Reduction chemistry yields stable and soluble divalent lanthanide tris(pyrazolyl)borate complexes.

Area of Science:

• Lanthanide chemistry
• Organometallic chemistry
• Coordination chemistry

Background:

• Lanthanide complexes are crucial in various applications.
• Understanding lanthanide(II) chemistry is less developed than lanthanide(III).
• Hydrotris(1-pyrazolyl)borate (Tp) and triflate (OTf) are common ligands.

Purpose of the Study:

• Synthesize novel, adduct-free homoleptic lanthanide(II) complexes.
• Characterize their stability, solubility, and electronic properties.
• Investigate the coordination modes of the Tp ligand.

Main Methods:

• Reduction of lanthanide(III) precursors using aluminyl(I) or KC8.
• Isolation and purification of lanthanide(II) complexes.
• Spectroscopic analysis (UV-Vis absorption, photoluminescence).
• Single-crystal X-ray diffraction.

Main Results:

• Successfully synthesized dimeric 1-Eu and monomeric 1-Yb complexes.
• Complexes exhibit good solubility and stability in various solvents.
• Observed intense coloration and photoluminescence in 1-Eu.
• Electronic absorption revealed 4f-5d transitions in Ln(II).
• X-ray diffraction identified a novel μ-κ1:η5-coordination of Tp to lanthanides.

Conclusions:

• Established a new route to homoleptic lanthanide(II) complexes.
• Demonstrated the versatility of the Tp ligand in lanthanide coordination.
• Highlighted the potential of these complexes in materials science and catalysis.