Dit wil voorkom asof metallasiekels ‘n betreklike nuwe generasie van kataliste is, wat nie volkome vir gebruik in die industrie bestudeer is nie. Meeste van die bekende metallasiekels is fosfor, en tot ‘n mindere mate, swael gebasseerde mono- en bidentate metallasiekels. Relatief min is bekend oor die ooreenkomstige stikstof gebasseerde metallasiekels. Die doelwit van hierdie studie was om vas te stel of metallasiekels van stikstof en swael ligande vergelykbaar is met metallasiekels van fosfor ligande en of enige van dié vergelyk kan word met die standaard palladium en fosfor kataliste wat gewoonlik in situ berei word. ‘n Paar probleme wat ondervind is met organometaal literatuur was, onderandere, ‘n gebrek aan volledige eksperimentele prosedures vir metallasiekel sintese asook ‘n tekort aan volledige karakteriseringsdata. Metallasiekelvorming behels die insersie van ‘n metal in ‘n geaktiveerde C-H binding. Organometaal literatuur beskou metallasiekel vorming as oksidatiewe addisie gevolg deur redutiewe eliminasie. Meganisties gesproke het hierdie terme nie veel betekenis nie. Dit is egter moontlik om die reaksie te rasionaliseer in terme van suur/basis interaksies asook elektrofiliese substitusie wat nie die metal se oksidasie toestand verander nie. Die kritiese afhanklikheid van palladasiekel vorming op die reaksiekondisies het duidelik geword gedurende die studie. Die vorming van metallasiekels van palladium is altyd in kompetisie met ander prosesse soos kompleksasie en reduksie van palladium(II). Direkte metallering met palladium asetaat was net suksesvol met fosfor ligande, terwyl palladium chloried weer net suksesvol met stikstof ligande was. Die asetaatioon speel ‘n baie belangrike rol, naamlik om as basis op te tree. Palladium chloried het nie sulke sterk basiese eienskappe nie en dus misluk palladasiekel vorming met fosfor ligande. Wanneer hierdie feite in ag geneem word, is dit duidelik hoekom dit so moeilik was om die swak beskryfde literatuur metodes te volg. Sommige metallasiekels kan nie deur direkte insersie berei word nie en moet dus deur oksidatiewe addisie van halogeen verbindings gevorm word. Kermerkende verskille tussen die KMR spektra van die metallasiekel en sy vry ligand maak dit moontlik om te onderskei tussen die vorming van eenvoudige komplese en die metallasiekel. FAB-MS karakterisering is ook ‘n goeie metode om die verloop van metallering to moniteer. Die bereide metallasiekels en die standaard Pd(OAc)2/PPh3 sisteem is met mekaar vergelyk as katalisatore in die Heck reaksie. Met ‘n ariel jodied as, toon die stikstof palladasiekels hoër aktiviteit as die fosfor palladasiekels, terwyl hul aktiviteit vergelykbaar is met die standaard nie-palladasiekel kataliste. Die pinser komplese het amper geen aktiviteit onder hierdie kondisies getoon nie. Wat die meganisme van die reaksie betref, is bewyse vir die omsetting van die palladasiekel na ‘n palladium(0) spesie al aangevoer, maar meeste outeurs verkies ‘n meganisme wat ‘n Pd(II)/Pd(IV) oksidatiewe verandering behels. Twee tipes reaksies wat van groot belang is vir Sasol is isomerisasie en hidroformilering/alkoksikarbonilering van alkene. Daar is gevind dat palladasiekels oneffektief is in die reaksies met koolstof monoksied, omdat hulle gereduseer word na palladium(0). Die moontlikheid dat hierdie verbindings kan optree as kataliste in hidrogenasie reaksies is dus onwaarskynlik. Palladasiekels hou tog belofte in as kataliste vir olefien isomerisasie. Wanneer die katalitiese eienskappe van metallasiekels bestudeer word, is dit duidelik dat metallasiekels ‘n verandering in oksidasie toestand ondergaan as deel van die katalitiese siklus. In gevalle waar ‘n Pd(II) na Pd(IV) oksidasietoestand verandering moet plaasvind, sal dit noodwendig ‘n baie hoë energie proses wees. Dit sal dan die lae tempo van kataliese verklaar. Dus is dit amper seker dat metallasiekels beperkte toepassing sal vind in die industrie. Die vermoë van metallasiekels om as kataliste op te tree in reaksies waar ‘n verandering in oksidasie toestand nie nodig is nie, is to dusver nog nie ondersoek nie. / Prof. C.W. Holzapfel

