Trimethylsilyl cyclopentadiene is an organosilicon compound with the chemical formula C<sub>5</sub>H<sub>5</sub>Si(CH<sub>3</sub>)<sub>3</sub>. It exists as a colorless liquid. It is used in the synthesis of some metal cyclopentadienyl complexes and has attracted interest for its fluxional structure.
Trimethylsilyl cyclopentadiene is an example of a molecule that undergoes rapid sigmatropic rearrangement. Observations of trimethylsilyl cyclopentadiene using gas phase NMR spectroscopy show that the protons on the ring are chemically equivalent, indicated by a single peak. This phenomenon, an example of fluxionality, is explained by the migration of the silyl group from carbon-to-carbon, thereby giving the appearance of equivalent CH signals.
It has a refractive index (n20/D) of 1.471.
Trimethylsilyl cyclopentadiene is prepared by the reaction trimethylsilyl chloride (Me<sub>3</sub>SiCl) with sodium cyclopentadienide (NaC<sub>5</sub>H<sub>5</sub>):