Description
Flyer: Prof. Robert Comito Flyer
Title: Bimetallic Main-Group Catalysts for the Synthesis of Advanced Biodegradable Polymers
Abstract: Aliphatic polyesters are biodegradable and biocompatible materials that could replace polyolefins in many applications. However, their synthesis with fine structural control remains challenging, limiting the ability to tailor these materials for specialty and advanced applications. Our laboratory has developed a class of bimetallic main group catalysts for lactone and lactide polymerization distinguished by their electronic and steric tunability. The catalysts are constructed from binucleating bis(pyrazolyl)alkane ligands, which we have prepared by a novel method. Targeting monomer selectivity, stereocontrol, and sequence control we have developed homobimetallic, heterobimetallic, and chiral analogues of these complexes. We show promising evidence for metal-metal cooperativity from significant enhancements in rate compared to monometallic analogues. Through systematic comparison of metal composition and ligand sterics, we have identified a highly selective catalyst for lactone incorporation into polylactide, providing copolymers with a highly alternating structure. We describe an unusual dilithium complex that polymerizes aldehydes with exceptional activity and selectivity, raising opportunities for more sophisticated and adaptable oxygenated polymers.