Investigation of PEPPSI precatalysts for controlled polymerization of π-conjugated polymers from cheap starting materials Thesis submitted in partial fulfilment of the requirement for a degree of Doctor of Philosophy at the University of London Benjamin John Groombridge Page | 1 Acknowledgements I would firstly like to thank my supervisors, Dr. Igor Larrosa and Dr. Stephen M. Goldup, for giving me the opportunity to carry out the research described in this thesis. Special gratitude to both of you, for the invaluable expert guidance and support during my PhD. I would like to thank the following people for the words of wisdom and practical input during the course of my PhD: Prof. Mike Watkinson, Dr. Chris Bray, Dr. Joby Winn, Dr. Jamie Lewis, Dr. Catherine Fletcher, Dr. Saidul Islam, Dr. Xacobe Couso Cambeiro, Dr. Nanna Ahlsten, Dr. Paolo Ricci, Dr. Carlos Arróniz, Dr. Sara Preciado, Dr. Francisco Juliá-Hernández, Dr. Josep Cornella, Dr. Tanya Boorman, Dr. Saidul Islam, Robert Bordoli, Ed Neal, Jessica Pancholi, Katrina Krämer, Rachel Grainger, Marco Simonetti, Junfei Luo, Adam Johnston, Gregory Perry and Nicky Willis. The research described would not have been possible without the fantastic support from both NMR and analytic services in particular Dr. Harold Toms and Dr. Ian Sanders. Finally, I would like to thank my friends and family for their support and advice throughout my PhD and during the writing up period. Page | 2 Declaration I declare that the scientific work presented in this thesis is my own and was carried out in the School of Biological and Chemical Science at Queen Mary, University of London between September 2010 and September 2014. No part of this work has been submitted in support of an application for another degree or qualification at this University or any other institution of learning. Signature: _____________________ Date: _____________________ Page | 3 Abstract Since the discovery of catalyst-transfer polymerization in 2004 there has been significant research into expanding the scope from Kumada couplings of poly-thiophenes mediated by nickel initiators. This thesis presents an investigation toward the synthesis of π-conjugated polymers by the elusive pseudo-living polymerization of chloroarene monomers. Chapter 1 sets the scene with an in-depth review of chain-growth polymerizations mediated by palladium catalysts. In chapter 2, we report the first examples of exhaustive substitution of poly-chloroarenes in the presence of a deficit of nucleophile in the sp 3-sp 2 Negishi coupling mediated by PEPPSI-IPr. These experiments demonstrated intramolecular transfer of the active catalyst which is essential for catalyst-transfer polymerization. Chapter 3 describes the synthesis of the highly active PEPPSI-IPent precatalyst from cheap commercially available starting materials with minimal purification. Subsequently in chapter 4, it was demonstrated that PEPPSI-IPent undergoes exhaustive substitution of poly-chloroarenes in the presence of a deficit of nucleophile in sp 2-sp 2 Kumada, Negishi and Suzuki cross-couplings. In chapter 5, optimization of current Kumada polymerization of bromo phenylene-based monomer mediated by PEPPSI-IPr is described. Direct comparison of model reactions and Kumada polycondensation confirmed high selectivity for exhaustive substitution is required to achieve polycondensation in a chain-growth manner. Initial research into catalyst-transfer polycondensation of chloroarene monomers did not achieve polymerization in a chain-growth manner using modified conditions from bromoarene monomers. Page | 4 Table of Contents Acknowledgements .............................................................................................................. 2 Declaration ........................................................................................................................... 3 Abstract ................................................................................................................................ 4 List of abbreviations .......................................................................................................... 11 1.0 Chapter 1 - Introduction 1.1 Polymers ...................................................................................................................... 13 1.2 Statistical terms ............................................................................................................ 13 1.3 Synthetic methods ........................................................................................................ 15 1.3.1 Step growth polymerizations ................................................................................. 15 1.3.2 Chain growth polymerizations .............................................................................. 17 1.3.2.1 Radical chain growth polymerizations ........................................................... 18 1.3.3 Living polymerization ........................................................................................... 20 1.3.3.1 Ionic polymerizations..................................................................................... 21 1.3.3.2 Chain growth polycondensation .................................................................... 22 1.3.3.3 Coordination polymerization ......................................................................... 23 1.4 π-Conjugated polymers ................................................................................................ 24 1.4.1 Selected applications of conjugated polymers ...................................................... 26 1.4.2 Synthesis of conjugated polymers ......................................................................... 27 1.4.3.1 Discovery of catalyst transfer polycondensation ........................................... 28 1.4.3.2 Model reactions to identify intramolecular oxidative addition ...................... 29 1.4.3.3 Mechanism of catalyst transfer polymerization ............................................. 30 1.4.3.4 Examples of Nickel Mediated Catalyst Transfer Polymerization .................. 31 1.4.3.3 Scope and limitations of Nickel mediated chain transfer polymerization ..... 33 Page | 5 1.4.4 Palladium and chain growth polymerization .................................................... 34 1.4.4.1 Model reactions to identify intramolecular oxidative addition with palladium catalysts ...................................................................................................................... 34 1.4.4.2 Catalyst-transfer polymerizations mediated by palladium catalysts .............. 37 1.4.4.3 Overview and outlook .................................................................................... 42 1.5. Model reactions mediated by PEPPSI-IPr .................................................................. 43 1.6 Chain growth polymerization mediated by PEPPSI-IPr .............................................. 47 1.7 Aims and Goals ............................................................................................................ 48 1.8 References .................................................................................................................... 49 2.0 Chapter 2 - Model reactions mediated by PEPPSI-IPr 2.1 Introduction .................................................................................................................. 55 2.2 Addition of functional groups to aryl dibromides........................................................ 55 2.3 Addition of functional groups to aryl dichlorides ........................................................ 56 2.4 Competition between aryl chlorides ............................................................................ 57 2.5 Poly-halogenated benzenes .......................................................................................... 59 2.6 Variation in reaction conditions ................................................................................... 61 2.6.1 Solvent ratio .......................................................................................................... 61 2.6.2 Temperature scan .................................................................................................. 62 2.6.3 Equivalents of 1,3-dichlorobenzene ...................................................................... 63 2.6.4 Catalyst loading ..................................................................................................... 64 2.6.5 Time Scan .............................................................................................................. 64 2.7 Conclusions .................................................................................................................. 65 2.8 References .................................................................................................................... 66 3.0 Chapter 3 - PEPPSI-IPent synthesis 3.1 Introduction .................................................................................................................. 68 Page | 6 3.2 Negishi coupling of 3-pentylzinc bromide .................................................................. 70 3.3 Route 1: Synthesis of aniline 33d ................................................................................ 72 3.4 Route 2: Synthesis of aniline 33d ................................................................................ 74 3.5 PEPPSI-IPent synthesis ..............................................................................................