| Summary: | Complexes with tetra- and hexadentate polyaminopyridyl ligating moieties were prepared and studied as part of a process to understand the coordination chemistry of oxorhenium and oxotechnetium metal centres as
potential radiopharmaceuticals.
N, N'-bis (2-pyridylmethyl) ethylenediamineoxorhenium(V) perrhenate,
[ReO(pmen)][Re0₄], N,N'-bis(2-pyridylmethyl)ethylenediamine- N,N'- diacetatooxorhenium(V7) bromide, [ReO(bped)]Br, N,N'-bis (2-pyridylmethyl) -
ethylenediamine-N,N'-diacetatooxotechnetium(V) chloride, [TcO(bped)]Cl, were prepared and characterized. In addition, three new potential ligands:
N,N'-bis (methylcarboxymethyl)-N, N'-bis(2-pyridylmethyl) etliylenediamine,
pmen-OMe, N,N'-bis(etiiylcarboxymethyl)-N,N'-bis(2-pyridylmethyl)-
ethylenediamine, pmen-OEt, and N,N'-bis(tert-butylcarboxymethyl)-N,N'-
bis(2-pyridylmethyl)ethylenediamine, pmen-OBut, were prepared for the first
time and characterized.
The oxorhenium and oxotechnetium complexes were characterized by
mass spectrometry, elemental analyses, infrared spectroscopy, and ¹H NMR
spectroscopy. H₂pmen and the pmen-esters are oils and elemental analyses
were not performed. Crystals suitable for X-ray diffraction studies were not
obtained for any of the complexes prepared.
Characterization of the oxorhenium(V) and oxotechnetium(V) complexes
revealed a number of possible geometries. [ReO(pmen][Re0₄] is proposed to be
a 5-coordinate square pyramidal or trigonal bipyramidal complex. The
[ReO(bped)]Br and [TcO(bped)]Cl complexes were thought to be either 5- or
7-coordinate complexes. ¹H NMR of the bped²⁻ complexes showed three AA'BB' patterns in CD₃OD indicative of coordinated acetate groups in a
7-coordlnate monocapped trigonal prism or pentagonal bipyramidal type
configuration. In D₂O, [ReO(bped)]+ showed two AA'BB' patterns and a singlet
in the ¹H NMR characteristic of pendant acetate groups. The similarity
between the bped²⁻ complexes and the pmen²⁻ complex suggests that the
bped²⁻ complexes have the same possible 5-coordinate configurations as
[ReO(pmen)]+. Based on steric interactions and ring strain associated with the
bped complexes, the monocapped trigonal prism or square pyramidal
configurations were believed to be favoured. It was not possible to identify the
true configuration without an X-ray diffraction study. === Science, Faculty of === Chemistry, Department of === Graduate
|
|---|