The design of catalysts for transition metal-mediated reactions is an active field in chemistry in the 21st century. It has been well recognised that ligands employed in these processes have a significant impact on the outcome of the reactions. The design and application of ligands in homogeneous catalysis reactions were the overarching aims of this project. Two areas were explored in this project, on the ligand synthesis side: 1. The use of directed ortho metallation (DoM) technology to synthesise unsymmetrical phosphines. 2. The synthesis of sterically hindered phosphines and their application to transition metal-mediated reactions. For the first sub-project, a range of N,N-dialkyl-diphenylphosphinic amides was synthesised in near quantitative yields. Deprotonation with s-BuLi and quenching the anion formed in the reaction with a range of electrophiles resulted in the desired ortho-substituted products in good yields. Differentiation of the second aromatic ring was possible, if the isolated mono-substituted products were used in further DoM reactions as starting materials. This methodology provided a range of highly substituted unsymmetrical phosphinic amides. Incorporation of other directing groups can change the selectivity of subsequent DoM reactions providing efficient routes to 2,2’ and 2,6-disubstituted products. Hydrolysis of the phosphinic amide moiety to the phosphinic acid with aqueous HCl, chlorination (SOCl2) and reaction of the acid chloride with a range of Grignard reagents provided an efficient method for the conversion of the phosphinic amide into a P-chirogenic but racemic phosphine oxide. Known methodology can convert this phosphine oxide into a phosphine that can be applied to transition metal catalysed reactions. This methodology provides an effective method for the synthesis of highly functionalised unsymmetrical phosphines. The approach facilitated substantial modifications to the ligand, which allows for efficient tailoring thereof for the metal-mediated reaction in which it is to be used. In the second sub-project, the DoM reaction was again employed but with (diaryl or dialkyl) phosphines as electrophilic quenches, resulting in the isolation of sterically hindered phosphines. Comparison between the ligands was made using the palladium-catalysed Suzuki reactions (catalytic approaches), Vaska type complexes (electronic effects) and phosphine selenium coupling constants (stereo-electronic effects). It was concluded that steric bulk and electronic characteristics affect the activity of catalysts formed from the ligands of this study, in line with the literature. The ligands were successfully applied to the palladium-catalysed Suzuki reaction using strongly deactivated aryl bromides and also some activated aryl chlorides as substrates at low (0.1% Pd) catalyst loadings. Significant improvements in catalytic activity were observed as the project progressed, using a structure-activity study as a guide. / Prof. D.B.G. Williams

In this study polar ligands that would be suitable for use in homogenous catalysis in aqueous-organic and/or ionic liquid systems were designed and synthesised. Initially an attempt was made to design a synthetic route that would incorporate an imidazolium into a phosphorus compound which would then allow the variation of the alkyl group on the imidazole or of the anion, thereby producing a series of ionic ligands with wide range of anticipated chemical and physical properties. This approach was partially successful: phosphines containing imidazolium moieties were synthesised by incorporating N-methyl imidazolium into bi- and tri-aryl phosphine compounds. As these ligands contain imidazolium residues, the retention of the catalyst in the ionic liquid to be used in the catalytic transformation would be enhanced. Water-soluble ligands that are suitable to aqueous-organic systems were also synthesised. The ligands were synthesised by first performing a Michael type reaction with diphenyl phosphine and a Michael acceptor, in this case, malonate esters. These were reduced and subsequently reacted with 1,4-butanesultone. The addition of butane sultone to these phosphorus compounds made them sufficiently water-soluble and therefore ideal for catalysis in aqueous biphasic or ionic solutions. Several water-soluble/ionic ligands were synthesised by incorporating