Quantum chemical interpretation of the effects induced by tetramethylethylenediamine and dimethoxyethane in RLi non-polar monomer systems

✍ Scribed by Alexander V. Yakimansky; Ludmila V. Vinogradova; Boris L. Erussalimsky

• Publisher: John Wiley and Sons
• Year: 1994
• Tongue: English
• Weight: 252 KB
• Volume: 3
• Category: Article
• ISSN: 1022-1344
• DOI: 10.1002/mats.1994.040030310

✦ Synopsis

Abstract

The energetic and electronic parameters of various mono‐ and bidentate complexes of CH~3~Li with N‐ and O‐containing electron donors were calculated by the MNDO method. It was shown that N,N,N′,N′‐tetramethylethylenediamine (TMD) forms a more stable bidentate complex with CH~3~Li than 1,2‐dimethoxyethane (DME). However, DME, in contrast to TMD, may form a bis‐bidentate complex with CH~3~Li in which the CLi bond is weakened to a higher degree than in complexes of CH~3~Li with N‐containing electron donors. Much lower steric hindrance of DME, as compared to that of TMD, makes an easy formation of bis‐ and tris‐monodentate complexes of DME with CH~3~Li possible; in these bis‐ and tris‐monodentate complexes DME was simulated by (CH~3~)~2~O. Parameters of the CLi bond in the tris‐monodentate complexes of (CH~3~)~2~O and tetrahydrofuran (THF) with CH~3~Li are comparable to those of the bis‐bidentate complex CH~3~Li · 2 DME. These results are in qualitative agreement with experimental data, according to which THF and DME, in contrast to TMD, can favor the formation of separated ion pairs as active sites in anionic polymerization.