The work described in this Thesis is a study of the synthesis and reactivity of some giant osmium carbonyl clusters and an investigation into their magnetic and electronic properties. Chapter One contains an overview of the concept of the chemical bond from Dalton to the present day ideas of Wade and Mingos, and their application to transition meial clusters. Chapter Two is an investigation into the fluxional and dynamic behaviour of mixed-metal clusters in solution using multinuclear N.M.R. (lH,iaC, and 3lP{1H}). The clusters [Os10C(CO)24MPR3]-(M = Cu, Ag or Au) and [Os1oC(CO)24(MPR3)(M>PR3)] (M = M'= Ag or Au, and M 5* M' Ag and Au) have been examined using these techniques. Chapter Three reports the synthesis of the dianion [Os11C(CO)27]2~, a cluster containing a trigonal prismatic geometry and its reaction with elec-trophiles such as H+, I2, [Cu(NCMe)4]PF6, AuPR3Cl and AgBF4. THe X-ray structure of [HOsnC(CO)27]~ is described, and the conversion of [OSllC(CO)27]2- to [Os10C(CO)24]2-. Chapter Four is concerned with the synthesis of giant osmium clusters using [Os10C(CO)24]2"~ as a precursor and reacting it with Hg(CF3COO)2 to form [Os20Hg(C)2(CO)42]2-, [Os30Hg2(C)3(CO)72]2-and [Os40Hg3(C)4(CO)oe] • The corresponding gold derivatives, [Os10C(CO)24AuBr]- and [Os20Au(C)2(CO)40]2~ have also been prepared and fully characterised by X-ray crystallography. Chapter Five describes the use of l87Os-1H satellites and Inversion-Recovery 1H n.m.r. as aids in the study of the dynamic behaviour of hydrido osmium carbonyl clusters in solution. In particular the work has focussed on differentiating between hydride ligands in tetrahedral or octahedral interstitial sites. The improved synthesis of [H4Osio(CO)24]3~ is reported and its reactions with electrophiles are discussed. The dianion reacts with H+ to form [H5Os10(CO)24]~ which has been characterised by an X-ray structural determination. Chapter Six presents UV/visible, magnetic and EPR measurements on a range of osmium carbonyl clusters prepared in Chapters Two to Five. A molecular orbital framework for understanding these results is presented. Finally Chapter Seven contains the experimental section and spectroscopic data.

A general interacting boson model of clustering in nuclei is presented. The model is then specialized to the case of n identical α-clusters [U(6) (CRTIMES) U(4)] , followed by a detailed study of the SU(3) dynamical limit. Many useful formulae are derived in this limit. The general problem of coexistence and configuration mixing is discussed, and a useful SU(3) bank mixing approximation (BMA) is presented. Formulae for the case of two mixed configurations are derived. The method of calculating the matrix elements for two-nucleon transfer reactions is demonstrated, and formulae for α-decay reduced widths are given. This model is then utilized for the study of the systematic trends of the data available for actinide nuclei. Most of the results presented here are for the well-deformed even-even mass actinides with A < 242; however, some trends in going to the spherical region and to larger A are studied. Tests, based on experimental data, are presented to discriminate between different limits of this model, and between this and other models. The limit of the model presented here satisfies all of the experimental tests found, while all other competing models were found to have serious deficiencies. This phenomenological study indicates that α-clustering effects are of fundamental importance for understanding the structure and dynamics of actinide nuclei. Suggestions for future research are made, some of which are based on preliminary work that has already been done.

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