A Halide-Induced Redox-Switchable Catalyst for the Hydroboration of Terminal Alkenes

Area of Science:

• Organometallic Chemistry
• Catalysis
• Supramolecular Chemistry

Background:

• Macrocyclic ligands offer unique steric and electronic environments for metal complexes.
• Naphthalenediimide (NDI) units can undergo redox processes, enabling potential switchable functionalities.
• Rhodium and iridium complexes are widely used in catalysis.

Purpose of the Study:

• To synthesize and characterize novel rhodium and iridium complexes with a diphenylene-NDI di-NHC macrocyclic ligand.
• To investigate the effect of halide anions (fluoride and chloride) on the properties and catalytic activity of these complexes.
• To explore the potential for a halide-induced redox-switchable catalytic system.

Main Methods:

• Synthesis of di-NHC macrocyclic ligands and their rhodium/iridium complexes.
• Spectroscopic techniques (e.g., NMR, UV-Vis) and mass spectrometry for characterization.
• Computational modeling (e.g., DFT) to understand electronic and steric effects.
• Catalytic testing for hydroboration of terminal alkenes.

Main Results:

• Successful synthesis of rhodium and iridium complexes with the diphenylene-NDI di-NHC ligand.
• Observation of distinct adducts/intermediates upon fluoride (reduction) and chloride (adduct) addition to the NDI unit.
• Significant enhancement of catalytic activity in hydroboration upon halide addition.
• Demonstration of reversible catalytic activity switching via sequential addition of halide and NOBF4.

Conclusions:

• The synthesized complexes exhibit tunable steric and electronic properties upon halide interaction.
• Halide addition activates the NDI unit, leading to enhanced catalytic performance in hydroboration.
• A novel halide-induced redox-switchable catalytic (HIRSC) system has been developed, offering potential for controlled catalysis.