Half-Sandwich Cerium and Lanthanum Dialkyl Complexes: Synthesis, Structure, and Reactivity Studies

Area of Science:

• Organometallic Chemistry
• Rare-Earth Chemistry
• Coordination Chemistry

Background:

• Lanthanide complexes with cyclopentadienyl ligands are valuable in catalysis and materials science.
• Understanding the reactivity of early lanthanide complexes is crucial for developing new synthetic methodologies.
• The tri-tert-butylcyclopentadienyl ligand offers steric protection and influences the electronic properties of metal centers.

Purpose of the Study:

• To synthesize novel cerium and lanthanum dialkyl complexes supported by a tri-tert-butylcyclopentadienyl ligand.
• To investigate the reactivity of these complexes with various small molecules, including diphenyl dichalcogenides, dibenzyl disulfide, dibenzyl diselenide, elemental selenium, and benzoxazole.
• To characterize the resulting products using spectroscopic methods and X-ray diffraction.

Main Methods:

• Synthesis of cerium and lanthanum dialkyl complexes.
• Reactions with diphenyl dichalcogenides (E=S, Se), dibenzyl disulfide, dibenzyl diselenide, elemental selenium, and benzoxazole.
• Characterization by NMR spectroscopy, mass spectrometry, and single-crystal X-ray diffraction.

Main Results:

• Successful synthesis of cerium and lanthanum dialkyl complexes [η⁵-1,2,4-(Me₃C)₃C₅H₂]Ln(CH₂C₆H₄-o-NMe₂)₂ (Ln = Ce 1 and La 2).
• Formation of lanthanide thiolates and selenolates via reaction with PhEEPh.
• Synthesis of tetranuclear rare-earth metallomacrocyclic compounds and lanthanide-lithium selenido clusters.
• Generation of unique ring-opening/C-C coupling/C-N coupling products upon reaction with benzoxazole.

Conclusions:

• The synthesized cerium and lanthanum complexes display versatile reactivity towards a range of small molecules.
• Novel lanthanide thiolates, selenolates, metallomacrocycles, and selenido clusters have been successfully prepared and characterized.
• The observed reactions highlight potential pathways involving sigma-bond metathesis and C-H activation in lanthanide chemistry.