COMMUNICATIONS
[3] a) S.-I. Murahashi, T. Naota, N. Hirai, J. Org. Chem. 1993, 58, 7318 ±
7319; b) J. E. Backvall, R. L. Chowdhury, U. Karlsson, J. Chem. Soc.
Chem. Commun. 1991, 473 ± 475.
[4] M. F. Semmelhack, C. R. Schmid, D. A. Cortes, C. S. Chou, J. Am.
Chem. Soc. 1984, 106, 3374 ± 3376.
[5] K. Krohn, I. Vinke, H. Adam, J. Org. Chem. 1996, 61, 1467 ± 1472.
[6] C.-G. Jia, F.-Y. Jing, W.-D. Hu, M.-Y. Huang, Y.-Y. Jiang, J. Mol. Catal.
1994, 91, 139 ± 147.
[7] J. Martin, C. Martin, M. Faraj, M. Bregeault, Nouv. J. Chim. 1984, 8,
141 ± 143.
[8] a) K. P. Peterson, R. C. Larock, J. Org. Chem. 1998, 63, 3185 ± 3189;
b) G.-J. ten Brink, I. W. C. E. Arends, R. A. Sheldon, Science 2000,
287, 1636 ± 1639.
[9] a) K. Kaneda, T. Yamashita, T. Matsushita, K. Ebitani, J. Org. Chem.
1998, 63, 1750 ± 1751; b) T. Matsushita, K. Ebitani, K. Kaneda, Chem.
Commun. 1999, 265 ± 266.
facilitates the formation of a peroxide species with molecular
oxygen. The hydride transfer from the aluminum alkoxide of
hydrotalcite is effected by the neighboring peroxide on the
nickel atom. Hydrotalcites are homogeneous mixtures of
heterobimetallic composition having a periodic composition
of MII and MIII ions. The cationic order of cat. A as revealed by
IR studies suggests that the presence of one aluminum atom
for every two nickel atoms substituted alternately in the
hydrotalcite provides the optimum use of nickel in cat. A,
better than is possible with the other compositions, and is thus
responsible for the display of higher activity.
In conclusion, Ni-Al hydrotalcite efficiently oxidizes a wide
range of alcohols, such as allylic and benzylic, and a-ketols to
the corresponding carbonyl compounds under mild reaction
conditions by employing molecular oxygen as the stoichio-
metric oxidant. This process is not only economically viable
but also applicable to large-scale reactions. Moreover, the
high yields of oxidized products can be obtained in hetero-
geneous catalysis using hydrotalcites as catalysts.
[10] T. Iwahama, S. Sakaguchi, Y. Nishiyama, Y. Ishii, Tetrahedron Lett.
1995, 36, 6923 ± 6926.
[11] a) F. Cavani, F. Trifiro, A. Vaccari, Catal. Today 1991, 11, 173 ± 301;
b) M. L. Kantam, B. M. Choudary, Ch. V. Reddy, K. K. Rao, F.
Figueras, Chem. Commun. 1998, 1033 ± 1034; c) B. M. Choudary,
M. L. Kantam, B. Kavitha, Ch. V. Reddy, K. K. Rao, F. Figueras,
Tetrahedron Lett. 1998, 39, 3555 ± 3558; d) B. M. Choudary, M. L.
Kantam, B. Bharathi, Ch. V. Reddy, Synlett 1998, 1203 ± 1204; e) P. S.
Kumbhar, J. S. Valente, J. Lopez, F. Figueras, Chem. Commun. 1998,
535 ± 536.
[12] a) W. T. Reichle, J. Catal. 1985, 94, 547 ± 557; b) E. C. Kruissink, L. L.
van Reijen, J. Chem. Soc. Faraday Trans. 1981, 77, 649 ± 663; c) J. Hu,
J. A. Schwarz, Y.-J. Huang, Appl. Catal. 1989, 51, 223 ± 233.
[13] M. J. Hernandez-Moreno, M. J. Ulibarri, J. L. Rendon, C. J. Serna,
Phys. Chem. Miner. 1985, 12, 34 ± 38.
Experimental Section
Various catalysts with varied composition of Ni-Al hydrotalcites (Ni:Al
2:1 (cat. A), 2.5:1, 3:1) were prepared by coprecipitation employing NaOH/
Na2CO3 as described in the literature.[12a] Catalyst A was rehydrated
according to our previous report[11b] and calcined at 4508C in a flow of air.
Ni-Al hydrotalcite (Ni:Al 2:1, cat. B) was prepared by coprecipitation
using ammonia solution.[12b] The samples of nickel impregnated on g-
alumina (2, 5, and 10%) were prepared by adding the required amounts of
Ni(NO3)2 ´ 6H2O in water to g-alumina and stirring occasionally while
heating on a water bath till complete evaporation of water had occurred.
