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Title: Anion and neutral molecule recognition by electron deficient boranes
Author: Tirfoin, Remi A.
ISNI:       0000 0004 5346 4079
Awarding Body: University of Oxford
Current Institution: University of Oxford
Date of Award: 2015
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This thesis reports on the synthesis of a series of Lewis acidic boranes used as detectors for the cyanide or fluoride ion, and for the activation of molecular oxygen. Chapter III focuses on the formation of monodentate boranes featuring a pendant ferrocenyl moiety. A systematic study of the fluoride and cyanide binding capabilities of isomeric ferrocenyl-functionalized phenyl boranes was conducted via spectroscopic, crystallographic and voltammetric techniques. The synthesis of receptors supported by an indenyl scaffold was also investigated and the binding properties of such systems studied in details. All receptors proved to be competent at binding both cyanide and fluoride in dry solvents; moreover one such indenyl receptor can selectively bind cyanide in aqueous media and signal the binding event by a green-to-red colour change. Chapter IV constitutes an extension of the previous chapter targeting bidentate receptors with an (indenyl)(cyclopentadienyl)iron(II) back bone. A principle objective was the development of systems offering the chelation of fluoride, and hence a measure of selectivity over the more strongly basic cyanide ion. While bis(dimesitylborane) receptors proved to be synthetically inaccessible, a series of phosphine- and phosphonium-borane species was prepared and their comparative F-/CN- binding abilities determined. Thus, while cationic phosphonium boranes favour fluoride binding by employing a bifunctional binding motif, the neutral phosphine boranes exclusively bind cyanide. Chapter V details the activation of molecular oxygen by pentafluorophenyl-boranes in presence of weak reductants featuring a ferrocene unit. The highly Lewis acidic ferrocenyl bis(pentafluorophenyl)borane was initially studied, and its reaction with dry dioxygen shown to generate a (fully characterized) ferrocenium peroxoborate. Similar reactivity was observed for simple metallocenes such as cobaltocene and ferrocene (or even organic reductants) in presence of a strong Lewis acid, with the trapping of the O22- ion by the borane thought to be a key thermodynamic driving force for the O2 reduction.
Supervisor: Aldridge, Simon Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Chemistry & allied sciences ; boranes ; molecular chemistry ; inorganic chemistry