A Low-Spin Three-Coordinate Cobalt(I) Complex and Its Reactivity toward H₂ and Silane

Area of Science:

• Inorganic Chemistry
• Organometallic Chemistry
• Coordination Chemistry

Background:

• Pincer ligands are crucial in stabilizing transition metal complexes.
• Low-spin cobalt(I) complexes offer unique reactivity for bond activation.
• Understanding reaction mechanisms like oxidative addition and atom transfer is key in catalysis.

Purpose of the Study:

• To synthesize and characterize a three-coordinate low-spin cobalt(I) complex with a pincer ligand.
• To investigate the coordination behavior of the cobalt(I) center with small molecules.
• To elucidate the mechanism of H-H and Si-H bond activation at the cobalt center.

Main Methods:

• Synthesis of a cobalt(I) complex featuring a pincer ligand.
• Spectroscopic characterization of the complex and its reaction products.
• Mechanistic studies to determine the pathway of H-H and Si-H bond cleavage.

Main Results:

• A stable three-coordinate low-spin cobalt(I) complex was successfully generated.
• The complex readily formed σ-complexes with H2 and PhSiH3 due to an exposed empty orbital.
• Homolysis of H-H and Si-H bonds occurred via bimolecular hydrogen atom transfer, not oxidative addition.
• H2 evolution was observed from the resulting Co(II)-H species upon exposure to N2 at ambient conditions.

Conclusions:

• Single-electron processes are favored at the structurally rigidified cobalt center.
• The study provides insights into the reactivity of low-spin cobalt complexes in bond activation.
• This work contributes to the understanding of catalytic mechanisms involving hydrogen and silicon compounds.