dimethylphosphoryl chloride into di- and tri-aryl phosphine ligands in high yields followed by subsequent hydrolysis of the phosphonate groups. All the ligands produce were tested in transition metal-catalysed reactions, namely the Heck reaction, the Suzuki cross coupling and the Hydroformylation reaction. Test reactions were carried out under conditions selected to show the effectiveness of the ligands in the reaction, and they were performed in organic and aqueous-organic systems, as well as in ionic liquids for the Heck reaction. The results of these reactions were compared to the benchmark triphenylphosphine and it was found that the new ligands produced results that were similar to the triphenylphosphine but there were numerous instances where the new ligands produced better results. This study, therefore allowed for the synthesis for a range of polar phosphine ligands that would be suitable for homogenous catalysis using aqueous and/or ionic liquid systems, and these ligands were shown to influence transition metal-catalysed reactions. / Prof. D.B.G. Williams

D.Phil. / Palladium chemistry has advanced dramatically in the last few years, with a huge number of wide-ranging studies, particularly with respect to the application of palladium complexes as catalysts, having been performed. The discovery of the phenomenon of hemilability (the ability of a ligand to be bidentately coordinated but with one donor atom more weakly bound and thus able to decoordinate in the presence of a catalytic substrate) has further assisted the growth, since it has allowed a greater understanding of the mechanisms of catalytic-reactions. However, the focus of much of this work has been on ligands containing phosphorus and oxygen as potential donor atoms, with little attention being turned to ligands with other donor atoms. The current study concentrates on a series of palladium complexes containing potentially hemilabile thioether, selenoether and telluroether carboxylate ligands with the oxygen as the strongly coordinating atom. Each complex was completed by the palladium coordinating to a phenyl ligand trans to the oxygen of the hemilabile ligand and either one or two triphenylphosphine ligands, depending on whether or not the -hemilabile ligand was monodentately or bidentately coordinated. These complexes are of interest as possible catalysts for the oligomerisation of ethene, and had been previously synthesised and characterised by NMR spectroscopy, mass spectrometry and catalytic studies. In the current work the crystal and molecular structures of the various complexes were determined. Since a number of pairs of complexes containing the monodentate and bidentate forms of the ligands were identified the hemilability of the ligands was confirmed.

Submitted in fulfilment of the academic requirements for the Degree of Master's in Chemistry, Durban University of Technology, 2017. / Hydrotalcites (HT) and hydrotalcites-like (HTLc) compounds were synthesized by the co-precipitation method under low supersaturation. The synthesized binary Mg-Al hydrotalcites and ternary Cu/Mg-Al hydrotalcite-like compounds were characterized by various physico-chemical techniques such as inductively coupled plasma-optical emission spectroscopy (ICP-OES), powder X-ray diffraction (XRD), Fourier transform- infrared spectroscopy (FT-IR), ultraviolet-visible (UV-VIS) spectroscopy, thermogravimetric analysis (TGA), scanning electron microscopy (SEM) and BET surface area analysis. Elemental composition generated from ICP-OES data revealed a value of x in the region of 0.25 to 0.33 for all the compounds except for the MgAl-11 sample which revealed an x value of 0.5 while XRD patterns exhibited characteristic features indicative of an ordered layered material. FT-IR spectra confirmed the presence of characteristic functional groups and interlayer anions. Only Cu2+ which has a d9 configuration was accountable for the bands identified in UV-VIS spectra, whereas both Mg and Al with their d0 electron configurations showed no absorptive bands in the UV-VIS spectra. During thermal treatment by TGA, typical weight loss of Cu-Mg/Al HTLcs with temperature elevation was observed. The SEM images clearly demonstrated that all