Divalent Lanthanide Metallocene Complexes with a Linear Coordination Geometry and Pronounced 6s-5d Orbital Mixing

Area of Science:

• Inorganic Chemistry
• Organometallic Chemistry
• Lanthanide Chemistry

Background:

• Divalent lanthanide compounds with 4f5d¹ configurations are rare.
• Most known compounds exhibit trigonal coordination geometries.
• Linear divalent metallocenes Ln(Cp^iPr5)₂ were previously reported for Tb and Dy.

Purpose of the Study:

• To synthesize and characterize the complete series of linear divalent metallocenes Ln(Cp^iPr5)₂ (1-Ln).
• To investigate the electronic configurations and structural properties of these compounds.
• To explore the magnetic properties and orbital interactions within the series.

Main Methods:

• Synthesis via salt metathesis and reduction reactions.
• Characterization using single crystal X-ray diffraction and ultraviolet-visible spectroscopy.
• Electron paramagnetic resonance spectroscopy for Yttrium (Y) and Lanthanum (La) compounds.

Main Results:

• Successful synthesis of the entire Ln(Cp^iPr5)₂ series, confirming linear coordination geometry and pseudo-D₅ symmetry.
• Established 4f electron configurations for Sm, Eu, Tm, Yb and 4f5d¹ for other lanthanides.
• Observed significant s-d orbital mixing and record hyperfine coupling constants in Y and La compounds.

Conclusions:

• The linear coordination geometry is maintained across the entire divalent lanthanide metallocene series.
• Pronounced 6s-5d orbital mixing in these linear compounds may correlate with weaker 4f-5d spin coupling.
• This study expands the understanding of divalent lanthanide organometallic chemistry and their electronic properties.