Reactions of Diethylamine and Ethylene Catalyzed by PtII or Pt0
Typical Procedures for Et2NH Transalkylation: The autoclave was
charged with K2PtCl4 or Pt black (0.13 mmol) and submitted to
Conclusions
This study has revealed that the catalytic systems I and argon/vacuum cycles. Et2NH or Et3N (45.5 mmol, 350 equiv.) was
added and the ethylene pressure (if needed) was adjusted to 25 bar
(ca. 100 mmol, 333 equiv.) at room temp. The remainder of the
experiment was carried out as above. A minor amount of D2O was
added to obtain the NMR lock.
IЈ do not efficiently add the N–H bond of Et2NH across
the C=C bond of ethylene, although a computational inves-
tigation suggests that they should be as competent to cata-
lyze this transformation as the addition of the aniline N–H
bond. The reason is attributed to rapid catalyst degradation
with reduction to metallic platinum, which is favoured by
the deprotonation of the key zwitterionic intermediate
(3Ј).[12] This deprotonation is also favoured by the high ba-
sicity of Et2NH.
Parallel studies have also shown that the metallic plati-
num produced is responsible for a transmetallation reac-
tion, which equilibrates Et2NH with Et3N, EtNH2 and even
NH3. This appears to be the first report of Pt0-catalyzed
amine transalkylation, a process that has previously been
well established for Pd0. This process is inhibited by the
olefin, presumably because of a surface saturation effect,
which blocks its access to the substrate C–H bonds. Among
two different mechanistic pathways involving the activation
of the amine α-CH and β-CH bonds, respectively, the latter
was shown to be present by a control experiment, although
the former could also play a role as previously suggested
for the Pd0-catalyzed process.[21]
Computational Details: The DFT calculations were carried out ac-
cording to the methodology described in detail in our recent studies
on the C2H4/PhNH2 reaction,[10–11] namely using the B3LYP func-
tional and the standard 6-31+G* basis set for all atoms except Pt,
for which the LANL2TZ(f) basis was used.[27] The calculations in-
cluded a frequency analysis for all minima and transition states
and solvation effects by single-point CPCM[28–29] corrections on
the gas-phase optimized geometries, from which the thermo-
dynamic ΔGCPCM values were derived. All new optimized geome-
tries are available in the SI.
Supporting Information (see footnote on the first page of this arti-
cle): List of optimized Cartesian coordinates for all new geometries.
Acknowledgments
We are grateful to the Centre National de la Recherche Scientifique
(CNRS), the Agence Nationale de la Recherche (ANR), grant
number NT09_442499, and the Institut Universitaire de France
(IUF) for financial support as well as the Centre Informatique
National de l’Enseignement Supérieur (CINES) and the Centre In-
teruniversitaire de Calcul de Toulouse (CICT), project CALMIP,
for granting free computational time. P. A. D. thanks the Ministère
de l’Éducation Nationale, de l’Enseignement Supérieur et de la Re-
cherche (MENESR) for a Ph.D. fellowship.
Experimental Section
General: All solvents were of HPLC grade and were used as re-
ceived. Et2NH (Fluka) was distilled and kept under argon in the
dark. PtBr2 (Alfa Aesar), K2PtCl4 (Alfa Aesar) and nBu4PBr
(Acros Organics) were used as received. Ethylene (purity Ն 99.5%)
was purchased from Air Liquide.
[1] J.-J. Brunet, D. Neibecker, in: Catalytic Heterofunctionalization
(Eds.: A. Togni, H. Grützmacher), Wiley-VCH, Weinheim,
Germany, 2001, pp. 91–141.
[2] J.-J. Brunet, N.-C. Chu, M. Rodriguez-Zubiri, Eur. J. Inorg.
Chem. 2007, 4711–4722.
[3] T. E. Müller, K. C. Hultzsch, M. Yus, F. Foubelo, M. Tada,
Chem. Rev. 2008, 108, 3795–3892.
