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Title: Mechanistic and reactivity studies of first-row complexes as catalysts in cross-coupling reactions
Author: Hernandez Fajardo, Oscar
ISNI:       0000 0004 7968 1952
Awarding Body: University of Bristol
Current Institution: University of Bristol
Date of Award: 2019
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Iron(II) complexes show activity in Negishi cross-coupling reactions. A series of mechanistic studies were conducted using spectroscopic techniques in order to improve the understanding of this reaction. It has been observed that Fe(II) is reduced to Fe(I) species when it interacts with the nucleophilic reagent in the reaction mixture. These reduced species show excellent catalytic activity. A kinetic study was conducted using UV-vis spectroscopy which demonstrates that the presence of Lewis acids and Lewis bases influence the speed of reaction. A free-energy relationship using the Hammett equation suggests a free radical mechanism. Activation parameters provided evidence for an associative transition step. The data obtained revealed a complex system of reactions. With the experimental results obtained in these studies, mechanisms for the iron(I) catalysed cross-coupling reaction were proposed. An X-ray absorbance spectroscopy study was conducted in iron complexes in order to illuminate the role of iron of the species. Reaction mixtures of typical cross-coupling reactions were examined at the end of the reaction in order to detect iron complexes and characterise them. A reaction time-dependent study was undertaken to determine the iron complexes in the reaction mixture. A kinetic study on the Negishi cross-coupling using iron(II) was conducted. The experimental results from the kinetic study on iron(I) and the kinetic study on iron(II) were used to propose a mechanism of reaction for the iron catalysed Negishi crosscoupling. The development of a new cross-coupling system using manganese as pre-catalyst was explored. The use of different ligands, additives and conditions of the reaction was tested.
Supervisor: Bedford, Robin Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Catalysis ; Iron ; First-row transition Metals ; Cross-Coupling