COMMUNICATIONS
amounts of ester. Additional reactions under different con-
ditions show that the limit of the palladium system has not yet
been reached. A yield of 3000% relative to palladium
[15] M. Lin, A. Sen, Nature 1994, 368, 613 ± 615.
[
[
16] M. Lin, T. E. Hogan, A. Sen, J. Am. Chem. Soc. 1996, 118, 4574 ± 4580.
17] J. Schwarz, V. P. W. Bohm, M. G. Gardiner, M. Grosche, W. A.
Herrmann, W. Hieringer, G. Raudaschl-Sieber, Chem. Eur. J. 2000,
(
TON 30) could be reached in 14 hours with 4c at 908C
6
, 1773 ± 1780.
[18] T. Strassner, M. Muehlhofer, W. A. Herrmann, unpublished results,
001.
and an initial methane pressure of 30 bar.
2
The use of trifluoroacetic acid has the additional advantage
that the formed ester can easilybe removed from the reaction
mixture bydestilation, h yd rolized, and the recovered acid
together with remaining methane can be transferred back.
Therefore, it is possible to run it as a cyclic process.
In summarya new field for the application of NHC
complexes has opened up with CÀH activation. Up to now
[
19] T. Strassner, unpublished results, 2001.
[
20] A. L. Spek, PLUTON, Utrecht University, Utrecht, The Netherlands,
2
001.
[21] C. Lee, W. Yang, R. G. Parr, Phys. Rev. B 1988, 37, 785 ± 789.
[22] A. D. Becke, J. Chem. Phys. 1992, 97, 9173 ± 9177.
[
[
23] A. D. Becke, J. Chem. Phys. 1993, 98, 5648 ± 5652.
24] Gaussian98 (RevisionA.7), M. J. Frisch, G. W. Trucks, H. B. Schlegel,
G. E. Scuseria, M. A. Robb, J. R. Cheeseman, V. G. Zakrzewski, J. A.
Montgomery, R. E. Stratmann, J. C. Burant, S. Dapprich, J. M.
Millam, A. D. Daniels, K. N. Kudin, M. C. Strain, O. Farkas, J. Tomasi,
V. Barone, M. Cossi, R. Cammi, B. Mennucci, C. Pomelli, C. Adamo,
S. Clifford, J. Ochterski, G. A. Petersson, P. Y. Ayala, Q. Cui, K.
Morokuma, D. K. Malick, A. D. Rabuck, K. Raghavachari, J. B.
Foresman, J. Cioslowski, J. V. Ortiz, A. G. Baboul, B. B. Stefanov, G.
Liu, A. Liashenko, P. Piskorz, I. Komaromi, R. Gomperts, R. L.
Martin, D. J. Fox, T. Keith, M. A. Al-Laham, C. Y. Peng, A.
Nanayakkara, C. Gonzalez, M. Challacombe, P. M. W. Gill, B. G.
Johnson, W. Chen, M. W. Wong, J. L. Andres, M. Head-Gordon, E. S.
Replogle, J. A. Pople, Gaussian, Inc., Pittsburgh, PA, 1998.
[
25±29]
theyhave been mainlyused for olefin metathesis,
hydro-
The unex-
formylation,[
30, 31]
[32±34]
or CÀC coupling reactions.
pected high stabilityin strong acids and under oxidative
conditions allows the use of the compounds described here for
catalytic CÀH activation of methane. In view of the signifi-
cantlylower bond energies of higher alkanes and arenes there
is a multitute of other applications, which are currentlyunder
investigation.
[
[
25] T. Weskamp, W. C. Schattenmann, M. Spiegler, W. A. Herrmann,
Angew. Chem. 1998, 110, 2631 ± 2633; Angew. Chem. Int. Ed. 1998, 37,
Experimental Section
2
490 ± 2493.
Catalytic oxidation of methane: Catalyst 4 (0.21 mmol) was dissolved in a
mixture of trifluoroacetic acid (60 mL) and trifluoroacetic acid anhydride
26] T. Weskamp, F. J. Kohl, W. Hieringer, D. Gleich, W. A. Herrmann,
Angew. Chem. 1999, 111, 2573 ± 2576; Angew. Chem. Int. Ed. 1999, 38,
2
(
10 mL) in a 200-ml autoclave. Potassium peroxodisulfate (5.70 g, 21 mmol)
416 ± 2419.
27] M. S. Sanford, J. A. Love, R. H. Grubbs, J. Am. Chem. Soc. 2001, 123,
543 ± 6554.
was then suspended in the solution and the autoclave closed and flushed
three times with methane (20 bar). Under stirring of the solution, the
autoclave was pressurized with methane (20 atm) and heated to 808C.
After 24 h the autoclave was cooled to À108C and the pressure slowly
reduced. The cold, liquid reaction mixture was isolated and characterized
byGC anal ys is.
