No description available.

No description available.

Many new complexes of tri- and tetra- valent lanthanide ions and divalent calcium with Schiff bases have been synthesised and their properties investigated by chemical analysis, infra-red, visible, and ultra-violet absorption spectroscopy, X-ray powder diffraction studies, and molar conductance and magnetic susceptibility measurements. The Schiff bases, which were mainly derivatives of sali-cylaldehyde and primary amines, formed complexes in two ways. In the first, the phenolic hydrogen atoms were un -ionised and the base behaved as a neutral ligand whilst in the second, the base reacted in the usual way as an anion. For the trivalent metal ions, complexes of the following types were obtained:- 1. Ln(L)Cl[3]. nH[2]O and La(Hsal-ane)Cl[3]. [2]EtOH. (Ln=Ce,La; n=1 and 2; L=NN'-ethylenebis(salicylideneimine) (H[2]salen) and NN'-1,3-propylenebis(salicylideneimine) (H[2]sal-1,3pn); N-salicylideneaniline (Hsal-ane); EtOH-ethanol). 2. Ln[2](L)[3]X[6]. nH[2]O. 3. Ln(L)[2]X[3]. nH[2]O and La(Hsal-ane)[2](NO[3])[3]. 2EtOH. 4. Ln(L)[3]X[3]. nH[2]O, (Ln=La,Ce,Pr,Nd,Sm,Gd,Ho,Yb; X=Cl-,Br-,NO[3-]; L=H[2]salen, H[2]sal-1,3pn, NN'-1,2-propylenebis(salicylideneimine) (H2sal-1,2pn), NN'-1,6-hexylenebis(salicylideneimine) (H[2]sal-1,6hex), and Hsal-ane ; n=0 - 2). A few exceptions are discussed in detail in Chapter 2. New series of complexes with tetravalent cerium with ionised and un-ionised Schiff bases of formulae below have been synthesised:- 5. Ce(L')2, 6. Ce(L)2(NO3)4. H2O (L' = the ionised Schiff bases: NN' -1,2-propylenebis(salicylideneiminate) (sal-1,2pn), NN'-1,3-propylenebis(salicylideneiminate) (sal-1,3pn), NN'-ethylenebis(3-inethoxysalicylideneiminate) (3-methoxy-salen), NN'-ethylenebis(5-nitrosalicylideneiminate) (5-nitrosalen), NN'-1,2-propylenebis(5-nitrosalicylideneiminate) (5-nitrosal-1,2pn), NN'-1,3-propylenebis(5-nitrosalicylideneiminate) (5-nitrosal-1,3pn) and L=H2salen, H2sal-1,2pn, H2sal-1,3pn and H2sal-1,6hex). Calcium complexes of the types shown below have been isolated:- 7. Ca(L)X2. nsolvent, 8. Ca(L)2X2. nsolvent (n=0 - 2; solvent = H2O or ethanol; L=H2salen, H2sal-1,2pn, H2sal-1,3pn, and H2sal-1,6hex and X=Cl- and NO3-). On the basis of the infra-red spectroscopy it was concluded that the un-ionised ligands behave as bidentate species with coordination taking place through the azomethine nitrogen atoms and not through the phenolic oxygen atoms. The ionised bases behave as tetra-dentate ligands in the well-established manner. There is evidence for coordinated nitrate in all the lanthanide nitrato- complexes. Far infra-red spectroscopy has shown the presence of the coordinated halide in some of the lanthanide complexes. The coordination numbers of a series of neodymium(III) Schiff base complexes have been deduced through the hypersensitive transitions observed in the visible region of the absorption spectrum by comparison with the spectra of complexes of known structure. The coordination numbers of the lanthanide complexes are probably 8 or 9 in the halide complexes and between 10 and 12 for the nitrates. The calcium complexes may have coordination numbers between 4 and 6. Furthermore, the X-ray powder photography has shown the complexes to be true compounds and not simple mixtures. Isomorphism was found in some cases for the trivalent lanthanum and neodymium complexes. The conclusions were consistent with those obtained from the other measurements.

