Organometallics
Note
warm to room temperature. After reaching this temperature the slurry
was stirred for an additional 30 min. The solvent and volatiles were
removed under reduced pressure, and the residue was dried in high
vacuum. The residue was taken up in n-hexane, and the product
isolated in several fractions from crystallization. The product 4b was
(3) (a) Hapke, M.; Weding, N.; Spannenberg, A. Organometallics
2010, 29, 4298. (b) Weding, N.; Jackstell, R.; Jiao, H.; Spannenberg,
A.; Hapke, M. Adv. Synth. Catal. 2011, 353, 3423.
(4) Pattacini, R.; Jie, S.; Braunstein, P. Chem. Commun. 2009, 890.
(5) Jonas, K.; Deffense, E.; Habermann, D. Angew. Chem., Int. Ed.
Engl. 1983, 22, 716.
1
isolated as black crystals (17 mg, 0.028 mmol, 36% yield). H NMR
(−20 °C, THF-d8, 300 MHz): δ 0.01 (s, 9H, SiCH3), 4.67 (s, 10H,
C5H5), 4.82 (bs, 10H, C5H5), 8.96 (s, 1H, CCH) ppm. MS (EI): 594
[MH+] (83), 528 [MH+ − Cp] (100), 470 [MH+ − CpCo] (28), 370
(6) (a) Wadepohl, H.; Borchert, T.; Pritzkow, H. J. Chem. Commun.,
Chem. Soc. 1995, 1447. (b) Wadepohl, H.; Borchert, T.; Pritzkow, H.
Chem. Ber. 1997, 130, 593.
(7) Further examples: (a) Jiang, F.; Fehlner, T. P.; Rheingold, A. L. J.
Am. Chem. Soc. 1987, 109, 1860. (b) Barnes, C. E.; King, W. D.; Orvis,
J. A. J. Am. Chem. Soc. 1995, 117, 1855. (c) Review: Wadepohl, H.;
Metz, A. In Metal Clusters in Chemistry; Wiley-VCH Verlag, 1999; p
269.
+
[(CpCo)3 ] (21), 189 [Cp2Co+] (73). HRMS (ESI): calcd for
[C25H30Co4Si]+ 593.9445, found 593.9446. Anal. Calcd for
[C25H30Co4Si]: C, 50.52; H, 5.09. Found: C, 50.33; H, 4.89. Crystals
suitable for X-ray crystal structure analysis were obtained by storing a
saturated n-hexane/toluene solution of 4b at −4 °C.
General Procedures for Reactions with Complexes 1 and 4b.
General Procedure for the Catalytic [2+2+2] Cycloaddition of 1,6-
Heptadiyne with Benzonitrile. 1,6-Heptadiyne (1.0 mmol) and
benzonitrile (2.0 mmol) were dissolved in THF (4 mL) and stirred
at 0 °C. The cluster complex 4b dissolved in Et2O (5 mol %, 0.25 mL
of Et2O) was added dropwise, and the solution was stirred for 2 h at
100 °C. Under photochemical conditions the reaction solution was
irradiated for 18 h at 25 °C. The product was separated via column
chromatography with n-hexane/EtOAc (4:1) as eluent, and 5 was
isolated as an oil. The product was identified by its NMR and GC-MS
data.3a
General Procedure for the Catalytic Hydrogenation of 1-
Octene (6). The olefin (6, 1.0 mmol) was added under argon to a
solution of the cluster complex 4b (2.0 mol %) in toluene (20 mL).
The reaction mixture was transferred into an autoclave, which was
then heated to 60 °C. Hydrogen was then introduced and heated for 2
h; then the reaction mixture was heated for 22 h at 80 °C. After the
reaction time, the autoclave was allowed to cool to room temperature,
and the pressure was released. The reaction mixture was analyzed
immediately by GC.
General Procedure for the Catalytic Hydroformylation of 1-
Octene (6). The olefin (6, 10.2 mmol) was added under argon to a
solution of the cluster complex 4b (0.1 mol %) in toluene (20 mL).
The reaction mixture was transferred into an autoclave, which was
then heated to 80 °C under introduction of syngas. After 2 h the
temperature of the reaction mixture was raised to 120 °C. Following
22 h reaction time, the autoclave was allowed to cool to room
temperature, and the pressure was released. The reaction mixture was
analyzed immediately by GC.
(8) For a compilation of the spectra, see the Supporting Information.
(9) For earlier studies on binuclear cobalt complexes in C−C bond
formation, see: Bergman, R. G. Acc. Chem. Res. 1980, 13, 113.
(10) We investigated the synthesis from cobaltocene and potassium
in the presence of trimethylvinylsilane in n-hexane at −5 °C, and after
workup and chromatography over alumina, 4b was identified in the
single main fraction, together with unreacted cobaltocene. However,
these reaction conditions have already been described as giving
sluggish products.6b
(11) Pyykko, P.; Atsumi, M. Chem.Eur. J. 2009, 15, 12770.
̈
(12) Srinivasan, P.; Leong, W. K. Eur. J. Inorg. Chem. 2006, 464.
(13) Selected reviews: (a) Kotha, S.; Brahmachary, E.; Lahiri, K. Eur.
J. Org. Chem. 2005, 2005, 4741. (b) Chopade, P. R.; Louie, J. Adv.
Synth. Catal. 2006, 348, 2307. (c) Gandon, V.; Aubert, C.; Malacria,
M. Chem. Commun. 2006, 2209. (d) Agenet, N.; Buisine, O.;
Slowinski, F.; Gandon, V.; Aubert, C.; Malacria, M. Org. React.
2007, 68, 1. (e) Heller, B.; Hapke, M. Chem. Soc. Rev. 2007, 36, 1085.
(f) Leboeuf, D.; Gandon, V.; Malacria, M. In Handbook of Cyclization
Reactions; Ma, S., Ed.; Wiley-VCH: Weinheim, 2010; Vol. 1, p 367.
(g) Dominguez, G.; Perez-Castells, J. Chem. Soc. Rev. 2011, 40, 3430.
(h) Weding, N.; Hapke, M. Chem. Soc. Rev. 2011, 40, 4525.
(14) Jennerjahn, R.; Jackstell, R.; Piras, I.; Franke, R.; Jiao, H.; Bauer,
M.; Beller, M. ChemSusChem 2012, 5, 734.
ASSOCIATED CONTENT
* Supporting Information
■
S
Tables of crystallographic data for complex 4b and temper-
ature-dependent NMR spectra for the formation of 4b from 1
for the high-field region. This material is available free of charge
AUTHOR INFORMATION
Corresponding Author
■
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
We thank Prof. Uwe Rosenthal for his enduring support and
helpful discussions and comments on the cluster complexes.
The technical support by Fabian Fischer is gratefully acknowl-
edged. We thank the DFG (HA3511/3-1) and the Leibniz-
Gemeinschaft for financial support.
REFERENCES
(1) Wadepohl, H.; Gebert, S. Coord. Chem. Rev. 1995, 143, 535.
(2) Lewis, L. N. Chem. Rev. 1993, 93, 2693.
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dx.doi.org/10.1021/om300503y | Organometallics 2012, 31, 5660−5663