Europium(II) Ynolate Complex: Synthesis, Bonding, and Reactivity.

Area of Science:

• Organometallic Chemistry
• Inorganic Chemistry
• Coordination Chemistry

Background:

• Anionic ketenes exist as two resonance forms: ketenyl anions and ynolate anions.
• While ketenyl complexes are well-characterized, crystalline ynolate complexes remain elusive in the literature.
• Lanthanide complexes offer unique electronic and steric properties for stabilizing reactive species.

Purpose of the Study:

• To synthesize and characterize the first lanthanide ynolate complex.
• To elucidate the electronic structure and bonding characteristics of the ynolate ligand in a lanthanide complex.
• To investigate the reactivity of the novel lanthanide ynolate complex.

Main Methods:

• Synthesis via sigma-bond metathesis reaction followed by carbonylation.
• Single-crystal X-ray diffraction for structural determination.
• Density Functional Theory (DFT) calculations for electronic structure analysis and mechanistic studies.

Main Results:

• The first lanthanide ynolate complex, a europium(II) ynolate, was successfully synthesized and characterized.
• X-ray diffraction and DFT calculations confirmed the dominance of the ynolate resonance form with significant negative charge on oxygen.
• Reactivity studies showed C-centered trapping products with various electrophiles, indicating ynolate character.

Conclusions:

• This work provides the first crystalline example of a lanthanide ynolate complex, overcoming a significant synthetic challenge.
• The study confirms the ynolate resonance form's dominance and reveals unique electronic properties.
• The observed reactivity, including a shift towards ketenyl character in reactions with carbodiimide, highlights the potential for novel transformations.