ACS Catalysis
Although lower activities of the complexes bearing bulky
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substituents clearly indicates the profound steric influence of
the phosphorus substituents on the catalysis, the electronic
effect might also be playing a key role. Superior activity of the
phenyl substituted complex over cyclohexyl or isopropyl verꢀ
sions gives hints in this direction.
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In conclusion, we have developed an efficient manganese
pincerꢀcatalyzed Guerbet process for the production of biofuel
from ethanol with a high conversion rate and selectivity. The
phosphorus substituent and the cooperativity between the metꢀ
al and ligand NꢀH moiety were found to play a key role in the
catalytic activity. High loading of base (25 mol %) is required
to maintain the catalytic activity and the water which formed
during the reaction was found to promote the major deactivaꢀ
tion pathway. Detailed experiments aimed at further mechanisꢀ
tic insight and improvements are in progress in our lab. Since
this is the first example of a manganese catalyst being successꢀ
fully employed in the Guerbet reaction of ethanol, this finding
promotes the development of new advanced early transition
metal based catalysts for this process.
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(17) (a) AndérezꢀFernández,M.; Vogt, L .K.; Fischer, S.; Zhou, W.;
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AUTHOR INFORMATION
Corresponding Author
* William D. Jones, jones@chem.rochester.edu
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2049ꢀ2052.
(20) Nguyen, D. H.; Trivelli, X.; Capet, F.; Paul, J.ꢀF.; Dumeignil,
F.; Gauvin, R. M. ACS Catal. 2017, 7, 2022ꢀ2032.
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ler, M. Angew. Chem. Int. Ed. 2016, 55, 14967ꢀ14971.
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ASSOCIATED CONTENT
Supporting Information. The SI for this article includes full
experimental procedures with additional data on the products
described in Tables S1ꢀS5. Table S6 summarizes results with Fe
and Co PNP catalysts. Xꢀray tables for the structure of complexes
7 and 8, deposited in the Cambridge Crystallographic Database
(CCDC# 1580557ꢀ8). This material is available free of charge via
ACKNOWLEDGMENT
This work was supported by the NSF under the CCI Center for
Enabling New Technology through Catalysis (CENTC), CHEꢀ
1205189. We also thank Prof. Tom Baker and Dr. Cassandra
Hayes (Univ. Ottawa) for helpful discussions.
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