From Ion‐Like Ethylzinc Aluminates to [EtZn(arene)2]+[Al(ORF)4]− Salts |
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Authors: | Dr Thies Olaf Petersen Dustin Simone Prof?Dr Ingo Krossing |
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Institution: | Institut für Anorganische und Analytische Chemie and Freiburger Materialforschungszentrum (FMF), Universit?t Freiburg, Freiburg, Germany |
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Abstract: | Attempts to prepare previously unknown simple and very Lewis acidic RZn]+Al(ORF)4]? salts from ZnR2, AlR3, and HO?RF delivered 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. |
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Keywords: | alkylzinc cations density functional calculations NMR spectroscopy weakly coordinating anions X-ray diffraction |
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