title: From Ion-Like Ethylzinc Aluminates to [EtZn(arene)2]+[Al(ORF)4]-Salts.
abstract: Attempts to prepare previously unknown simple and very Lewis acidic [RZn]+[Al(ORF)4]-salts from ZnR2, AlR3, and HO-RFdelivered the ion-like RZn(Al(ORF)4) (R=Me, Et; RF=C(CF3)3) with a coordinated counterion, but never the ionic compound. Increasing the steric bulk in RZn+to R=CH2CMe3, CH2SiMe3, 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(ORF)4) compound with arenes yielded the [EtZn(arene)2]+[Al(ORF)4]-salts with arene=toluene, mesitylene, or o-difluorobenzene (o-DFB)/toluene. In contrast to the ion-like EtZn(η3-C6H6)(CHB11Cl11), which co-crystallizes with one benzene molecule, the less coordinating nature of the [Al(ORF)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.
authors.affiliation: Institut für Anorganische und Analytische Chemie and Freiburger Materialforschungszentrum (FMF), Universität Freiburg, Albertstrasse 21, 79104, Freiburg, Germany.
authors.forename: Thies Olaf
authors.initials: TO
authors.lastname: Petersen
authors.affiliation: Institut für Anorganische und Analytische Chemie and Freiburger Materialforschungszentrum (FMF), Universität Freiburg, Albertstrasse 21, 79104, Freiburg, Germany.
authors.forename: Dustin
authors.initials: D
authors.lastname: Simone
authors.affiliation: Institut für Anorganische und Analytische Chemie and Freiburger Materialforschungszentrum (FMF), Universität Freiburg, Albertstrasse 21, 79104, Freiburg, Germany. krossing@uni-freiburg.de.
authors.forename: Ingo
authors.initials: I
authors.lastname: Krossing
keywords: NMR spectroscopy; X-ray diffraction; alkylzinc cations; density functional calculations; weakly coordinating anions