Fluorine complexes single bridged

Hhcker et al. independently reported single-component catalysts that consist of methylene-bridged zirconocene complexes 40 and 41 [138, 139]. It is noteworthy that these catalysts polymerize MMA with the BPh4 anion instead of fluorinated boranes. The advantage of a methylene bridge seems to be its large gap aperture [140]. 

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