Uranium(III) chemistry is reviewed and contrasted with relevant aspects of the chemistries of the tervalent transuranium elements, and tetravalent and pentavalent uranium. The preparation and chemical properties of a number of hydrated and anhydrous uranium(III) compounds , including a new hydrated uranium(III) fluoride, are reported, and the stability of the hydrated uranium(III) cation in the presence of a large number of inorganic anions is described. The complex chemistry of uranium(III) is shown to be very limited and only with the oxygen donor ligands phenazone and 4-dimethylaminophenazone have solid complexes been prepared. An uncharacterised uranium(III) hexamethylphosphoramide complex has also been isolated. The presence of uranium(III) is demonstrated in these compounds. The electronic spectrum of the uranium(III) ion has been studied in various compounds and the results are discussed in terms of the chemical environment, particularly the effects on the 5f[3]-5f[3] and 5f[3]-5f[2] 6d[1] transitions. The magnetic behaviour of the uranium(III) ion is interpreted in terms of crystal field effects rather than intramolecular antiferromagnetism. No available theoretical treatment satisfactorily accounts for the spectral and magnetic properties of uranium(III).

Fine mercury whiskers have been grown from the vapour on a cold glass substrate. These whiskers attained a length of about 1 mm. Electron microscopy revealed that this type of crystal has a square cross section bounded by the {011} and {110} planes. Mercury platelets were also grown from the vapour by a similar method. Optical microscopy showed that these platelets have two different shapes: rhombus and parallelogram shaped crystals were observed. Electron microscopy showed that the rhombus shaped crystals have a lateral face parallel to the {111} plane, which is the closest packed plane in mercury; the parallelogram shaped crystals were found to have a lateral face parallel to the {011} plane in mercury. The as-grown platelets were found to be too thick for transmission electron microscopy, so they had to be deformed in order to reduce their thickness. The deformed crystals revealed some very interesting features from which valuable information on the defects structure in mercury was obtained. The thickness of the deformed crystals was measured and errors have been found in previously published investigations. Stacking faults in solidified mercury were observed and found to lie on the closest packed plane having either the [011] direction or the [110] direction. The slip mode of crystalline mercury near its melting point was studied by the observation of traces in the foils, the slip elements were found to be {111} and {111} . Dislocation networks have been observed and the investigations carried out suggest that the dislocation interaction could represent the following type of reaction; 1/2 [110] + 1/2 [101] → 1/2 [011] It was not possible to have a thin enough crystal with a lateral face parallel to the (110) plane even after deformation and this indicated that the parallelogram shaped specimens were thicker than the rhomboid specimens. All the diffraction patterns obtained from them showed distinctive streaks coming from stacking faults lying on the {111} plane which is perpendicular on the {110} plane. Errors have been found in published tables of interplanar spacings for the mercury lattice and corrected values are included in table 2.1 and discussed in Appendix I. Electron microscopy of crystalline ethyl alcohol showed that its structure is consistent with the face-centred cubic structure, with a lattice parameter of 3.29 +/- 0.02 A.

No description available.

No description available.

It is well reported that the grain size of polycrystalline materials is important in determining mechanical properties. Within this thesis investigations are reported from an inter-comparison of grain size methods, the impact of an incomplete network of grain boundaries after chemical etching (missing boundaries) on grain size measurements and finally the relationship between grain size and the misorientation of grains. The experimental techniques used are manual grain size measurement methods, automatic image analysis and Electron Backscatter Diffraction (EBSD). The materials used are a ferritic, single phased, equi-axed steel (mild steel) and a ferrite/pearlite steel. The relative simplicity of the mild steel microstructure effectively removes complicating factors such as multi-phases or grain elongation allowing a more focused investigation into grain size methods. The ferrite/pearlite steel can be found more readily in industrial applications where impact toughness is an important property. Manual measurement methods and automatic image analysis are used for the inter-comparison of grain size methods. The manual methods are described in the standard ASTM E112, and are the lineal, planimetric, single circle and three circle methods. It is shown that there is a difference across the methods in the number of measurements required to obtain a specified accuracy. Also that sampling is critical to ensure that the measurements made are representative of the microstructure in that it is more important to measure more specimens than more fields of view within one specimen or many grains within one field of view. Automatic image analysis can provide a substantial database and thus is a useful grain sizing method. It is demonstrated that the number of pixels in a digital image forming a grain boundary, determined by the pixel resolution, will influence the measurements. Also from using digital images a specific number of grain boundaries are removed thus artificially creating missing boundaries making their impact on grain size measurements quantifiable. Manual and automatic measurements are conducted and it is shown that the mean grain size is relatively less affected by missing boundaries than might be perceived from a visual inspection. An EBSD map provides a complete network of grain boundaries since a boundary is formed from the orientation of one grain to another (misorientation), compared to standard metallographic techniques, e.g. chemical etching. EBSD maps are compared with optical images of the same fields of view and missing boundaries are then located. From this it is shown that there is a significant difference between two operators in determining the location of boundaries. EBSD is also used to investigate the correlation between the location of missing boundaries and the misorientation of the grains at that boundary and shows a trend of higher misorientation for boundaries not chemically etched up. The final section of this thesis is concerned with the relationship between the misorientation of small/small, small/large and large/large grains and the size of grains of the ferrite phase from the ferrite/pearlite steel. EBSD maps provide the misorientation data and are also used for grain sizing conducted on the automatic image analysis system. From the misorientation data the boundaries can be categorised as low or high angle and it is found that there are more low angle boundaries between small/small grains and small/large grains than between large/large grains.

