that structural control and
modification of molecular vanadium oxides is a viable tool to
optimize the oxidative catalytic reactivity.
Acknowledgements
The Vector Foundation and Ulm University are gratefully
acknowledged for financial support.
Keywords: Polyoxometalate • Polyoxovanadate • Catalysis •
Self-Assembly • Oxidation
Notes and references
[1]
[2]
C. D. Weber, C. Bradley, M. C. Lonergan, J. Mater. Chem. 2014, 2,
303.
J. S. J. Hargreaves, D. S. Jackson, Metal Oxide Catalysis, WILEY-
VCH Verlag Weinheim, 2009.
In sum, this study demonstrates that the development of new
aerobic oxidation catalysts needs to be combined with advanced
reactor design considerations to achieve maximum catalytic
performance. Examples of suitable reactor types to maximize O2
transfer into the liquid phase for the system presented are
currently under investigation and could involve e.g. bubble
column or biphasic microflow reactors.[22]
[3]
[4]
[5]
S. Wang, G. Yang, Chem. Rev. 2015, 115, 4893–4962.
C. L. Hill, J. Mol. Catal. A Chem. 2007, 262, 2–6.
C. L. Hill, C. M. Prosser-McCartha, Coord. Chem. Rev. 1995, 143,
407–455.
[6]
[7]
J. Reichert, B. Brunner, A. Jess, P. Wasserscheid, J. Albert, Energy
Environ. Sci. 2015, 8, 2985–2990.
J. Albert, R. Wölfel, A. Bösmann, P. Wasserscheid, Energy Environ.
Sci. 2012, 5, 7956.
Experimental Section
[8]
[9]
J. Albert, P. Wasserscheid, Green Chem. 2015, 17, 5164–5171.
K. Kamata, K. Yonehara, Y. Nakagawa, K. Uehara, N. Mizuno, Nat
Chem 2010, 2, 478–483.
Synthesis of {Ba4V14}: (nBu4N)4[V4O12] • 4 H2O (= {V4}; 12 g, 8.35 mmol,
1 eq.) was reacted with Ba(NO3)2 (5.8 g, 22.2 mmol, 2.66 eq.) in dimethyl
sulfoxide (DMSO, 180 ml). The solution was stirred at 70°C for 4 h. After
cooling the yellow solution to room temperature, aqueous nitric acid (3 M,
6.25 mL) was added dropwise and the solution turned deep red. The
solution was stirred for 2 h at room temperature. Diffusion of acetone or
ethyl acetate into the mother liquor gave red block crystals suitable for
single-crystal X-ray diffraction. The red crystals were filtered off, washed
with acetone and diethyl ether and were air-dried. Yield: 7.13 g, 2.35 mmol,
98 % based on V). Elemental analysis of C28H84Ba4NO55S14V14 (calculated
values in brackets): C 11.09 (C 11.11), H 2.89 (H 2.80), N 0.60 (N 0.46),
S 14.68 (S 14.83), Ba 17.34 (Ba 18.15), V 20.44 (V 23.57). FT-IR
spectroscopy (in cm-1): 2998 (w), 2912 (w), 1434 (w), 1386 (m), 1314 (w),
1026 (vs), 988 (vs), 957 (m), 854 (m), 822 (m), 758 (m), 703 (m), 629 (s).
[10]
[11]
[12]
N. Mizuno, K. Yamaguchi, K. Kamata, Coord. Chem. Rev. 2005,
249, 1944–1956.
A. Sartorel, M. Carraro, F. M. Toma, M. Prato, M. Bonchio, Energy
Environ. Sci. 2012, 5, 5592.
H. Lv, Y. V. Geletii, C. Zhao, J. W. Vickers, G. Zhu, Z. Luo, J. Song,
T. Lian, D. G. Musaev, C. L. Hill, Chem. Soc. Rev. 2012, 41, 7572.
R. Neumann, Inorg. Chem. 2010, 49, 3594–3601.
A. M. Khenkin, L. Weiner, Y. Wang, R. Neumann, J. Am. Chem.
Soc. 2001, 123, 8531–8542.
[13]
[14]
[15]
[16]
A. M. Khenkin, R. Neumann, C. M. Che, Z. Mao, V. M. Miskowski,
M. C. Tse, C. K. Chan, K. K. Cheung, D. L. Phillips, K. H. Leung, A.
M. Khenkin, R. Neumann, Angew. Chemie 2000, 39, 4088–4090.
W. Adam, P. L. Alsters, R. Neumann, C. R. Saha-Möller, D.
Sloboda-Rozner, R. Zhang, J. Org. Chem. 2003, 68, 1721–1728.
R. Neumann, M. Levin, J. Am. Chem. Soc. 1992, 114, 7278–7286.
C. Doornkamp, V. Ponec, J. Mol. Catal. A Chem. 2000, 162, 19–32.
T. Punniyamurthy, S. Velusamy, J. Iqbal, Chem. Rev. 2005, 105,
2329–2364.
