T-Shaped Stannyliumylidene Ion: Synthesis, Reactivity, and Redox Catalysis

Area of Science:

• Organometallic Chemistry
• Main Group Chemistry

Background:

• Organotin compounds are typically studied for their toxicity and limited catalytic applications.
• The electronic structure of low-valent main group elements often differs significantly from transition metals, limiting their catalytic potential.

Purpose of the Study:

• To synthesize and characterize a novel 8-electron stannyliumylidene ion with a pincer ligand.
• To investigate the ambiphilic reactivity and catalytic capabilities of the synthesized tin(II) complex.
• To explore the potential of main group elements to mimic transition metal reactivity in catalysis.

Main Methods:

• Synthesis of a T-shaped stannyliumylidene ion using an acridane-based pincer ligand.
• Characterization using nuclear magnetic resonance (NMR) spectroscopy, single crystal X-ray diffraction, and high-resolution mass spectrometry.
• Density functional theory (DFT) calculations to elucidate electronic structure and reactivity.

Main Results:

• A cationic 8-electron stannyliumylidene ion (Sn(II)) was successfully synthesized and characterized.
• The complex exhibits ambiphilic reactivity, engaging in electrophilic, nucleophilic, and σ-bond activation reactions.
• The tin center possesses both a lone pair and a vacant 5p-orbital, enabling dual reactivity.
• The organotin(II) complex efficiently catalyzes the transfer hydrogenation of azoarenes and imines using ammonia borane.
• A Sn(II)/Sn(IV) redox cycle at the tin(II) center was identified as the catalytic mechanism.

Conclusions:

• The synthesized stannyliumylidene ion demonstrates remarkable transition metal-like reactivity.
• This study presents the first example of Sn(II)/Sn(IV) catalyzed reduction of unsaturated bonds.
• Rationally designed main group systems can effectively mimic transition metal catalysis for diverse chemical transformations.