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Posterpreis für Ian Ridlestone

Auf dem 22. Internationalen Symposium für Fluorchemie vom 22-27July in Oxford, GB, erhielt Dr. Ian Riddlestone, Postdoc im AK Krossing, für sein Präsentation einen der begehrten Posterpreise aus einem Feld den 151 ausgestellten Postern.

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Development of the Novel Perfluoropyridinoxy Based WCAs [E(OC5F4N)4]- (where E = B or Al)

Ian M. Riddlestone, Sarah Keller, Florian Kirschenmann and Ingo Krossing

Institut für Anorganische und Analytische Chemie, Albertstraße 21, University of Freiburg, Freiburg-im-Breisgau, D-79104

 

Weakly Coordinating Anions (WCAs) permit the preparation of cations that (almost) do not interact with their counter-ion. The evolution of modern WCAs has seen them used not only to permit the formation, isolation and structural characterisation of cationic species but evolve into specialized components in electrolytes,[1] room temperature ionic liquids[2] and catalysis.[3] One of the most weakly coordinating and versatile anions in the literature is the perfluoroalkoxyaluminate [Al(ORF)4]- (where RF = C(CF3)3).[4] Despite its high performance and versatility it remains susceptible to decomposition in the presence of extreme electrophiles and shows a tendency towards crystallographic disorder. Alternative alkoxy and aryloxy ligand residues to improve the performance of aluminate based WCAs are therefore of considerable interest.

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Orienting DFT calculations identified the extreme electron withdrawing capabilities of the tetrafluoropyridoxy ligand and the extreme Fluoride Ion Affinity (FIA) of the Lewis acid Al(OC5F4N)3 (FIA = 590 kJ mol-1; c.f. 489 kJ mol-1 for SbF5). Synthetic work to prepare this Lewis acid and the corresponding borate and aluminate based WCAs [E(OC5F4N)4]- (where E = B or Al) has shown this chemistry to be dominated by the extreme Lewis acidity imparted by the tetrafluoropyrdinoxy ligand. This is highlighted by the structural characterisation of the 6-coordinate neutral aluminium species Al2(OC5F4N)4(µ-OC5F4N)2(NCMe)4 (1) (figure 1) and the 5-coordinate aluminium dianion Na2(OEt2)[Al(OC5F4N)4] (2).

References:

 [1]       S. Seki, Y. Kobayashi, H. Miyashiro, Y. Ohno, A. Usami, Y. Mita, M. Watanabe and N. Terada, 
Chem. Commun., 2006, 2, 544. 


[2]        I. Krossing, in Comp. Inorg. Chem. II. Vol 1., Oxford Elsevier, 2013, p. 681. 


[3]        E. Y. Chen and T. J. Marks, Chem. Rev. 2000, 100, 1391. 


[4]        I.M. Riddlestone, A. Kraft, J. Schaefer and I. Krossing, Angew. Chem. Int. Ed.,   
             2018,
10.1002/anie.201710782

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