[4] J. J. Brunet, M. Cadena, N. C. Chu, O. Diallo, K. Jacob, E.
Mothes, Organometallics 2004, 23, 1264–1268.
[5] J. J. Brunet, N. C. Chu, O. Diallo, Organometallics 2005, 24,
3104–3110.
Instrumentation: NMR investigations were carried out with a
Bruker AV400 spectrometer at 298 K operating at 400.1 MHz (1H),
100.6 MHz (13C) and 28.9 MHz (14N). The spectra were calibrated
with the residual solvent resonance relative to tetramethylsilane
(1H, 13C) and MeNO2 (14N).
Typical Procedures for the Attempted Hydroamination of Ethylene
by Et2NH: (a) with PtBr2/nBu4PBr: An autoclave was charged with
PtBr2 (46 mg, 0.13 mmol) and nBu4PBr (440 mg, 1.3 mmol,
10 equiv.) and submitted to argon/vacuum cycles. Et2NH (4.7 mL,
45.5 mmol, 350 equiv.) was syringed into the autoclave. Finally, the
ethylene pressure was adjusted to 25 bar (ca. 100 mmol, 333 equiv.)
at room temp. The temperature was then raised to 150 °C. After
10 h, the autoclave was allowed to cool to room temperature and
then slowly vented. An external standard (EtOH or 1,4-dioxane,
1.3 mmol) was added to the mixture. The solution was then ana-
lyzed by NMR spectroscopy with traces of CDCl3 to obtain an
instrument lock.
[6] P. A. Dub, M. Rodriguez-Zubiri, C. Baudequin, R. Poli, Green
Chem. 2010, 12, 1392–1396.
[7] X. Wang, R. A. Widenhoefer, Organometallics 2004, 23, 1649–
1651.
[8] D. Karshtedt, A. T. Bell, T. D. Tilley, J. Am. Chem. Soc. 2005,
127, 12640–12646.
[9] P. A. Dub, M. Rodriguez-Zubiri, J.-C. Daran, J.-J. Brunet, R.
Poli, Organometallics 2009, 28, 4764–4777.
[10] P. A. Dub, R. Poli, J. Mol. Catal. A 2010, 324, 89–96.
[11] P. A. Dub, R. Poli, J. Am. Chem. Soc. 2010, 132, 13799–13812.
[12] P. A. Dub, J.-C. Daran, V. A. Levina, N. V. Belkova, E. S. Shu-
bina, R. Poli, J. Organomet. Chem. 2011, 696, 1174–1183.
[13] J. K. K. Sarhan, M. Green, I. M. Al-Najjar, J. Chem. Soc., Dal-
ton Trans. 1984, 771–777.
[14] G. Lorusso, C. R. Barone, N. G. Di Masi, C. Pacifico, L.
Maresca, G. Natile, Eur. J. Inorg. Chem. 2007, 2144–2150.
[15] G. Balacco, G. Natile, J. Chem. Soc., Dalton Trans. 1990, 3021–
3024.
(b) with K2PtCl4/HBr: The autoclave was charged with K2PtCl4
(54 mg, 0.13 mmol) and submitted to argon/vacuum cycles. Water
(or D2O), Et2NH (4.7 mL, 45.5 mmol, 350 equiv.) and aqueous
HBr (gently), if necessary, were syringed into the autoclave and the
ethylene pressure was adjusted to 25 bar (ca. 100 mmol, 333 equiv.)
at room temp. The remainder of the experiment was carried out as
above, except that D2O was used to obtain the NMR lock. The
amount of D2O was the minimum needed to homogenize the sys-
tem.
[16] P. A. Dub, A. Béthegnies, R. Poli, submitted.
[17] R. Poli, Comments Inorg. Chem. 2009, 30, 177–228.
[18] B. Schlummer, J. F. Hartwig, Org. Lett. 2002, 4, 1471–1474.
Eur. J. Inorg. Chem. 2011, 5167–5172
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