Synthesis and Reactivity of an Antimony(III) Dication
In enzyme catalysis, the proximity effect is a common phenomenon that forces reactions to occur by bringing two or more molecules close together. To achieve this effect, the active center requires multiple binding sites to preorganize reactants before the reaction. Although this effect has been extensively studied in enzyme catalysis, its application in main-group element compounds is rarely reported. This study aims to explore the realization of this concept in main-group compounds, particularly through the synthesis and characterization of a trivalent antimony dication ([tpme2sb]2+), and to investigate its reactivity with different ligands, thereby revealing its potential in catalytic reactions.
Source of the Paper
This paper was co-authored by Deepti Sharma, Annabel Benny, Alex P. Andrews, Thayalan Rajeshkumar, Laurent Maron, and Ajay Venugopal. The research team is affiliated with the Indian Institute of Science Education and Research (IISER Thiruvananthapuram) and the National Institute of Applied Sciences (INSA Toulouse) in France. The paper was published in Nature Synthesis in April 2025, with the DOI 10.1038/s44160-024-00724-0.
Research Process
1. Synthesis of the Trivalent Antimony Dication [tpme2sb]2+
The first step of the research was the synthesis of the trivalent antimony dication [tpme2sb]2+. The team synthesized tpme2sbcl2 (1) by reacting anhydrous SbCl3 with Ktpme2 in toluene. Subsequently, they attempted to extract two chloride ions from 1 using Ag[SbF6] in dichloromethane, but this failed due to the decomposition of the [SbF6]− anion. However, in the presence of tetrahydrofuran (THF) as a coordinating solvent, the reaction successfully generated the stable solvated dication [tpme2sb(thf)][SbF6]2 (2).
2. Reactivity of [tpme2sb]2+ with Different Ligands
Next, the team explored the reactivity of [tpme2sb]2+ with different ligands. First, they reacted [ag(ch2cl2)2][al{oc(cf3)3}4] with 1 to generate [tpme2sb{oc(cf3)3}]al{oc(cf3)3}4. The team then attempted to stabilize [tpme2sb]2+ using the [b{3,5-(cf3)2c6h3}4]− anion but was unsuccessful. Finally, they successfully synthesized the dication [tpme2sb][b(c6f5)4]2 (6) using [et3si][b(c6f5)4].
3. Catalytic Activity of [tpme2sb]2+
The team further investigated the catalytic activity of [tpme2sb]2+. They found that [tpme2sb]2+ could react with diphenylamine (HNPh2) and styrene to form stable complexes, ultimately promoting a hydroamination reaction. Through density functional theory (DFT) calculations, the team revealed the structures of reaction intermediates and transition states, demonstrating the potential of [tpme2sb]2+ in catalytic reactions.
Key Results
1. Synthesis and Characterization of [tpme2sb]2+
The team successfully synthesized [tpme2sb]2+ and characterized it using X-ray diffraction and nuclear magnetic resonance (NMR) spectroscopy. X-ray diffraction data showed that the coordination geometry of [tpme2sb]2+ is a slightly distorted tetrahedral structure, consistent with the predictions of VSEPR theory.
2. Reactivity of [tpme2sb]2+ with Ligands
The team found that [tpme2sb]2+ could form stable complexes with various ligands, such as THF, Et3PO, PPh3, and HNPh2. The structures of these complexes were verified by X-ray diffraction and DFT calculations.
3. Catalytic Activity of [tpme2sb]2+
The team discovered that [tpme2sb]2+ could catalyze the hydroamination reaction of styrene with diphenylamine. Through DFT calculations, the team revealed the structures of reaction intermediates and transition states, demonstrating the potential of [tpme2sb]2+ in catalytic reactions.
Conclusions and Significance
This study successfully synthesized and characterized the trivalent antimony dication [tpme2sb]2+ and revealed its potential in catalytic reactions. The research demonstrated that [tpme2sb]2+ can form stable complexes with various ligands and promote hydroamination reactions. This discovery provides new insights into the application of main-group element compounds in catalytic reactions and opens new avenues for exploring intermolecular processes involving low-oxidation-state main-group compounds.
Research Highlights
- Novel Synthesis Method: The team successfully synthesized the trivalent antimony dication [tpme2sb]2+ and characterized it using X-ray diffraction and NMR spectroscopy.
- Broad Reactivity: [tpme2sb]2+ can form stable complexes with various ligands, demonstrating its potential in catalytic reactions.
- Catalytic Activity: The team found that [tpme2sb]2+ can catalyze the hydroamination reaction of styrene with diphenylamine, providing new ideas for the application of main-group element compounds in catalytic reactions.
Additional Valuable Information
The team also revealed the structures of reaction intermediates and transition states through DFT calculations, further demonstrating the potential of [tpme2sb]2+ in catalytic reactions. These computational results provide important theoretical support for understanding the reaction mechanism.
This paper not only offers a new perspective on the study of main-group element compounds but also provides important experimental and theoretical foundations for the development of novel catalysts. By revealing the synthesis methods, reactivity, and catalytic activity of [tpme2sb]2+, the research team has laid a solid foundation for future studies on catalytic reactions.