the Cu-Mg/Al HTLcs retained their characteristically layered structure morphologies. The BET surface area measurements showed no trend, however the surface area decreased with an increase in the copper concentration in some cases. For the heterogeneous hydroxylation of phenol using H2O2 as an oxidant, several reaction parameters such as solvent systems, catalyst amount, temperature, substrate/oxidant ratio, time and solvent volume were investigated. The product stream, monitored by gas chromatography showed that catechol (CAT) and hydroquinone (HQ) were the main products. Non-catalytic (blank) experiments were investigated to determine whether the reactants and the internal standard contributes to the conversion of phenol without the use of a catalyst. All blank reactions showed very low phenol conversions which were less than 1%, whereas the Mg/Al HTs showed low phenol conversions as well. All the Cu-Mg/Al catalysts showed measurable phenol conversion with Cu-Mg/Al-51a giving the highest conversion of 29.9% and a 56 and 44% selectivity towards CAT and HQ, respectively. The Cu-Mg/Al-15b catalyst, which had the lowest copper concentration, showed the lowest phenol conversion of 8.3% with a 55 % CAT selectivity and 45% HQ selectivity. In general, the phenol conversion increased with an increase in copper concentration. This reinforced the hypothesis that copper was the active centre in this reaction, since no measurable conversion was observed with Mg/Al HTs. / M

Magister Scientiae - MSc / In this work a modified polyol method was developed to synthesize in-house catalysts. The method was modified for maximum delivery of product and proved to be quick and efficient as well as cost effective. The series of IH catalysts were characterized using techniques such as UV-vis and FT-IR spectroscopy, TEM, XRD, ICP and CV. The polyol method developed effectively reduced and deposited Pt nanoparticles onto different carbon supports. Functionalization of some of the supports was also successfully carried out through acid oxidative treatment which introduced carboxylic acid and hydroxyl groups onto the surface of the supporting material, which was supported by FT-IR which demonstrated that there was a relative increase in absorbance of functionalities viz., carboxylic acid (1270 cm-1) and hydroxyl groups on the surface of the acid treated MWCNT’s-F compared to the untreated MWCNT’s. Addition of a sedimentation promoter proved to increase the amount of metal deposition on the support thereby improving the loading dramatically. It was also found that addition of a specific amount of water in the polyol method allowed one to control the particle growth during the deposition phase on the various carbon supports investigated namely; XC-72 carbon, MWCNT’s and MWCNT’s-F. The in-house catalysts synthesized namely; Pt/C-IH, Pt/MWCNT’s-IH and Pt/MWCNT’s-F-IH all displayed narrow particle size distributions with average mean particle sizes of 2-5 nm, 2-6 nm and 3-6 nm respectively which was in good agreement with particle size measurements obtained from XRD using the Scherrer formula. All measured CV’s obtained for the series of IH catalysts prepared by this protocol were comparable with the commercial catalyst. The IH catalysts displayed the characteristic XRD peaks associated with Pt on carbon supports in acidic media. The ORR measurements for Pt/MWCNT’s-F-IH (functionalised) proved to be slightly superior (0.058 A/cm2) compared to that of the commercial catalyst (0.047 A/cm2) at a potential of 0.3V. This was attributed to the fact that the addition of water effectively controlled particle growth and deposition onto the support, and the fact that MWCNT’s-F offered a larger surface area and with the functionalized surface offering anchorage sites for Pt nanoparticles through carboxylic and hydroxyl functional groups. Further attempts to modify the developed polyol method using NaOAc as an electrostatic stabilizer to control the growth of Pt nanoparticles were made. It was found that although the stabilizer employed effectively stabilized Pt nanoparticles supported on XC-72 carbon, in our hands we were not able to produce the same results in the case of Pt supported on the MWCNT’s. TEM images revealed