In this thesis the technique of X-ray crystal structure analysis is applied to the study of molecular structure, conformation and bonding in some platinum(ll) and platinum(I) complexes. The contents are divided into three parts. In Part I some of the theoretical and practical aspects of the X-ray diffraction methods, pertinent to the work described in Parts II and III, are surveyed. Part II, which is presented in six Chapters, is concerned with the structures of eight square-planar platinum(ll) complexes. Current views on trans- and cis-influence of ligands and some aspects of metal-phosphorus bonding are first reviewed (Chapter 1). This is followed by a description of the crystal structure analyses of three platinum(II) complexes containing the novel ligand PMe2C6F5 (Chapter 2). The interest is centred on the effect of electron-withdrawal of phosphine substituents on the metal-ligand bonding. Chapter 3 is devoted to the structure analyses of the complexes cis-PtCl2(PEt3)L, where L=PEt3 and CO. This work completes a systematic study of such complexes and the results are discussed in terms of the cis and trans-influence of the ligands. The constancy of the observed triethyl-phosphine conformation in square-planar platinum complexes has led to molecular mechanics calculations on the triethylphosphine molecule, which are also described. In Chapter 4 the structure of a platinum(II) complex which provides the first known example of a metallated phosphine-carborane is described. The interest in the effect of strongly electron-withdrawing substituents on sulphur- donor atom on metal-ligand bonding has led to determination of the crystal structure of cis-PtCl2(CF3SCH2CHMeSCF3), presented in Chapter 5. Chapter 6 is devoted to the structure analysis of trans-[PtCl(COEt)(PMe2Ph)2 . This complex displays an unusually large 1J(Pt-P) coupling constant. The X-ray study was carried out in order to examine the correlation between Pt-P bond lengths and coupling constants in bridged binuclear platinum(II) species. Part III is concerned with the structure analyses of two closely similar and novel platinum(l) complexes, which contain direct metal-ligand bonds
