COMMUNICATIONS
atoms, which again is exactly opposite to our findings.
We will continue these regioselective cofactor regeneration
[1] a) H. K. Chenault, G. M. Whitesides, Appl. Biochem. Biotech. 1987, 14,
47; b) J. M. Fang, C. H. Lin, C. W. Bradshaw, C. H. Wong, J. Chem.
1
Soc. Perkin Trans 1 1995, 967.
studies using electrochemical techniques to form the
[
2] a) R. Ruppert, S. Herrmann, E. Steckhan, J. Chem. Soc. Chem.
Commun. 1988, 1150; b) E. Steckhan, S. Herrmann, R. Ruppert, E.
Dietz, M. Frede, E. Spika, Organometallics 1991, 10, 1568, and
references therein; c) R. T. Hembre, S. McQueen, J. Am. Chem. Soc.
[
Cp*Rh(bpy)H] complex, attempt to synthesize the indenyl
[
8]
analogue of 2 for further evidence of the ring-slippage
mechanism, and also synthesize a new, water soluble NAD
1
994, 116, 2141; d) J. P. Collman, P. S. Wagenknecht, N. S. Lewis, J. Am.
model to fully comprehend the effect of pH on the rates, the
turnover frequency, and if enzymes recognize the 1,4-dihydro
derivative in chiral reduction reactions.
Chem. Soc. 1992, 114, 5665, and references therein; e) J. P. Collman,
Nat. Struct. Biol. 1996, 3, 213, and references therein; f) M. Beley, J.-P.
Collin, J. Mol. Catal. 1993, 79, 133; g) K. Umeda, H. Ikeda, A.
Nakamura, F. Toda, Chem. Lett. 1992, 353; h) K. Umeda, A. Nakamura,
F. Toda, Bull. Chem. Soc. Jpn. 1993, 66, 2260, and references therein.
3] E. Steckhan, S. Herrmann, R. Ruppert, J. Thommes, C. Wandrey,
Angew. Chem. 1990, 102, 445; Angew. Chem. Int. Ed. Engl. 1990, 29,
[
[
3
88.
Experimental Section
4] a) R. Ruppert, S. Herrmann, E. Steckhan, Tetrahedron Lett. 1987, 28,
6583; b) D. Westerhausen, S. Herrmann, W. Hummel, E. Steckhan,
Angew. Chem. 1992, 104, 1496; Angew. Chem. Int. Ed. Engl. 1992, 31,
1529.
General procedure for the synthesis of NAD model substrates: The
chloride or bromide salts of the NAD model substrates were prepared by
related published methods;[ however, THF was used as the reaction
solvent so as to simplify the purification process. Anion exchange was
conducted either by utilizing AgOTf (1.0 equiv in MeOH) or NaOTf
6]
[
5] a) An analogue of [Cp*Rh(bpy)H] , [Cp*Rh(6,6'-dimethyl-2,2'-
1
[2b]
bpy)H] , was identified by H NMR spectroscopy; b) Pathways for
the hydride decomposition were discussed, see U. Kölle, B.-S. Kang,
P. Infelta, P. Compte, M. Grätzel, Chem. Ber. 1989, 122, 1869.
6] a) D. Mauzerall, F. H. Westheimer, J. Am. Chem. Soc. 1955, 77, 2261;
b) E. Kimura, M. Shionoya, A. Hoshino, T. Ikeda, Y. Yamada, J. Am.
Chem. Soc. 1992, 114, 10134.
(
1.05 equiv in acetone). After solvent removal from the filtrate the crude
products were further purified by recrystallization from acetone/CH Cl
1/1) and Et
O, followed by refrigeration at � 158C. The resulting crystals
were collected on a glass-fritted funnel and washed with acetone (08C),
then dried in vacuo over P (yield 86 ± 97%).
-Benzyl-N-methylnicotinamide (triflate salt, 1b): 1H NMR (D
2
2
[
[
(
2
2
O
5
7] The coordination of the �CN substitutent as a 2e or 4e donor through
1
9
8
2
O): d
the p electrons has been reported, see F. A. Cotton, G. Wilkinson,
Advanced Inorganic Chemistry, 5th ed., Wiley, New York, 1988, p. 254,
and references therein.
.20 (s, 1H, H2 on Py), 8.96 (d, J 5.8 Hz, 1H, H6 on Py), 8.75 (d, J
.0 Hz, 1H), 8.08 (app.t, J 7.2 Hz, 1H), 7.43 (app.s, 5H), 5.81 (s, 2H,
-
2 15 3 2 4
CH Ph), 2.88 (s, 3H); elemental analysis calcd for C15H F N O S (376.39):
[
8] a) J. M. OꢁConnor, C. P. Casey, Chem. Rev. 1987, 87, 307; b) For an
example of a ring-slippage mechanism with the Cp* ligand, see W. D.
Jones, V. L. Kuykendall, A. D. Selmeczy, Organometallics 1991, 10,
1577.
C 47.86, H 4.03, N 7.44; found: C 47.66, H 4.35, N 7.08.
