Formation of Alkanes by Aerobic Carbon-Carbon Bond Coupling Reactions Catalyzed by a Phosphovanadomolybdic Acid

Article abstract of DOI:10.1021/acscatal.7b00461

The valorization of alkanes is possible via carbon-carbon coupling reactions. A series of dialkyl cobalt complexes [(RCH₂)₂Co^III(bpy)₂]ClO₄ (R = H, Me, Et, and Ph) were reacted with the H₅PV₂Mo₁₀O₄₀ polyoxometalate as a catalyst, leading to a selective oxidative carbon-carbon bond coupling reaction. The reaction is initiated by electron transfer from [(RCH₂)₂Co^III(bpy)₂]⁺ to H₅PV^V₂Mo₁₀O₄₀ to yield an intermediate [(RCH₂)₂Co^IV(bpy)₂]²⁺-H₅PV^IVV^VMo₁₀O₄₀, as identified by a combination of EPR and X-ray photoelectron spectroscopy experiments. The reaction is catalytic with O₂ as terminal oxidant representing an aerobic C-C bond coupling reaction.

Full text of DOI:10.1021/acscatal.7b00461

Subscriber access provided by University of Newcastle, Australia
Letter
Formation of Alkanes by Aerobic Carbon-Carbon Bond Coupling
Reactions Catalyzed by a Phosphovanadomolybdic Acid
Miriam Somekh, Hagai Cohen, Yael Diskin-Posner, Linda Shimon,
Raanan Carmieli, Jeffrey N Rosenberg, and Ronny Neumann
ACS Catal., Just Accepted Manuscript • DOI: 10.1021/acscatal.7b00461 • Publication Date (Web): 14 Mar 2017
Downloaded from http://pubs.acs.org on March 14, 2017
Just Accepted
“Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted
online prior to technical editing, formatting for publication and author proofing. The American Chemical
Society provides “Just Accepted” as a free service to the research community to expedite the
dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts
appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been
fully peer reviewed, but should not be considered the official version of record. They are accessible to all
readers and citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered
to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published
in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just
Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor
changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers
and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors
or consequences arising from the use of information contained in these “Just Accepted” manuscripts.
ACS Catalysis is published by the American Chemical Society. 1155 Sixteenth Street
N.W., Washington, DC 20036
Published by American Chemical Society. Copyright © American Chemical Society.
However, no copyright claim is made to original U.S. Government works, or works
produced by employees of any Commonwealth realm Crown government in the course
of their duties.

Page 1 of 5
ACS Catalysis
1
2
3
4
5
6
7
8
9
Formation of Alkanes by Aerobic Carbon-Carbon Bond Coupling Reac-
tions Catalyzed by a Phosphovanadomolybdic Acid
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Miriam Somekh,† Hagai Cohen,‡ Yael Diskin-Posner,‡ Linda J. W. Shimon,‡ Raanan Carmieli,‡ Jeffrey N. Ros-
enberg,† and Ronny Neumann*†
† Department of Organic Chemistry, Weizmann Institute of Science, Rehovot, Israel 76100
‡ Department for Chemical Research Support, Weizmann Institute of Science, Rehovot, Israel 76100
ABSTRACT: The valorization of alkanes is possible via carbon-carbon coupling reactions. A series of dialkyl cobalt complexes
[(RCH2)2CoIII(bpy)2]ClO4 (R = H, Me, Et, and Ph) were reacted with the H5PV2Mo10O40 polyoxometalate as a catalyst leading to a selective
oxidative carbon-carbon bond coupling reaction. The reaction is initiated by electron transfer from [(RCH2)2CoIII(bpy)2]+ to H5PVV Mo10O40
2
to yield an intermediate [(RCH2)2CoIV(bpy)2]2+–H5PVIVVVMo10O40 as identified by a combination of EPR and X-ray photoelectron spectros-
copy experiments. The reaction is catalytic with O2 as terminal oxidant representing an aerobic C-C bond coupling reaction.
oxidative C-C bond coupling reaction with dialkyl cobalt(III) sub-
strates, Scheme 1.
