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Updated: Jun 8, 2026

Controlled Photoredox Ring-Opening Polymerization of O-Carboxyanhydrides Mediated by Ni/Zn Complexes
Published on: November 21, 2017
Cationic alkylaluminum-complexed zirconocene hydrides as participants in olefin polymerization catalysis
Steven M Baldwin1, John E Bercaw, Hans H Brintzinger
1Arnold and Mabel Beckman Laboratories of Chemical Synthesis, California Institute of Technology, Pasadena, California 91125, United States.
Abstract:
The alkylaluminum-complexed zirconocene trihydride cation [(SBI)Zr(μ-H)(3)(Al(i)Bu(2))(2)](+), which is obtained by reaction of (SBI)ZrCl(2) with [Ph(3)C][B(C(6)F(5))(4)] and excess HAl(i)Bu(2) in toluene solution, catalyzes the formation of isotactic polypropene 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 AlMe(3), however, exposure to propene causes the trihydride cation to be completely converted, under concurrent consumption of all hydride species by propene hydroalumination, to the doubly Me-bridged cation [(SBI)Zr(μ-Me)(2)AlMe(2)](+). The latter then becomes the resting state for further propene polymerization, which produces, by chain transfer to Al, mainly AlMe(2)-capped isotactic polypropene.
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