Angewandte
Communications
Chemie
using 7a as the catalyst,[34] thus suggesting that the reaction
occurs under homogeneous conditions.
Acknowledgments
Other experiments were performed to understand the
nature of the catalyst using the carbonylation of n-hexylamine
as a model system.[35] Thus, when the reaction mixture was
filtered after 45 minutes through a HPLC filter (PTFE
0.2 mm) and Celite, 8b was still obtained in 86% yield.[34]
After addition of amine at the end of the carbonylation, the
reaction restarted, thus forming 8b again (73% yield). We
also isolated a small amount of insoluble black solid in the
filtration of the reaction mixture, and it did not dissolve in the
presence of an amine and also did not show any catalytic
activity. Although the mechanism for the formation of
isocyanates and ureas under the oxidative carbonylation
reaction is not totally clear, in contrast to that observed by the
group of Bertrand,[7] no reaction of either 3, 4, or 7a with CO
(5 bar) was observed even after 24 hours. Interestingly,
formation of a new species was detected upon reaction of
7a with CyNH2, and it showed a single signal in the 31P NMR
spectrum at d = 31 ppm and a cluster of peaks at m/z 2455–
2462 (MALDI-TOF) which corresponds to the quasi-molec-
ular ion of pentanuclear complex [L2Au4Ag(NHCy)2](SbF6)3
(Figure 1).
We thank MINECO [Severo Ochoa Excellence Accreditation
2014-2018 (SEV-2013-0319) CTQ2013-42106-P and
CTQ2014-52824-R], the European Research Council
(Advanced Grant No. 321066), the AGAUR (2014 SGR
818), and the ICIQ Foundation. N.A.G.B. gratefully acknowl-
edges COFUND/Marie Curie action 291787-ICIQ-IPMP for
funding. We also thank the ICIQ X-ray diffraction unit for the
X-ray structures.
Keywords: carbonylation · heterometallic complexes ·
homogeneous catalysis · gold · structure elucidation
How to cite: Angew. Chem. Int. Ed. 2016, 55, 7487–7491
Angew. Chem. 2016, 128, 7613–7617
[1] a) A. A. Herzing, C. J. Kiely, A. F. Carley, P. Landon, G. J.
Dimitratos, C. E. Chan-Thaw, C. Hammond, L. Prati, G. J.
[2] a) M. Haruta, Chem. Rec. 2003, 3, 75 – 87; b) M. Haruta, Faraday
Discuss. 2011, 152, 11 – 32.
[3] a) M. C. Daniel, D. Astruc, Chem. Rev. 2004, 104, 293 – 346; b) B.
K. Min, C. M. Friend, Chem. Rev. 2007, 107, 2709 – 2724.
[4] a) Lead references on small gold clusters:Y. Gao, N. Shao, Y. Pei,
Z. Chen, X. C. Zeng, ACS Nano 2011, 5, 7818 – 7829; b) H. Qian,
M. Zhu, Z. Wu, R. Jin, Acc. Chem. Res. 2012, 45, 1470 – 1479;
c) G. Li, C. Liu, Y. Lei, R. Jin, Chem. Commun. 2012, 48, 12005 –
12007; d) G. Li, R. Jin, Acc. Chem. Res. 2013, 46, 1749 – 1758;
e) Z. Wu, R. Jin, Chem. Eur. J. 2013, 19, 12259 – 12263; f) J.
Chen, Q.-F. Zhang, T. A. Bonaccorso, P. G. Williard, L.-S. Wang,
J. Am. Chem. Soc. 2014, 136, 92 – 95; g) Y. Shichibu, M. Zhang,
Y. Kamei, K. Konishi, J. Am. Chem. Soc. 2014, 136, 12892 –
12895; h) X.-K. Wan, S.-F. Yuan, Z.-W. Lin, Q.-M. Wang,
Angew. Chem. Int. Ed. 2014, 53, 2923 – 2926; Angew. Chem.
2014, 126, 2967 – 2970; i) M. Boronat, A. Leyva-PØrez, A.
Corma, Acc. Chem. Res. 2014, 47, 834 – 844; j) G. Li, H.
Abroshan, Y. Chen, R. Jin, H. J. Kim, J. Am. Chem. Soc. 2015,
137, 14295 – 14304.
Figure 1. MALDI-TOF spectrum of 7a + CyNH2. L=(Ph2P)2Py.
[5] a) P. S. D. Robinson, G. N. Khairallah, G. da Silva, H. Lioe, R. A.
OꢀHair, Angew. Chem. Int. Ed. 2012, 51, 3812 – 3817; b) Angew.
Chem. 2012, 124, 3878 – 3883; M. Boronat, T. López-Ausens, A.
Corma, J. Phys. Chem. C 2014, 118, 9018 – 9029.
[6] a) J. O. Oliver-Meseguer, J. R. Cabrero-Antonino, I. Domín-
b) J. Oliver-Meseguer, A. L. PØrez, A. Corma, ChemCatChem
[7] L. Jin, D. S. Weinberger, M. Melaimi, C. E. Moore, A. L.
In summary, we have developed a simple synthesis of
a linear tetracationic tetranuclear [AuI4] complex in one step
À
from [Au2Cl2{(Ph2P)2Py}], and it induces C H functionaliza-
tion of carbonyl compounds under mild reaction conditions.
We have also prepared a pentanuclear [AuI4AgI] complex by
reaction of [AuI4] with AgI, which is highly catalytically active
for the oxidative carbonylation of primary amines to form
ureas under homogeneous conditions, with efficiencies com-
parable to other transition-metal-catalyzed processes and
higher than those achieved by gold nanoparticles. We have
also obtained an octanuclear complex with an unprecedented
and almost planar [AuI8] core, and it is formally the product of
a 4 + 4 reaction of two [Au4] complexes. Further studies on
the synthesis of other complexes along these lines and further
mechanistic studies are under way.
[9] O. Herd, A. Hessler, H. Hingst, M. Tepper, O. Stelzer, J.
[10] a) A different complex [L3Au2](ClO4)2 [L = (Ph2P)2Py] has been
reported, in which gold(I) is coordinated face to face only to the
phosphines: S.-J. Shieh, D. Li, S.-M. Peng, C.-M. Che, J. Chem.
observed for ([Au2(PNPtBu)2](BF4)2: J. I. van der Vlugt, M. A.
[11] Other gold or gold-silver complexes with (Ph2P)2Py as a ligand:
ꢀ 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Angew. Chem. Int. Ed. 2016, 55, 7487 –7491