Synthesis and characterization of [(C5Me4H)2Al]+, an initiator for the polymerization of isobutene.: X-ray crystal structures of [(C5Me4H)2Al(μ-Cl)]2 and [(C5Me4H)2Al][B(C6F5)4]

The octamethylaluminocenium cation [ Cp'Al-2](+) ( Cp') C5Me4H) was formed both by halide abstraction in the reaction between [ Cp'2AlCl](2) and AlCl3 and by cyclopentadienide abstraction in the reaction between Cp'Al-3 and [ CPh3][ B( C6F5)](4). [ Cp'Al-2](+) is less thermally stable than [ Cp*Al-2]+ ( Cp*) C5Me5) but is more active as an initiator for isobutene polymerization. The X-ray crystal structures of [ Cp'2AlCl](2) and [ Cp'Al-2][ B( C6F5)(4)] are reported.