Organometallics
Communication
(3) (a) Gupta, M.; Hagen, C.; Flesher, R. J.; Kaska, W. C.; Jensen, C.
M. Chem. Commun. 1996, 2083. (b) Liu, F.; Pak, E. B.; Singh, B.;
Jensen, C. M.; Goldman, A. S. J. Am. Chem. Soc. 1999, 121, 4086.
(c) Kuklin, S. A.; Sheloumov, A. M.; Dolgushin, F. M.; Ezernitskaya,
M. G.; Peregudov, A. S.; Petrovskii, P. V.; Koridze, A. A.
Organometallics 2006, 25, 5466. (d) Huang, Z.; Brookhart, M.;
Goldman, A. S.; Kundu, S.; Ray, A.; Scott, S. L.; Vicente, B. C. Adv.
Synth. Catal. 2009, 351, 188. (e) Adams, J. J.; Arulsamy, N.; Roddick,
D. M. Organometallics 2012, 31, 1439. (f) Shi, Y.; Suguri, T.; Dohi, C.;
Yamada, H.; Kojima, S.; Yamamoto, Y. Chem. Eur. J. 2013, 19, 10672.
(4) Selected examples: (a) Fujii, T.; Saito, Y. J. Chem. Soc.; Chem.
Commun. 1990, 757. (b) Aoki, T.; Crabtree, R. H. Organometallics
1993, 12, 294. (c) Xu, W.; Rosini, G. P.; Gupta, M.; Jensen, C. M.;
Kaska, W. C.; Krogh-Jespersen, K.; Goldman, A. S. Chem. Commun.
1997, 2273. (d) Punji, B.; Emge, T. J.; Goldman, A. S. Organometallics
2010, 29, 2702.
upon the addition of sulfuric acid to 4a. However, we also have
evidence that 4a is not formed when the reaction is carried out
in the presence of acetic acid. The reaction of 4a and acetic acid
does lead to 1a, but the reaction is too slow for 4a to be
considered a kinetically competent intermediate in the
formation of 1a from the reaction of 2a with acetic acid and
oxygen. It appears that the interaction of 2a with acetic acid
allows a faster reaction with oxygen to generate 3a. The
intermediate 3a observed in the reaction of 2a and acetic acid
with oxygen may also be a hydroperoxide species, but it is not
4a. Several possibilities for 3a−c include protonated hydroperoxo,
hydroxo or peracetate complexes.17
We have previously reported that (dmPhebox)Ir(OAc)2(OH2)
(1a) reacts with octane to give octene, (dmPhebox)Ir(OAc)H
(2a), acetic acid, and water. In this work we have demonstrated
that 2a reacts with oxygen (in the presence of acetic acid
and water) to regenerate 1a in high yield. The derivatives
(dmPhebox)Ir(X)2(H) (2b,c; X = OBz, OPiv) show similar
behavior. These reactions occur at room temperature and
proceed through a (dmPhebox)Ir intermediate, possibly an
Ir−OOH species. Generation of 1a−c from 2a−c with oxygen
represents the key regeneration step needed to achieve aerobic
dehydrogenation of alkanes. In contrast, most of the well-known
homogeneous alkane dehydrogenation catalysts are incompat-
ible with oxygen. This work involving high-oxidation-state IrIII
complexes for alkane activation thus suggests a novel approach
toward developing alkane functionalization systems that can utilize
oxygen as a hydrogen acceptor. Current studies are focused on
determining the identities of the intermediate species and the
mechanism of this reaction, as well as applying these findings
toward the development of a catalytic system.
(5) (a) Lee, D. W.; Kaska, W. C.; Jensen, C. M. Organometallics 1998,
17, 1. (b) Morales-Morales, D.; Lee, D. W.; Wang, Z.; Jensen, C. M.
Organometallics 2001, 20, 1144. (c) Ghosh, R.; Kanzelberger, M.;
Emge, T. J.; Hall, G. S.; Goldman, A. S. Organometallics 2006, 25,
5668. (d) Williams, D. B.; Kaminsky, W.; Mayer, J. M.; Goldberg, K. I.
Chem. Commun. 2008, 4195.
(6) Allen, K. E.; Heinekey, D. M.; Goldman, A. S.; Goldberg, K. I.
Organometallics 2013, 32, 1579.
(7) Catalytic n-octane dehydrogenation using 2a was not observed at
200 °C with air (1 atm). While some oxidation of n-octane was
observed, similar results in the absence of Ir were noted. An oxygen
atmosphere at high temperature may be incompatible with these Ir
complexes and/or intermediates, but further studies are needed.
