Reactivity Study of the Bis(phosphine)-Stabilized Antimony(I) Cation

The 5,6-Bis(diisopropylphosphino)acenaphthene <b>L</b>-stabilized Sb(I) cationic compound [LSb][OTf] (OTf = CF₃SO₃) <b>1</b> possessing two lone pairs of electrons on the Sb(I) center showed nucleophilic behavior toward methyl trifluoromethanesulfonate forming the oxidized product [LSbMe][OTf]₂ <b>2</b> (OTf = CF₃SO₃). Reaction of compound <b>1</b> with Lewis acids such as GaCl₃ and AlBr₃ led to changes in the counteranions only giving products [LSb][GaCl₄] <b>3</b> and [LSb][SbBr₄] <b>4</b>, respectively. A metathesis reaction was observed when compound <b>1</b> was reacted with PI₃. The Sb(I) cation in <b>1</b> underwent the metathesis reaction with the P(I) cation, forming the more stable product [LP][OTf] <b>5</b>. The Sb(I) center in <b>1</b> was completely oxidized to Sb(V) by reacting with two equivalents of <i>o</i>-chloranil to give the Bis(phosphine)-stabilized Bis(perchloro catecholato)stibonium cation [L(O₂C₆Cl₄)₂Sb][OTf] <b>6</b>. Both compounds <b>1</b> and <b>6</b> were employed as proof-of-concept Lewis acid catalysts for the hydrosilylation of <i>p</i>-methyl benzaldehyde. All the compounds were characterized using single-crystal X-ray diffraction analysis, multinuclear nuclear magnetic resonance spectroscopy, mass spectrometry, and absorbance spectroscopy. Density functional theory calculations were performed on the relevant compounds.