KEYWORDS – Aerobic Oxidation, C-C Bond Coupling, Poly-
oxometalate, XPS, Electron Transfer
N
N
RCH2CH2R
+
Solv
CH2R
CH2R
N
N
N
N
+ H5PVV2Mo10O40 + 2 H+
+
INTRODUCTION
CoIII
N
CoIII
N
Solv
H7PVIV2Mo10O40
Oxidative sp3-sp3 C-C bond coupling reactions of metal-dialkyl
compounds through an oxidative reductive elimination pathway is
quite well known. For example, early work by Kochi and colleagues
showed that thermolysis of Et2Fe(bpy)2 yielded ethene and ethane,
products of β-hydrogen elimination, however, a two-electron oxi-
dation process led to selective reductive elimination and formation
of n-butane only.1 More recent research has been focused on square
planar Pd(II) compounds where reactions proceed via higher va-
lent Pd(III) or Pd(IV) intermediates.2 Such reactions have much
present relevance also in the context of valorization of light alkanes,
especially methane. Recently, there have been some reports on
similar intermolecular C-C bond coupling reactions from both
Pd(II) and Ni(II) square planar precursors.3 Generally speaking
oxidation at the metal center has been achieved by using both 1-
electron and 2-electron stoichiometric oxidants, often in excess.
The use of ferrocenium cations,4 Ag+,5 benzoquinone,6 and pyri-
dinium compounds7 among others is notable.
H7PVIV2Mo10O40 + 1/2 O2
H5PVV2Mo10O40 + H2O
Scheme 1. Aerobic oxidative C-C bond formation in dialkylco-
balt(III) compounds catalyzed by H5PV2Mo10O40.
RESULTS AND DISCUSSION
A series of dialkyl cobalt complexes [(RCH2)2CoIII(bpy)2]ClO4
where R= H (1a), CH3 (1b), CH3CH2 (1c), Ph (1d), and for cy-
clic-CH2CH2CH2CH2 (1e) was synthesized by adaptation of a
literature method that involves the in situ reductive alkylation of a
Co(II) salt in the presence of 2,2’-bipyridine, NaBH4 and the ap-
propriate alkylhalide.10 The red complexes that were obtained were
diamagnetic. Crystal structures were obtained for 1c-d, Figure 1
and 1e Figure S11.
Surprisingly, the use of O2 as terminal oxidant has not been
shown for the oxidative coupling reactions mentioned above. To
facilitate such a transformation a one or two electron oxidant to the
metal-dialkyl species that could be then recovered by reoxidation
with O2 would be very advantageous towards an aerobic catalytic
transformation. Indeed it has been shown in the past that phospho-
vanadomolybdates of the a-Keggin structure such as
H5PV2Mo10O40 are excellent electron transfer oxidants of many
substrate types that upon reduction by one or two electrons are
quite easily re-oxidized by O2.8 It should be specifically noted that
tetra-alkyltin compounds also can be activated and aerobically oxi-
dized with H5PV2Mo10O40 but in that case oxygen insertion into the
metal-carbon bond occurs to yield an alcohol as the product.9 In the
research presented in this paper, we demonstrate such an aerobic
Figure 1. ORTEP drawing (50% probability) of 1c (left) and 1d
(right). Co-magenta, C-black and N-blue. Hydrogen atoms and the
ClO4 anion are not shown.
ACS Paragon Plus Environment

ACS Catalysis
Page 2 of 5
The crystal structures revealed the expected 6 coordinate regular
After demonstrating selective aerobic catalytic C-C bond cou-
pling we turned our attention to the reaction mechanism and the
identification the apparent reaction intermediate, the blue precipi-
1
2
3
4
5
6
7
8
octahedral complex with the alkyl moieties in the a-cis positions.
We were unable to crystallize complexes 1a-b, however, they were
unequivocally identified by their NMR spectra (see the supporting
information).
tate. Given that H5PV2Mo10O40 reacts with to create a more elec-
1
tron poor metal center via electron transfer, two realistic reaction
mechanisms can be contemplated, (i) Co-alkyl bond homolysis,
and (ii) direct reductive elimination, Scheme 2.
