ACS Catalysis
Research Article
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NHCs and in situ-generated NHCs were effective ligands for
a PdCl2(CH3CN)2 electrocatalyst in the galvanostatic electro-
carbonylation of PhOH to DPC. The stronger electron-
donating ability of the NHCs enhanced the stoichiometric
and electrochemical formation of DPC. In situ-generated SItBu
from SItBuHCl and PhONa was the most effective ligand in the
Pd electrocatalyst among the tested NHC and in situ-generated
NHC groups. The steady and stable electrocarbonylation of
PhOH to DPC was performed for 12 h with a CE of 80%,
which was improved in comparison with 50%, which was
previously obtained at the Pd0/KB anode.24 In addition, the
electrochemical formation of DPC at the Pd0/KB anode was
drastically suppressed to 6% CE by addition of SItBuHCl to the
electrolyte. SItBuHCl is not effective for the heterogeneous Pd
electrocatalyst. When the galvanostatic electrolysis was
conducted using new solutions without PdCl2(CH3CN)2 and
the Au wire anode used for the electrocarbonylation, the
electrolysis could not be continued more than 1 h because of
over range of the terminal voltage. DPC and CO2 were not
produced during the electrolysis. This result proves that the
actual active species of Pd is not deposited on the Au surface
and is in the electrolyte solutions. Homogeneous Pd(NHC)
species function as electrocatalysts and can be applicable in
various syntheses.25−27
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Acta 2011, 56, 2926−2933.
ASSOCIATED CONTENT
* Supporting Information
■
(24) Murayama, T.; Hayashi, T.; Kanega, R.; Yamanaka, I. J. Phys.
Chem. C. 2012, 19, 10607−10616.
S
(25) Gonzal
3612−3676.
́
ez, S. D.; Marion, N.; Nolan, S. P. Chem. Rev. 2009, 109,
Experimental details, a diagram of the one-compartment
electrolysis cell, effects of IMes addition, UV−vis absorptions
of IMes, CVs of PdCl2(CH3CN)2. This material is available free
(26) Arentsen, K.; Caddick, S.; Cloke, F. G. N. Tetrahedron 2005, 61,
9710−9715.
(27) Herrmann, W. A. Angew. Chem., Int. Ed. 2002, 41, 1290−1309.
(28) 1,3-Dimesitylimidazolium chloride, IMesHCl; 1,3-di(iso-propyl)
imidazolium chloride, IPrHCl; 1,3-di(tert-butyl)imidazolium chloride,
ItBuHCl; and 1,3-di(tert-butyl)imidazoline chloride, SItBuHCl.
AUTHOR INFORMATION
Corresponding Author
■
Present Address
†Department of Chemistry and Materials Science, Graduate
School of Science and Engineering, Tokyo Institute of
Technology, 2-12-1-S1-16 Ookayama, Meguro-ku, Tokyo
1528552, Japan.
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
This work was supported by Grants-in Aid for Scientific
Research by the Japanese government (Ref. No: 2365608).
■
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dx.doi.org/10.1021/cs300725j | ACS Catal. 2013, 3, 389−392