Six different salts of the weakly coordinating anion [Al(OTeF5)4]– were synthesized and characterized spectroscopically. The alkali and silver salts M[Al(OTeF5)4] (M = Ag, Li, Na, K, Rb) were obtained by a protonation reaction involving the Brønsted acid H[Al(OTeF5)4](solv). In the case of the lithium and silver salt, crystals of the solvent‐coordinated [Li(thf)4][Al(OTeF5)4(thf)2] and [Ag(thf)6][Al(OTeF5)4(thf)2] were characterized by low‐temperature X‐ray diffraction, revealing a sixfold coordinated central aluminum atom. By a metathesis reaction, the oxidizing nitrosonium salt [NO][Al(OTeF5)4] was obtained and its reactivity was demonstrated by a reaction with white phosphorus. By low‐temperature NMR spectroscopy the selective formation of [NOP4]+ species was confirmed. All of the prepared salts represent useful starting materials for the further introduction of the weakly coordinating anion [Al(OTeF5)4]– into a given system.
The pentafluoroorthotellurate group (teflate, OTeF 5 ) is able to form species, for which only the fluoride analogues are known. Despite nickel fluorides being widely investigated, nickel teflates have remained elusive for decades. By reaction of [NiCl 4 ] 2À and neat ClOTeF 5 , we have synthesized the homoleptic [Ni(OTeF 5 ) 4 ] 2À anion, which presents a distorted tetrahedral structure, unlike the polymeric [NiF 4 ] 2À . This highspin complex has allowed the study of the electronic properties of the teflate group, which can be classified as a weak/ medium-field ligand, and therefore behaves as the fluoride analogue also in ligand-field terms. The teflate ligands in [NEt 4 ] 2 [Ni(OTeF 5 ) 4 ] are easily substituted, as shown by the formation of [Ni(NCMe) 6 ][OTeF 5 ] 2 by dissolving it in acetonitrile. Nevertheless, careful reactions with other conventional ligands have enabled the crystallization of nickel teflate complexes with different coordination geometries, i.e. [NEt 4 ] 2 [trans-Ni(OEt 2 ) 2 (OTeF 5 ) 4 ] or [NEt 4 ][Ni(bpyMe 2 )(OTeF 5 ) 3 ].
Herein, we present two different routes for the synthesis of the perfluorinated trityl cation, which allowed the handling of the free, uncoordinated species in organic solvents for the first time. The usage of the weakly coordinating anion [Al(OTeF 5 ) 4 ] À and its derivatives allows the characterization of this species by NMR spectroscopy and most importantly by single-crystal Xray diffraction. The high hydride ion affinity of the cation is shown by hydrogen abstraction from isobutane. Furthermore, cyclic voltammetry reveals its oxidative potential which is supported by the reaction with tris(4bromophenyl)amine, giving rise to the formation of the ammoniumyl radical cation, also known as "magic blue".
Preparation and characterization of the dimeric Lewis superacid [Al(OTeF5)3]2 and various solvent adducts is presented. The latter range from thermally stable adducts to highly reactive, weakly bound species. DFT calculations on the ligand affinity of these Lewis acids were performed in order to rank their remaining Lewis acidity. An experimental proof of the Lewis acidity is provided by the reaction of solvent‐adducts of Al(OTeF5)3 with [PPh4][SbF6] and OPEt3, respectively. Furthermore, their reactivity towards chloride and pentafluoroorthotellurate salts as well as (CH3)3SiCl and (CH3)3SiF is shown. This includes the formation of the dianion [Al(OTeF5)5]2−.
An anion‐doped aluminium chlorofluoride AlCl0.1F2.8(OTeF5)0.1 (ACF‐teflate) was synthesized. The material contains pentafluoroorthotellurate (teflate) groups, which mimic fluoride ions electronically, but are sterically more demanding. They are embedded into the amorphous structure. The latter was studied by PDF analysis, EXAFS data and MAS NMR spectroscopy. The mesoporous powder is a Lewis superacid, and ATR‐IR spectra of adsorbed CD3CN reveal a blue‐shift of the adsorption band by 73 cm−1, which is larger than the shift for SbF5. Remarkably, ACF‐teflate catalyzes dehydrofluorination reactions of monofluoroalkanes to yield olefins in C6D6. In these cases, no Friedel‐Crafts products were formed.
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