After preparation of 1a-e, they were each reacted with an equiva-
lent amount of H5PV2Mo10O40 as oxidant under Ar. Thus, 30 µmol
and 30 µmol H5PV2Mo10O40 in 6 mL n-butyronitrile were reacted
N
Solv
N
1
CoIII
+
CH2R
RCH2CH2R
i
N
CH2R
at RT. Immediately a blue precipitate of the signature heteropoly
blue compound was formed signifying that the polyoxometalate
was instantaneously reduced. Analysis of the reaction mixture at
this point showed no significant formation of product indicating
that the precipitate is a reaction intermediate (see below). Subse-
quent heating of the solution at 50 °C for 3 h revealed the quantita-
tive formation of ethane, n-butane, n-hexane, bibenzyl and cyclobu-
tane for 1a-e, respectively. No oxygen transfer from the polyoxo-
metalate by an ET-OT mechanism8 to obtain an oxygenated prod-
uct such as RCH2OH was observed as occurred with Sn(alkyl)4
substrates.9 Rather, the results point to a highly selective head to
head oxidative carbon-carbon coupling with no formation of by-
products. For example, from 1c no propane, propene, acetone, or
other hexane isomers were formed. A control experiment without
N
N
N
9
CH2R
CH2R
CH2R
CH2R
N
N
N
N
CoIV
N
CoIII
N
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
N
ii
Solv
Solv
N
CoII
N
+
RCH2CH2R
N
+
H5PVV2Mo10O40
H5PVVVIVMo10O40
Intermediate
Scheme 2. Pathways for C-C bond coupling of
H5PV2Mo10O40.
1 with
The Co-alkyl bond homolysis can be excluded as such a pathway
would likely yield various alkane isomers since one could expect
stabilization of secondary carbon radicals versus primary ones.
Thus, for alkyl = n-propyl 2,3-dimethylbutane would be a more
likely product compared to the n-hexane. The formation of pro-
pane would also be possible in such a case by a hydrogen atom
transfer step. In addition, a crossover experiment where a 1:1 ratio
of RCH2 = Et and n-Pr were used as substrates only n-butane and n-
hexane were formed with no pentane product whatsoever. Dispro-
portionation (not shown) was the likely pathway for oxidative C-C
bonding coupling from square planar Pd(II) and Pt(II) complex-
es,2a,12 however, this seems very unlikely in this case, since this
would require the formation of a heptacoordinate Co(V) complex
and a Co(III) complex from an initially formed Co(IV) intermedi-
ate. Furthermore, a crossover experiment as mentioned above
would be expected to yield butane, pentane and hexane in a 1:2:1
ratio. Thus, the results would appear to support a direct reductive
elimination pathway as the most reasonable option to explain the
high selectivity of the reaction.
H5PV2Mo10O40 showed that
tions. Only upon heating to 220 °C was a mixture of products
formed. Similar stoichiometric reactions of and H5PV2Mo10O40
1
was stable under the reaction condi-
1
under 1.5 bar O2 also yielded only the C-C coupling products ex-
cept for 1d (R = Ph) where both benzaldehyde (83%) and bibenzyl
(17%) were formed in a quantitative reaction. Since oxygen transfer
from the polyoxometalate was not observed for 1a-e one can con-
clude that for 1d only, O2 directly reacted with an intermediate to
yield benzaldehyde. This was confirmed by carrying out a reaction
with 18O2 that yielded PhCH18O.
Since it is known as discussed above that the reduced polyoxo-
metalate, e.g. H7PVIV Mo10O40 can be oxidized to H5PVV Mo10O40
2
2
with O2, catalytic reactions were carried out as summarized in Ta-
ble 1. As seen in Table 1 the reaction products were identical to
those obtained in the stoichiometric reactions under O2. Further-
more, the yields and turnover numbers were very similar for all
substrates suggesting that in these reactions the rate determining
step for the catalytic reaction is the re-oxidation of H7PVIV Mo10O40
2
with O2. Note that since in the oxidative reductive elimination pro-
cess no protons are formed, their addition considerably improves
the efficiency of the re-oxidation reaction in the catalytic cycle
(third entry); see also Scheme 1.11
Table 1. Aerobic Catalytic C-C Bond Coupling.
Substrate
1a (R = H)
1b (R = Me)
1c (R = Et)
1c (R = Et)[a]
1d (R = Ph)
Product
Yield , mol%
TON
35
100% ethane
100% n-butane
100% n-hexane
100% n-hexane
61
64
37
Figure 2. X-band EPR spectrum of the intermediate species.
