The oxidation and exchange reactions of simple phosphorus compounds and the behaviour of a range of low valent triphenylphosphine complexes of the transition metals in liquid hydrogen chloride at room temperature were studied by (^31)P nuclear magnetic resonance spectroscopy. When oxidation did occur, the phosphorus was oxidised from the +3 to the +5 oxidation state. In general, five co-ordinate fluorine containing phosphorus(V) species were produced from the oxidation of phosphorus(III) fluoride and four co-ordinate species of type PBr(_x)C1(_4-x)(^+) (O ≤ x ≤ 4) from the oxidation of phosphorus(ill) bromide or chloride. The (^31)P n.m.r. chemical shifts of the complete series PBr(_x)C1(_4-x)(^+) (O ≤ x ≤ 4) were recorded in solution for the first time, stabilised by tetrachloroborate anions in liquid hydrogen chloride. The protonation of a series of oxygen containing phosphorus (V) compounds in the solvent at room temperature was investigated using P n.m.r. spectroscopy. A measure of the "acidity" of liquid hydrogen chloride was obtained from comparison of chemical shift values with values for the protonated species in other acidic room temperature solvents. The behaviour of the boron trihalides and tetrahaloborate ions in the solvent at room temperature was studied by (^11)B n.m.r. spectroscopy. The behaviour of low valent triphenylphosphine complexes of iron, cobalt, nickel, copper, ruthenium, rhodium, palladium, iridium, platinum31and gold in the solvent was investigated using (^31)P n.m.r., and where appropriate (^11)B n.m.r., spectroscopy. Protonation of the iron(O)complexes Fe(CO)(_5-x)(Ph(_3)P)(_x)(x = 1,2) in the presence of the Lewis acid BC1(_3) was observed. Oxidative addition reactions took place between the iridium(l) and rhodium(l) complexes (Ph(_3)P)(_2)M(CO)C1 (M = Ir,Rh) and the solvent. Finally, the oxidation of platinum(O) to platinum(II) in reactions between tris- and tetrakis (triphenylphosphine)platinum(0) and liquid hydrogen chloride was observed. Products were characterised by elemental analysis, Raman and infrared, and (^31)P and (^11)B nuclear magnetic resonance spectroscopy.

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An introduction to microporus materials, their individual properties and uses is presented. The rational synthesis of these materials is also discussed in terms of suitable 'building blocks'. The work focuses on the structure, synthesis and reactions of the aluminium chlorophosphate ethanoate tetramer known as ACPE using x-ray diffraction and solution and solid state n.m.r. techniques. The synthesis route of this small structure has been studied and its crystal structure re-determined enabling its complex hydrogen-bonded structure to be fully determined. The ACPE unit has been used as the starting material for the non-templated synthesis of the aluminophosphate AlP04-H3 and also the templated synthesis of AlPO-15, UiO-15 and AlPO-12. Reaction mechanisms for these materials have also been suggested based on the use of the ACPE starting material as a building block. It was shown that certain addition reduced the rate of formation of some of these phases. The structure of the krypton sorbed complex microporous material, chabazite, has been studied. The krypton sites have been determined over a range of temperatures. This has enabled the preferential desorption of krypton atoms from specific sites to be determined for the first time in a microporous material using single diffraction. In addition at 190K, a change in the mode of desorption was seen which was accompanied by an anomalous cell change.

