Abstract
M.Sc.
The main objective of the research described in this dissertation was to prepare several logical series of
ligands, being variously substituted at different positions of the aryl ring attached to the P atom. These
ligands were evaluated by several techniques including 31P NMR shift measurements, 31P-77Se NMR
coupling constant measurements, CO stretching frequency measurements in rhodium(I) Vaska-type
complexes of the ligands, application of the ligands in the Rh-catalysed hydroformylation reaction, X-ray
studies on single crystals of some of the ligands and computational studies all with the view to establish if
phosphorus atoms in arylphosphines could be used as a handle to probe steric and electronic effects of
aromatic systems.
A series of triarylphosphine ligands containing either ester, fluoro, nitrile, tolyl or a combination of
functional groups was prepared by reacting Grignard- or organolithium reagents with P-Cl reagents. The
results of this aspect of the work showed that, under the right reaction conditions, these organometal
reagents can tolerate certain functional groups.
On evaluation of these ligands with the different techniques described above it was found that: 31P NMR
shift measurements cannot be used in correlations with the data from the other methods of evaluation used
in this study, 31P-77Se coupling constant measurements and CO stretching frequency measurements in
rhodium(I) Vaska-type complexes of the ligands can be correlated to a relatively good extent with Rhcatalysed
hydroformylation reaction results (provided that ortho-substituted phosphine data are
disregarded), 31P-77Se NMR coupling constant measurements and CO stretching frequency measurements
in rhodium(I) Vaska-type complexes of the ligands correlated well with computational studies, and
finally, computational studies at the level of theory used in this dissertation also correlate quite well with
the Rh-catalysed hydroformylation reaction results.
In all it was found from this study that the phosphorus atom in arylphosphines can be used as a handle to
probe the electronic and steric effects of aromatic systems, and that the most versatile method of ligand
evaluation were the 31P-77Se coupling constant measurements and CO stretching frequency measurements
in rhodium(I) Vaska-type complexes.