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J. Yoshino et al. / Tetrahedron Letters 52 (2011) 4295–4298
4
4
/10
/10
4
4
2
0
2
0
850
650
250
450
850
450
250
650
/nm
/nm
Figure 3. Electronic absorption spectral changes by adding 0.0 equiv (red), 10 equiv (purple), and 50 equiv (blue) of AgNO3 into AN solution (ca. 1.1 ꢀ 10ꢁ5 mol dmꢁ3) of
(right) 3 and (left) 4.
6
p
-electron cyclic system, as also mentioned in 1H NMR spectral re-
at the University of Toyama for their supporting measurements
of physical properties of the new compounds.
sults. Secondly, besides such a strengthened aromaticity of the Cp
ring in 3, a possibility of the spatial interaction between the Cp-Th
conjugation constituents in syn or synclinal conformation with more
significance in 3 might not still be abandoned (Chart 2), although the
clarification on the electrochemical stabilization of 3 should wait for
further experimental study.11
References and notes
1. (a) Arnold, D.; Johnson, A. W.; Winter, M. J. Chem. Soc., Perkin Trans. 1 1977,
1643–1647; (b) Sugiura, K.; Ponomarev, G.; Okubo, S.; Tajiri, A.; Sakata, Y. Bull.
Chem. Soc. Jpn. 1997, 70, 1115–1123.
2. Borovkov, V. V.; Lintuluoto, J. M.; Inoue, Y. J. Am. Chem. Soc. 2001, 123, 2979–
2989 and many other references.
In connection with highly electron-donor ability of the Fc deriv-
atives, the affinity behavior of 3 and 4 for several transition-metal
ions were preliminarily examined,17 by means of electronic absorp-
tion spectral measurement in acetonitrile (AN). Among them, the
Fc-Th2 derivative 3 was particularly sensitive to Ag+ ion to afford
a new absorption band at 500–800 nm, probably due to MLCT tran-
sition band,18 while the Fc-Th derivative 4 showed no particular
spectral change under the same conditions (Fig. 3). Supposing the
complexation with Ag+ ion took place intermolecularly, the Fc-Th
4 should also exhibit the MLCT transition band similar to the Fc-
Th2 3 to some extent even under the applied conditions. Taking
the structural difference between 3 and 4 into consideration, this
result suggests that the Th-diacetylene conjugation constituents
in 3 work cooperatively for an intramolecular complexation with
Ag+ ion somehow. At present, it is premature to deduce the coordi-
nation sites for complexation between Th-diacetylene constituent
and Ag+ ion. However, the two diacetylene-groups connected Cp-
Th constituents likely face each other to associate with Ag+ ion like
a tweezers structure in a syn or synclinal conformation (Chart 2).
In conclusion, the 1,10-bis(diacetylene-group) connected Fc-Th2
derivative 3 has been synthesized in high yield under the improved
cross-coupling conditions between TMS-protected acetylenes 9 and
10. 1H NMR and UV–vis spectra and oxidation potential of 3 indi-
cated that the diacetylene linkage works as a mediator for commu-
nication with Th and Cp rings smoothly, induces Cp ring to reduce
its electron-density efficiently, and stabilizes Fc electrochemically.
It is also suggested that the diacetylene-group connected Cp-Th
constituents in 3 play a cooperative role for an intramolecular com-
plexation with Ag+ ion. Further study on the synthesis and proper-
ties of 1,10-bis(diacetylene-group) connected Fc derivatives
3. Borovkov, V. V.; Yamamoto, T.; Higuchi, H.; Inoue, Y. Org. Lett. 2008, 10, 1283–
1286.
4. Hayashi, N.; Naoe, A.; Miyabayashi, K.; Yamada, M.; Miyake, M.; Higuchi, H.
Tetrahedron Lett. 2004, 45, 8115–8119.
5. (a) Kealy, T. J.; Pauson, P. L. Nature 1951, 168, 1039–1040; (b) Miller, S. A.;
Tebboth, J. A.; Tremaine, J. F. J. Chem. Soc. 1952, 632–635; (c) Eiland, P. F.;
Pepinsky, R. J. Am. Chem. Soc. 1952, 74, 121–122.
6. Muraoka, T.; Kinbara, K.; Aida, T. Nature 2006, 440, 512–515 and many other
references.