(8) In the absence of oxygen, only degenerate exchange of the acetate
ligand and the hydride moiety of 2a with the added acetic acid was
observed. Exchange of the acetate was evidenced by a single broad
resonance at 1.87 ppm in the 1H NMR spectrum that corresponded to
the methyl groups of both acetate and acetic acid. In addition, a slower
H/D exchange between the hydride ligand and acetic acid-d4 (3 equiv)
occurs under these conditions; 50% deuterium incorporation into the
hydride position was observed after 2 h at room temperature.
(9) Ito, J.; Shiomi, T.; Nishiyama, H. Adv. Synth. Catal. 2006, 348,
1235.
ASSOCIATED CONTENT
* Supporting Information
■
S
Full experimental details including X-ray crystallographic data
for 1b. This material is available free of charge via the Internet
(10) See Supporting Information for synthesis of 1b and 1c.
(11) Ito, J.; Kaneda, T.; Nishiyama, H. Organometallics 2012, 31,
4442.
(12) (a) Wick, D. D.; Goldberg, K. I. J. Am. Chem. Soc. 1999, 121,
11900. (b) Denney, M. C.; Smythe, N. A.; Cetto, K. L.; Kemp, R. A.;
Goldberg, K. I. J. Am. Chem. Soc. 2006, 128, 2508. (c) Konnick, M. M.;
Gandhi, B. A.; Guzei, I. A.; Stahl, S. S. Angew. Chem. Int. Ed. 2006, 45,
2904. (d) Look, J. L.; Wick, D. D.; Mayer, J. M.; Goldberg, K. I. Inorg.
Chem. 2009, 48, 1356. (e) Szajha-Fuller, E.; Bakac, A. Inorg. Chem.
2010, 49, 781. (f) Boisvert, L.; Goldberg, K. I. Acc. Chem. Res. 2012,
45, 899.
(13) (a) Teets, T. S.; Nocera, D. G. J. Am. Chem. Soc. 2011, 133,
17796. (b) Keith, J. M.; Teets, T. S; Nocera, D. G. Inorg. Chem. 2012,
51, 9499.
(14) (a) Heiden, Z. M.; Rauchfuss, T. B. J. Am. Chem. Soc. 2007, 129,
14303. (b) Chowdhury, S.; Himo, F.; Russo, N.; Sicilia, E. J. Am. Chem.
Soc. 2010, 132, 4178.
AUTHOR INFORMATION
Corresponding Author
Notes
■
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
This work was supported by the NSF through the Center for
Enabling New Technologies through Catalysis (CENTC),
CHE-1205189. We thank Dr. Werner Kaminsky for X-ray crystallo-
graphy and Prof. Tom R. Cundari, Mr. Dale Pahls, Dr. Ash Wright,
and Prof. Alexander J. M. Miller for helpful discussions.
(15) Jiang, B.; Feng, Y.; Ison, E. A. J. Am. Chem. Soc. 2009, 130,
14462.
REFERENCES
■
(16) For examples of hydrogen peroxide detection see: (a) Coggins,
M. K.; Sun, X.; Kwak, Y.; Solomon, E. I.; Rybak-Akimova, E.; Kovacs,
J. A. J. Am. Chem. Soc. 2013, 135, 5631. (b) Kim, S.; Saracini, C.;
Siegler, M. A.; Drichko, N.; Karlin, K. D. Inorg. Chem. 2012, 51, 12603.
(17) For an example of a proposed Fe peracetate species see: Wang,
Y.; Janardanan, D.; Usharani, D.; Han, K.; Que, L., Jr.; Sharik, S. ACS
Catal. 2013, 3, 1334.
(1) Choi, J.; MacArthur, A. H. R.; Brookhart, M.; Goldman, A. S.
Chem. Rev. 2011, 111, 1761.
(2) (a) Crabtree, R. H.; Mihelcic, J. M.; Quirk, J. M. J. Am. Chem. Soc.
1979, 101, 7738. (b) Crabtree, R. H.; Mellea, M. F.; Mihelcic, J. M.;
Quirk, J. M. J. Am. Chem. Soc. 1982, 104, 107. (c) Burk, M. J.;
Crabtree, R. H. J. Am. Chem. Soc. 1987, 109, 8025. (d) Maguire, J. A.;
Boese, W. T.; Goldman, A. S. J. Am. Chem. Soc. 1989, 111, 7088.
(e) Fekl, U.; Kaminsky, W.; Goldberg, K. I. J. Am. Chem. Soc. 2003,
125, 15286. (f) Kostelansky, C. N.; MacDonald, M. G.; White, P. S.;
Templeton, J. L. Organometallics 2006, 25, 2993. (g) Khaskin, E.;
Zavalij, P. Y.; Vedernikov, A. N. J. Am. Chem. Soc. 2006, 128, 13054.
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