P-Agostic interactions

Low-temperature NMR spectroscopic data for a cobalt complex with a p-agostic interaction. 

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. 

The existence of intramolecular short Ln...C(Me) contacts is the main structural feature of considered monomeric bis(trimethylsylyl)amide derivatives. These contacts reflect evidently the "P-agostic interaction found in the structures of organolanthanoid complexes with CH(SiMe3)2 ligands (Chapter I). 

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