Three different types of mixed-valence complexes are studied in this thesis, namely, homonuclear d<sup>4</sup>/d<sup>5</sup>, heteronuclear d<sup>5</sup>/d<sup>6</sup> and homonuclear d<sup>5</sup>/d<sup>6</sup> binuclear metallic species. The electrochemical syntheses of the mononuclear complexes [OsC1<sub>5</sub>(N-cypy)]<sup>-/2-</sup> (N = 2,3, 4; cypy = cyanopyridine), and the asymmetrical homonuclear complexes, [C1<sub>5</sub>Os(N-cypy)OsC1<sub>5</sub>]<sup>n-</sup> (N = 3, 4; n = 4, 5, 6) are reported. The mononuclear cyanopyridine complexes produce two isomeric forms, the cyanopyridine can be bound through either the pyridine nitrogen or the cyano nitrogen. Electrochemical investigations confirm that the isomer bound through the pyridine nitrogen is most stable. The X-ray crystal structure of this isomer for 3- and 4-copy is reported. The complexes have also been investigated using UV/Vis spectroelectrochemistry. The mononuclear complexes have been found to be very similar electronically. That is, the exact position of the cyano moiety has little effect on the overall electronic nature of the complex. This is in accordance with these ligands been principally s-donating ligands. The binuclear complexes of 3- and 4-cypy have also been synthesised and investigated electrochemically. The redox chemistry of the binuclear complex differs from the monoclear compounds. This is indicative of some communication between the two metal centres, K<sub>c</sub> for the 4-cypy complex was found to be 17000 and for 3-cypy to be 1100. Thus the degree of communication is larger for 4-cypy compared to 3-cypy, in agreement with results published previously using these ligands, with different metal fragments. These complexes are described as class II mixed-valence complexes.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:649985 |
| Date | January 2001 |
| Creators | Elliot, Marie |
| Publisher | University of Edinburgh |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://hdl.handle.net/1842/13786 |
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