New macrocycles for polymerisation catalysis

Abstract

This thesis concerns the synthesis of diphenylamine-based macrocycles for generating new dimetallic polymerisation catalysts. Chapter 1 introduces the target polymerisations we aim to catalyse, and reviews the current literature on existing catalysts. Macrocyclic compounds are introduced and discussed, along with the relevant previous work carried out within this research group. Chapter 2 details the synthesis, according to the literature, of the key diphenylamine head unit, 2,2’-diformyldiphenylamine (HU1), used throughout this project, and of the two [2+2] Schiff base macrocycles H2LEtand H2LPr (from condensation with 1,2-diaminoethane and 1,3-diaminopropane respectively). A sub-sectionconcerning the metalation and testing of the dizinc complexes of H2LEt and H2LPr is also included, along with abrief discussion of the characterisation techniques used to analyse the resulting polymers. Chapter 3 contains the paper on which I am a co-author, “Di-zinc Lactide Polymerisation Catalysts: Hyper-Activity by Control of Ligand Conformation and Metallic Cooperativity”, as published in Angewandte Chemie International Edition volume 55, pages 8680–8685. The manuscript was originally drafted by collaborators at Imperial College London (now at the University of Oxford), and has been reformatted for inclusion in this thesis. My contributions to this study are detailed on the first page of this chapter. Chapter 4 details the synthesis of three new homoditopic macrocycles. Two were prepared by variation of the commercially available diamine lateral unit employed, 2,2-dimethyl-1,3-propanediamine or 4,4’-methylenedianiline, in the [2+2] condensation with HU1, giving H2LDMP and H2LMDA. The other was prepared bymodification of HU1, forming bisphenylacetylene-substituted HU3 which, on [2+2] condensation with 1,3-diaminopropane, gave H2LPh-Et. Chapter 5 starts with a description of the advantages of heterodimetallic complexes in catalysis, and examples of routes to access heteroditopic macrocycles. It then describes the design of a new pair of heteroditopic macrocycles, HLSEt and HLSPr, which offer two distinctly different binding pockets. Like all of the above macrocycles, they feature one diphenylamine diimine end, but unlike those macrocycles, the other end is based on a pyridine dithioether moiety. Four different synthetic routes to these macrocycles are described, and the challenges encountered for the two attempted routes are discussed. Additionally, the design of a heteroditopic mixed imine-amine diphenylamine-based macrocycle, H2Laim, is discussed. The thesis concludes with project summary in Chapter 6.