ACS Catalysis
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method of catalyst identification with iron catalysis,29,31
substoichiometric ligand poisoning experiments are a
simple and effective means of assessing whether a given
precatalyst forms a catalyst of higher nuclearity.32 Com-
plete poisoning of catalysis was observed with 2 equiv.
PMe3 (Figure S6). In contrast, in the presence of 0.1 and
0.5 equiv. PMe3, the product distribution remained un-
changed. These results are inconsistent with a heteroge-
neous and nanoparticle system where low surface area
aggregates are typically poisoned by <<1 equiv. ligand poi-
son. Finally, in the absence of any poisoning reagent, non-
sigmoidal reaction profiles and a lack of induction period
are consistent with a homogeneous iron complex as the
active catalytic species.
(2) (a) Raynal, M.; Ballester, P.; Vidal-Ferran, A.; van Leeuwen,
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In conclusion, this work demonstrates the application
of using a catalyst’s secondary coordination environment
to facilitate facile electronic modifications that can
change reaction activity and selectivity. We have
developed Fe-bMepi complexes capable of catalyzing the
hydroboration of olefins and alkynes at room
temperature. Although prior reports demonstrated iron-
catalyzed olefin hydroboration, our systems are unique
because they feature control over activity and
regioselectivity by modifications at a remote site on the
ligand backbone, which serve to tune the ligand’s
electronic environment. Of particular note, higher
reaction rate and distinct regioselectivity were observed
for olefin hydroboration when using the more
electrophilic
Fe(bMepiMe)OTf2
complex.
Because
modification of the catalyst occurred at the last step, this
late-stage functionalization strategy may be exploited as a
general, highly modular protocol that may be adapted to
other catalysts. Future efforts will further explore the
impact of secondary coordination sphere interactions on
transition-metal complexes as a means for improving the
activity, stability, and selectivity of metal-based catalytic
systems.
(7) Ikariya, T.; Shibasaki, M. Bifunctional Molecular Catalysis;
Springer, New York, 2011.
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Am. Chem. Soc. 2013, 135, 9612-9615. (b) Wang, W.-H.; Hull, J. F.;
Muckerman, J. T.; Fujita, E.; Himeda, Y. Energy Environ. Sci.
2012, 5, 7923-7926. (c) Dixon, N. A.; McQuarters, A. B.; Kraus, J.
S.; Soffer, J. B.; Lehnert, N.; Schweitzer-Stenner, R.; Papish, E. T.
Chem. Commun. 2013, 49, 5571-5573. (d) Gary, J. B.; Cook, A. K.;
Sanford, M. S. ACS Catal. 2013, 3, 700-703. (e) Stradiotto, M.;
Hesp, K. D.; Lundgren, R. J. Angew. Chem., Int. Ed. 2010, 49, 494-
512. (f) Betley, T. A.; Peters, J. C.; Angew. Chem., Int. Ed. 2003, 42,
2385-2389.
ASSOCIATED CONTENT
Supporting Information.
Experimental procedures and data. This information is avail-
AUTHOR INFORMATION
(9) Tutusaus, O.; Ni, C.; Szymczak, N. K. J. Am. Chem. Soc.
2013, 135, 3403-3406.
Corresponding Author
(10) (a) Tseng, K.-N. T.; Kampf, J. W.; Szymczak, N. K. Organ-
ometallics 2013, 32, 2046-2049. (b) Tseng, K.-N. T.; Rizzi, A. M.;
Szymczak, N. K. J. Am. Chem. Soc. 2013, 135, 16352-16355.
(11) (a) Pap, J. S.; Cranswick, M. A.; Balogh-Hergovich, É.; Ba-
ráth, G.; Giorgi, M.; Rohde, G. T.; Kaizer, J.; Speier, G.; Que, L.
*nszym@umich.edu
Notes
The authors declare no competing financial interests.
Eur. J. Inorg. Chem. 2013, 2013, 3858-3866.
(b) Siggelkow,
ACKNOWLEDGMENT
B.; Meder, M. B.; Galka, C. H.; Gade, L. H. Eur. J. Inorg. Chem.
2004, 2004, 3424-3435. (c) Anderson, O. P.; la Cour, A.; Berg, A.;
Garret, A. D.; Wicholas, M. Inorg. Chem. 2003, 42, 4513-4515. (d)
Balogh-Hergovich, É.; Kazier, J.; Speier, G.; Huttner, G.; Jacobi,
A. Inorg. Chem. 2000, 39, 4224-4229.
(12) Vries, J. G.; Elsevier, C. J. Handbook of Homogeneous Hy-
drogenation; Wiley-VCH: Weinheim, Germany, 2007; Vol. 1.
(13) Ananikov, V. P.; Tanaka, M. Hydrofunctionalization;
Springer, New York, 2013
This work was supported by the ACS PRF (53760-DNI3), the
University of Michigan Department of Chemistry, and the
NSF (CHE-0840456) for X-ray instrumentation. NKS is an
Alfred P. Sloan Research Fellow.
REFERENCES
(1) Lehninger, A. L.; Nelson, D. L.; Cox, M. M. Principles of Bi-
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