The activation of small molecules using frustrated Lewis pairs

Thesis

This thesis describes the activation of small molecules using frustrated Lewis pairs, in particular investigating their use to reduce CO₂ to methanol, thus producing a new route towards a renewable fuel.

Chapter One summarises the requirement for a renewable fuel source, the alternative methods currently available and previous research conducted into converting CO₂ to methanol using FLPs and other reducing agents.

Chapter Two describes the synthesis of a new family of electron-deficient tris(aryl)boranes, B(C₆F₅)_3-x(C₆Cl₅)_x (x = 1-3), allowing the electronic effects, resulting from the gradual replacement of C₆F₅ with C₆Cl₅ ligands, to be studied. The novel Lewis acids have been fully characterised and their Lewis acidities have been determined using NMR spectroscopy, electrochemistry and DFT studies.

Chapter Three discusses the synthesis of nine novel FLPs and their use to successfully split H2. Each borohydride salt has been spectroscopically fully characterised and five of the salts have been characterised using single crystal X-ray diffraction. To determine the exact positions of the H atoms, single crystal neutron diffraction and DFT experiments were carried out on [1-H][H-TMP].

Chapter Four details attempts to use the borohydride salts, synthesised in Chapter Three, to reduce CO₂ to methanol. Each experiment was been fully investigated and their catalytic viability was determined. The X-ray crystal structure of [1-OCHO][H-TMP] is described and each formatoborate and methoxyborate salt were fully characterised.

Chapter Five describes experimental procedures and characterisation data.

Authors: Zaher, H

• Publication date: 2012
• Type of award: DPhil
• Level of award: Doctoral
• Awarding institution: University of Oxford
• Language: English
• Keywords: frustrated Lewis pairs; methanol economy; hydrogen activation
• Subjects: Chemistry & allied sciences; Hydrogen Storage; Catalysis