ACS Catalysis
Letter
efficiency of the catalysts in the oxidation reaction. Through
careful synthetic design of the bimetallic precursor, one can
ensure that the Ir and Bi metals are in close proximity to one
another; a feature that cannot be readily controlled or
guaranteed with the preparation of the bimetallic physical
mixture. By using a cluster-based precursor, where the
structural and compositional integrity can be controlled at the
molecular level, it is possible to exploit the individual benefits of
the two metals to facilitate a synergistic enhancement in overall
catalytic behavior resulting in significant improvements in
catalytic turnover. Thus, the Bi atoms are able to readily
activate the oxidant, while the adjacent Ir atoms selectively form
the niacin via CH activation processes upon the 3-picoline,
ultimately creating an effective spillover catalyst.
The catalyst derived from the Ir5Bi3 cluster exhibited the best
activity for both conversion and catalytic efficiency (TON).
This may be attributed to the Ir/Bi ratio becoming closer to
unity, thereby promoting a more efficient transfer of activated
intermediates between the two metal sites. As with the Ir3Bi,
the cluster derived Ir5Bi3 catalyst was far superior to the
analogous physical mixture catalyst (5Ir:3Bi), further high-
lighting the importance of the structural and compositional
integrity provided by the cluster precursor.
In summary, the first higher nuclearity iridium−bismuth
cluster complex 2 has been synthesized and structurally
characterized. The first examples of bimetallic IrBi nano-
particles have been synthesized from the bimetallic IrBi
molecular cluster complexes 1 and 2. In a proof-of-concept
study, these bimetallic nanoparticles exhibit superior catalytic
activity for the direct oxidation 3-picoline to niacin, compared
to their monometallic analogues. By using cluster-based
bimetallic precursors, where the compositional integrity can
be better controlled at the molecular level, it is possible to
produce superior nanocatalysts to better exploit the benefits of
the individual metals by synergistic complementarity in the
overall catalytic behavior. It is believed that these new iridium−
bismuth catalysts will exhibit superior catalytic activity for other
types of hydrocarbon oxidation reactions and will pave the way
to an emerging family of precious metal-heavy main group
metal bimetallic catalysts.2,16,29
REFERENCES
■
(1) Hermans, S.; Raja, R.; Thomas, J. M.; Johnson, B. F. G.; Sankar,
G.; Gleeson, D. Angew. Chem., Int. Ed. 2001, 40, 1211−1215.
(2) Adams, R. D.; Blom, D. A.; Captain, B.; Raja, R.; Thomas, J. M.;
Trufan, E. Langmuir 2008, 24, 9223−9226.
(3) Adams, R. D.; Boswell, E. M.; Captain, B.; Hungria, A. B.;
Midgley, P. A.; Raja, R.; Thomas, J. M. Angew. Chem., Int. Ed. 2007, 46,
8182−8185.
(4) Hungria, A. B.; Raja, R.; Adams, R. D.; Captain, B.; Thomas, J.
M.; Midgley, P. A.; Golovko, V.; Johnson, B. F. G. Angew. Chem., Int.
Ed. 2006, 45, 4782−4785.
(5) Thomas, J. M.; Adams, R. D.; Boswell, E. M.; Captain, B.;
Gronbeck, H.; Raja, R. Faraday Discuss. 2008, 138, 301−315.
̈
(6) Gianotti, E.; Shetti, V. N.; Manzoli, M.; Blaine, J. A. L.; Pearl, W.
C., Jr.; Adams, R. D.; Coluccia, S.; Raja, R. Chem.Eur. J. 2010, 16,
8202−8209.
(7) (a) Humphrey, S. M.; Grass, M. E.; Habas, S. E.; Niesz, K.;
Somorjai, G. A.; Tilley, T. D. Nano Lett. 2007, 7, 785−790.
(b) Vicente, B. C.; Nelson, R. C.; Singh, J.; Scott, S. L.; van
Bokhoven, J. A. Catal. Today 2011, 160, 137−143. (c) Bal, R.; Tada,
M.; Sasaki, T.; Iwasawa, Y. Angew. Chem., Int. Ed. 2006, 45, 448−452.
(8) (a) Ide, M. S.; Hao, B.; Neurock, M.; Davis, R. J. ACS. Catal.
2012, 2, 671−683. (b) Lobo-Lapidus, R. J.; McCall, M. J.; Lanuza, M.;
Tonnesen, S.; Bare, S. R.; Gates, B. C. J. Phys. Chem. C 2008, 112,
3383−3391. (c) Boucher, M. B.; Zugic, B.; Cladaras, G.; Kammert, J.;
Marcinkowski, M.; Latwon, T. J.; Sykes, E. C. H.; Flytzani-
Stephanopoulos, M. Phys. Chem. Chem. Phys. 2013, 15, 12187−12196.
