Discrete Lanthanide Aryl(alk)oxide Trimethylaluminum Adducts as Isoprene Polymerization Catalysts

• Published in: Macromolecules Vol. 39; no. 20; pp. 6811 - 6816
• Main Authors: Fischbach, Andreas, Meermann, Christian, Eickerling, Georg, Scherer, Wolfgang, Anwander, Reiner
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 03.10.2006
• Subjects: Applied sciences; Exact sciences and technology; Organic polymers; Physicochemistry of polymers; Polymerization; Preparation, kinetics, thermodynamics, mechanism and catalysts; Diene polymer; Rare earth metal complex; Aryloxy complex; Composition effect; Aluminium complex; Complex catalyst polymerization; Complex catalyst; Experimental study; Cis stereoisomer; Monodispersed polymer; Structure activity relation; Heteronuclear complex; Polynuclear complex; Reaction mechanism; Stereospecificity; Aluminium Organic compounds; Stereospecific polymerization; Catalyst activity; Isoprene polymer; Crystalline structure
• ISSN: 0024-9297; 1520-5835
• DOI: 10.1021/ma061149j

The structure−reactivity relationship of the rare-earth metal aryl(alk)oxide-promoted coordination polymerization of isoprene was investigated using binary initiating systems Ln(OR)3(AlMe3) x /Et2AlCl (Ln = La, Nd, Y). Depending on the degree of the rare-earth metal aryl(alk)oxide prealkylation (x = 1, 2, 3), such discrete trimethylaluminum (TMA) adduct complexes of rare-earth metal alkoxide and aryloxide components displayed a distinct initiating capability. The heterobimetallic bis-TMA adducts Ln(OAr i Pr)3(AlMe3)2 and tris-TMA adducts Ln(OCH2 tBu)3(AlMe3)3 (Ln = La, Nd) produced highly reactive initiators, whereas the mono-TMA adducts Ln(OAr t Bu)3(AlMe3) were catalytically inactive. The highest reactivities and stereoselectivities (>99% cis) were obtained for a n Ln:n Cl ratio of 1:2. The alkoxide-based tris-TMA adducts gave narrower molecular weight distributions than the aryloxide-based bis-TMA adduct complexes (M w/M n = 1.74−2.37 vs 2.03−4.26). A plausible mechanistic activation/deactivation scenario of the formation of the catalytically active/inactive species is presented.