Cyclopentadiene, derivatives kinetic stabilization

The kinetic stability of group 14 metalloles towards [4 + 2] dimerization is dependent on the nature of the heteroatom and on the substituents bonded to it and the ring carbons. Like cyclopentadiene, the silole 2 is unstable as a monomer. The silicon methylated derivatives (3 and 4) are also unstable, but two mesityl groups provide stabilization by steric hindrance of the [4 + 2] dimerization transition state15. The same effect has been observed for 1,1-dimesitylgermole24. 

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