7. As
a
few limited examples of 1,10-bis(diacetylene-group) connected Fc
derivatives, cyclophanes which are sterically hindered and multiply
protected with bulky tert-butyl groups on both Cp rings had been reported:
Fabian, K. H. H.; Lindner, H.-J.; Nimmerfroh, N.; Hafner, K. Angew. Chem., Int. Ed.
2001, 40, 3402–3405.
8. (a) Benkeser, R. A.; Fitzgerald, W. P. J. Org. Chem. 1961, 26, 4179–4180; (b)
Rosenblum, M.; Brawn, N.; Papenmeier, J.; Applebaum, M. J. Organomet. Chem.
1966, 6, 173–180.
9. Compound 8 is purchasable from Aldrich Chemical Co., CAS No. [40231-03-6].
10. Eglinton, G.; Galbraith, A. R. Chem. Ind. 1956, 737–738.
11. Mass (EI) and 1H NMR (300 MHz, CDCl, J/Hz) spectral data are preliminarily
shown. Other physical properties will be discussed elsewhere properly.
Compound 3: MS: m/z, 446 (M+) for C26H14S2Fe; 1H NMR, d = 7.27–7.25 (m, 4H,
Th-H), 6.94 (t, J = 4.8, 2H, Th-H), 4.58 (dd, J = 2.0 and 2.0, 4H, Cp-H), 4.38 (dd,
J = 2.0 and 2.0, 4H, Cp-H). Compound 4: MS: m/z, 316 (M+) for C18H12SFe; 1H NMR,
d = 7.30 (m, 2H, Th-H), 6.98 (t, J = 5.2, 1H, Th-H), 4.53 (dd, J = 2.0 and 2.0, 2H, Cp-
H), 4.27 (dd, J = 2.0 and 2.0, 2H, Cp-H), 4.26 (S, 5H, Cp-H). Compound 5: MS: m/z,
418 (M+) for C24H18Fe2; 1H NMR, d = 4.51 (dd, J = 2.0 and 2.0, 4H, Cp-H), 4.26 (s,
10H, Cp-H), 4.24 (dd, J = 2.0 and 2.0, 4H, Cp-H). Compound 6: MS: m/z, 214 (M+)
for C12H6S2; 1H NMR, d = 7.34–7.30 (m, 4H, Th-H), 6.99 (t, J = 4.8, 2H, Th-H).
12. (a) Pudelski, J. K.; Callstrom, M. R. Organometallics 1992, 11, 2757–2759; (b)
Pudelski, J. K.; Callstrom, M. R. Organometallics 1994, 13, 3095–3109. Also see
Ref. 7.
13. (a) Shimizu, R.; Hayashi, N.; Higuchi, H. Phosphorus, Sulfur Silicon 2010, 185,
952–956; (b) Yoshino, J.; Shimizu, R.; Hayashi, N.; Higuchi, H. Bull. Chem. Soc.
Jpn. 2011, 84, 110–118.
14. (a) Weinmayr, V. J. Am. Chem. Soc. 1955, 77. 3009 and 3012; (b) Yamada, S.;
Nakahara, A.; Tsuchida, R. Bull. Chem. Soc. Jpn. 1955, 28, 465–469.
15. Menczel, S. Z. Physik. Chem. 1927, 125, 161–166.
carrying much larger sized p
ES like OEP(M) is now in progress.17
16. (a) Coutiere, M.-M.; Demuynck, J.; Veillard, A. Theor. Chim. Acta (Berlin) 1972,
27, 281–285; (b) Bagus, P. S.; Walgren, U. I.; Almlof, J. J. Chem. Phys. 1976, 64,
2324–2334.
Acknowledgments
17. The Fc-Th2
3 was suggested to form a
complex with Hg2+ as well. The
complexation aspects of 3 will be reported conclusively, as compared with
those of other related derivatives, in view of complex structure, association
constant kass, solvent effect and so on.
Financial support by a Grant-in-Aid for Scientific Research from
the Ministry of Education, Science, Sports, Culture and Technology
(Integrated Organic Synthesis; No. 22106512), is gratefully acknowl-
edged. H.H is also grateful to the Center of Instrumental Analyzes
18. Lever, A. B. P.; Dodsworth, E. S. In Inorganic Electronic Structure and
Spectroscopy; Solomon, E. I., Lever, A. B. P., Eds.; Wiley Interscience
Publication, John Wiley and Sons Inc.: New York, 1999; Vol. II, pp 227–289.