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 tetrachloro-ortho-benzoquinone (o-chloranil) gave (F₅C₂)₂Sb(CH₂)(μ-E)P(tBu)₂·Cat^Cl (Cat^Cl = o-O₂C₆Cl₄) with a central four-membered ring heterocycle for E = O, S, and Se. For E = Te the elimination of elemental tellurium led to an oxidation product with two equivalents of o-chloranil, (F₅C₂)₂SbCH₂P(tBu)₂·2Cat^Cl, 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.