Title:
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Studies of ruthenium and osmium carbonyl clusters with unsaturated cyclic hydrocarbons
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Chapter one contains a brief summary of the cluster-surface analogy, with a structural comparison between metal clusters and the chemisorbed state. Particular emphasis is directed towards the adsorption sites adopted by benzene on the metal surface, and the analogous coordination modes found in cluster compounds. Chapter two describes the synthesis and characterisation of a number of benzene and cyclic C6 alkene containing clusters based on an osmium tetrahedral framework, in which the chemistry is dominated by C-H bond activation reactions. Chapter three deals with the analogous ruthenium chemistry, in which a butterfly arrangement of the four metal atoms seems to predominate. An example of cluster mediated ring contraction and its relevance to surface chemistry is discussed, as is the synthesis of an octaruthenium benzene cluster. The molecular organization of arene cluster complexes in the solid-state is also presented. Chapter four introduces the [2.2]paracyclophane molecule as a new class of π-ligand in organometallic chemistry, and describes the synthesis of a number of ruthenium cluster derivatives, one of which is considered to be a key intermediate in the formation of carbido-atoms in such species. Unique metal polyhedra, and an unusual coordination mode for CO are described. Chapter five gives a detailed account of the reactivity of the triruthenium and hexaruthenium-carbido [2.2]paracyclophane clusters with ligands such as alkynes, phosphines and dienes. Products are discussed which serve as models for the chemisorption of benzene on the metal (111) surface. Chapter six presents the experimental details and spectroscopic and crystallographic data for all compounds synthesised throughout the work described in this thesis.
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