66
38
A qualitative determination of the blue intermediate species ob-
tained from an equimolar mixture of 1c and H5PV2Mo10O40 as por-
trayed in Scheme 2 can be obtained by low temperature X-band
EPR spectroscopy, Figure 2. One can discern two peaks; the typi-
cal anisotropic spectrum at g = ~2.1 for a vanadium(IV) species
associated with the one-electron reduced polyoxometalate13 and a
peak at g = ~4.3 that we associate with a small amount of a S = 3/2
Co(II) species that is formed in the reaction (see below).14 A peak
assignable to Co(IV)is not apparent.14 Under conditions where the
100
64
58
37
89% PhCHO
11% Bz-Bz
Reaction conditions: 150 µmol 1a-d, 2.6 µmol H5PV2Mo10O40, 15
mL of n-butyronitrile, 5 bar O2, 24 h, 60 °C. [a] 4 µmol H2SO4 added,
12 h.
ACS Paragon Plus Environment

Page 3 of 5
ACS Catalysis
intermediate is let to react in the solid state, the peak associated oxometalate to yield a Co(III) compound and more V(IV) species
1
2
3
4
5
6
7
8
with the S = 3/2 Co(II) species is more significant, Figure S15.
thus explaining all the experimental XPS results.
CONCLUSION
Despite the obvious redox reaction between 1c and
H5PV2Mo10O40 and the formation of V(IV) as shown by EPR, and
since the peak associable to Co(IV) was not observed we turned to
XPS measurements to obtain further information and to quantita-
tively decipher the cobalt and vanadium species as a function of
their oxidation states. Thus, 1c and H5PV2Mo10O40 were reacted in
a 1:1 ratio, the blue precipitate that was formed was immediately
vacuum filtered; dried under high vacuum, transferred to a carbon
tape and promptly taken to the spectrometer to minimize air expo-
sure of the sample. Compounds 1c and [CoII(bpy)2(CH3CN)2]Cl2
were used as references for cobalt(III) and cobalt(II),15 respective-
ly. H5PV2Mo10O40 was used as a reference for vanadium(V). The X-
ray photoelectron spectroscopy (XPS) Co 2p3/2 line of the inter-
mediate and the control compounds for Co(II) and Co(III) are
presented in Figure 3, left. The first point of note is that unusually
the Co(II) compound has a higher binding energy, 780.9 eV, than
the Co(III) compound, 779.7 eV, which is opposite to the general
trend of chemical shifts in XPS; where the higher the oxidation
state the higher the binding energy is. This phenomenon has al-
ready been reported and explained by the presence of strong elec-
tron interactions: the occupied dz2 valence orbital in Co(II) in-
creases the binding energy,16 while the absence of an electron in the
valence orbital of Co(III) leads to a lower binding energy, despite
the higher oxidation state. Clearly, the intermediate has a signifi-
cantly higher binding energy, 782.5 eV, see Figure 3, than the two
reference samples. It is assigned to a Co(IV) metal center. Notably,
additional Co(II) and Co(III) are found as well in this case and is
discussed below.
An aerobic oxidative catalytic C-C bond coupling reaction of an
octahedral dialkyl-cobalt(III) complex, [(RCH2)2CoIII(bpy)2]+,
yielded the head-head product only, for example n-hexane from R=
Et. The reaction was shown to take place by using H5PVV Mo10O40
2
as an electron transfer catalyst, forming a [(RCH2)2CoIV(bpy)2]2+–
H5PVIVVVMo10O40 intermediate at room temperature. By heating to
50 °C the C-C bond coupling takes place through a reductive elim-
ination step. For RCH2 = Bz, oxygenation also occurs in significant
amounts in a kinetically competitive reaction. The working hy-
pothesis is that O2 can react with the reduced polyoxometalate in
the intermediate to yield a superoxide (VV-OO•) that leads to oxy-
genation and formation of the aldehyde. Interestingly, the EPR
spectrum indicates that the Co(II) species formed is high spin, S =
3/2. This species is re-oxidized to yield a diamagnetic Co(III) spe-
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
cies and H5PVIV Mo10O40. Since the latter is easily oxidized in the
2
presence of protons and O2 as terminal oxidant, catalytic turnover
is observed under aerobic conditions, a novel finding in this area
where the use of one and two electron stoichiometric oxidants is
the norm. Future research will be focused on combining alkane
activation with oxidative C-C bond coupling as described.
