Hydrogen transfer reaction, agostic interaction

The agostic interaction is considered to be important in such reactions as a elimination, /1-hydrogen elimination, and orthometalation. For example, in a/i-hydrogen elimination, a H atom on Lhc/i-C atom of an alkyl group is transferred to the metal atom and an alkene is eliminated. This reaction proceeds through an agostic-bond intermediate, as shown below ... 

The key assmnption in the scheme is that the Ti-CH CH species is unique in that it is relatively stable. This stability may arise from a strong P-agostic interaction between the hydrogen atom of the methyl group and the Ti atom. Other Ti-alkyl species proposed in the scheme do not possess this stability. In this scheme, formation of the Ti-CH CH species occurs as a result of an ethylene insertion reaction into the T-H bond or after a chain transfer reaction with ethylene. 

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