[(η1-Flu)Ti(μ-OiPr)(OiPr)2]2 (1) and (η1-Flu)(η5-Flu)Ti(OiPr)2 (2) were easily prepared from FluLi and ClTi(iPrO)3 and demonstrated a remarkable thermal stability in comparison with known (fluorenyl)titanium complexes. Both complexes were characterized by X-ray analysis and temperature-dependent NMR spectroscopy. In combination with methylaluminoxane, both compounds are highly efficient initiators for styrene polymerization, producing highly syndiotactic polymers.

Bivalent organolanthanides with unbridged substituted indenyl or fluorenyl ligands (1‐SiMe3Ind)2YTHF (I), (9‐SiMe3Flu)2YTHF (II), were found to efficiently catalyze the stereoregular polymerization of methyl methacrylate. The microstructure of resultant polymers was shown to be dependent of a conformation that the ligands adopt at the polymerization temperature. The formation of isotactic rich PMMAs from complex II was proposed to be associated with the fluctuation of the 9‐trimethylsilylfluorenyls around a C2 symmetric twisted‐conformation. The formation of the multi(syndioPMMA‐block‐iso‐PMMA) polymers from the mixture of rac‐ and meso‐isomers of I was rationalized on the basis of competing conjugate addition and inversion of the metallocene conformation. Surprisingly, both rac‐ and meso‐isomers of I were found to operate with similar activity and stereospecifity, although the stereospecific operation of the meso‐form was not completely understandable. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1599–1606, 1998

No abstract

No abstract

No abstract