Journal of the American Chemical Society
COMMUNICATION
Figure 6. Putative mechanism for the ruthenium-catalyzed allyl alcohol isomerization within the cavity of 1.
While substrate inhibition made it difficult to extract true first-
order rate constants for this catalysis, qualitative comparison of
the reaction rates was possible. Comparison of the encapsulated
and unencapsulated complexes reveals that encapsulation of
[RuCp(PMe3)(MeCN)2]+ within 1 causes mild attenuation of
the rate, decreasing the turnover frequency at 42 °C from 44 to
16 MÀ1 hÀ1 (Figure 5). Both catalysts are able to isomerize allyl
alcohol completely at 42 °C in good yield. Significantly, the
encapsulated catalyst has an extremely long lifetime in water and
is able to turn over 1070 times, a higher turnover than that
demonstrated by the free catalyst in halogenated organic solvents.7
In summary, an organometallic catalyst was incorporated into
water-soluble supramolecular assembly 1. The encapsulated
complex was protected from decomposition by the supramole-
cular assembly. Despite a slight reduction in the rate of catalysis,
the incorporated catalyst remains highly active and has, to the
best of our knowledge, the highest turnover reported for a
supramolecular catalyst. This study demonstrates the potential
of supramolecular encapsulation of organometallic complexes in
developing efficient, “green” catalysts for organic synthesis.
M.W.J. acknowledges support from National Science Founda-
tion Graduate Fellowship no. DGE1106400.
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’ ASSOCIATED CONTENT
S
Supporting Information. Experimental procedures and
b
kinetic data. This material is available free of charge via the
’ AUTHOR INFORMATION
Corresponding Author
rbergman@berkeley.edu; raymond@socrates.berkeley.edu
(7) Slugovc, C.; Ruba, E.; Schmid, R.; Kirchner, K. Organometallics
1999, 18, 4230.
’ ACKNOWLEDGMENT
This research was supported by the Director, Office of
Science, Office of Basic Energy Sciences, and the Division of
Chemical Sciences, Geosciences, and Biosciences of the U.S.
Department of Energy at LBNL (DE-AC02-05CH11231).
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