Oxidation-Dependent Lewis Acidity in Chalcogen Adducts of Sb/P Frustrated Lewis Pairs

Abstract

The reactions of the Frustrated Lewis Pair (F5C2)2SbCH2P(tBu)2 with oxygen, sulphur, selenium and tellurium led to the mono-oxidation products (F5C2)2SbCH2P(E)(tBu)2 (E = O, S, Se, Te). Further oxidation of these chalcogen adducts with tetra¬chloro-ortho-¬benzo-quinone (o-chloranil) gave (F5C2)2Sb(CH2)(µ-E)P(tBu)2∙CatCl (CatCl = o-O2C6Cl4) with a central four-membered ring heterocycle for E = O, S, Se. For E = Te the elimination of elemental tellurium led to an oxidation product with two equivalents of o-chloranil, (F5C2)2SbCH2P(tBu)2∙2CatCl, which is also accessible by reaction of (F5C2)2SbCH2P(tBu)2 with o-chloranil. The synthesised compounds were characterised by NMR spectroscopy and X-ray structure analyses, and the structural properties were analysed in the light of the altered Lewis acidity due to the oxidation of the antimony atoms.