The synthesis and characterisation of macrocrylic ligands with N, O and S donor atoms and related transmission metal complexes of these ligands
Date
2018-07-17
Authors
Ingham, Alison Mary
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Abstract
The ligand 1-oxa-4,8-diazacyclodecane ([10]aneN2O) was synthesised, along with the [special characters omitted] complexes. Bis-ligand complexes are formed with facial coordination of
the ligand to the transition metals, with two nitrogen donors from each ligand forming an
equatorial plane around the metal ion. The crystal structure of
[special characters omitted] was determined, as is described. The copper(II), nickel(II)
and palladium(II) complexes have been characterised by FAB MS, electronic spectroscopy,
elemental analysis and where possible by NMR and EPR spectroscopy. The nickel(II) and
copper(II) complexes have distorted octahedral geometries, while the palladium(II) complex
has square planar geometry with no observable axial interaction from the ether donors. The
redox characteristics of the complexes formed have been determined, and are described
within.
The synthesis of the novel tricyclic ligand, 7,16-dioxa-1,4,10,13-
tetraazatricyclo[11.5.3.3]octadecane [special characters omitted] is described. The [special characters omitted]
conplex has been synthesised and characterised. The complex gives an unusually stable [special characters omitted]
complex compared to complexes where a similar donor set is present
A novel template synthesis was utilised to synthesise the bicyclic ligand 1,2-bis(1-oxa-5,8-diazacyclodecanyl)ethane ([special characters omitted] earmuff). This synthesis involved reaction of
secondary amines which are coordinated to a copper(II) ion, a method which to our
knowledge has not been used before in the synthesis of macrocyclic ligands. The copper(II)
complex synthesised during this reaction has been characterised, and the redox reactions have
been examined.
The synthesis of 17-oxa-1,4,8,11-tetraazabicyclo[6.6.5]tetradecane (bicyclo[12-12] [special characters omitted]) is
reported. Copper(II) and nickeI(II) complexes of this ligand have been synthesised and
characterised. The chloride ion substitution reaction of [Ni(bicyclo[12-12] [special characters omitted] has
been examined. The reaction was found to have an inverse dependence on the acid
concentration. A tentative mechanism has been proposed to explain the origin of the acid
dependence. The equilibrium constant for this reaction, determined by visible
spectrophotometry, was found to be [special characters omitted].
The cobalt(III) bis-ligand complex of the previously synthesised ligand, 8-aza-1,5-
dithiacyclodecane ([special characters omitted]) was synthesised. Under the conditions used, two isomers
were formed - a facially coordinate bis-ligand complex where the equatorial plane is defined
by two sulfur and two nitrogen donors, and a more symmetrical isomer where all four sulfur
donors are coordinated equatorially. Isomerisation of the unsymmetrical isomer to the
symmetrical isomer occurs in solution.
The [special characters omitted] complexes of the ligand 1,2-bis(8-aza-1,5-dithiacycIodecanyI)ethane
([special characters omitted] earmuff) were synthesised and characterised. The ligand coordinates to [special characters omitted] in
a pseudo five coordinate manner as determined by NMR spectroscopy. A solvent molecule
or anion is likely to be coordinated to the [special characters omitted] centre in order to achieve distorted octahedral
coordination. The complexes were characterised by FAB MS, electronic spectroscopy,
elemental analysis and ESR spectroscopy. Although the [special characters omitted] centre was found to be in the
low spin state, the electron transfer self exchange rate constant could not be determined by
NMR spectroscopy. The [special characters omitted] complex of this ligand was also synthesised and found to
coordinate in a five coordinate manner. Evidence of axial coordination of nitrogen in the
palladium complex was observed in the electronic spectrum, therefore a distorted square
pyramidal geometry has been proposed for the [[special characters omitted] earmuff)] complex.
The potentially binuclear ligand, 1,9-bis(4-aza-1,8-dithiacyclononane)-4,7-diaza-2,8-dionenonane, was synthesised and characterised. Preliminary results indicate that reaction with two
equivalents of nickel(II) produced a binuclear complex.
Description
Keywords
Ligands, Macrocrylic compounds