Abstract available in pdf file.

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.

The work described in this thesis concerns the synthesis and study of the coordination behaviour of the 6-anilino-2,2'-bipyridyl (Habipy), 6-N-methylanilino-2,2'-bipyridyl (mabipy), 6-piperidyl2,2'.- bipyridyl (pipbipy) and 2,2'-bipyridin-6-one (Hobipy) ligands. Chapter one reviews the coordination chemistry of the 2-aminopyridyl (Rap), 2-hydroxypyridyl (Hhp) and the 2-(2-pyridyl)-I,8-naphthyridine (pynp) ligands. These ligands are closely related to Habipy, mabipy, pipbipy and Hobipy in that they share a common NCN or NCO fragment. Thus the review of their coordination behaviour provides insight into the expected coordination of the Habipy, mabipy, pipbipy and Hobipy ligands. The synthesis and characteristaion of the novel Habipy, mabipy and pipbipy ligands are reported in Chapter two. X-ray crystal structure determinations of mabipy and pipbipy reveal that the geometry about the exocyclic nitrogen atom in both ligands is nearly planer, suggesting substantial overlap of the nitrogen lone pair orbital with the 1t electron system of the bipyridyl rings. In both mabipy and pipbipy the N3-C 10 bond lengths are shorter then normal N-C single bonds. In Chapter three -the synthesis and characterisation of copper(I) complexes containing mabipy, pipbipy and Habipy, and a copper(II) complex containing mabipy are reported. The copper(I) complexes have the general formula [Cu(l12-L)2r, where L= mabipy 1, pipbipy 2 or Habipy 3. The structures of complexes 1 and 2 are determined by X-ray crystallography. In complexes 1- 3 the bipyridyl fragments of mabipy, pipbipy and Habipy chelate while the exocyclic nitrogen atoms remain free. The crystal structures of 1 and 2 reveal that the exocyclic nitrogens have a planar geometry as was the case in the uncoordinated ligand. The crystal structure of [Cu(1l2-mabipY)2f+ (4) is determined by X-ray crystallography and is very similar to that of the copper(I) species. Coordination of the mabipy ligand in 4 is the same as that in 1 and the exocyclic nitrogen in 4 is also planar. The redox couple 4/1 is shown to be electrochemically reversible with EV2= 0.45 V. In Chapter four the synthesis and chararcterisation of dinuclear complexes containing the Ru2 2+, Ru/+, Mo24+and ~4+ cores are reported in which the abipy ligand bridges two metal centres. The complexes [Rulll-L)lCO)4], where L= abipy 5 or obipy 6, were synthesised by the r~action of the free ligands with [{RuiCO)102CCH3)2}n] in toluene. The structures of5 and 6 are determined by X-ray crystallography and show the ligands bridging the Ru(I) atoms in a head to tail fashion and occupy mutually cis positions about the octahedral Ru(I) atoms. The Ru-Ru separations in 5 and 6 are 2.668(1) and 2.671(1) A respectively. The reaction of Habipy with [Rui02CCH3)4CI]n was found to afford the mixed valence species [Ruill-abipy)(02CCH3)3CI] (7), the structure of which is determined by X-ray diffraction methods. The structure of7 reveals one abipy ligand bridging the two ruthenium atoms as in 5. The Ru-Ru separation in 7 is 2.294(2) A. The reaction of [Moi02CCH3)4] with habipy in methanol affords (Moill-abipy)(02CCH3)3] (8). The structure of 8 is determined by X-ray diffraction methods and reveals one abipy ligand bridging two quadruply bonded molybdenum atoms which have a Mo-Mo separation of 2.094(2) A. The [Rhlll~abipy)(02CCH3)iH20)] (9) is formed from the reaction of [Rh i02CCH3)4] with Habipy in methanol. The structure of [Rh2(Il-abipy)(02CCH3)iNCPh)] is determined by X-ray diffraction methods and shows the abipy ligand bridging two Rh(II) atoms which are separated by 2.399(1) A. This chapter is concluded with a discussion of the possiblity of substitution of more than one acetate ligand by the abipy ligand in terms of 'hard' and' soft' acid-base theory and synthetic methods. / Thesis (M.Sc.)-University of Natal, Pietermaritzburg, 1996.

Abstract available in pdf file.