Small molecule activation by titanium PCP pincer complexes
File(s)
Author(s)
Belazregue, Sara
Type
Thesis
Abstract
The activation and sustainable transformation of inert small molecules such as N2, CO2, and H2, is a rapidly growing area of research. Metals provide low-barrier reaction pathways for the activation of these small molecules; pincer-supported complexes, particularly those with PCP ligands, offer tuneable frameworks that enable high catalytic performance. However, their application with early transition metals like titanium—an earth-abundant and non-toxic metal—remains underexplored. The indispensable modularity of these pincer ligands presents an opportunity to study how subtle changes, such as varying phosphine substituents, influence small molecule activation.
This thesis presents a library of novel cyclohexyl- and tert-butyl- PCP-supported Ti(III) and Ti(IV) complexes for the activation of small molecules. By employing a range of analytical techniques, this work aims to correlate ligand derivatisation with reactivity, offering insights into the design of more effective small molecule activation catalysts.
Chapter 1 provides a general introduction to small molecule activation and pincer chemistry, with a particular focus on homogeneous titanium systems.
Chapter 2 describes the synthesis and characterisation of cyclohexyl- and tert-butyl- PCP Ti(IV) and Ti(III) halides, alongside their derivatisation to deliver alkyl- and aryl-substituted Ti(III) complexes.
Chapter 3 investigates the behaviour and reactivity of the dineopentyl Ti(III) species and its propensity to activate C-H bonds in arenes and alkanes via a transient highly reactive Ti(III) alkylidene.
Chapter 4 discusses the observed activation of CO, CO2, and H2 by bisalkyl Ti(III) complexes.
Chapter 5 presents the first PCP-supported Ti dinitrogen complexes from the reduction of the Ti(III) halide precursors and scopes the effect the Ti coordination sphere has on the extent of N2 activation.
This thesis presents a library of novel cyclohexyl- and tert-butyl- PCP-supported Ti(III) and Ti(IV) complexes for the activation of small molecules. By employing a range of analytical techniques, this work aims to correlate ligand derivatisation with reactivity, offering insights into the design of more effective small molecule activation catalysts.
Chapter 1 provides a general introduction to small molecule activation and pincer chemistry, with a particular focus on homogeneous titanium systems.
Chapter 2 describes the synthesis and characterisation of cyclohexyl- and tert-butyl- PCP Ti(IV) and Ti(III) halides, alongside their derivatisation to deliver alkyl- and aryl-substituted Ti(III) complexes.
Chapter 3 investigates the behaviour and reactivity of the dineopentyl Ti(III) species and its propensity to activate C-H bonds in arenes and alkanes via a transient highly reactive Ti(III) alkylidene.
Chapter 4 discusses the observed activation of CO, CO2, and H2 by bisalkyl Ti(III) complexes.
Chapter 5 presents the first PCP-supported Ti dinitrogen complexes from the reduction of the Ti(III) halide precursors and scopes the effect the Ti coordination sphere has on the extent of N2 activation.
Version
Open Access
Date Issued
2025-10-23
Date Awarded
2026-04-01
Copyright Statement
Attribution-NonCommercial 4.0 International Licence (CC BY-NC)
License URL
Advisor
Chadwick, Mark
Britovsek, George
Publisher Department
Department of Chemistry
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)