AbstractUsing iron complexes as homogeneous catalysts for bond forming and functionalisation reactions is both highly desirable and a research field of growing interest. In this thesis, iron complexes are used as catalysts for a range of transformations, and the transformations themselves are investigated for reactivity, scope, and mechanistic insight. A range of approaches to understanding catalysis are used in order to gain a more complete picture of chemical behaviour.
Following a general introduction, literature review and discussion in Chapter 1, Chapter 2 builds on previously reported alkene functionalisation reports to study the isomerisation of alkenes catalysed by iron complexes. Following examination of conditions and substrate scope, mechanistic studies attempt to prove, and subsequently disprove, an initially proposed catalytic cycle. Using a multifaceted approach including density functional theory, electron paramagnetic resonance spectroscopy, cyclic voltammetry and deuteration studies a second catalytic cycle can be proposed which can more fully account for all observations.
Chapter 3 shifts the choice of substrate from alkenes to allenes. Using the same conditions generates divergent reactivity — rather than isomerisation, polymerisation is instead the primary reaction observed. The resulting poly(phenylallene) is relatively unusual, and the structural properties of the polymers are investigated. Through mechanistic investigation it is clear that this process has some mechanistic similarities with the findings in Chapter 2, and some attempts to perform and study [2+2] cycloaddition reactions are also reported.
Allenes are then used as substrates in hydrophosphination chemistry in Chapter 4, merging previously reported hydrophosphination studies with some of the findings observed in Chapters 2 and 3. This generates novel phosphorus compounds and interesting regioselectivity findings, and the tolerance of the reaction to various allenes and phosphines is studied. Again the mechanism is studied, and a catalytic cycle proposed, although this has some significant differences to the previous studies.
In Chapter 5 the focus shifts away from using organic substrates to coupling phosphorus compounds, and investigating a route to phosphorus–phosphorus bonds using phosphines and chlorophosphines as reagents. Dehydrochlorination of a secondary phosphine and chlorophosphine generates a diphosphine, and the effects of substituent and conditions are investigated, as well as the effects when using primary phosphines as substrates. Although this reaction requires a catalytic amount of an iron complex, it has some marked difference in mechanism and reactivity compared to the previous chapters which are examined.
|Date of Award||11 Oct 2021|
|Supervisor||Ruth Webster (Supervisor) & David Carbery (Supervisor)|