Chromium carbides and cyclopropenylidenes

Area of Science:

• Organometallic Chemistry
• Coordination Chemistry
• Synthetic Organic Chemistry

Background:

• Chromium carbido complexes are valuable synthetic intermediates.
• Understanding the reactivity of carbido ligands is crucial for developing new synthetic methodologies.

Purpose of the Study:

• To synthesize and characterize a novel dinuclear chromium carbido complex.
• To investigate the reactivity of this carbido complex with various organic substrates.
• To elucidate the mechanism of carbido transfer in organic transformations.

Main Methods:

• Reduction of carbon tetrabromide with CrBr2 in tetrahydrofuran (THF).
• X-ray diffraction (XRD) analysis of the pyridine adduct to determine the dinuclear structure.
• Reactions of the carbido complex with aldehydes, alkenes, and alkynes.
• Isotope labeling studies using a 13C-enriched carbido complex.

Main Results:

• Formation of a dinuclear chromium carbido complex, [CrBr2(thf)2)][CrBr2(thf)3](μ-C).
• The carbido complex reacted with aldehydes to yield α,β-unsaturated ketones.
• Double-cyclopropanation of alkenes to form spiropentanes, with confirmed carbide transfer.
• Formation of cyclopropenylidene complexes from reactions with alkynes.

Conclusions:

• The synthesized dinuclear chromium carbido complex exhibits versatile reactivity.
• Carbide transfer from the complex is a key step in spiropentane formation.
• This carbido complex serves as a valuable precursor for synthesizing diverse organic molecules.