EXPERIMENTAL PART
Synthesis of complexes 1a-d. An orange deaerated solution of 0.78 g (5
mmol) 2,2-bipyridine and 0.60 g (2.5 mmol) of CoCl2•6H2O in 50 mL
methanol was prepared and then the corresponding alkyl halide (7.5 mmol
RI; R = Me Et, n-Pr or 5.o mmol BzCl) was added to the solution under a
slight positive pressure of Ar. NaBH4 (0.2 g, 5 mmol) was added under
vigorous stirring in small portions during a period of 40 min. After every
addition of NaBH4 a blue Co(I) intermediate was formed. The next portion
was added only after the blue color disappeared. After a few portions, the
solution slowly became dark red. Note that an excess of NaBH4 needs to be
avoided. The red solution was treated with 0.3 g NaClO4 dissolved in 10
mL of water followed by evaporation to 15 mL. Addition of 30 mL cold
H2O yielded a precipitate that was collected by centrifugation. The precipi-
tate was washed with cold water until the wash was almost colorless. Water
1
was removed by lyophilization and products were stored at –80 °C. H
NMR and 13C NMR were recorded on Bruker Avance 300 MHz and 500
MHz spectrometers at 298K and referenced to solvent shift. The NMR and
HR-MS spectra of 1a-d and their analysis can be found in the supporting
information.
Synthesis of complex 1e. An orange deaerated solution of 0.78g (5.0
mmol) 2,2-bipyridine and 0.60 g (2.5 mmol) CoCl2•6H2O in 30 mL meth-
anol and 20 mL dimethoxy ethane was prepared and then 0.2 g (0.625
mmol) 1,4-diidobutane was added. The solution was deaerated for 15 min
with Ar, then 2.5 mmol NaBH4 was added as described above and then left
to react for an additional 20 min. 0.3g (2.5 mmol). The product was isolat-
ed as described above. Note that the use of 1.25 mmol 1,4-diidobutane
yielded a dialkyl complex with two iodo-butane ligands and not the metal-
locycle. This compound also underwent C-C coupling to yield 1,8-
diiodooctane.
X-Ray crystallography. Samples (10 mg) were dissolved in 1 mL
CH3CN in a 2 mL vial. The open vial was inserted in a 20 mL vial in which
with 3 mL of diethyl ether. The bigger vial was tightly close and left two
weeks at 4 °C. Single crystal X-ray data were collected on a Bruker APEX-II
Kappa CCD or Rigaku XtaLab PRO equipped with PILATUS 200 diffrac-
tometer with Mo Kα (λ = 0.71073 nm) radiation and graphite mono-
chromator. Measurement were performed at 100K under liquid N2 to
achieve better quality data. The data were processed using Bruker Apex2
suite for complex 1c and 1d, and CrysAlisPro 1.171.39.4c for 1e. Structures
were solved by direct methods with SHELXS or SHELXT. Full-matrix
least-squares refinement was based on F2 with SHELXL-2014. The crystal-
lographic data are presented in Table S1.
Figure 3. X-ray photoelectron spectra of the reaction intermediate, 1c
,
and reference compound, [(Solv)2CoII(bpy)2]Cl2. Left - the Co 2p3/2
spectral window; Right – the V 2p3/2 line.
In Figure 3, right, we present the XPS V 2p3/2 line of the inter-
mediate. As would be expected for a one electron transfer process,
the reaction of 1c and H5PVV Mo10O40 should yield an intermediate
2
containing [PVIVVVMo10O40]6– that would have an equimolar
amount of V(IV) and V(V). Figure 3 suggests that this is approxi-
mately though not exactly correct. The measured higher amount of
V(IV) versus V(V) and the small amounts of Co(II) and even
Co(III) can be attributed to impurities in the intermediate due to
its further reaction under the vacuum conditions and low flux X-ray
irradiation to yield n-hexane and a Co(II) compound by reductive
elimination, Scheme 2. The latter can then be oxidized by the poly-
ACS Paragon Plus Environment

ACS Catalysis
Page 4 of 5
X-ray photoelectron spectroscopy. 1c and H5PV2Mo10O40 were reacted
This research was supported by the Israel Science Foundation (grant #
at a 1:1 ratio, the blue precipitate that was formed was immediately vacuum
filtered; dried under high vacuum, transferred to a carbon tape and prompt-
ly taken to the spectrometer to minimize oxygen exposure of the sample.