The work presented in this thesis describes the synthesis, structure and reactivities of a range of low oxidation state main group metal complexes. The work upon this subject is divided into six chapters. Chapter 1 provides a general introduction to the group 13 elements, low oxidation state group 13 chemistry and group 13 diyls. This chapter also describes the synthesis, theoretical treatments and reactivities of N-heterocyclic carbenes and their main group 13, 14 and 15 analogues, with a focus on the group 13 N-heterocyclic carbene analogues. Chapter 2 describes an investigation into the formation of transition metal complexes of an anionic gallium(I) N-heterocyclic carbene analogue, K(tmeda) Ga{ N(Ar)C(H) 2} , Ar = 2,6- diisopropylphenyl. These studies highlighted three different mechanistic pathways by which complexes could be isolated. Initially, substitution of a carbonyl ligand by the gallium carbene analogue in transition metal half sandwich carbonyl complexes was investigated. This yielded, for example, the first structurally authenticated Ga-V bond in K(tmeda) CpV(CO)3 Ga{ N(Ar)C(H) 2} , Cp = cyclopentadienyl. Secondly, the direct donation of the gallium carbene analogues lone pair of electrons towards a manganese dialkyl fragment gave the complex K(tmeda) Mn{CH(SiMe3)2}2 Ga{ N(Ar)C(H) 2} . Finally, the salt metathesis reactions of the gallium carbene analogue with a series of Lewis base stabilised transition metal di-halides were explored. Results include, a series of complexes taking the structural form M(tmeda) Ga{ N(Ar)C(H) 2} 2 , M = Mn, Fe, Co, Ni, Zn and the first structurally authenticated Ga-Cu bond in Cu(dppe) Ga{N(Ar)C(H)}2 , dppe = Bis(diphenylphosphino)ethane-P,P Chapter 3 details a study into the reactions of a gallium(III) heterocycle, l2Ga{ N(Ar)C(H) 2'} , by the group 2 metals calcium or magnesium. A series of gallium-group 2 metal bonded complexes have been isolated including, for example the first structurally authenticated group 13-group 2 bond in the complex Ca{Ga (N(Ar)C(H))2 }2(THF)4 . Furthermore, a subsequent investigation into the reactivity of an anionic gallium(I) N-heterocyclic carbene analogue, K(tmeda) Ga{ N(Ar)C(H) 2} , towards N-heterocyclic carbenes and imidazolium cations gave, in one case, the novel group 13 hydride complex HGa{ N(Ar)C(H) 2}(IMes) , IMes = l,3-bis(2,4,6-trimethylphenyl)imidazol-2-ylidene. Chapter 4 describes the reactions of a paramagnetic gallium(II) dimeric complex, {(Bul- DAB )GaI}2 , with the alkali metal pnictides, ME(SiMe3)2 (M = Li or Na E = N, P or As). These reactions have led to a series of paramagnetic gallium(III)-pnictide complexes, (Bul- DAB)Ga{E(SiMe3)2}I (E = N, P, As) and (Bul-DAB)Ga{E(SiMe3)2}2 (E = P, As). The complex (Bul-DAB)Ga{As(SiMe3)2}I possesses the shortest Ga-As single bond yet recorded. Chapter 5 details an investigation into the reactivity of a amidinato germanium chloride complex, (Cl)Ge{N(Ar)C(But)N(Ar)} . This complex has been shown to participate in a range of different reactions. These are, salt metathesis giving, for example, the complex {(CO)2Fe(n5- Cp)}Ge{N(Ar)C(Bul)N(Ar)} and donation of a lone pair of electrons giving {(CO)5W}(Cl)Ge{N(Ar)C(But)N(Ar)} . Furthermore, an investigation into the synthesis of a range of amidinato bismuth complexes by salt metathesis is described. The first structurally characterised amidinato bismuth complexes, for example (u2-Br)Bi(Br) {(2,6- 'Pr2C6H3)N}2C(H) (THF) 2 , have been isolated and subsequent reductions have been attempted in some cases. Finally, chapter 6 describes some aspects of group 13 hydride chemistry and details the attempted syntheses of group 13 metal(II)-metal(II) bonded species. Complexes, for example QuinAl(H)2 tempo , Quin = l-azabicyclo 2.2.2 octane, tempo = 2,2,6,6-Tetramethyl-l- piperidinyloxy were isolated from reactions of a radical abstraction agent with Lewis base adducts of group 13 trihydrides.

