Cationic Alkylaluminum-Complexed Zirconocene Hydrides as Participants in

Abstract: The alkylaluminum-complexed zirconocene trihydride cation [(SBI)Zr(µ-H)3(AliBu2)2]+, which is obtained by reaction of (SBI)ZrCl2 with [Ph3C][B(C6F5)4] and excess HAliBu2 in toluene solution, catalyzes the formation of isotactic polypro-pene when exposed to propene at-30 °C. This cation remains the sole observable species in catalyst systems free of AlMe compounds. In the presence of AlMe3, however, exposure to propene causes the trihydride cation to be completely con-verted, under concurrent consumption of all hydride species by propene hydroalumination, to the doubly Me-bridged cation [(SBI)Zr(µ-Me)2AlMe2]+. The latter then becomes the resting state for further propene polymerization, which produces, by chain transfer to Al, mainly AlMe2-capped isotactic polypropene. Polymerization of R-olefins by zirconocene-based catalystsswhile being applied on industrial scalessis still not sufficiently understoo