Measurements were performed in a Kratos AXIS-Ultra DLD spectrometer
at a base pressure of 10-9 torr, using monochromatic Al ka source at a high-
ly reduced power, up to 15 W at most. Charge compensation by an electron
flood gun was needed in all measurements of these powders. Due to large
spot-dependent charging variations and, on the other hand, small yet im-
portant binding energy chemical shifts in the organic species, we used the
two leading C 1s lines of the bipyridine ligands for energy-scale calibration
(cross checked with the bipyridine nitrogen and with the Mo 3d of the
polyoxometalate signal). This referencing procedure reduced the uncer-
tainty in binding energies to values much smaller than the differences ob-
served in the Co line. A particular care was taken as of sample degradation
under the x-ray irradiation, by using extremely low fluxes and repeated
scans such as to follow those processes and eventually extract the data at
minimal damage conditions.17
1
2
3
4
5
6
7
8
2046/14). Bidyut B. Sarma is thanked for his assistance. R.N. is the
Rebecca and Israel Sieff Professor of Organic Chemistry.
REFERENCES
1. Tsou, T. T.; Kochi, J. K. J. Am. Chem. Soc. 1978, 100, 1634-1635.
2. (a) Lanci, M. P.; Remy, M. S.; Kaminsky, W.; Mayer, J. M.; Sanford,
M. S. J. Am. Chem. Soc. 2009, 131, 15618-15620. (b) Lanci, M. P.; Remy,
M. S.; Lao, D. B.; Sanford, M. S.; Mayer, J. M. Organometallics 2011, 30,
3704-3707. (c) Khusnutdinova, J. R.; Rath, N. R.; Mirica, L. M. J. Am.
Chem. Soc. 2012, 134, 2414-2422. (d) Byers, P. K.; Canty, A. J.; Skelton,
B. W.; White, A. H. J. Chem. Soc., Chem. Commun. 1986, 1722-1724. (e)
Byers, P. K.; Canty, A. J.; Crespo, M.; Puddephatt, R. J.; Scott, J. D. Organ-
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
ometallics 1988, 7, 1363-1367. (f) Dücker-Benefer, C.; van Eldik, R.;
Canty, A. J. Organometallics 1994, 13, 2412-2414. (g) Canty, A. J. Dalton
Trans. 2009, 10409-10417. (h) Khusnutdinova, J. R.; Qu, F.;Zhang, Y.;
Rath, N. P.; Mirica, L. M. Organometallics 2012, 31, 4627-4630. (i) Tang,
F.; Zhang, Y.; Rath, N. P.; Mirica, L. M. Organometallics, 2012, 31, 6690-
6696.
3. (a) Lotz, M. D.; Remy, M. S.; Lao, D. B.; Ariafard, A.; Yates, B. F.;
Canty, A. J.; Mayer, J. M.; Sanford, M. S. J. Am. Chem. Soc. 2014, 136,
8237-8242. (b) Xu, H.; Diccianni, J. B.; Katigbak, J.; Hu, C.; Zhang, Y.;
Diao, T. J. Am. Chem. Soc. 2016, 138, 4779-4786.
4. Sato, M.; Mogi, E.; Kumakura S. Organometallics, 1995, 14, 3157-
3159.
5. (a) Kraatz, H. B.; van der Boom, M. E.; Ben-David, Y.; Milstein, D.
Isr. J. Chem. 2001, 41, 163-172. (b) MacLeod, K.C.; Patrick, B. O.; Smith,
K. M. Organometallics, 2012, 31, 6681-6689.
6. Albéniz, A.; Espinet, P.; Martín-Ruiz, B. Chem.–Eur. J. 2001, 7, 2481-
2489.
7. Ball, N. D.; Kampf, J. W. Sanford, M. S. J. Am. Chem. Soc., 2010, 132,
2878-2879.
8. (a) Neumann, R. Inorg. Chem. 2010, 49, 3594-3601. (b) Neumann,
R.; Khenkin, A. M. Chem. Commun. 2006, 2529-2538.
9. Khenkin, A. M.; Efremenko, I.; Martin, J. M. L.; Neumann, R. J. Am.
Chem. Soc. 2013, 135, 19304-19310.
