A Mössbauer Effect study of a number of complexes of iron with sulphur containing ligands has been carried out, in order to further the understanding of iron-sulphur chemistry and hence eventually provide suitable model complexes for the study of the non-haem iron proteins. The complexes investigated have been considered in three main sections, some dialkyldithiocarbamate complexes, some complexes that have been proposed as models for the non-haem iron proteins, and some complexes of some 2-substituted pyridines. The iron(III) N,N dialkyldithiocarbamates exhibit anomalous magnetic properties which have been ascribed by other workers to a high-spin, low-spin equilibrium. All the iron(III) N,N dialkyldithiocarbamates that we have studied showed a single Mandouml;ssbauer spectrum at all temperatures, so that the rate of exchange between the high-spin and low-spin states must be greater than 1.5 andtimes; 10⁺⁷ sec.^-1. The isomer shifts observed were large for low-spin ferric ions and suggest that the metal s-electrons are screened from the nucleus by electrons donated from the ligands. The isomer shifts and quadrupole splittings for all the complexes, except the high-spin iron(III) pyrrolidyldithiocarbamate, exhibited anomalous dependences on temperature due to the existence of the spin equilibrium. Iron(III) pyrrolidyldithiocarbamate exhibited long electron spin relaxation times at 4.2°K. The other compounds, which are low-spin at low temperatures, also showed relaxation effects, though with shorter times. The magnetic hyperfine interactions in the Mandouml;ssbauer spectrum of iron(III) N,N dimethyldithiocarbamate gave information on the nature of the ground state of the complex, which was found to consist of almost equal amounts of d_xz and d_yz holes, with slightly less of d_xy. Mandouml;ssbauer Effect and epr measurements on samples of this complex diluted in cobalt(III) N,N dimethyldithiocarbamate confirmed this result. Estimates for the orbital separations were obtained as andDelta;d_xz, d_yz = 1.2 cm.^-1 and andDelta;d_yz, d_xy = 91 cm.^-1 The dependence of the Mandouml;ssbauer spectrum of iron(III) pyrrolidyldithiocarbamate upon temperature and magnetic field has been interpreted in terms of a model with a large negative zero field splitting of the ⁶S state. The magnitude of the zero field splitting (4D) has been estimated as -9.3°K. Bis(N,N diethyldithiocarbamato)iron(III) chloride and bis(N,N diisopropyldithiocarbamato)iron(III) chloride exhibited similar Mandouml;ssbauer spectra to iron(III) pyrrolidyldithiocarbamate at low temperatures. We have confirmed that the former compound is ferromagnetic, while the diisopropyl derivative is paramagnetic with the Kramer's doublet |±3/2andrang; lying lowest. Another complex of iron with dialkyldithiocarbamate ligands that has been studied is the formally iron(I) complex, nitrosyliron bis(N,N diethyldithiocarbamate). A high isomer shift was again observed. The quadrupole splitting showed little dependence on temperature and the application of an external magnetic field showed the sign of the major component of the electric field gradient to be positive. Magnetic hyperfine interactions arc observed in large external magnetic fields at low temperatures. The variation of the effective field at the nucleus with H/T followed the Brillouin function for S = 1/2, and the value of the saturation hyperfine field was found to be -110 ±5kG. The orbital ground state of the iron atom could not be deduced from the sign of the quadrupole splitting, due to large contributions from the lattice and bonding electrons. From the magnetic hyperfine interactions it was deduced to be d_z2.</p> The model complexes Fe(TTD)₂(DTT) and Fe(TTD)(DTT)₂ which contain an Fe-S-S- linkage, as well as the related complex Fe(DTT)₃ have been studied. (TTD = thio-p-toluoyldisulphide, DTT = dithio-p-toluate) The isomer shifts have been interpreted in terms of the relative ability of the TTD and DTT ligands to delocalise electrons from the metal. The sign of the major component of the electric field gradient has been found to be negative for Fe(TTD)₂(DTT) and Fe(TTD)(DTT)₂ but positive for Fe(DTT)₃. The Mandouml;ssbauer results have been used in conjunction with epr measurements to obtain information on the ground state of the complexes containing ligands. The ground state is deduced to be a d_xy hole in both cases, but the agreement between the Mandouml;ssbauer and epr data is not very satisfying. Mandouml;ssbauer Effect measurements on the model Fe(sacsac)₂Cl₄, where sacsac is dithioacetylacetonate, have shown that the complex contains tetrahedral FeCl₄^2- ions, and does not have the structure originally proposed in which the iron is coordinated by the dithioacetylacetonate groups. The related complex (Ph₂C₃MS₂)₂FeCl₄ contains FeCl₄^2- ions in two different environments at high temperatures. Tristetraphenylphosphonium trisdicyano-1,2-dithiolene iron was proposed as a model complex on the basis of its epr spectrum, which is qualitatively similar to that of the non-haem iron proteins. Mandouml;ssbauer Effect investigations have been made on this complex and are reported here. The temperature dependence of the line widths and the relative line intensities has been interpreted in terms of the relative magnitudes of the spin-lattice and spin-spin relaxation times. An attempt to correlate the temperature dependence of the quadrupole splitting with that of the magnetic moment was only partially successful. Measurements in externally applied magnetic fields showed the sign of the major component of the electric field gradient to be negative; lattice contributions to the electric field gradient are not important in determining its sign. The ground state of the complex was deduced to be a d_xy hole well separated from higher states, from both the Mandouml;ssbauer and epr measurements. The complex (andpi;-C₅H₅Fe(CO)SMe)₂SbF₆ has been investigated, and is proposed as a model complex for the non-haem iron proteins, on the basis of similarities in its structure and epr spectrum. The Mandouml;ssbauer Effect measurements have shown that the single unpaired electron is equally shared by the two iron atoms, which results in an anomalously small value for the hyperfine field at the iron nuclei. The epr spectrum has been interpreted in terms of a model in which a high-spin ferric ion and a high-spin ferrous ion are antiferromagnetically coupled to give a total spin S of 1/2. Estinates of the relative energies of some of the orbitals of the ferrous ion have been made. A number of complexes of iron with 2-substituted pyridine ligands have been prepared and studied. The preparation of complexes of thiopicolinic acid anilide, thiopicolinamide, pyridine-2-aldehyde thiosemicarbazone, 2-mercaptomethylpyridine, o-aninobenzenethiol and 2,2andprime;-dipicolyldisulphide are reported. A number of these complexes are described and characterised for the first tine. With one exception all the complexes contain ferrous ion; oxidation of the ligand usually occurred when the preparation of ferric complexes was attempted. The Mandouml;ssbauer parameters of these complexes are reported and discussed. The values of the isomer shifts of the low-spin ferrous complexes of thiopicolinic acid anilide, thiopicolinamide and pyridine-2-aldehyde thiosemicarbazone are interpreted in terms of the relative andsigma;-donor powers of the ligands. The complexes of o-amino-benzenethiol and 2-mercaptomethylpyridine were found to contain high-spin ferrous ions. The former complex was found to be antiferromagnetic at low temperatures, whilst at 77°K it exhibited the largest quadrupole splitting yet reported for an iron compound, 4.06 mm.sec.^-1 The latter complex also chowed a large quadrupole splitting at 77°K. The Mandouml;ssbauer spectrum observed at low temperatures suggested the presence of some weak antiferromagnetism. The single ferric complex of these ligands that was prepared, is a complex of 2,2andprime;-dipicolyldisulphide and is the first complex of iron with a disulphide ligand to be reported. Further work is necessary before it is fully characterised. Finally, the value of the information obtained from Mandouml;ssbauer spectroscopy and epr in the elucidation of molecular and electronic structure is discussed. A correlation between the magnitude of the Fermi contact contribution to the hyperfine field is considered in the light of the data obtained during this work.

