[AlCp₂]⁺: Structure, Properties and Isobutene Polymerization

Abstract

Abstract Reaction of the protonic ether compound [H(OEt 2 ) 2 ][Al(OR F ) 4 ] (R F = C(CF 3 ) 3 ) with AlCp 3 leads to the formation of the [AlCp 2 ] + ‐cation, which is stabilized by the weakly coordinating [Al(OR F ) 4 ] – ion. Besides [AlCp 2 ] + , the ion [AlCp 2 ·2Et 2 O] + , which is stabilized by two ether molecules, is formed in an equilibrium reaction. The so far unknown molecular structure of [AlCp 2 ] + and the molecular structure of [AlCp 2 ·2Et 2 O] + are presented in this work. To get insight in the formation and the equilibrium between these two cations, quantum mechanical calculations were performed. Moreover, the influence of counterions like [Al(OR F ) 4 ] – and [MeB(C 6 F 5 ) 3 ] – on the activity of [AlCp 2 ] + to act as a polymerization initiating agent for isobutene was investigated.