The residue was dried in an oven at 1108C for 16 h.
Highly Reactive SmII Macrocyclic Clusters:
Precursors to N2 Reduction**
Typical oxidation procedure: Oxygen was bubbled at atmospheric pressure
through a reaction mixture containing p-nitrobenzyl alcohol (2 mmol) and
catalyst (0.5 g) in toluene (10 mL) at 908C under stirring. The reaction was
monitored by thin-layer chromatography and purified by column chroma-
tography (hexane:ethyl acetate, 95:5, v:v) to afford the p-nitrobenzalde-
Mani Ganesan, Sandro Gambarotta,* and
Glenn P. A. Yap
Divalent samarium complexes have been prepared with a
wide variety of ligand systems,[1] but the extreme level of
reactivity and the uniqueness of transformations displayed by
the samarocene derivatives[2] was never reproduced. To date,
the SmII polypyrrolide derivatives[3] are the only systems
which share with decamethylsamarocene[4] the ability to react
with an exceedingly inert molecule such as dinitrogen. Unlike
samarocene, however, these species may perform four-elec-
tron reduction of dinitrogen, thus indicating that their
reducing power is particularly strong. Particularly versatile
with this respect are divalent samarium complexes of
dipyrrolide dianions,[5] which are reminiscent of the ansa-
metallocene ligand systems. So far these species have led to
three novel dinitrogen complexes.[6, 7] However, attempts to
isolate the presumably highly reactive divalent precursors
hyde as
a
pale yellow solid: 0.296 g (98%), m.p. 1058C, 1H NMR
(200 MHz, CDCl3, 258C, TMS): d 8.1 (d, 3J(H,H) 8.3 Hz, 2H, aryl-
H), 8.4 (d, 3J(H,H) 8.3 Hz, 2H, aryl-H), 10.2 (s, 1H, CHO); IR (KBr
1
pellets) nÄ 1700 cm (sh, C O); MS (70 eV) m/z (%): 151 (64) [M ], 150
(61) [M
H], 105 (20) [C7H5O ], 77 (93) [C6H5 ], 51 (100) [C4H3 ].
TPR profiles were recorded on Micromeritics (Auto Chem 2910) using
0.05 g of the uncalcined sample. The sample was dried at 1208C in an argon
flow and then helium was replaced by a flow of a mixture of 5% hydrogen
in helium at room temperature.
Received: August 25, 2000 [Z15705]
Â
[1] a) I. E. Marko, P. R. Giles, M. Tsukazaki, S. M. Brown, C. J. Urch,
Â
Science 1996, 274, 2044 ± 2046; b) I. E. Marko, M. Tsukazaki, P. R.
Giles, S. M. Brown, C. J. Urch, Angew. Chem. 1997, 109, 2297 ± 2299;
Angew. Chem. Int. Ed. Engl. 1997, 36, 2208 ± 2210; c) I. E. Marko, P. R.
Â
Giles, M. Tsukazaki, I. Chelle-Regnaut, A. Gautier, S. M. Brown, C. J.
[*] Prof. S. Gambarotta, Dr. M. Ganesan, Dr. G. P. A. Yap
Department of Chemistry
Â
Urch, J. Org. Chem. 1999, 64, 2433 ± 2439; d) I. E. Marko, P. R. Giles,
M. Tsukazaki, I. Chelle-Regnaut, C. J. Urch, S. M. Brown, J. Am.
Chem. Soc. 1997, 119, 12661 ± 12662; e) M. Kirihara, Y. Ochiai, S.
Takizawa, H. Takahata, H. Nemoto, Chem. Commun. 1999, 1387 ±
1388; f) P. A. Shapley, N. Zhang, J. L. Allen, D. H. Pool, H.-C. Liang, J.
Am. Chem. Soc. 2000, 122, 1079 ± 1091.
University of Ottawa
Ottawa, ON, K1N 6N5 (Canada)
Fax : (1)613-562-5170
[**] This work was supported by the Natural Sciences and Engineering
Council of Canada (NSERC). We are deeply indebted to Mr. M. P.
Lalonde for helpful discussions and proofreading.
[2] a) A. K. Roby, J. P. Kingsley, CHEMTECH 1996, 39 ± 46; B. M. Trost,
Science 1991, 254, 1471 ± 1477; b) B. M. Trost, Angew. Chem. 1995, 107,
285 ± 307; Angew. Chem. Int. Ed. Engl. 1995, 34, 259 ± 281.
766
ꢀ WILEY-VCH Verlag GmbH, D-69451 Weinheim, 2001
1433-7851/01/4004-0766 $ 17.50+.50/0
Angew. Chem. Int. Ed. 2001, 40, No. 4