A new (CNC) pmcer ligand, (2,6-bis(2,6-diisopropylphenyl)imidazol-2-ylidene)-3,5dimethylpyridine, has been synthesised. the previously reported ligand (2,6bis( 2,6-diisopropylphenyl)imidazol-2-ylidene)pyridine, (CNC) pincer complexes of transition metals across the from titanium to iridium, have been synthesised, fully characterised and investigated. NHCs, trialkylphosphines and imines as canied out. complexes of (CNC) and (PNP) were better a-donors than tpJI,;TP) ligands, in complexes of (CNC), (PNP) and (NNN) better a-donors, contrary to literature reports. keeping ligands A comparison of the cr-dlon:ltlnlg nroDlerties part of pincer ligands ligands revealed to coordinated vinyl groups have been observed (CNC) ligands. Proposed mechanisms indicate the to the CNHC followed by base-catalysed thougflt the latter occurs via a 4-membered nitrogenbinding mode for NnCs also been un:suullrated backbone of an imidazol-2-ylidene ring bonds in an 172 is centre.

Inorganic oxynitride materials, with potential applications as pigments, have been synthesised and characterised in terms of their crystal structure, band gap energies and physical properties using powder X-ray and powder neutron diffraction (PXD,PND), solid state UV-Visible spectroscopy, L*a*b* colour measurements, scanning electron microscopy (SEM), energy dispersive analysis of X-rays and thermal analysis. Oxynitride perovskites, AII,IIIBV(O,N)3, where A is a group 2 or lanthanide metal and B an early transition metal have been synthesised by the direct ammonolysis of stoichiometric metal oxides and carbonates at high temperatures, typically 850°C, with the inclusion of group 1 and 2 metal halide salts acting as mineralisers. Powder X-ray diffraction studies show the synthesised perovskites to have primarily an orthorhombic distortion, crystallising in the space group Pnma, similar to CaTaO2N. Exceptions include compounds crystallising in a rhombohedral system, Ca0.77Eu0.23TaO1.77N1.23 or in a monoclinic system, LaTaON2. PXD profiles have highlighted the presence of a competing pyrochlore phase, which becomes more prevalent as the radius of the divalent and trivalent cations decreases such that perovskite phases for smaller lanthanides do not form. Neutron diffraction studies show that the oxygen to nitrogen ratio in the orthorhombic perovskite is Ca0.5Nd0.5TaO1.5N1.5 and there is a slight ordering of O/N over the two anionic sites. In the octahedra forming the framework, the axial positions have greater nitrogen occupancy, whereas the equatorial positions favour oxygen. In contrast to this, the group 2 substitutions onto the lanthanide position in LaTaON2 yielding A(1-x)LaxTaO(2-x)N(1+x), have shown a random distribution of oxygen and nitrogen over both positions. UV-Visible spectroscopy of these oxynitrides reveal broad reflectance bands and a steep absorption edge, which is directly related to the and gap energy of the compound. By varying the doping levels on the B site with transition elements other than Ta such as Nb, Ti, W and Zr, the colour of the compound can be seen to visibly alter. Solution methods, such as co-precipitation techniques, have been employed to deposit oxide precursors onto mica flakes, which are then fired under flowing ammonia to target thin films of oxynitride pigment on mica to produce interference effects. SEM has shown the presence of two separate morphologies, mica and pigment, thus resulting in unsuccessful depositions. Although the pearlescent nature of mica remains after heat treatment with ammonia, solution methods do not yield the same intense colours seen by the solid state route. This necessitates the use of halide salts to target pigments with high quality hues but this destroys the pearlescent effects seen in mica.

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Inorganic framework materials, with structures based on arsenate As04 tetrahedra and a variety of additional trigonal, tetrahedral or octahedral units have been synthesised by hydrothermal methods. The framework topologies of these materials have been characterised by single crystal X-ray diffraction; additional techniques, including thermogravimetric analysis and SQUID magnetoinetry, have been used to assess properties ofsome materials. Iron arsenates with 2D and 3D framework topologies are reported; these include structures templated by piperazine; 1,4-diaminobutane, DABCO, Fe2As207·2H20 and LiFeAs040H. The boron arsenic system has been investigated using a molten salt technique and a variety of alkali metal templates. A total of ten boroarsenate materials have been characterised, including [Cs2CBAs030H)s(As04)2] [(CsCI4)]CI, which is templated on both anions and cations and a family of materials XBAs04F ex = Cs, Rb, NHt). Hydrothermal techniques have been used to produce arsenate frameworks in combination with molybdenum, zinc and scandium. Two 'zinc arsenate materials with new framework topologies have been synthesised; a chiral framework with 16-ring channels and a 2D layer framework, both with caesium templates. Five scandium arsenate frameworks have been synthesised and are characterised; three have the same basic framework structure but with differing amine templates. Further new compounds have been synthesised by evaporating solutions of ainines with metal chloride or arsenate covnter-ions; these include three arsenate DABCO structures and a related phosphate DABCO material. Zinc chloride, cobalt chloride and hydrated manganese chloride salts with piperazinium counter-ions were also synthesised. Hydrothermal syntheses with vanadium reagents resulted in the formation of five new structures - a vanadium arsenate; a vanadium oxalate; a nickel vanadate cluster cap'ped by 2,2bipyridyl and isostructural nickel and cobalt metavanadates, NiV20 6·H20 and CoV206·H20. Powder neutron diffraction was used to show the isostructural,materials possessed differing magnetic cells. During investigations into copper arsenate framework materials, four new copper halide coordination polymers were discovered. Two materials with tetramethylammonium (TMA) templates - CU2Br3(TMA) and CU2I3(TMA) - and a DABCO templated structure CU2Ch(DABCO) share a common stoichiometry but were shown to possess different structural motifs. A fourth material discovered, CU7I7(DABCOhs, forms a· complex 3D organic-inorganic hybrid framework.

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