(9) Herzing, A. A.; Kiely, C. J.; Carley, A. F.; Landon, P.; Hutchings,
G. J. Science 2008, 321, 1331−1335.
(10) Ishia, T.; Kinoshita, N.; Okatsu, H.; Akita, T.; Takei, T.; Haruta,
M. Angew. Chem., Int. Ed. 2008, 47, 9265−9268.
(11) Corma, A.; Serna, P. Science 2006, 313, 332−334.
(12) Kesavan, L.; Tiruvalam, R.; Ab Rahim, M. H.; bin Saiman, M. I.;
Enache, D. I.; Jenkins, R. L.; Dimitratos, N.; Lopez-Sanchez, J. A.;
Taylor, S. H.; Knight, D. W.; Kiely, C. J.; Hutchings, G. J. Science 2011,
331, 195−199.
(13) Hinde, C. S.; Van Aswegen, S.; Collins, G.; Holmes, J. D.; Hor,
T. S.; Raja, R. Dalton Trans. 2013, 42, 12600−12605.
(14) Manzoli, M.; Shetti, V. N.; Blaine, J. A. L.; Zhu, L.; Isrow, D.;
Yempally, V.; Captain, B.; Coluccia, S.; Raja, R.; Gianotti, E. Dalton
Trans. 2012, 41, 982−989.
(15) (a) Dumitriu, D.; Bar
̂
jega, R.; Frunza, L.; Macovei, D.; Hu, T.;
vulescu, V. I.; Kaliaguine, S. J. Catal. 2003, 219, 337−351.
Xie, Y.; Par
̂
(b) Zhao, J.; Qian, G.; Li, F.; Zhu, J.; Ji, S.; Li, L. Chin. J. Catal. 2012,
33, 771−776. (c) Qian, G.; Ji, D.; Lu, G.; Zhao, R.; Qi, Y.; Suo, J. J.
Catal. 2005, 232, 378−385.
ASSOCIATED CONTENT
■
(16) Hanna, T. A. Coord. Chem. Rev. 2004, 248, 429−440.
(17) Rass, H. A.; Essayem, N.; Besson, M. Green Chem. 2013, 15,
2240−2251.
S
* Supporting Information
Experimental details on catalyst synthesis, crystallographic data
collection and analysis, TEM (before and after catalysis) and
catalysis protocols. Also included is EDS analysis, and
associated catalytic and kinetic results. This material is available
(18) Wenkin, M.; Ruiz, P.; Delmon, B.; Devillers, M. J. Mol. Catal. A:
Chem. 2002, 180, 141−159.
(19) He, Y.; Wu, Y.; Yi, X.; Weng, W.; Wan, H. J. Mol. Catal. A:
Chem. 2010, 331, 1−6.
(20) Kruppa, W.; Blaeser, D.; Boese, R.; Schmid, G. Org. Chem. 1982,
37B (2), 209−213.
(21) Adams, R. D.; Chen, M.; Elpitiya, G.; Zhang, Q. Organometallics
2012, 31, 7264−7271.
AUTHOR INFORMATION
■
Corresponding Authors
(22) Crystallographic Data for 2 are as follow: Crystal System =
orthorhombic, Space Group: Pnma, a = 16.3842(13) Å, b =
14.3198(11) Å, c = 9.2009(7) α = β = γ = 90.00°, V = 2158.7(3)
Å, 1982 reflections, R = 0.0286, Rw = 0.0830, GOF = 0.99. See
Supporting Information for additional details.
(23) Kirkland, J. B. Niacin. In Handbook of Vitamins 4th ed.; Rucker,
R., Zempleni, J., Suttie, J. W., McCormick, D. B., Eds.; Taylor and
Francis: New York, 2007; pp 191−232.
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
(24) (a) Ali, K. M.; Wonnerth, A.; Huber, K.; Wojta, J. Br. J.
Pharmacol. 2012, 167, 1177−1194. (b) Grundy, S. M. Am. J. Cardiol.
1992, 70, I27−I32.
This research was supported by the National Science
Foundation CHE-1111496 (R.D.A.). R.R. wishes to thank
Honeywell International (U.S.A.) for financial support.
(25) Chuck, R. Appl. Catal. A 2005, 280, 75−82.
3109
dx.doi.org/10.1021/cs400880k | ACS Catal. 2013, 3, 3106−3110