Rare-earth-metallocene alkylaluminates trigger distinct tetrahydrofuran activation

Area of Science:

• Organometallic Chemistry
• Lanthanide Chemistry
• Main Group Chemistry

Background:

• Organometallic compounds of early transition metals and lanthanides are crucial in catalysis and materials science.
• The reactivity of metal-alkyl and metal-amide complexes with Lewis bases like tetrahydrofuran (THF) is not fully understood.
• Understanding the thermal decomposition pathways of these complexes is key to controlling product formation.

Purpose of the Study:

• To investigate the thermal reactivity of pentamethylcyclopentadienyl yttrium and lanthanum complexes with methylaluminum moieties.
• To elucidate the reaction mechanisms and identify the products formed upon thermal treatment in THF.
• To compare the reactivity trends between yttrium and lanthanum in these organometallic systems.

Main Methods:

• Synthesis of Cp*2YMe(thf) from Cp*2Y(AlMe4) via donor-induced AlMe3 cleavage.
• Thermal treatment of Cp*2YMe(thf) in THF and Cp*2La(AlMe4) in THF/n-hexane.
• Characterization of reaction products using spectroscopic techniques (implied).

Main Results:

• Thermal treatment of Cp*2YMe(thf) in THF led to the formation of vinyl oxide Cp*2Y(OC2H3)(thf) and 2-ethylene-tetrahydrofuranyl complex Cp*2Y(2-C2H4-OC4H7) with methane release.
• In contrast, Cp*2La(AlMe4) in THF/n-hexane quantitatively formed the AlMe3-stabilized 2-tetrahydrofuranyl complex Cp*2La(2-AlMe3-OC4H7) with methane elimination.
• The observed products indicate different decomposition pathways for yttrium and lanthanum complexes under similar conditions.

Conclusions:

• The thermal decomposition of organoyttrium complexes in THF proceeds via pathways involving C-H activation and ring-opening of THF.
• Organolanthanum complexes exhibit a different reactivity, favoring the formation of a Lewis acid-stabilized alkyl complex.
• These findings highlight the distinct chemical behavior of yttrium and lanthanum in organometallic transformations.