ChemComm
Communication
Notes and references
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D. Schr ¨o der, C. A. Schalley, J. N. Harvey and H. Schwarz, Int. J. Mass
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A. C. Schmidt, A. V. Nizovtsev, A. Scheurer, F. W. Heinemann and
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Fig. 1 Molecular structure of 1Á4C
6 6
D . Thermal ellipsoids are shown at 50%
probability. Four co-crystallised benzene solvent molecules and carbon bound
hydrogen atoms are omitted for clarity. The structure features a crystallographic
inversion centre in the middle of the oxalate C–C bond.
9
A. R. Sadique, W. W. Brennessel and P. L. Holland, Inorg. Chem.,
2
008, 47, 784.
1
1
0 R. Angamuthu, P. Byers, M. Lutz, A. L. Spek and E. Bouwman,
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1 D. S. Laitar, P. M u¨ ller and J. P. Sadighi, J. Am. Chem. Soc., 2005,
spectrum of 1 dissolved in benzene-d
6
shows one set of signals
corresponding to the protons of the b-diketiminate over a range
127, 17196.
of Æ150 ppm (see ESI,‡ Fig. S7). At r.t. in solution 1 exhibits a 12 C. H. Lee, D. S. Laitar, P. Mueller and J. P. Sadighi, J. Am. Chem. Soc.,
2
8
2007, 129, 13802.
magnetic moment of m = 3.96 m (Evans’ method, thf-d ),
eff
B
8
1
3 B. C. Fullmer, H. Fan, M. Pink and K. G. Caulton, Inorg. Chem., 2008,
II
which is consistent with the expectations for two high spin Ni
ions (two uncoupled spins of S = S = 1, ms.o. = 4 m
Antiferromagnetic coupling should become visible only at low
temperatures. The IR spectrum of 1 shows a broad intense
absorption band centred at 1650 cm representing the oxalate
dianion vibration. Also, the dinickel(II) oxalate complex, 1, can
be reduced by potassium graphite in the presence of dinitrogen
regenerating the dinickel(I) precursor complex, IV (Scheme 3).
Again, in order to get some ideas on mechanistic possibi-
lities orienting DFT calculations were performed (see ESI‡).
4
7, 1865.
). 14 C. Bianchini, C. Mealli, A. Meli and M. Sabat, Inorg. Chem., 1984,
3, 2731.
5 (a) K. S. Ratliff, R. E. Lentz and C. P. Kubiak, Organometallics, 1992,
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1
2
B
2
1
2
6
1
À1
2005, 24, 96.
1
6 M. Rudolph, S. Dautz and E.-G. J ¨a ger, J. Am. Chem. Soc., 2000,
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1
7 J.-H. Jeoung and H. Dobbek, Science, 2007, 318, 1461.
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1
R. Metzinger, Z. Anorg. Allg. Chem., 2011, 637, 1169.
Surprisingly, an initial step consisting of the replacement of the 20 B. Horn, C. Limberg, C. Herwig, M. Feist and S. Mebs, Chem.
tBu
tBu
Commun., 2012, 48, 8243.
1 Yields given here represent the average of at least 3 independent
runs of an experiment.
N
2
ligand in IV by CO
2
with formation of a [L Ni(CO
2
)NiL
]
2
compound or the reaction with two CO
2
molecules to give
tBu
[L
Ni(CO
2
)] was found to be endothermic on all reasonable 22 In order to test the viability of an intermediate occurrence of the
potential energy surfaces, so that the initiation of the reaction
appears to be more complicated than should be expected. The
tBu
nickel(0) carbonyl complex K
2 2 2
[L NiCO] , it was treated with CO ,
and again II and III were obtained besides other intractable pro-
tBu
2
ducts. In contrast, [L NiCO], II, does not react with CO over a
overall reaction between IV and two CO
2
molecules to give 1 was
period of 18 h, and it thus represents the dead end of CO
2
À1
activation.
found to be highly exothermic though (À179.6 kJ mol ).
tBu
2
3 K
6
[
3 6
NiCO ] , III, was detected as a byproduct accounting for the
I
In conclusion, reaction of the dinuclear Ni complex
2À
2
missing O ion delivered from CO reduction. We assume that the
tBu
I
2À
I tBu
K
2
[L Ni (N
2
)Ni L ], I, with CO
2
results in the formation of the
formation of III resulted from residual impurities of potassium
bromide originating from the synthesis of the starting complex IV.
2
À
CO or CO
the dinickel(I) compound [L Ni (N
3
containing complexes II and III, respectively, whereas
2
À
2À
3
Beyond that O
isolated.
or CO
containing products could not be
tBu
I
I tBu
2
)Ni L ], IV, mediates the reduc-
tive coupling of CO to give a nickel(II) oxalate complex 1. In both 24 X-ray diffraction analysis revealed a solid solution of 1 and
2
tBu
[
L
NiBr], V (unconsumed starting material from the synthesis of IV).
cases reduction of the carbonate and oxalate products, respectively,
with KC in a dinitrogen atmosphere yielded back the corresponding
starting materials, so that the synthetic cycles could be closed. While
some nickel complexes mediating reductive cleavage of CO exist
examples that are able to reductively couple
2
5 It is difficult to determine the relative yields of II, III and 1 within
the crude product as there is no common spectroscopic tool for
their detection and comparison at the same time. Small amounts of
other unidentified products are formed, too.
6 (a) A. Bencini, A. Bianchi, P. Paoli, E. Garc ´ı a-Espa n˜ a, M. Julve and
V. Marcelino, J. Chem. Soc., Dalton Trans., 1990, 2213; (b) H.-D. Bian,
W. Gu, Q. Yu, S.-P. Yan, D.-Z. Liao, Z.-H. Jiang and P. Cheng,
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O. Cador, M. Zeller, S. Trofimenko, L. Ouahab, A. W. Addison,
V. V. Pavlishchuk and A. D. Hunter, Dalton Trans., 2012, 41, 11319.
8
2
2
1
2,14,29
in the literature,
CO to generate C
continued studies on the activation of CO
We are grateful to the Cluster of Excellence ‘‘Unifying
2À
2
2
O
4
are rather rare. These observations motivate
I
2
by Ni compounds.
Concepts in Catalysis’’ funded by the Deutsche Forschungs- 27 N. A. Eckert, E. M. Bones, R. J. Lachicotte and P. L. Holland, Inorg.
Chem., 2003, 42, 1720.
gemeinschaft (DFG), as well as the Humboldt-Universit ¨a t zu Berlin
for financial support. We also thank C. Matlachowski for EPR
measurements.
2
2
8 D. F. Evans, J. Chem. Soc., 1959, 2003.
9 L. Gonz ´a lez-Sebasti ´a n, M. Flores-Alamo and J. J. Garc ´ı a, Dalton
Trans., 2011, 40, 9116.
This journal is c The Royal Society of Chemistry 2013
Chem. Commun., 2013, 49, 10923--10925 10925