Through billions of years of evolution, nature has assembled a multitude of polymeric macromolecules capable of exquisite molecular recognition. This functionality is achieved by the precise control of amino acid sequence during the assembly of proteins, producing three-dimensional macromolecules with key residues anchored in the correct positions to interact with their targets. Developing ‘wholly-synthetic’ macromolecular analogues which mimic this function presents a considerable challenge to chemists, who lack the ‘biological machinery’ used by nature in the precision-assembly of polymers. In addressing this challenge, familiar chemical concepts, such as combinatorial methods and supramolecular interactions, have been adapted for application in the macromolecular arena. Working from a limited set of residues, synthetic macromolecules have been produced which display surprisingly high binding affinities towards target proteins, even possessing useful in vivo activities. These observations are all the more surprising when one considers the heterogeneity inherent within these synthetic macromolecular receptors, and provoke intriguing questions regarding our assumptions about the design of receptors.

The fearsome reputation of primary phosphines, with many considered toxic, pyrophoric and sometimes even explosive, has meant that these versatile compounds are often underused in synthetic chemistry. There is however a limitied number of air-stable examples in the literature, whose air-stability has either been accounted for by steric factors or for reasons that could not be explained. Recently (S)-1a and (R)-1b have been prepared and they are considered to be air-stable due to electronic effects of the 1,1’- binaphthyl backbone. In Chapter 2 of this work we report the synthesis of the valuable precursors (S)-1a and (R)-1b in improved yields and in multigram quantities using palladium-catalysed crosscouplings producing a reliable and convenient method for the synthesis of these 1,1’- binapthyl based primary phosphines. The functionalization of the primary phosphine precursors (S)-1a and (R)-1b has been explored, examining the novel phosphetane analogues in Chapter 3 and phospholane analogues in Chapter 4. The σ-donor and π-acceptor properties of these ligands have been investigated through their coordination to selenium, platinum and rhodium. The dynamic behaviour of the ligands at palladium and platinum has been examined by NMR spectroscopy and X-ray analysis. An investigation into the performance of the ligands in asymmetric catalysis, including palladium-catalysed cross-couplings and rhodium-catalysed hydroformylations, has also been conducted An examination into the range of aryl carbon-phosphorus bond forming techniques has also been carried out in the pursuit of novel ortho-substitued diprimary phosphines from arylbromides in Chapter 5. These user-freindly diprimary phosphines have then been successfully functionalised into ortho-substituted bisphospholane ligands and tested a rhodium-catalysed hydrogenation reaction, matching the performance of DuPhos.

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