Structural and Physical Studies of Co(III) Salen Derivatives.
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Date
2007
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Abstract
A number of ligands that belong to the salen-type family were synthesized in this thesis.
These ligands were synthesized from salicylaldehyde and 1,2-phenylenediamine, 1,3-
diamino-2-hydroxypropane, 1,2-diamino-ethane, N-(3-aminopropyl)-1,3-propanediamine,
diethylenetriamine, diaminomaleonitrile, 2,2-dimethyl-1,3-propanediamine and 1,3-
diaminopropane. From this range of ligands, H2salophen was chosen as the ligand for further
studies.
This work is aimed primarily at elucidating the structures and spectroscopic properties of
[Co(salophen)(amine)2](OAc) derivatives, where salophen is N,N’-disalicylidene-1,2-
phenylenediamine and the amines used were butylamine, benzylamine, a-
methylbenzylamine, dibutylamine, N-methylpiperazine and piperidine. Three novel crystal
structures of [CoIII(salophen)L2]Cl derivatives, where L = butylamine, benzylamine, and
piperidine, with Co-N distances that range from 1.901 Å to 2.024 Å, have been reported in
this thesis. The novel crystal structure of [Co(salophen)(N-MePipz)(OAc)] is also reported in
this thesis. These cobalt complexes have been analysed by 1H, 13C and 59Co NMR as well as
electronic and IR spectroscopy. A 59Co NMR spectrum was obtained for the
[Co(salophen)(BuNH2)2]CH2Cl2×Cl complex. The spectrum exhibits a single line at 8504
ppm.
The binding constants of all [Co(salophen)(amine)2](OAc) complexes, where amine =
butylamine, benzylamine, a-methylbenzylamine, dibutylamine, N-methylpiperazine and
piperidine, were determined by spectroscopic titrations. The titrations were carried out at
various concentrations of the amine and at temperatures ranging from 25°C to 45°C. It was
found that the primary amines had much larger values of K1 and K2 compared to the
secondary amines. Typical values of K1 and K2 were 8000 M-1 and 63.6 M-1 respectively at
25°C, for a-methylbenzylamine. Of the primary amines, it was found that a-
methylbenzylamine had the largest value of K1 and K2 compared to the other two amines.
For the secondary amines, it was found that N-methylpiperazine had the bigger value of K1
compared to that of dibutylamine.
Description
Thesis (M.Sc. )-University of KwaZulu-Natal, Pietermaritzburg, 2007.
Keywords
Cobalt compounds--Synthesis., Theses--Chemistry.