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S.J. Na et al. / Journal of Organometallic Chemistry 692 (2007) 5523–5527
methylsilane. Coupling constants are reported in Hertz
(Hz). Carbon-13 nuclear magnetic resonance (13C NMR)
spectra were recorded with a Varian Mercury plus
(100 MHz) spectrometer. Chemical shifts are reported in
delta (d) units, part per million (ppm) relative to the center
of the triplet at 77.00 ppm for deuteriochloroform. Elemen-
tal analysis was carried out at the Inter-University Center
Natural Science Facilities, Seoul National University. Elec-
trochemical data were recorded on a potentiostat/galvano-
stat (PARC (Princeton Applied Research), model 263) with
Electrochemistry Power Suite Module and Cyclic
voltammetry software. The three-electrode cell consisting
of Pt disc (the working electrode), Ag wire (the reference
electrode), and Pt wire (the auxiliary electrode) was
employed. Dirhodium complexes (5 · 10À4 M) were dis-
solved in THF solution containing 0.1M tetrabutylammo-
nium perchlorate. The resulting solutions were subject
to cyclic voltammetry experiments at a scan rate of
100 mV/s.
No. R01-2006-000-10271-0), the Korea Research Founda-
tion Grant funded by the Korean Government
(MOEHRD) (Grant No. KRF-2006-331-C00173), and
Ajou University.
References
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3.1. Synthesis of Rh2(OAc)4(NHC) (II)
The reaction of Rh2(OAc)4 (150 mg, 0.34 mmol) and
carbene ligand (NHC) I, 1,3-bis(2,6-diisopropylphenyl)-
imidazol-2-ylidene, (270 mg, 0.69 mmol) was performed
in THF (5 ml) for 5 h at ambient temperature under an
atmosphere of nitrogen. Color change was observed imme-
diately from blue to red. Upon the removal of THF, the
residual mixture was purified via column chromatography
using hexane:ethyl acetate 2:1 to afford analytical pure pur-
ple crystals (272 mg) in 93% yield. 1H NMR (CDCl3,
400 MHz) d 7.35 (t, J = 8.8 Hz, 2H), 7.19 (d, J = 8.8 Hz,
4H), 7.17 (s, 2H), 3.24 (sep, J = 7.6 Hz, 4H), 1.43 (br,
12H), 1.28 (d, J = 7.6 Hz 12H), 1.07 (d, J = 7.6 Hz,
12H); 13C NMR (CDCl3, 100 Hz) d 22.99, 25.43, 28.33,
122.85, 124.56, 128.73, 137.82, 145.59, 189.04. Anal. Calc.
(C35H48N2O8Rh2): C, 50.06; H, 5.84; N, 3.37. Found: C,
50.10; H, 5.86; N, 3.34%.
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To a stirred mixture of Rh2(OAc)4(NHC), II (10 mg,
0.012 mmol), crashed potassium carbonate (83 mg,
0.60 mmol) and 1-phenyl cyclohexene (190 mg, 1.20 mmol)
in dichloromethane (2.5 ml) was added a solution of TBHP
(176 mg, 5.0–6.0 M in decane solution) slowly at room
temperature. The resulting mixture was stirred overnight.
The solvent was removed with a rotary evaporator to
produce a residue which was purified by column chroma-
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Acknowledgements
This work is supported by the Basic Research Program
of the Korea Science and Engineering Foundation (Grant
(h) A.J. Catino, J.M. Nichols, H. Choi, S. Gottipamula, M.P. Doyle,
Org. Lett. 7 (2005) 5167;