The hydrogen evolution reaction (HER) has been examined on a variety of Pt and Pt-group metal surfaces to investigate the rate of the reaction. Pt stepped single crystal surfaces were investigated in relation to the HER using cyclic voltammetry, linear sweep voltammetry and multi-frequency AC voltammetry. It was found that the hydrogen evolution reaction activity did not show a dependence on the structure of single crystal platinum electrode surfaces. Thick films of Au, Rh and Pd were deposited onto Pt {111} and successfully annealed to give pseudomorphic surfaces of the bulk metal. The aim of such measurements was to investigate whether strains within the crystal lattice of these films would result in enhanced HER activity. None of the surfaces investigated showed significant HER enhancement. Rather, results similar to those observed using the bulk metals were obtained. Rough Ir and Pt deposits on Pt{111} were also investigated. Enhanced HER activity was observed on these surfaces. This enhancement was interpreted in terms of the structural arrangement of the Ir and Pt deposits. For Pd films on Pt {111} (0 < fVPd < 2 monolayers) it was observed that Pt dominated the HER kinetics for Pd coverages up to one monolayer and was still influential on the HER at two monolayers of Pd. Similarly Pd-Pt surface alloys also showed that Pd had little or no influence on the HER kinetics even with 75 % Pd in the surface layer. Possible mechanisms for this behaviour have been proposed, in particular, the role of subsurface hydrogen in HER on Pt is discussed.

The work presented in this thesis describes the synthesis, structure and stability of a range of halido, hydrido and heterocyclic complexes of the group 13 elements. The underlying theme is the synthesis of low valent group 13 complexes. The work upon this subject is divided into five chapters. Chapter 1 provides a general introduction to the members of group 13 and to low oxidation state group 13 halide chemistry. The history of binary group 13 metal trihydride complexes and the reasons behind their inherent instability are also discussed. Chapter 2 details the use of a stable nucleophilic N-heterocyclic carbene, l,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene. (IPr), and nitrogen donor ligands, namely a bulky diazabutadiene (Ar-DAB), Ar = 2.6-Pr'2C6H3. quinuclidine and formamidinate, in the formation of group 13 trihalide complexes. A series of metal trihalide complexes have been prepared and characterised, e.g. InBr3(L) . L = IPr or Ar-DAB, whose reduction reactions with alkali metals did not yield low valent metal metal bonded group 13 species. In addition, the reactivity of "Gal" towards pyridine based ligands is described: 'Gal* reacts, for example, with 2.2'-bipyridine (bipy) to give salts of composition Ga(bipy)3 I 3, ((bipy)2Ga}2(u-OH)2 : Ga2l6 l 6 or {(bipy)2Ga 2(u-OH)2 I 4. depending upon the reaction conditions. All new compounds have been crystallographically characterised. Chapter 3 introduces the reactivity of diazabutadienes (Ar-DAB or Bul-DAB) towards low oxidation state group 13 iodides which afforded, for example, the paramagnetic compounds. {IGa(But-DAB)}2, I2Al(Ar-DAB) and {CHn(Ar-DAB)}2 which have been characterised by X-ray crystallography and EPR spectroscopy. In addition, the synthesis of the second example of an anionic gallium(I) N-heterocyclic carbene analogue. {(TMEDA)KGa(Ar-DAB)}2, is described. This complex displays a Ga Ga interaction in the solid state which is unprecedented for this complex type. Chapter 4 lists reactivity studies of a new gallium(I) carbene analogue, {(TMEDA)KGa(Ar-DAB)} 2. towards main group halide complexes. These studies led to some decomposition products which are paramagnetic and have been studied both crystallographically and by EPR spectroscopy. The reactivity of the gallium carbene analogue towards sources of oxygen has been investigated and the complex, ((u-0)Ga(Ar-DAB)2}2 2 from the reaction with N2O. has been isolated and structurally characterised. In addition, an unprecedented 7t-cyclopentadienyl bridged digallane complex, {Ga(Ar-DAB)2h{u-CpK(TMEDA)2}. incorporating the first structurally characterized -interaction with a Ga(II) center, results from the oxidative coupling of an anionic gallium(I) heterocycle with cyclopentadienyl thallium(I). Chapter 5 introduces the known hydride chemistry of indium and describes the synthesis of a number of novel group 13 hydride complexes. These include the preparation and characterisation of the first examples of amido indium hydride complexes, one of which has unprecedented thermal stability. In addition, these studies led to the first covalently bonded metal complexes derived from an anionic gallium carbene analogue, one of which, InH2{Ga(Ar-DAB)}2 Li(TMEDA)2, contains the first example of a structurally authenticated In Ga bond. This chapter also includes the preparation and characterisation of a subvalent pentaindium cluster compound.

