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M. Gustafsson, T. Frejd / Journal of Organometallic Chemistry 689 (2004) 438–443
RhI-based catalysts with strong donating ligands (for
example PAr3) gave isomer I as the main-product
(typical ratio I:II was 70:30). Change in the electronic
nature of p-substituted triaryl phosphine ligands had
little influence on the regioselectivity, although a ten-
dency towards an increased formation of isomer II was
seen using more electron donating groups (p-Cl com-
pared to p-OMe). RhCl(CO)(PPh3)2 favoured produc-
tion of isomer II (I:II 15:85), while the corresponding
thiocarbonyl complex, RhCl(CS)(PPh3)2, gave I as the
major isomer (I:II 70:30).
4.2. Synthesis of rhodium (I) complexes of the type
RhCl((p-X–C6H4)3P)3 X ¼ Cl, Me, OMe and H and the
following hydrosilylation of isoprene
[RhCl(COD)]2 (2.5 mg, 0.01 mmol) and the respective
ligand (0.06 mmol) were mixed in benzene. Hydroge-
nation of the reaction mixture for 10 h (3 atm) resulted
in slightly yellow solutions. Argon was thoroughly
bubbled through the solution for 5 min, whereafter
HSiMe2Ph (0.50 g, 3.6 mmol) and isoprene (0.50 ml, 5.1
mmol) were added sequentially. Workup as described
above gave the yields reported in Table 2.
4.3. Synthesis of ‘‘doped’’ Wilkinson’s catalyst
4. Experimental section
A standard procedure described in [31] was followed.
The respective transition metal chloride (5%) was added
to each preparation. The isolated catalyst batches had a
similar (reddish) colour as the non-doped RhCl(PPh3)3.
The only exception was when CoCl2 was used. In that
case, the colour shifted towards red-orange.
GC analyses were performed on a Varian 3400 gas
chromatograph using a SPB-5 column (Supelco, 30
m ꢂ 0.25 mm i.d. ꢂ 0.25 lm film thickness). NMR spectra
were recorded at 400 MHz (Bruker DRX spectrometer),
if nothing else is mentioned. Preparative chromato-
graphic separations were performed on Matrex Amicon
normal phase silica gel 60 (0.035–0.070 mm). Thin-layer
chromatography was performed on Merck precoated
TLC plates with Silica gel 60 F-254, 0.25 mm. After
elution, the TLC plates were visualized with UV light
followed by spraying with a solution of p-methoxy-
benzaldehyde (26 ml), glacial acetic acid (11 ml) con-
centrated sulfuric acid (35 ml), and 95% ethanol (960 ml)
followed by heating. All solvents were dried over 4A ms
(5% m/w) for 24 h prior to use, unless otherwise men-
tioned. The molecular sieves were activated at 400 °C for
6 h and then allowed to cool under argon. All solvents
were thoroughly degassed by purging with argon.
RhCl(PPh3)3 [31], [RhClCOD]2 [32], RhCl(CS)(PPh3)2
[33], RhCl(CO)(PPh3)2 [34], Rh(NO)(PPh3)3 [35],
Rh(OH)(PPh3)3 [36], HSiMe2(p-CF3C6H4) [37] and
HSiMe2(p-OMeC6H4) [37] were prepared according
to literature procedures. 1-[Dimethyl(phenyl)silyl]-3-
methyl-but-2-ene (I) and ðZÞ-1-[dimethyl(phenyl)silyl]-
2-methylbut-2-ene (II) had identical spectroscopic data
with those previously reported [12].
Acknowledgements
We thank the Swedish Research Council, the Crafo-
ord Foundation, the Knut and Alice Wallenberg
Foundation, and the Royal Physiographic Society in
ꢀ
Lund for financial support. Ms Katarina Barrestal is
gratefully acknowledged for her initial work.
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4.1. Typical procedure for the hydrosilylation reaction
Benzene (15 ml) was thoroughly degassed by purging
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column of silica gel and evaporation of the solvent af-
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