This thesis describes an investigation into the effects of fluorine substituents on the regioselectivity of intramolecular C–H activation reactions at different transition metals, including Pd, Ir, Rh and Ru. A range of mono- and di-fluorinated N,N-dimethylbenzylamines were synthesised initially and their behaviour towards cyclometallation at Pd was studied (Chapter 2), revealing an unprecedented difference in the regioselectivity of the C–H activation between the formation of acetate- and chloro-bridged palladacycles. The spectroscopic and crystallographic properties of all of these palladacycles are described and analysed in detail. Acetate-bridged palladacycles present a “clam-shell” structure, which shows a dramatic variation with the number and the position of the fluorine atoms on the aromatic ring of the ligand. Conversely the planar chloride-bridged palladacycles do not show any structural variation. Biological assays have been performed on two of the fluorinated amino-derived palladacycles against ovarian cancer cells, revealing promising activity. A series of fluorinated diphenylbenzylphosphines and their corresponding chloride-bridged phosphapalladacycles have also been synthesised (Chapter 3), and a similar regioselectivity observed to that seen for the corresponding amino-derived palladacycles. Various successful attempts at cyclometallation reactions using the fluorinated amines as substrates at Rh, Ir and Ru demonstrate a preference for C–H activation ortho to fluorine (Chapter 4). Finally the synthesis of a novel pentafluorobenzyl phosphine, and some preliminary work towards C–F activation reactions using this substrate at Pt is described (Chapter 5).

Catalytic processes often involve organometallic complexes, the aims of this thesis were to study some specific ruthenium and rhodium complexes using photochemistry. This allowed their behaviour towards small molecules to be investigated since the coordination and activation of small molecules are fundamental parts of catalytic cycles. A further aim was to study suitable complexs with parahydrogen using time-resolved NMR methods with the intention of measuring p-H2 addition and/or the evolution of the p-H2-derived singlet state The photochemistry of CpRh(CH2CHSiMe3)2 (2.1), CpRh(COE)2 (2.2) and CpRh(COD) (2.3) with DMSO PhSOMe, trimethylvinylsilane and triethylsilane was probed. The photoactivity of 2.3 proved minimal with the main products being associated with the loss of the COD ligand. By contrast, 2.1 and 2.2 undergo the substitution of one or both of the alkene ligands, depending on the nature of the reacting ligand. Complexes 2.1, CpRh(CH2CHSiMe3)(DMSO) (2.4) and CpRh(P*Ph)(C2H4) (3.2) were deemed suitable for time-resolved studies with p-H2. 2.1 was found to form the expected dihydride (3.1) on a 50 ms timescale. 2.4 was also formed 3.1 but its PHIP enhancement was poor and whilst 3.1 did form the expected dihydride product PHIP was not observed. [Ru(H)2(CO)(PPh3)(Xantphos)] 5.1 was also synthesised and its reactivity towards a range of small molecules, which included DMSO, CO, ethene and Et3SiH, investigated. These studies revealed that its H2, CO and PPh3 ligands could all be lost photochemically and that the xantphos ligand could switch between κ2-PP and κ3-POP coordination. Time-resolved NMR studies on 5.1, with p-H2, found the H2 addition to the intermediate to occur with a rate of the order of 0.5 s−1. cis-[Ru(H)2(dppp)2] 6.1 was also studied using time-resolved NMR, in this case the rate of H2 addition was faster than the NMR timescales. This allowed the evolution of the p-H2 singlet state to be probed and shown to be as a function of the difference in scalar coupling between the hydrides and the equatorial 31P nuclei.