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

Abstract

The 5,6-Bis(diisopropylphosphino)acenaphthene L-stabilized Sb(I) cationic compound [LSb][OTf] (OTf = CF₃SO₃) 1 possessing two lone pairs of electrons on the Sb(I) center showed nucleophilic behavior toward methyl trifluoromethanesulfonate forming the oxidized product [LSbMe][OTf]₂ 2 (OTf = CF₃SO₃). Reaction of compound 1 with Lewis acids such as GaCl₃ and AlBr₃ led to changes in the counteranions only giving products [LSb][GaCl₄] 3 and [LSb][SbBr₄] 4, respectively. A metathesis reaction was observed when compound 1 was reacted with PI₃. The Sb(I) cation in 1 underwent the metathesis reaction with the P(I) cation, forming the more stable product [LP][OTf] 5. The Sb(I) center in 1 was completely oxidized to Sb(V) by reacting with two equivalents of o-chloranil to give the Bis(phosphine)-stabilized Bis(perchloro catecholato)stibonium cation [L(O₂C₆Cl₄)₂Sb][OTf] 6. Both compounds 1 and 6 were employed as proof-of-concept Lewis acid catalysts for the hydrosilylation of p-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.