Mono- and Multimetallic Catalysts: Applications in Small Molecule and Macromolecule Synthesis
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Replacing petroleum-derived feedstocks with renewable sources is an attractive method to improve the sustainability of chemical production, with desired targets ranging from small to macro-molecules. These processes usually require the presence of a catalyst; some of the most efficient are homogeneous metal complexes. This presentation will discuss the development of homo- and hetero-metallic catalysts for upcycling CO2 into polycarbonates or cyclic carbonates, and lactide into poly(lactic acid).
In the reaction between CO2 and epoxides, catalyst design can direct product formation towards polycarbonates or cyclic carbonates. A series of heterobimetallic Mg/Zn complexes based on a macrocyclic ligand have been developed which give >99% selectivity for polycarbonates. These synergic heterobimetallic complexes display catalytic activities up to 40 times higher than the homobimetallic analogues, either alone or in combination (TOF <8800 h-1). We have also developed a series of monometallic phenoxyimine Fe(III)-chloride complexes which exploit enhanced ligand flexibility to promote cyclic carbonate formation (>99% selectivity). Notably, these robust and selective Fe(III) catalysts are tolerant to air and water, and successfully convert the internal epoxide, cyclohexene oxide, to cyclohexene carbonate.
The ring-opening polymerisation of lactide is a useful means to prepare biodegradable materials with well controlled polymer architectures and bespoke material properties. This presentation will describe a series of highly active Al-chloride catalysts based on a functionalisable salen ligand. Incorporating Lewis basic NEt2 groups into the ligand scaffold not only improves the initiation efficiency but also avoids the need for a Lewis basic co-catalyst and excess epoxide. Studies of our amino-substituted catalysts reveal that the formation of a hexacoordinate aluminate species may hinder rather than enhance the catalyst activity.
Theatre C, Purdie
May 22, 2019
From: 14h00 To: 15h00
University of St Andrews
The oldest university in Scotland, with international renown for both research and education of undergraduates and postgraduates.