The preparation of the modified silane [special characters omitted]; a phosphinoalkylsilane or PSi) via an alkylzirconium intermediate is reported. The synthesis of [special characters omitted] was carried out by the reaction of organolithium reagents with chloro-silanes at low temperature. The PSi compounds are isolated as air-sensitive, thermally stable and very viscous liquids. The reactivity of two of the silanes was investigated with the platinum group metal complex [special characters omitted] (cod = cycloocta-1,5-diene). In both cases, square planar platinum (II) complexes were isolated. The reactivity of [special characters omitted] produces five coordinate M (III) complexes which undergo stereomutation. The isomerisation of the syn to anti forms of [special characters omitted] has been examined at several temperatures via NMR spectroscopy and the activation parameters determined for the conversion of the syn to the intermediate isomer form [special characters omitted]. The implications of the stereomutation phenomona are discussed in relation to catalysis. None of the isomers of this complex forms a stable six coordinate adduct when reacted with a number of common nucleophiles. The analogous compound where M = Ir and related complexes of the formula [special characters omitted] are reactive towards CO to form stable six coordinate adducts containing two M-P and one M-Si, M-H, M-CO and a M-Cl bond. Some of these adducts can be made directly by the reaction of the PSi ligand precursor with [special characters omitted] (M = Rh, Ir) at room temperature. The reaction of the silane [special characters omitted] produces six coordinate complexes directly. For M = Ir, the compound reacts with CO to produce a six coordinate cation by displacement of a chloride ligand, the latter of which then acts as a non-coordinating counterion. A series of organosilicon dendrimers of the type : [special characters omitted] ([G-1] : x = 3, y = 2 = q = 0; [6-2] : y = 3, x = 9 , z = q = 0; [G-3] : z = 3, y = 9, X = 27, q = 0; [G-4] : q = 3, z = 9, y = 27, x = 81) are sythesised and examined spectroscopically. All of the dendrimers are air stable liquids. Species G3 has a marked tendency to undergo what appears to be self-condensation polymerisation. End and core group substitution is presented for a carbosilane dendrimer containing one shell of identical exterior Si atoms. The dendrimeric end groups can be modified by the replacement of a terminal chloride by fluoride, hydrogen, alkyl groups or metal complexes. The selective removal of a core phenyl group can be accomplished with the strong acid [special characters omitted]. The resulting silyl triflate can in turn be used as a precusor to a silyl ether, hence facilitating selective core group modification. / Graduate

The aim of this study was to synthesise mono-phosphite complexes of type [Rh(OX)(CO){P(OY)3}], (where Y = the different phosphites that were used and OX = 8-hydroxyquinoline) and to do a kinetic study of iodine oxidative addition to these rhodium(I) square planar complexes in order to determine the rate constants and the reaction mechanism. Part of the characterization was X-ray crystallographic structure determinations which were done on two complexes, namely the [Rh(OX)(CO){P(O(2,4-t-BuPh))3}] and the [Rh(OX)(CO){ P(O(2,6-diMePh))3}]. From the characterization methods it can be said with certainty that the synthesis of the mono-phosphite rhodium(I) complexes was successfully achieved. Table 1 - Selected crystal data as obtained for the two Rh(I) crystal structures solved in this study. [Rh(OX)(CO){P(O(2,4-t- / Prof. A. Roodt

This work has focussed on the preparation of a variety of tridentate ligands, designed to form ruthenium complexes as potential metathesis catalysts. Various approaches to the tridentate, malonate-tethered imidazolidine system have been investigated, and a promising route to accessing ligands of this type is discussed. A tridentate malonate-tethered pyridine ligand has been successfully prepared and its dithallium salt has been accessed by hydrolysis with thallium carbonate; approaches to a longer-chain analogue have also been investigated. A thallium pyridine-2,6- dicarboxylate ligand has been has been successfully prepared, as have a range of pyridine diamine ligands, with various alkyl and aromatic substituents on the amine donor atoms. Preliminary investigations into the potential of these compounds as ligands for alkylidene ruthenium complexes are reported using molecular modelling techniques. The geometries and steric energies of the ligands and their corresponding complexes have been analysed, and results obtained from two different software packages are compared. Finally, some preliminary complexation studies have been undertaken.

