Heterobimetallic dinuclear lanthanide alkoxide complexes as acid-base difunctional catalysts for transesterification

Area of Science:

• Organic Chemistry
• Catalysis
• Organometallic Chemistry

Background:

• Transesterification is a key organic reaction for synthesizing esters.
• Developing efficient catalysts for transesterification of less reactive substrates like carbonates and silicates remains a challenge.
• Lanthanide complexes are known for their catalytic activity in various organic transformations.

Purpose of the Study:

• To develop a practical lanthanide(III)-catalyzed transesterification method.
• To investigate the efficacy of heterobimetallic dinuclear lanthanide alkoxide complexes as catalysts.
• To explore the transesterification of challenging substrates including carboxylic esters, carbonates, and ethyl silicate.

Main Methods:

• Synthesis and characterization of heterobimetallic dinuclear lanthanide alkoxide complexes: [Ln2Na8{(OCH2CH2NMe2)}12(OH)2] (Ln = Nd, Sm, Yb).
• Application of these complexes as catalysts in transesterification reactions with primary and secondary alcohols.
• Optimization of reaction conditions to achieve good to high yields.

Main Results:

• Successful transesterification of carboxylic esters, carbonates, and ethyl silicate with various alcohols was achieved.
• The dinuclear lanthanide alkoxide complexes demonstrated high catalytic activity.
• Mild reaction conditions were sufficient to drive the transformations, yielding products in good to high yields.
• The catalytic system exhibited higher reactivity compared to simple acid/base catalysts.

Conclusions:

• A practical and efficient lanthanide(III)-catalyzed transesterification protocol was established.
• Heterobimetallic dinuclear lanthanide alkoxide complexes serve as highly active and versatile catalysts.
• The cooperative acid-base difunctional catalytic nature of the complexes is proposed as the reason for their enhanced reactivity.