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

Area of Science:

• Organometallic Chemistry
• Inorganic Chemistry
• Catalysis

Background:

• The exploration of low-valent main group element compounds is crucial for understanding fundamental chemical bonding and reactivity.
• Stabilized low-valent antimony (Sb(I)) compounds are relatively underexplored, presenting opportunities for novel chemical transformations.
• Phosphine ligands play a key role in stabilizing reactive main group species.

Purpose of the Study:

• To synthesize and characterize a novel 5,6-Bis(diisopropylphosphino)acenaphthene (L)-stabilized Sb(I) cationic compound.
• To investigate the reactivity of the Sb(I) center towards various reagents, including alkylating agents, Lewis acids, and other main group halides.
• To evaluate the catalytic potential of the synthesized Sb(I) and Sb(V) compounds in hydrosilylation reactions.

Main Methods:

• Synthesis of the Sb(I) compound [LSb][OTf] (1) and its subsequent reactions.
• Characterization of all synthesized compounds using single-crystal X-ray diffraction, multinuclear NMR, mass spectrometry, and absorbance spectroscopy.
• Computational studies using Density Functional Theory (DFT) to understand electronic structures and reaction mechanisms.

Main Results:

• The Sb(I) compound [LSb][OTf] (1) was successfully synthesized and characterized.
• Compound 1 exhibited nucleophilic behavior, undergoing oxidation with methyl trifluoromethanesulfonate to [LSbMe][OTf]2 (2).
• Reactions with Lewis acids (GaCl3, AlBr3) resulted in counteranion exchange, while reaction with PI3 led to a metathesis forming [LP][OTf] (5).
• Oxidation of Sb(I) to Sb(V) was achieved using o-chloranil, yielding [L(O2C6Cl4)2Sb][OTf] (6).
• Compounds 1 and 6 showed proof-of-concept Lewis acid catalytic activity in the hydrosilylation of p-methyl benzaldehyde.

Conclusions:

• The study successfully synthesized and characterized a novel Sb(I) compound, demonstrating its rich reactivity profile.
• The findings highlight the versatility of phosphine-stabilized Sb(I) species in undergoing oxidation, metathesis, and acting as Lewis acid catalysts.
• This work expands the scope of low-valent main group chemistry and offers potential for developing new catalytic systems.