In this dissertation novel non-leaving groups were employed to synthesize platinum complexes which can contribute to the understanding or improvement of anticancer action. These complexes basically consist of (NS)-chelate and amineplatinum complexes. Bidentate (NS)-donor ligands were used as non-leaving ligands in the syntheses of platinum(II) complexes with iodide, chloride, bromide and oxalate anions as leaving groups. These complexes were synthesized and studied since many questions regarding the interaction of sulfur donors and platinum still exists. These relate to thermodynamic and kinetic factors and their influence on anticancer action. In this dissertation the properties of novel platinum(II) complexes of a bidentate ligand having an aromatic nitrogen-donor atom in combination with a thioethereal sulfur atom capable of forming a five membered ring with platinum(II) were studied. The general structure of the (NS) -ligands used were N-alkyl-2-methylthioalkyl imidazole. Alkyl groups used were methyl, ethyl and propyl. Although amine complexes of platinum have been extensively studied there are some new aspects of these that are worthwhile investigating. In this dissertation amines having planar attachments which will be at an angle with the coordination plane viz. benzylamine and amines having cyclic aliphatic groups namely cyclopropyl and cyclohexyl were investigated. Some of the (NS) - and amineplatinum(II) complexes were oxidised to their mononitroplatinum(IV) analogues . The motivation for the synthesis of these complexes was the greater kinetic stability of platinum(IV) and recent research has shown that a specific type of platinum(IV) compound shows suitable properties as an anticancer agent. These complexes were characterised by a variety of spectral means (IR, NMR, mass spectroscopy) as well as elemental analysis, solubility determinations, thermal analysis (TGA), ionization studies and finally their anticancer behaviour towards three different cell lines(Hela, MCF 7, Ht29) and in this process they were compared to the behaviour of cisplatin as a reference. A few have shown promising anticancer behaviour.

Novel non-leaving groups were employed in this dissertation to synthesize platinum complexes which can assist in the understanding or improvement of anticancer action. Emphasis was placed on (NS)-chelate and (NN)-chelate platinum complexes. Bidentate (NS)-donor ligands were used as non-leaving ligands in the synthesis of platinum(II) complexes with iodo, chloro, bromo and oxalato groups as leaving groups. These complexes were synthesized and studied since many questions regarding the interaction of sulfur-donors and platinum still exist. These relate to thermodynamic and kinetic factors and their influence on anticancer action. In this dissertation the properties of novel platinum(II) complexes of a bidentate ligand having an aromatic nitrogen-donor atom in combination with a thioethereal sulfur atom capable of forming a five-membered ring with platinum(II) were studied. The general structure of the (NS)-ligands used was 2-((alkylthio)methyl)pyridine. Alkyl groups used were methyl, ethyl, propyl, benzyl and phenyl. Amine complexes of platinum have been studied extensively in the past. However, attention was given to novel aspects of substituted pyridine and imidazole ligands and their corresponding complexes. Amongst these are 2-(2-methylaminoethyl)pyridine, 1-methyl-2-methylaminoethylimidazole and 1-methyl-2-methylaminobenzylimidazole. The leaving groups included chloro, bromo and oxalato. Mononitroplatinum(IV) complexes were prepared using novel synthetic methods. Selected platinum(II) amine complexes were used as starting materials for this synthesis. Some of these compounds exhibit promising anticancer behaviour. (Trans-(R,R)-1,2-diaminocyclohexane)(oxalato)(mononitrochloro)platinum(IV) is a particularly good anticancer agent and has been patented internationally. All these complexes were characterized using mass spectrometry, chromatography, thermogravimetric analysis, kinetic aspects such as ligand exchange rates and finally their anticancer action against three different cancer cell lines was evaluated via cytotoxicity assays. Some of the compounds exhibited particularly good anticancer potential.

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