From Ion‐Like Ethylzinc Aluminates to [EtZn(arene) 2 ] + [Al(OR F ) 4 ] − Salts

Attempts to prepare previously unknown simple and very Lewis acidic [RZn] + [Al(OR F ) 4 ] − salts from ZnR 2 , AlR 3 , and HO−R F delivered the ion‐like RZn(Al(OR F ) 4 ) (R=Me, Et; R F =C(CF 3 ) 3 ) with a coordinated counterion, but never the ionic compound. Increasing the steric bulk in RZn + to R=CH 2 CMe 3 , CH 2 SiMe 3 , or Cp*, thus attempting to induce ionization, failed and led only to reaction mixtures including anion decomposition. However, ionization of the ion‐like EtZn(Al(OR F ) 4 ) compound with arenes yielded the [EtZn(arene) 2 ] + [Al(OR F ) 4 ] − salts with arene=toluene, mesitylene, or o ‐difluorobenzene ( o ‐DFB)/toluene. In contrast to the ion‐like EtZn(η 3 ‐C 6 H 6 )(CHB 11 Cl 11 ), which co‐crystallizes with one benzene molecule, the less coordinating nature of the [Al(OR F ) 4 ] − anion allowed the ionization and preparation of the purely organometallic [EtZn(arene) 2 ] + cation. These stable materials have further applications as, for example, initiators of isobutene polymerization. DFT calculations to compare the Lewis acidities of the zinc cations to those of a large number of organometallic cations were performed on the basis of fluoride ion affinity. The complexation energetics of EtZn + with arenes and THF was assessed and related to the experiments.