A new generation of diode lasers is being developed using quantum dots as the gain generating medium. A detailed understanding of the carrier recombination mechanisms and optical gain generation is essential for optimisation of their performance. The aim of this work is to further understand the optical processes occurring in quantum dots. In particular, the effect of the localisation of the energy states in the dots on the recombination mechanisms and the gain/absorption is studied. It is often assumed that the rates of nonradiative recombination via defects, radiative recombination and Auger recombination are proportional to linear, quadratic and cubic functions of the carrier number respectively. The derivation of these functional forms is possible in quantum well and bulk structures because the extended electronic states make it meaningful to talk of a global carrier population. In a quantum dot system the dependence of the recombination processes on the total number of electrons populating the dots is modified by the localisation of all the recombination processes. In this thesis a computer model has been developed in which the dots are occupied by integer numbers of electrons and holes, with electron and hole occupancies controlled by Fermi-Dirac statistics. The recombination processes have similar dependences on the electron number and there is no clear transition from one process to another as the injection level is increased. These dependences cannot be represented by simple power law functions of the carrier number. An alternative model, in which each dot is electrically neutral, has also been studied, and the two models show significant differences for the hole distribution as the injection is increased. It is found that analyses based on power law relations between recombination rates and carrier number, as used for extended state systems, cannot be applied to localised recombination in dots.

This thesis describes the theoretical and experimental study of group 9 and 10 transition metal N-heterocyclic carbene complexes in catalytic reactions. In order to overcome decomposition reactions discovered in the use of carbene complexes for carbon monoxide/ethylene copolymerisation, chelating thiazolium salts were prepared for the synthesis of corresponding palladium complexes. Complex formation proved difficult and experimental attempts to overcome possible side reactions caused by reactant-metal interactions were unsuccessful. Theoretical studies indicated a sulfur-palladium interaction may be contributing to alternative products, with the use of the bulky lBu coordination at the thiazolium 5 position likely to block this interaction enough to allow C2 carbene formation. Theoretical calculations for the oxidative addition of azolium salts to a model Wilkinson's catalyst (RhCl(PH3)3) is described. According to free energy calculations, a six ligand associative route with a concerted three-centred transition structure may be competitive to a route in which phosphine predissociation occurs. Exchange of the phosphine molecule on the metal centre with trimethylphosphine had a significant effect in lowering the barrier to oxidative addition and decreasing the endothermicity of the reaction, while explicit and bulk solvation was found to have a moderate effect on the overall reaction. Extension of the oxidative addition of azolium salts to rhodium carbene complexes have been examined, in which a range of ligands is described from the pi-acidic carbon monoxide ligand to multiple carbene ligands. Increasing basicity decreases activation barriers while increasing the exothermicity of the overall reaction for C-H activation, however the complex most successful at C-H activation was not considered hospitable enough for related C-C activation of 2-methylazolium salts. Switching to iridium indicated a large benefit in C-H activation. Unfortunately, C-C activation remained unfavourable for iridium due to a high barrier to reaction. A mechanism for the experimentally successful C-C coupling of azolium salts to alkenes by nickel complexes is studied, indicating an oxidative addition, alkene insertion and reductive elimination cycle seems likely. Experimentally, the switching of catalytically active phosphine ligands to the related carbenes causes the reaction to be halted. Theoretical calculations imply minor changes to reaction conditions may significantly affect the outcome of catalytic reactions by stabilisation of important reaction intermediates. Further studies of the alternative C4 activation of the azolium salts and use of related azoles show C4 activation and coupling may be possible, while the unactivated azoles are unlikely to be coupled using the same mechanism. (Abstract shortened by UMI.)