Abstract
M.Sc.
2-(Pyrazol-1-ylmethyl)pyridine ligands were synthesised by phase transfer
alkylation of 2-picolyl hydrochloride with the appropriate pyrazole. These
ligands were subsequently reacted with NiCl2, NiBr2, FeCl2 or CoCl2 to form
the respective complexes. The substituents on the pyrazole included phenyl
and tert-butyl groups as well as electron withdrawing CF3 groups. The
substituents played an important role in the steric and electrophilic nature of
the metals.
A second ligand design is 2,6-bis(pyrazol-1-ylmethyl)pyridine and were
prepared by phase transfer alkylation of 2,6-bis(chloromethyl)pyridine with two
mole equivalents of the appropriate pyrazole. These ligands were reacted with
NiCl2, NiBr2, FeCl2 or CoCl2 to form the respective complexes. A third ligand
design is 2-(chloromethyl)- or 2-(bromomethyl)-6-(pyrazol-1-ylmethyl)pyridine
and were prepared by the selective alkylation of 2,6-bis(chloromethyl)pyridine
with one mole equivalent of the appropriate pyrazole. These ligands were also
reacted with NiCl2, NiBr2, FeCl2 or CoCl2 to form the respective complexes.
Characterisation of all compounds was done by a range of spectroscopic
techniques as well as X-ray crystallography and elemental analysis. The data
showed good fit to the proposed structures and in a few cases were confirmed
by X-Ray crystallography.
All complexes were tested as catalysts for ethylene and higher olefin
oligomerisation and showed good activity. The production of alkenes were
confirmed in toluene and hexane, however, due to the use of EtAlCl2 and
toluene the oligomers were alkylated to form the Friedel-Crafts alkylation
products. Similar alkylation was observed for the higher olefin reactions. In
comparison, the same reactions in hexane resulted in only C4, C6 and C8
oligomers. When higher olefin reactions were also conducted in hexane,
polymeric solids were observed.