T-Shaped Stibenium(III) Cation: Hydrostibination Without Sb─H Bond

Area of Science:

• Organometallic Chemistry
• Main Group Chemistry
• Synthetic Methodology

Background:

• Hydrostibination of alkenes is an underdeveloped transformation due to the instability of antimony-hydride (Sb─H) reagents.
• Existing methods often rely on labile E─H bonds, limiting their applicability in synthetic chemistry.

Purpose of the Study:

• To develop a novel hydrostibination strategy that circumvents the need for traditional Sb─H reagents.
• To explore the reactivity of a structurally constrained stibenium(III) ion in alkene functionalization.
• To establish a viable method for hydroelementation with heavy p-block elements.

Main Methods:

• Synthesis and characterization of a T-shaped amidophenolato-pyridyl supported stibenium(III) ion.
• Investigation of the anti-Markovnikov hydrostibination of diverse alkenes using the stibenium(III) ion.
• Spectroscopic (NMR, X-ray crystallography) and computational (DFT) analyses to elucidate the electronic structure and reaction mechanism.
• Mechanistic studies to probe element-ligand cooperativity (ELC).

Main Results:

• The stibenium(III) ion successfully mediated anti-Markovnikov hydrostibination of a broad range of alkenes in excellent yields.
• Spectroscopic and computational data revealed a polarizable, redox-confused Sb-π system, with reactivity characteristic of a Lewis-acidic Sb(III) center.
• Mechanistic studies indicated element-ligand cooperativity, where the hydride equivalent originates from the ligand scaffold.
• The resulting stiba-alkanes were quantitatively converted into haloalkanes.

Conclusions:

• A robust and efficient hydrostibination method has been established, overcoming the limitations of labile Sb─H reagents.
• The study demonstrates the utility of a novel stibenium(III) ion for hydroelementation with heavy p-block elements.
• This work opens new avenues for synthetic applications involving heavy main group elements.