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Oxorhenium(v) and osotechnetium(v) complexes with tetra- and hexadentate polyaminopyridyl molecules

University of British Columbia

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.

Thesis/Dissertation

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2009-05-05

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http://hdl.handle.net/2429/7877

Chemistry

University of British Columbia

UBCV

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