Thorium oxo and sulfido metallocenes: synthesis, structure, reactivity, and computational studies

Area of Science:

• Organometallic Chemistry
• Actinide Chemistry
• Synthetic Inorganic Chemistry

Background:

• Thorium metallocenes are important in organometallic chemistry.
• Understanding their reactivity is key to developing new synthetic methods.

Purpose of the Study:

• To synthesize and characterize thorium oxo and sulfido metallocenes.
• To investigate the reactivity of these compounds.
• To compare the behavior of thorium with other elements.

Main Methods:

• Synthesis of thorium imido metallocenes via heating dimethyl and bis-amide precursors.
• Preparation of oxo and sulfido thorium metallocenes through cycloaddition-elimination reactions.
• Reactivity studies including reactions with alkylsilyl halides, carbonyls, thiocarbonyls, carbon disulfide, and alkynes.
• Density functional theory (DFT) calculations to understand reaction mechanisms and electronic effects.

Main Results:

• Successfully synthesized base-free imido thorium metallocene precursor.
• Prepared oxo and sulfido thorium metallocenes via cycloaddition-elimination.
• Oxo metallocene 5 is nucleophilic; sulfido metallocene 15 is not.
• Both oxo and sulfido metallocenes undergo [2+2] cycloaddition with specific reagents but not with alkynes.
• DFT studies revealed interplay of steric and electronic effects governing reactivity.
• Thorium(4+) exhibits actinide-like behavior, distinct from group 4 transition metals.

Conclusions:

• Thorium oxo and sulfido metallocenes can be synthesized and display unique reactivity patterns.
• The reactivity is influenced by both steric and electronic factors, as supported by DFT.
• Thorium(4+) in these metallocenes functions more like an actinide than a transition metal, offering insights into f-element chemistry.