Mononuclear organogermanium(IV) catalysts for a [3 + 2] cycloaddition reaction

Area of Science:

• Organometallic Chemistry
• Catalysis
• Organic Synthesis

Background:

• Germanium(IV) compounds are explored for catalytic applications.
• The [3+2] cycloaddition reaction is a key transformation for synthesizing heterocyclic compounds.

Purpose of the Study:

• To synthesize and characterize novel mononuclear germanium(IV) compounds.
• To evaluate the catalytic activity of these compounds in the [3+2] cycloaddition reaction between azides and nitriles.
• To elucidate the reaction mechanism using experimental and computational methods.

Main Methods:

• Synthesis of three mononuclear Ge(IV) compounds.
• Characterization using FT-IR and NMR spectroscopy.
• Single crystal X-ray diffraction analysis.
• Screening as Lewis acid catalysts in [3+2] cycloaddition reactions.
• Density Functional Theory (DFT) calculations.

Main Results:

• Three mononuclear Ge(IV) complexes with varying pro-ligands were successfully synthesized.
• X-ray diffraction confirmed a five-coordinated germanium(IV) center in two compounds.
• The synthesized Ge(IV) compounds demonstrated excellent catalytic activity in the [3+2] cycloaddition reaction, achieving yields up to 96%.
• 5-substituted 1H-tetrazoles were efficiently produced.

Conclusions:

• The novel mononuclear Ge(IV) compounds are effective Lewis acid catalysts.
• These catalysts facilitate the synthesis of 5-substituted 1H-tetrazoles with high yields.
• A plausible catalytic mechanism for the [3+2] cycloaddition reaction was proposed.