Catalytic test reaction: The oxidation experiments were performed in a
miniclave steel laboratory pressure reactor system from büchiglas using a
normal stir bar for mixing. Therefore 46 mM of substrate (DHA) where
dissolved together with 0.45 – 1.8 mM of catalyst in 50 mL DMF and put
into the pressure reactor. The pressure of pure oxygen (4 – 8 bar) could
be varied and monitored with a pressure gauge. With the integrated
sample taking system it was possible to take a sample out of the reactor
every hour. An exact volume of 0.5 mL of reaction mixture was taken out
and added to 4 mL of diethyl ether to precipitate the catalyst. After
centrifuging the mixture, the reaction products could easily be separated
from the catalyst and 1.5 mL of this clear solution were transferred into
HPLC-vials and stored in the fridge. To quantify the reaction components
(DHA, anthracene, anthrone, anthraquinone) a HPLC system was used.
[17]
[18]
[19]
[20]
[21]
B. B. Sarma, R. Neumann, Nat. Commun. 2014, 5, 4621.
G.-J. ten Brink, I. W. C. E. Arends, R. A. Sheldon, Science 2000,
287, 1636–1639.
[22]
M. Lechner, R. Güttel, C. Streb, Dalton Trans. 2016, 45, 16716–
16726.
High performance liquid chromatography (HPLC): HPLC was used to
quantify the reaction components. Therefore, a PerkinElmer Altus A-10
solvent and sample module with a separation module and a column oven
was used. For detection an Altus A-10 PDA detector was used together
with a C18 symmetry column (Waters). The following solvent mixtures
were used for product eluation: phase 1: linear gradient (for 20 min eluation
time) from MeCN:H2O (4:6) to MeCN:H2O (7:3); phase 2: further eluation
for 15 min at MeCN:H2O (7:3). Calibration curves of pure DHA, anthracene,
anthrone and anthraquinone were used to calculate the reagent
conversion and intermediate/product yield.
[23]
[24]
C. Streb, Springer Verlag, Berlin, Heidelberg, 2017, pp. 1–17.
W. G. Klemperer, T. A. Marquart, O. M. Yaghi, Angew. Chem. Int.
Ed. Engl. 1992, 31, 49–51.
[25]
[26]
Y. Hayashi, Coord. Chem. Rev. 2011, DOI: 10.10.
K. Kastner, J. T. Margraf, T. Clark, C. Streb, Chem. Eur. J. 2014,
20, 12269–12273.
[27]
K. Kastner, J. Forster, H. Ida, G. N. G. N. Newton, H. Oshio, C.
Streb, Chem. Eur. J. 2015, 21, 7686–7689.
This article is protected by copyright. All rights reserved.

10.1002/chem.201706046
Chemistry - A European Journal
COMMUNICATION
[28]
J. Tucher, C. Streb, Beilstein J. Nanotechnol. 2014, 5, 711–716.
[29]
J. Tucher, L. C. L. C. Nye, I. Ivanovic-Burmazovic, A. Notarnicola,
C. Streb, Chem. Eur. J. 2012, 18, 10949–10953.
A. Seliverstov, C. Streb, Chem. Eur. J. 2014, 20, 9733–9738.
B. Schwarz, J. Forster, M. K. Goetz, D. Yücel, C. Berger, T. Jacob,
C. Streb, Angew. Chem. Int. Ed. 2016, 55, 6329–6333.
M. H. Anjass, K. Kastner, F. Nägele, M. Ringenberg, J. F. Boas, J.
Zhang, A. M. Bond, T. Jacob, C. Streb, Angew. Chem. Int. Ed.
2017, 56, 14749–14752.
[30]
[31]
[32]
[33]
[34]
[35]
K. Kastner, M. Lechner, S. Weber, C. Streb, ChemistrySelect 2017,
2, 5542–5544.
Y. Ji, J. Hu, J. Biskupek, U. Kaiser, Y.-F. Song, C. Streb, Chem.
Eur. J. 2017, 23, 16637–16643.
E. A. Mamedov, V. Cortés Corberán, Appl. Catal. A, Gen. 1995,
127, 1–40.
[36]
[37]
I. Wachs, L. Briand, US Patent No US20050038299, 2005
K. Kastner, B. Puscher, C. Streb, Chem. Commun. 2013, 49, 140–
142.
[38]
K. Kastner, C. Streb, CrystEngComm 2013, 15, 4948.
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10.1002/chem.201706046
Chemistry - A European Journal
COMMUNICATION
FULL PAPER
The first molecular barium vanadium
oxide catalyst is reported. The
M. Lechner, K. Kastner, C.J. Chan, R.
Güttel,* C. Streb*
compound, [Ba4(dmso)14V14O38(NO3)],
is capable of the three-step aerobic
oxidation of the model reagent 9,10-
dihydroanthracene to anthraquinone,
it can be recycled without loss of
activity and provides critical insights
into the challenges arising from liquid-
gas phase catalysis using O2 as
environmentally benign oxidant.
Page No. – Page No.
Aerobic Oxidation Catalysis by a
Molecular Barium Vanadium Oxide
This article is protected by copyright. All rights reserved.