Organo-Lewis Acids As Cocatalysts in Otionic Metallocene Polymerization Catalysis. Unusual Characteristics of Sterically Encumbered Tris (perfluorobiphenyl) borane

摘要

Organo-Lewis acids such as methyl alumoxane (MAO) and B(C_6P_5)_3 (I) play pivotal roles as alkide/hydride abstractors/ cocatalysts in generating highly active, cationic olefia polymerization catalysts~3 (II; L,L' = anionic ancillary ligands; X~- = weakly coordinating anion). Growing evidence argues that catalyst activity, lifetime, high-temperature stability, chain transfer characteristics, and stereoregulalion are significantly influenced by the nature of X~-, and that it would be of great interestto investigate the properties of sterically/electronically modified organo-Lewis acid abstractors. We communicate here the unusual cocatalytic characteristics of the new, Sterically encumbered fluoroarylborane, tris(2,2',2"-perfluorobiphenyl)-borane (PBB, III). Characteristics include substantially different abstractive and ion pair structure/reactivity relationships vis-a-vis I.