that Pt/CNaOAc displayed narrow particle size distribution with a mean particle size of 2-5 nm whereas particle agglomeration was observed for Pt/MWCNT’s-NaOAc and Pt/MWCNT’s-F-NaOAc with a broader particle size distribution and average mean particle sizes of 2-7 and 2-8 nm in diameter respectively. The CV’s obtained for these modified IH catalysts were in the main comparable to that of the commercial catalyst. However ORR activities of the IH Pt/C-NaOAc catalysts when carefully compared to the commercial catalyst revealed that it was indeed slightly superior (0.064 A/cm2). This is mainly attributed to the narrow particle size and even distribution of particles on the carbon support and resembled the best particle required to provide maximum activity in the ORR as a consequence of the facial kinetics involved. / South Africa

The principle aims of this thesis have been to develop well-defined heterogeneous catalysts for potential applications in tandem hydrocarbon upgrading. Catalysts for olefin oligomerisation and metathesis of &alpsha;-olefins and transfer hydrogenation of alkanes based on tungsten mono-imido and PCP pincer iridium complexes have been synthesised and immobilised on solid supports. The reactivity of the immobilised catalysts has been tested and compared with the precursor complexes. Co-immobilisation of the two complexes on the same support has been undertaken. <b>Chapter One</b> provides a background to the olefin metathesis reaction and the development of highly active tungsten mono-imido and ruthenium alkylidene complexes. A summary of the implementation of the olefin oligomerisation reaction by industry and the development of highly active systems based on group 6 metals is discussed, along with a mechanistic discussion. The SOMC grafting procedure is considered and the immobilisation of catalysts for alkane and olefin metathesis and oligomerisation discussed; with focus on support materials: silica, sMAO and AMO-LDHs. Finally, tandem catalysis and its use in hydrocarbon upgrading and copolymerisation are presented. <b>Chapter Two</b> details the synthesis of W(NR)Cl₄(THF) complexes and their conversion to W(NR)Me₃Cl complexes employing TMA. The products are characterised by single crystal X-ray diffraction, NMR and FTIR spectroscopy. W(NR)Me₃Cl complexes are shown to be active for the selective dimerisation of ethylene to 1-butene. Attempted formation of possible intermediates in the reaction is presented, and efforts to form mimics for silica supported species are also discussed. <b>Chapter Three</b> describes the preparation of AMO-LDHs for use as catalyst supports. The effect on the surface hydroxyl content and structural properties of these materials by thermally treating them under vacuum is analysed. Their capability to act as supports for ethylene polymerisation after impregnation with MAO and (ⁿBuCp)₂ZrCl₂ is described. <b>Chapter Four</b> investigates the immobilisation and characterisation of synthesised tungsten mono-imido complexes on sMAO, AMO-LDHs and silica, utilising SSNMR, FTIR and X-ray absorption spectroscopy. The reactivity of the grafted complexes towards ethylene oligomerisation is discussed. For the immobilised species effects of varying the imido ligand, temperature and solvent medium are reported. Attempts to immobilise ruthenium carbene complexes on AMO-LDHs and sMAO is detailed. <b>Chapter Five</b> gives an account of the immobilisation of Ir(^tBuPCP)HCl on sMAO which is characterised by SSNMR and FTIR spectroscopy. Molecular analogues of the supported species are synthesised and reactivity for the hydrogenation of ethylene compared. Transfer hydrogenation reaction with sMAO-Ir(^tBuPCP)HCl and COA or ethane with TBE as a sacrificial H₂ acceptor are discussed. Finally, co-immobilisation of W{N(2,6-F-C₆H₃)}Cl₄(THF) and Ir(^tBuPCP)HCl on sMAO was carried out and the solid characterised by SSNMR spectroscopy. <b>Chapter Six</b> provides experimental details and characterising data for the preceding chapters. An <b>Appendices</b> with crystallographic data, and characterising spectra for each chapter is provided, while the <b>Electronic Appendix</b> contains a combined CIF and checkcif for all the molecular structures presented.

