QUANTUM-CHEMICAL INTERPRETATION OF THE EFFECTS INDUCED BY TETRAMETHYLETHYLENEDIAMINE AND DIMETHOXYETHANE IN RLI NONPOLAR MONOMER SYSTEMS

The energetic and electronic parameters of various mono- and bidentate complexes of CH3Li with N- and O-containing electron donors were calc ulated by the MNDO method. It was shown that N,N,N',N'-tetramethylethy lenediamine (TMD) forms a more stable bidentate complex with CH3Li tha n 1,2-dimethoxyethane (DME). However, DME, in contrast to TMD, may for m a bisbidentate complex with CH3Li in which the C-Li bond is weakened to a higher degree than in complexes of CH3Li with N-containing elect ron donors. Much lower steric hindrance of DME, as compared to that of TMD, makes an easy formation of bis- and tris-monodentate complexes o f DME with CH3Li possible; in these bis- and tris-monodentate complexe s DME was simulated by (CH3)2O. Parameters of the C-Li bond in the tri s-monodentate complexes of (CH3)2O and tetrahydrofuran (THF) with CH3L i are comparable to those of the bis-bidentate complex CH3Li . 2 DME. These results are in qualitative agreement with experimental data, acc ording to which THF and DME, in contrast to TMD, can favor the formati on of separated ion pairs as active sites in anionic polymerization.