Quantum-chemical study of the effect of the association phenomenon on the active sites structure in butadiene polymerization reaction initiated by organolithium compounds

The electronic and geometric structures of monomeric and associated forms of crotyllithium (models for the active sites in the anionic polymerization of butadiene) have been calculated using a CNDO method. It appears that the cisoid configuration of the chain ends is energetically preferred for monomeric and dimeric forms of living macromolecules; in the case of tetramer, the transoid configuration is the more stable. The characteristics of C_α and C_γ atoms of substituted allylic groups undergo a certain bringing together when passing from monomer to dimer. The results are used for interpretation of the dependence of polybutadiene microstructure upon conditions during polymerization.