The large number of new heteronuclear bidentate ligands recently reported in the literature has unveiled a new area of research, namely that the use of different heteroatoms in bidentate ligands has led to new avenues towards more selective processes especially in asymmetric transformations. Instead of employing the traditionally used bidentate bisphosphine ligands, the dual objective of this study was therefore to design and synthesise P-N based bidentate ligands, and to apply these in catalytic transformations. A general route towards the synthesis of different series of P-N based ligands was followed. This path involved, as initial step, the condensation of o-diphenylphosphinobenzaldehyde with a series of primary amines to afford a series of iminophosphine ligands. Upon subsequent reduction of the iminophosphine ligands, a series of secondary aminophosphine analogues was obtained, and upon alkylation of the latter in the presence of a base, their tertiary aminophosphine derivatives were isolated. In these three series of ligands, the oxidation state of the nitrogen atom, as well as the degree of alkylation on this atom, was varied. These ligands were further elaborated by the incorporation of a second phosphorus atom to the already bidentate P-N ligands. This was achieved by reacting the secondary aminophosphine ligands with a base and chloro-diphenylphosphine. In order to vary the electronic nature of the newly introduced second phosphorus atom, a method for the incorporation of a dicyclohexyl phosphine moiety was developed. By introducing this group into the P-N backbone of these ligands, it was thus possible to electronically distinguish between two different phosphorus atoms in one ligand. Apart from the nature of the nitrogen and phosphorus atoms in these ligands, the use of different R-groups derived from the primary amines, enabled further variance in the inherent characteristics of these ligands: the variation in R-groups included aliphatic moieties, aromatic groups, and groups that contained additional heteroatoms. In these cases, the variation in R-groups thus also influenced the denticity of these ligands, which could render them more versatile in catalytic applications. In addition, a series of S-N based ligands, as well as some chiral P-N based ligands, was synthesised by using the previously-developed protocol. The oxygen sensitive nature of phosphines sometimes requires protection of these phosphines during different synthetic steps, and borane is often used for this purpose. However, deprotection of these phosphine ligands is required before they can be used in metal-catalysed reactions. As an adjunct to the present synthetic strategy, the concept of deprotecting phosphine-borane complexes such that new, extractable borane complexes are formed, was investigated, and formed a small part of this overall study. The deprotection of phosphine-boranes was performed using various “new” deprotecting reagents, and the borane species were separated from the free phosphines by using water / organic phase separations. The various extraction coefficients of the amine-borane complexes were determined. All the newly prepared heteronuclear ligands were used in a variety of catalytic transformations, including reactions catalysed by palladium, chromium and rhodium. The results obtained from these catalytic transformations indicated that most of these ligands afforded highly active catalysts in the different applications, and results were, in many cases, better than those obtained with commercially available ligands such as triphenylphosphine and dppp. To end off this study, an investigation towards the ó-donating properties of a selection of phosphine ligands was performed by converting the phosphines into their corresponding phosphine selenides, and calculating the 1J(77Se-31P) coupling constants. From this study, it was found that the electronic nature of different phosphine atoms in the same ligand could be characterised, and such information, in turn, can be used for the design of new ligands for specific catalytic systems. / Prof. D.B.G. Williams

The objective of the research described in this dissertation was the search for optimum ligand-metal complex combination that would facilitate the contrathermodynamic isomerisation of internal olefins. To this end a variety of ligands where synthesised and subsequently tested, firstly for their ability to isomerise alpha olefins and secondly their ability to isomerise internal olefins. Due to the lack of information obtainable from literature about catalytic isomerisation of olefins, the general reaction parameters had to be investigated. Various factors that could play a role in the isomerisation of olefins where investigated and these included the effect that solvents have on the isomerisation as well as the possibility of