[
[
[
[
[
6
28] A. Fuerstner, O. R. Thiel, L. Ackermann, H.-J. Schanz, S. P. Nolan, J.
Org. Chem. 2000, 65, 2204 ± 2207.
29] M. Scholl, S. Ding, C. W. Lee, R. H. Grubbs, Org. Lett. 1999, 1, 953 ±
9
56.
30] W. A. Herrmann, C. W. Kohlpaintner, Angew. Chem. 1993, 105,
588 ± 1609; Angew. Chem. Int. Ed. Engl. 1993, 32, 1524 ± 1544.
Received: December 7, 2001 [Z18342]
1
31] W. A. Herrmann, J. A. Kulpe, W. Konkol, H. Bahrmann, J. Organo-
met. Chem. 1990, 389, 85 ± 101.
[
[
1] Y. Fujiwara, T. Jintoku, Y. Uchida, New J. Chem. 1989, 13, 649 ± 650.
2] R. A. Periana, D. J. Taube, S. Gamble, H. Taube, T. Satoh, H. Fujii,
Science 1998, 280, 560 ± 564.
[32] V. P. W. Bohm, T. Weskamp, C. W. K. Gstottmayr, W. A. Herrmann,
Angew. Chem. 2000, 112, 1672 ± 1674; Angew. Chem. Int. Ed. 2000, 39,
1602 ± 1604.
[
[
3] A. E. Shilov, A. A. Shteinman, Kinet. Katal. 1977, 18, 1129 ± 1145.
4] H. Arakawa, M. Aresta, J. N. Armor, M. A. Barteau, E. J. Beckman,
A. T. Bell, J. E. Bercaw, C. Creutz, E. Dinjus, D. A. Dixon, K. Domen,
D. L. DuBois, J. Eckert, E. Fujita, D. H. Gibson, W. A. Goddard,
D. W. Goodman, J. Keller, G. J. Kubas, H. H. Kung, J. E. Lyons, L. E.
Manzer, T. J. Marks, K. Morokuma, K. M. Nicholas, R. Periana, L.
Que, J. Rostrup-Nielson, W. M. H. Sachtler, L. D. Schmidt, A. Sen,
G. A. Somorjai, P. C. Stair, B. R. Stults, W. Tumas, Chem. Rev. 2001,
[33] W. A. Herrmann, M. Elison, J. Fischer, C. Koecher, G. R. J. Artus,
Angew. Chem. 1995, 107, 2602 ± 2605; Angew. Chem. Int. Ed. Engl.
1995, 34, 2371 ± 2374.
[34] S. Caddick, F. G. N. Cloke, G. K. B. Clentsmith, P. B. Hitchcock, D.
McKerrecher, L. R. Titcomb, M. R. V. Williams, J. Organomet. Chem.
2001, 617 ± 618, 635 ± 639.
1
01, 953 ± 996.
[
[
[
[
[
5] H.-U. W¸stefeld, F. Sch¸th, W. C. Kaska, G. D. Stucky, GdCh Annual
Conference, Wuerzburg, 2001.
6] G.-J. ten Brink, I. W. C. E. Arends, R. A. Sheldon, Science 2000, 287,
1
636 ± 1639.
7] S. Stahl, J. A. Labinger, J. E. Bercaw, Angew. Chem. 1998, 110, 2298 ±
311; Angew. Chem. Int. Ed. 1998, 37, 2181 ± 2192.
8] D. Wolf, Angew. Chem. 1998, 110, 3545 ± 3547; Angew. Chem. Int. Ed.
998, 38, 3351 ± 3353.
9] R. H. Crabtree, Chem. Rev. 1995, 95, 987 ± 1007.
2
1
[
[
10] R. H. Crabtree, Chem. Rev. 1995, 95, 2599.
11] K. Nakata, Y. Yamaoka, T. Miyata, Y. Taniguchi, K. Takaki, Y.
Fujiwara, J. Organomet. Chem. 1994, 473, 329 ± 334.
[
[
[
12] M. Kurioka, K. Nakata, T. Jintoku, Y. Taniguchi, K. Takaki, Y.
Fujiwara, Chem. Lett. 1995, 244.
13] Y. Taniguchi, T. Hayashida, H. Shibasaki, D. Piao, T. Kitamura, T.
Yamaji, Y. Fujiwara, Org. Lett. 1999, 1, 557 ± 559.
14] M. Asadullah, T. Kitamura, Y. Fujiwara, Angew. Chem. 2000, 111,
2
609 ± 2612; Angew. Chem. Int. Ed. 2000, 39, 2475 ± 2478.
Angew. Chem. Int. Ed. 2002, 41, No. 10 ¹ WILEY-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002
1433-7851/02/4110-1747 $ 20.00+.50/0
1747