1
1
8
-Benzylthionicotinamide (triflate salt, 1d): 1H NMR (D
H, H2 on Py), 8.88 (d, J 6.4 Hz, 1H, H6 on Py), 8.71 (d, J 8.4 Hz, 1H),
.00 (dd, J 6.0, 8.1 Hz, 1H), 7.41 (app.s, 5H), 5.77 (s, 2H, -CH Ph);
(378.43): C 44.43, H 3.47, N
2
O): d 9.31 (s,
2
[9] a) G. Büchi, D. L. Coffen, K. Kocsis, P. E. Sonnet, F. E. Ziegler, J. Am.
Chem. Soc. 1966, 88, 3099, and references therein; b) R. R. Schmidt, G.
Berger, Chem. Ber. 1976, 109, 2936.
elemental analysis calcd for C14
13 3 2 3 2
H F N O S
7.40; found: C 44.36, H 3.56, N 7.65.
1
1
-Benzyl-3-acetylpyridinium triflate (1e): H NMR (D
2
O): d 9.35 (s, 1H,
H2 on Py), 8.97 (d, J 6.6 Hz, 1H, H6 on Py), 8.93 (d, J 8.0 Hz, 1H), 8.11
app.t, J 7.2 Hz, 1H), 7.40 (app.s, 5H), 5.81 (s, 2H, -CH Ph), 2.65 (s, 3H);
elemental analysis calcd for C15 NO S (361.37): C 49.85, H 3.91, N 3.88;
found: C 50.12, H 3.57, N 3.89.
(
2
H
14
F
3
4
1
1
-Benzyl-3-methylpyridinium triflate (1h): 1H NMR (D
H, H2 on Py), 8.61 (d, J 5.0 Hz, 1H, H6 on Py), 8.25 (d, J 7.8 Hz, 1H),
Ph), 2.40 (s,
S (333.36): C 50.44, H 4.24,
2
O): d 8.62 (s,
7.81 (app.t, J 7.2 Hz, 1H), 7.37 (app.s, 5H), 5.64 (s, 2H, -CH
2
Reversible Fixation of Ethylene on a
3
H); elemental analysis calcd for C14
H
14
F
3
NO
3
II
Sm Calix-Pyrrole Complex**
N 4.20; found: C 50.01, H 4.56, N 4.64.
1
1
2
5
-Benzylpyridinium triflate (1i): H NMR (D
2
O): d 8.82 (d, J 5.9 Hz,
Tiffany Dub e , Sandro Gambarotta,* and
Glenn P. A. Yap
H), 8.48 (app.t, J 7.8 Hz, 1H), 7.98 (t, J 6.5 Hz, 2H), 7.42 (app.s, 5H),
.73 (s, 2H, -CH Ph); elemental analysis calcd for C13 NO S (319.33):
2
H
12
F
3
3
C 48.89, H 3.80, N 4.39; found: C 49.01, H 3.78, N 4.55.
The chemistry of lanthanides has become a very important
field of inorganic chemistry since the 1980s when a series of
reports describing the unique richness and variety of reactivity
1
1
-Methylnicotinamide (triflate salt, 4): H NMR (D
2
O): d 9.19 (s, 1H, H2
on Py), 8.88 (d, J 6.0 Hz, 1H, H6 on Py), 8.80 (d, J 8.7 Hz, 1H), 8.10
app.t, J 7.1 Hz, 1H), 4.39 (s, 3H, CH ); elemental analysis calcd for
S (286.26): C 33.56, H 3.18, N 9.79; found: C 33.80, H 3.23, N
(
3
II[1]
[2]
of Sm
rejuvenated the interest in this field. Cyclopenta-
8 9 3 2 4
C H F N O
1
0.02.
dienyl (Cp) and related ligands have been used to develop the
major part of the chemistry of Sm . Given the caliber of
II [3]
Electrochemical measurements: These were carried out by means of cyclic
voltammetry using a standard three electrode cell with a glassy carbon
electrode and a Ag/AgCl reference electrode. The solutions were generally
a water/THF mixture with an appropriate buffer salt. All of the electro-
chemical responses of the compounds 1a ± i exhibited a chemically
transformations afforded by [Cp*Sm] (Cp* C Me ), it is not
2
5
5
surprising that several attempts have been made to prepare
complexes of divalent samarium in different ligand environ-
�
1
irreversible peak in the voltammetric experiments when a 20 ± 50 mVs
sweep rate was used.
[*] Prof. S. Gambarotta, T. Dub e , Dr. G. P. A. Yap
Department of Chemistry, University of Ottawa
Ottawa, ON, K1N 6N5 (Canada)
Received: November 4, 1998 [Z12617IE]
German version: Angew. Chem. 1999, 111, 1524 ± 1527
Fax: (1)613-562-5170
E-mail: sgambaro@oreo.chem.uottawa.ca
Keywords: cofactors ´ hydrido complexes ´ reductions ´
regioselectivity ´ rhodium
[
**] This work was supported by the Natural Sciences and Engineering
Council of Canada (NSERC) and by NATO (travel grant).
1
432
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