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Ligands involving CNC structures have been of intense interest in research. With an aim to investigating this area, a modular synthesis was developed using condensation reactions between a base unit of 2,6-dichloroisonicotinic acid and N-alkyl imidazoles toprovide a range of 2,6-bis(imidazolium) salts. From this point several methods wereavailable to incorporate an active metal centre, however, state of the art microwaveaccelerated synthesis was found to be the most successful technique in forming the tridentate palladium complexes. Several strategies were investigated to attach these complexes to polymer resins, exploring a range of linking groups, coupling procedures and resins. The most effective strategy involved forming an acid functionalised palladium complex to allow loading onto an amino-functionalised resin. Although several reagents were investigated it was found that the commercially available reagent PyBop® was the most effective in forming the stable amide bond from the palladium complex to the polymer resin. By using an excess of coupling reagent and an excess of the acid functionalised palladium complex complete loading onto an amino functionalised resin could be achieved.The supported complexes were found to be highly stable catalysts in Heck, SuzukiMiyauraand Stille reactions, and capable of cross-coupling a range of aryl iodides in very high yields. The active catalysts showed very little leaching of palladium (ICPMS) and could be recycled up to fourteen times with no loss of activity. Long reaction times were overcome using tetra-n-butylammonium bromide as an additive or by using microwave irradiation. Following these catalytic studies and with an aim to using less active electrophiles, several strategies were investigated to develop enhanced activity catalysts. These strategies involved replacing one of the N-Heterocyclic carbene ligands with either an "inert" bulky group or with another alternative ligand. Full details of this research are presented in chapters 2 to 5.

The thesis describes the synthesis, characterisation and magnetic properties of some novel well-defined paramagnetic polymetallic arrays based on the 3d metal ions Fe(III), Ni(II) and Cu(II). Chapter 1 begins with an overview of modern applications of paramagnetic assemblies and then examines synthetic strategies that can be employed for their preparation before identifying the aims and objectives set for the thesis. In Chapter 2, the reactivity of a ligand blend consisting of a combination of two different bifunctional 2-pyridine alcohols [drawn from 2-{(CH­2)nOH}-6-X-C5H3N] (X = H or halide; n = 0 -- 3) towards M(OAc)2.xH2O (M = Ni, Cu) in the presence of triethylamine is systematically examined. In Chapter 3, neutral and charged {M2}, {M3} and {M4} (M = Ni or Cu) species are accessible on treatment of M(OAc)2.xH2O with a ligand blend consisting of benzilic acid and [2-{(CH2)nOH}-6-X-C5H3N] (X = H, or halide; n = 0 -- 3). A study of the role of the base employed (NEt3 vs. NaOMe) on product type has also been investigated. The presence of very weak magnetic exchange interactions is a feature of the open dicuboidal dianion {Ni4}2- prepared. In Chapter 4, isophthalic acid and [2-{(CH2)nOH}-6-X-C5H3N] (X = H or halide; n = 1 -- 3) are used as components of the ligand blend in combination with M(OAc)2.xH2O affording polynuclear mixed-ligand {M2} (M = Ni, Cu) complexes. In contrast, the combination of isophthalic acid and an aryl-substituted formamidine leads to the neutral spheroidal {Cu24} clusters (nanoballs) and in one case to a 1-D {Cun} polymer; strong antiferromagnetic behaviour is a feature of the nanoball. In Chapters 5 and 6, a selection of discrete polynuclear iron complexes [e.g., {Fe2}, {Fe4}, {Fe6}, {Fe8}, {Fe10} and {Fe11}] containing mixed-ligand sets have been prepared. In Chapter 7, full details of the experimental procedures along with spectroscopic, analytical and X-ray data (ca. 50 structures) are reported.

The reaction of PQQ-dependent methanol dehydrogenase (MDH) has been studies by steady-state and stopped-flow kinetic methods, with particular reference to multiple ligand binding and kinetic isotope effects (KIEs). Phenazine ethosulphate (PES; an artificial electron acceptor) and cyanide (a suppressant of endogenous activity), but not ammonium (an activator of MDH), compete for binding at the catalytic methanol-binding site. MDH activity is dependent on activation by ammonium, bit is inhibited at high ammonium concentrations. Glycine ethyl ester (GEE; an alternative activator) does not inhibit enzyme activity to the same degree as ammonium. Data suggest a close spatial relationship between the Ks and Ki activator-binding sites such that binding of GEE to the Ks site sterically impairs binding of GEE to the Ki site. Cyanide is less effective at suppressing endogenous activity with GEE, which is attributed to impaired binding of cyanide at the catalytic site through steric interaction with GEE at the Ks site. Combined, this data suggests that the catalytic methanol-binding site and the K s and Ki sites are in close proximity. PES and substrate influence the stimulatory and inhibitory effects of activator through competitive binding, giving rise to unusual KIEs as a function of activator and PES concentration. The KIEs are independent of temperature, consistent with the proposed competitive binding model. Stopped-flow studies indicate that at high ammonium concentrations, the oxidative half-reaction becomes more rate-limiting. With GEE, the oxidative half-reaction makes a larger contribution to rate limitation, stopped-flow method has enabled study of the reductive half-reaction of MDH. A kinetic mechanism for the reaction cycle of MDH is proposed. Furthermore, this study emphasises the need for caution in using KIEs, and the temperature dependence of KIEs, as a probe for enzymatic hydrogen tunnelling.

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