Bibliography: pages 117-120. / A series of para-phenyl substituted N,N-dialkyl-N'-benzoylthioureas where para-phenyl substituents are H, Cl, Br, I, NO₂ and OCH₃ and alkyl chains are -CH₂CH₃, -(CH₂)₃CH₃ and and -CH₂C₆H₅ as well as their corresponding neutral bis complexes of type cis [ML₂] where M = Pd(II) and Pt(II) have been prepared and characterized. The structures of these compounds has been studied using high resolution nuclear magnetic resonance technique. Studies were also carried out to investigate possible use of these N,N-dialkyl-N-benzoylthioureas as ligands suitable for the chromatographic separation of Pt(II), Pd(II), Ni(II) and Cu(II). To this end the possible selective extraction of these complexes from acidic aqueous phases was examined. This layer normal phase chromatography has been mainly used, using a variety of organic phases as eluent. A preliminary investigation of the suitability of using normal phase HPLC for the separation of the platinum and palladium complexes was undertaken.

The thesis is divided into three parts. The first part looks at the reactivity difference between [Pt(terpy)(OH2)f+ and [Pt(bpma)(OH2)]2+ where terpy is 2,2' :6',2"-terpyridine and bpma is bis(2-pyridylmethyl)amine, towards thiols namely, L-cysteine, DLpenicillamine and glutathione. This is followed by a comparative study of [Pt(bpma)(OH2)]2+ and [pd(bpma)(OH2)f+. Finally the reactivity differences between [Ru(terpy)(bipy)(OH2)f+ and [Ru(terpy)(tmenXOH2)]2+ are reported. Included are the synthesis and characterization ofthe complexes. The substitution behaviour of [pt(terpy)(OH2)]2+and [Pt(bpma)(OH2)f+ was studied as a function of entering thiol concentration and temperature. The reactions between the Ptcomplexes and DL-penicillamine, L-cysteine and glutathione were carried out in a 0.10 mol dm03 aqueous perchloric acid medium using stopped-flow or conventional UV-Vis spectrophotometry as required. The observed pseudo-first-order rate constants for the substitution reactions are given by kobs = k2[thiol] + k 2. The k 2 term represents the reverse solvolysis reaction. This term was found to be zero for Ptn(terpy) which was the most reactive complex. The second-order rate constants, ka; for the three thiols varied between 0.107±0.001 M·l S·l and 0.517±0.025 M"l sol for PtlI(bpma) and 10.7±0.7 M"l S·l to 711.9±18.3 M"l S·l for PtlI(terpy), with glutathione being the strongest nucleophile. Analysis of the activation parameters, Mf' and .1.S", clearly shows that the substitution process is associative in nature. The second study has looked at the substitution of the coordinated water molecule from [Pt(bpma)(OH2)f+ and [pd(bpma)(OH2)f+ by a series of nucleophiles [Nu] viz. TU, DMTU, TMTU and as well as Be", Cl', SCN", and r for the Ptn(bpma) complex. The investigation was conducted under pseudo-first-order conditions as a function of concentration of [Nu] as well as temperature for PtlI(bpma) complex using stopped flow spectrophotometry. Reactions involving PdII(bpma) were done at 10°C. The observed pseudo-first-order rate constants obeyed the equation kobs= k2[Nu]. The second-order rate constants, kz, at 10 "C for the sulfur donor nucleophiles have been found to vary between 70.35 M I sol and 223.06 M I sol for PtII(bpma) and (1.24 ± 0.01) x 105 M I sol to (2.17 ± 0.02) x 105 M-Is-l for PdII(terpy), with DMTV being the strongest nucleophile. The second-order rate constant, ka; at 25 "C fur PtII(terpy) was found to increase in the following order cr < Be" < TMfU < SCN < TV < DMTV < f. This order is in agreement with the polarizability of the nucleophiles, the nucleophilic discrimination factor being 0.38. The temperature studies for PtII(bpma) suggest that the substitution process is associative in nature.n The third part looked at the reactivities of [Ru(terpy)(bipy)(OHz)]z+ and [Ru(terpy)(tmen)(OHz)]z+ where bipy is 2,2'-bipyridine and tmen is N,N,N ',N 'tetramethylethylenediamine with three nucleophiles TV, DMTV and CH3CN. The pKa values for the complexes were found to be 9.99 and 10.27 for [Ru(terpy)(bipy)(OHz)]z+ and [Ru(terpy)(tmen)(OHz)f+, respectively. The substitution of water involving the two complexes was studied under pseudo-first order conditions using UV-Visible Spectrophotometry. The pseudo-first-order rate constant fitted the simple rate law kobs = kz [Nu] + k-z. The k.z term was found to be zero for [Ru(terpy)(bipy)(OHz)f+ but nonzero for [Ru(terpy)(tmen)(OHz)]z+. The values of the second order rate constants (kz) for the three nucleophiles were found to be between (1.08 ± 0.02) x 10-4 M l sol and (15.0 ± 0.27) x 10-4 M-l sol for [Ru(terpy)(bipy)(OHz)]z+ and (0.82 ± 0.04) x 10-4 M-l sol and (21.90 ± 0.69) x 10-4 M-I sol for [Ru(terpy)(tmen)(OHz)]z+. The results suggests that nback donation accounts for the difference in reactivity. / Thesis (M.Sc.)-University of Natal, Pietermaritzburg, 2003.