Chemistry Letters 2001
973
those of structurally analogous diimine complexes
[PtMe(C2H4)(diimine)]+ (δH = 3.68–3.72, δC = 72.2–74.0).9
1
Thus the H NMR signal is rather close to that of free ethylene
(δ 5.30), and the 13C NMR value falls under the category of the
lowest chemical shifts of platinum–ethylene complexes.10
In conclusion, we have found a highly selective catalyst (1)
for dehydrogenative silylation of ketones. The reactions can be
conducted without solvent when the substrate ketone is liquid,
and dihydrogen gas is the sole by-product. Accordingly,
extremely clean and simple reaction systems for synthesizing
silyl enol ethers have been realized. The high-performance of 1
may be attributed to highly π-acidic nature of the platinum cen-
ter, which is provided by the coordination with the sp2-
hybridized phosphorus ligand.
This work was supported by a Grant-in-Aid for Scientific
Research from the Ministry of Education, Science, Sports and
Culture, Japan.
Dedicated to Professor Hideki Sakurai on the occasion of
his 70th birthday.
References and Notes
1
For reviews, see: a) P. Le Floch and F. Mathey, Coord. Chem. Rev.,
179-180, 771 (1998). b) F. Mathey, Acc. Chem. Res., 25, 90 (1992).
c) M. Yoshifuji, J. Chem. Soc., Dalton Trans., 1998, 3343.
a) F. Mathey and P. Le Floch, Chem. Ber., 129, 263 (1996). b) F.
Knoch, F. Kremer, U. Schmidt, U. Zenneck, P. Le Floch, and F.
Mathey, Organometallics, 15, 2713 (1996). c) B. Breit, Chem.
Commun., 1996, 437. d) B. Breit, J. Mol. Catal. A, 143, 143 (1999).
e) B. Breit, R. Winde, T. Mackewits, R. Paciello, and K. Harms,
Chem. Eur. J., 7, 3106 (2001).
2
3
4
a) X. Sava, L. Ricard, F. Mathey, and P. Le Floch, Organometallics,
19, 4899 (2000). b) C. Ganter, C. Glinsböckel, and B. Ganter, Eur.
J. Inorg. Chem., 1998, 1163. c) R. Shintani, M. M.-C. Lo, and G. C.
Fu, Org. Lett., 2, 3695 (2000). d) K. Tanaka, S. Qiao, M. Tobisu, M.
M.-C. Lo, and G. C. Fu, J. Am. Chem. Soc., 122, 9870 (2000).
a) K. Toyota, K. Masaki, T. Abe, and M. Yoshifuji, Chem. Lett.,
1995, 221. b) S. Ikeda, F. Ohhata, M. Miyoshi, R. Tanaka, T.
Minami, F. Ozawa, and M. Yoshifuji, Angew. Chem. Int. Ed., 39,
4512 (2000).
5
6
a) E. W Colvin, “Silicon Reagents in Organic Synthesis,” Academic
Press, New York (1988). b) P. Brownbridge, Synthesis, 1983, 1. c)
P. Brownbridge, Synthesis, 1983, 185.
a) Y. Nagai, K. Uetake, T. Yoshikawa, and H. Matsumoto, J. Syn.
Org. Chem. Jpn., 31, 759 (1973). b) H. Sakurai, K. Miyoshi, and Y.
Nakadaira, Tetrahedron Lett., 31, 2671 (1977). c) H. Nagashima, T.
Ueda, H. Nishiyama, and K. Itoh, Chem. Lett., 1993, 347. d) T.
Fuchikami, Y. Ubukata, and Y. Yanaka, Tetrahedron Lett., 32, 1199
(1991). e) M. Igarashi, Y. Sugihara, and T. Fuchikami, Tetrahedron
Lett., 40, 711 (1999), and references cited therein.
7
8
a) R. Appel, V. Winkhause, and F. Knoch, Chem. Ber., 120, 243
(1987). b) M. Yoshifuji, Y. Ichikawa, N. Yamada, and K. Toyota,
Chem. Commun., 1998, 27, and references cited therein.
Selected NMR data for 1 (CDCl3, 20 °C). 1H NMR: δ 1.06 (dd, JPH
= 2.7, 9.9 Hz, 3H, PtMe), 1.42, 1.44, 1.63, 1.63, 1.66, 1.66 (each s,
each 9H, t-Bu), 6.79 (d, JHH = 7.5 Hz, 2H, o-Ph), 6.83 (d, JHH = 8.4
Hz, 2H, o-Ph), 6.91 (t, JHH = 8.1 Hz, 4H, m-Ph), 7.17 (t, JHH = 7.2
Hz, 1H, p-Ph), 7.19 (t, JHH = 7.2 Hz, 1H, p-Ph), 7.53 (d, JPH = 2.7
Hz, 2H, PAr), 7.65 (d, JPH = 4.2 Hz, 2H, PAr). 13C{1H} NMR: δ 5.0
(dd, JPC = 101, 6 Hz, JPtC = 545 Hz, PtMe), 149.3 (dd, JPC = 59, 33
Hz, P=C), 151.7 (dd, JPC = 54, 27 Hz, P=C), 162.2 (dd, JPC = 92, 25
Hz, P=C–C), 166.3 (dd, JPC = 48, 5 Hz, P=C–C). 31P{1H} NMR: δ
Highly electron-deficient nature of 1 is reflected in the
98.1 (d, JPP = 14 Hz, JPtP = 6819 Hz), 186.2 (d, JPP = 14 Hz, JPtP
=
1618 Hz). Anal. Calcd for C54H71F3O3P2SPt: C, 58.21; H, 6.42%.
Found: C, 57.99; H 6.48%.
NMR data for its ethylene-coordinated derivative
1
[PtMe(C2H4)(P–P)]+. This complex shows the H and 13C
9
M. Fusto, F. Giordano, I. Orabona, F. Ruffo, and A. Panunzi,
Organometallics, 16, 5981 (1997).
NMR signals of ethylene ligand at δ 5.11 (t, JPH = 5.1 Hz, JPtH
=
10 B. E. Mann and B. F. Taylor, “13C NMR Data for Organometallic
Compounds,” Academic Press, London (1981).
57.1 Hz) and 89.7 (d, JPC = 13 Hz, JPtC = 103 Hz), respectively
(CD2Cl2). These chemical shifts are significantly lower than