EPR spectroscopy. 1c and H5PV2Mo10O40 were reacted at a 1:1 ratio, the
blue precipitate that was formed was immediately transferred into an EPR
capillary tube and analyzed on the spot. X-band EPR spectra were recorded
on a Bruker ELEXSYS 500 spectrometer equipped with a Bruker
ER4122SHQE resonator at 20 K with microwave power of 20 mW, 0.1 mT
modulation amplitude and 100 kHz modulation frequency.
Carbon-carbon coupling reactions. Stoichiometric reactions: 1a-e (30
18
µmol) and 30 µmol (69 mg) H5PV2Mo10O40•32H2O each in 3 mL n-
butyronitrile were mixed in a Ace glass pressure tube, frozen, degassed and
then filled with 1.5 atm of Ar or O2 The mixture was stirred at 50 °C for 3 h,
cooled to ~0 °C and analyzed by gas chromatography. Catalytic reactions:
1a-d (150 µmol) were reacted with 2.6 µmol (6 mg) H5PV2Mo10O40
•32H2O in 15 mL of n-butyronitrile for 24 h at 60 °C under 5 bar O2. Gas
phases were analyzed by GC-TCD equipped with 2 m, 0.53 µm i.d. Restek
ShinCarbon ST 80/100 column and quantified using standards. Liquids
were qualitatively analyzed GC-MS and quantified by GC-FID for quanti-
tative analysis using a Restek 5% phenyl methylsilicone 0.32 mm i.d., 0.25
mm coating, 30 m column with He as carrier gas.
10. Mestroni, G.; Camus, A.; Mestroni, E. J. Organometallic Chem.
1970, 24, 775-781.
11. In a reaction cycle including alkane activation the needed protons
would come from the activation step.
12. Johansson, L.; Ryan, O. B.; Romming, C.; Tilset M. Organometal-
INFORMATION
Corresponding Author
* Email: Ronny.Neumann@weizmann.ac.il
lics, 1998, 17, 3957-3966.
Present Addresses
13. (a) Kaminker, I.; Goldberg, H.; Neumann, R.; Goldfarb, D. Chem.,
A Eur. J. 2010, 16, 10014-10020. (b) Goldberg, H.; Kaminker, I.; Goldfarb,
D.; Neumann, R. Inorg. Chem. 2009, 48, 7947-7952.
14. (a) McAlpin, J. G.; Surendranath, Y.; Dinca, M.; Stich, T. A.; Stoian,
S. A.; Casey, W. H.; Nocera, D. G.; Britt, R. D. J. Am. Chem. Soc. 2010, 132,
6882-6883. (b) Jiménez, H. R.; Salgado, J.; Moratal, J. M.; Morgenstern-
Badarau, I. Inorg. Chem. 1996, 35, 2737-2741.
15. Sobkowiak, A.; Sawyer, D. T.; J. Am. Soc. Chem. 1996, 113, 9520-
9523.
16. (a) Burger, K.; Furlani, C.; Mattogno, G. J. Electron. Spectrosc.
Relat. Phenom. 1980, 21, 249-256. (b) Ivanova,T.; Naumkin, A.; Sidorov,
Jeffrey N. Rosenberg – California Institute of Technology, jrosen-
be@caltech.edu
Author Contributions
The manuscript was written through contributions of all authors and
they have given their approval to the final version of the manuscript.
ASSOCIATED CONTENT
Supporting Information
A.; Eremenko, I.; Kiskin, M. J. Electron. Spectrosc. Relat. Phenom. 2007
156, 200-203.
,
Additional NMR and X-ray diffraction including cif files. This material
is available free of charge via the Internet at http://pubs.acs.org.
17. Frydman, E.; Cohen, H.; Maoz, R.; Sagiv, J. Langmuir 1997, 13,
5089-5106.
18. Tsigdinos, G. A.; Hallada, C. J. Inorg. Chem. 1968, 7, 437-441.
ACKNOWLEDGMENT
ACS Paragon Plus Environment

Page 5 of 5
ACS Catalysis
SYNOPSIS TOC
1
2
3
4
5
N
N
Solv
Solv
N
N
CH2R
CH2R
N
N
CoII
N
+ RCH2CH2R
CoIII
N
O2
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
5
ACS Paragon Plus Environment