metalhydride formation. The possible formation of metal-hydrides was tested by adding a variety of acids and also the addition of hydrogen gas to the solution. All of these factors played an important role in the subsequent isomerisation of alkenes and valuable data could be obtained from these experiments. Solvents were found to have an effect on the isomerisation, but a trend could not be established. The effect of added acid was more pronounced and a correlation between acid strength and isomerisation could be established. It was also found that hydrogen gas added to the reaction mixture generally increased the reactivity of the metal catalysts and some experiments were done to optimise the use of hydrogen in these reactions. The use of commercially available ligands for the isomerisation reaction was also investigated and gave a broad indication of possible active ligands. After these initial reactions and information gathered from literature, it was decided to synthesise a set of di-imine ligands and also a set of bis-phisphite ligands. Due to tautomerism of the di-imines to the corresponding enamines, a set of enamine/imine ligands was synthesised and tested with two rhodium and two palladium catalysts. The synthesis of bis-phosphite ligands was initially problematic, but ideal conditions were found and a set of bis-phosphite ligands was synthesised and tested. Results obtained from the testing of both the enamine/imine lignds as well as the bisiii phosphite ligands were of value and a great many trends could be observed. Many of these observations had correlations to either the electronic nature of the various ligands as well as that of the metal centre. The testing of a set of palladium(II) metallocycles also gave an insight into the electronic properties necessary for the successful isomerisation of olefins. These electronic properties are always a combination of ligand and metal centre effects and thus a fine balance must be struck between these two factors. As a final conclusion to the work that was performed, internal olefins were subjected to tandem isomerisation-hydroformylation reactions using some of the more active metal-ligand systems. Internal olefins were isomerised and hydroformylated in the same reaction vessel to afford branched and linear aldehydes. In these reactions, it was proved that isomerisation as a primary reaction could be coupled to a secondary reaction and be of use in industry and further research in this field might prove to be of some value. / Prof. D.B.G. Williams

M.Sc. / The main objective of the research described in this dissertation was to prepare several logical series of ligands, being variously substituted at different positions of the aryl ring attached to the P atom. These ligands were evaluated by several techniques including 31P NMR shift measurements, 31P-77Se NMR coupling constant measurements, CO stretching frequency measurements in rhodium(I) Vaska-type complexes of the ligands, application of the ligands in the Rh-catalysed hydroformylation reaction, X-ray studies on single crystals of some of the ligands and computational studies all with the view to establish if phosphorus atoms in arylphosphines could be used as a handle to probe steric and electronic effects of aromatic systems. A series of triarylphosphine ligands containing either ester, fluoro, nitrile, tolyl or a combination of functional groups was prepared by reacting Grignard- or organolithium reagents with P-Cl reagents. The results of this aspect of the work showed that, under the right reaction conditions, these organometal reagents can tolerate certain functional groups. On evaluation of these ligands with the different techniques described above it was found that: 31P NMR shift measurements cannot be used in correlations with the data from the other methods of evaluation used in this study, 31P-77Se coupling constant measurements and CO stretching frequency measurements in rhodium(I) Vaska-type complexes of the ligands can be correlated to a relatively good extent with Rhcatalysed hydroformylation reaction results (provided that ortho-substituted phosphine data are disregarded), 31P-77Se NMR coupling constant measurements and CO stretching frequency measurements in rhodium(I) Vaska-type complexes of the ligands correlated well with computational studies, and finally, computational studies at the level of theory used in this dissertation also correlate quite well with the Rh-catalysed hydroformylation reaction results. In all it was found from this study that the phosphorus atom in arylphosphines can be used as a handle to probe the electronic and steric effects of aromatic systems, and that the most versatile method of ligand evaluation were the 31P-77Se coupling constant measurements and CO stretching frequency measurements in rhodium(I) Vaska-type complexes.