Main Group Redox Catalysis: New Frontiers with Germanium and Tin

Area of Science:

• Organometallic Chemistry
• Catalysis
• Sustainable Chemistry

Background:

• Precious transition metals are traditionally used in redox catalysis.
• Main group elements offer sustainable alternatives.
• Low-valent group 14 compounds (tetrylenes, tetryliumylidenes) possess electronic properties mimicking transition metals.

Purpose of the Study:

• To overcome the challenge of reductive elimination in low-valent group 14 catalysis.
• To develop catalytic redox cycles using germanium and tin.
• To demonstrate sustainable alternatives to transition metal catalysts.

Main Methods:

• Synthesis of carbodiphosphorane (CDP) and acridine-based pincer ligands.
• Stabilization of low-valent Ge(II) and Sn(II) centers.
• Investigation of catalytic C-F bond activation, N2O activation, and nitroarene reduction.
• Mechanistic studies using spectroscopy and radical trapping.

Main Results:

• CDP-ligated Sn(II) and Ge(II) complexes enable complete E(II)/E(IV) or E(II)/E(III)/E(IV) catalytic cycles.
• Catalytic activation of C(sp2)-F and C(sp3)-F bonds achieved.
• Selective defluorination of trifluoromethyl alkenes.
• Chemodivergent reduction of nitroarenes to anilines, arylhydroxylamines, azoxybenzenes, or hydrazines.
• Transfer hydrogenation of azoarenes and imines via FLP-type or single-electron transfer pathways.

Conclusions:

• Divalent group 14 compounds represent a new class of main group redox catalysts.
• Rational ligand design and element selection unlock diverse catalytic transformations.
• These systems offer sustainable and novel alternatives to transition metal catalysis.