An investigation into the complex formation and potential solvent extraction of Os(IV/III) with N, N - dialkyl - N′- acyl(aroyl)thioureas

Klopper, Reynhardt (2006-03)

Thesis (MSc (Chemistry and Polymer Science))--University of Stellenbosch, 2006.


This study involved the preliminary investigation into the potential liquid-liquid extraction of Os(IV/III) from hydrochloric acid solutions with ligands of type N,N-dialkyl-N′-acyl(aroyl)thioureas (HL), and ultimate selective pre-concentration and separation of Os(IV/III) from the other platinum group metals. Investigations have also been focused towards understanding the speciation of Os(IV) in hydrochloric acid medium. A series of osmium complexes with ligands of type HL have been synthesised and characterised. This has been done with a view towards understanding the interaction of Os(IV/III) with the HL ligands, and what the resultant stereochemical influences would be on the solvent extraction capabilities of the ligands. The structures of two novel osmium-containing compounds have been verified by means of X-ray crytallography. Firstly, the ion pair OsCl6[(C4H9)4N]2 was obtained as a result of liquid-liquid extraction experiments. Secondly, the only known example (in our knowledge) of an Os(III) - N,N-dialkyl-N′- aroylthiourea complex, in this case tris(N,N-diethyl-N’-benzoylthioureato)osmium(III), was successfully synthesised and characterised. Lastly, preliminary studies into the substitution reactions of ruthenium-polypyridine complexes with N,N-dialkyl-N′-acyl(aroyl)thioureas were conducted. A series of cis-bis(2,2′-bipyridine)(N,N-dialkyl-N′-acyl(aroyl)thioureato)ruthenium(II) complexes have been successfully synthesised and characterised. The electronic absorption behaviour of the formed complexes have been investigated in detail via UV-Vis spectrophotometry.

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