Pentamethylcyclopentadienyl
rhodium dichloride is
an organometallic compound with the formula [(C5(CH3)5RhCl2)]2,
commonly abbreviated [Cp*RhCl2]2 This dark red
air-stable diamagnetic solid is a reagent in organometallic chemistry.1
Cp*RhCl2
dimer has been widely used as a homogeneous catalyst for C-H bond
activation,2 C-C bond formation,3 and alkenylation and annulation
of arenes and heteroarenes with alkynes.4, 5 The synthesis of the
catalyst can be readily achieved by reacting rhodium trichloride trihydrate
with 1,2,3,4,5-pentamethylcyclopentadiene in hot methanol.
Chemicals
1.
Rhodium
trichloride trihydrate (2.0 g, 8.4 mmol, 国药集团
Sinopharm Group Co. Ltd.)
2.
pentamethylcyclopentadiene
(1.2 g or 1.380 mL, 8.8 mmol, Alfa Aesar)
3.
methanol
(60 mL)
Procedure
Rhodium
trichloride trihydrate (2.0 g, 8.4 mmol, 国药集团
Sinopharm Group Co. Ltd.), pentamethylcyclopentadiene (1.2 g or 1.380 mL, 8.8
mmol, Alfa Aesar), methanol (60 mL) and a magnetic stirring bar are placed in a
100-mL round-bottomed flask fitted with a reflux condenser.
The
mixture is refluxed gently under nitrogen for 48h with stirring. The reaction mixture
is allowed to cool to room temperature and the dark red precipitate is filtered
off in air through a glass sinter.
The red filtrate is reduced involume to 10-mL using a rotary evaporator to give more red crystals that were combined with the first crop and washed with diethyl ether (3 x 10 mL).
Air drying gives 2.25g (95% yield) of [Rh(η5-C5Me5)C12]2, which is pure enough for most purposes. If required, the product may be recrystallized by dissolving in a minimum volume of chloroform, filtering if necessary, and slowly adding twice that volume of hexane.
(The
procedure was modified form White et. al. )
Note: The
procedure was modified from White’s et. al. work1
References
(1) White, C.; Yates, A.; Maitlis, Peter M.
(1992). "(η5-Pentamethylcyclopentadienyl)Rhodium
and -Iridium Compounds". Inorg.
Synth., 29, 2007, 228-234. doi:10.1002/9780470132609.ch53.
(2) Colby, D. A., Tsai, A.
S., Bergman, R. G., & Ellman, J. A., "Rhodium catalyzed
chelation-assisted C–H bond functionalization reactions." Acc.Chem. Res., 2012, 45 (6), pp 814–825
(3)
Colby, D. A., Bergman, R. G., & Ellman, J. A., “Rhodium-catalyzed C− C bond
formation via heteroatom-directed C− H bond activation.” Chem.Rev., 2010, 110 (2),pp 624–655
(4)
Boyarskiy, V. P., Ryabukhin, D. S., Bokach, N. A., & Vasilyev, A. V., “Alkenylation
of arenes and heteroarenes with alkynes.” Chem. Rev., 2016, 116 (10),pp 5894–5986
(5)
Manan, R. S., & Zhao, P., “Merging rhodium-catalysed CH activation and
hydroamination in a highly selective [lsqb] 4+ 2 [rsqb] imine/alkyne
annulation.” Nat.
Commun., 2016, 7, 11506. doi:10.1038/ncomms11506
