[Formulae and special characters can only be approximated here. Please see the pdf version of the abstract for an accurate reproduction.] Group 15 Lewis base adducts of Group 11 coinage metal salts of the form MX : L (1:n), where M=Cu(I),Ag(I),Au(I); X=(pseudo-)halide (Cl,Br,I,SCN,CN) and oxyanion; L-uni- or bi-dentate pnicogen ligand and n=1-4, may adopt monomeric, dimeric, oligomeric or polymeric structural forms. For the purpose of this study, the pnicogen bases are divided into two groups: the 'harder' nitrogen base ligands and 'softer' phosphine/arsine/stibine ligands. A sizeable body of structural data exits for adducts of silver(I) salts. Those with uni-dentate nitrogen base ligands are usually restricted to readily accessible liquid bases such as pyridine and its derivatives. The extension of such series to encompass ligands with more varied base characteristics may assist in the access of new bonding modes and stereochemistry, leading to control of these and of stoichiometry. Herein a number of complexes of copper(I) salts with uni-dentate nitrogen and bi-dentate phosphine/arsine/stibine adducts with differing degrees of complexity have been characterized, extending the known range of structural forms. Systematic variations in stoichiometry, halide, ligand and solvent of crystallization have provided a range of complexes whose structures have been determined by single crystal X-ray diffraction techniques. The structural relationship between these and other known adducts, often including their silver analogues, are considered, permitting comparisons of various common features and differences. The first section of this thesis (Chapter 3 and Chapter 4) reports a number of complexes of the form CuX : L (1:n) (CuX)Ln, L=uni-dentate nitrogen base ligand with n=1-3, the second section (Chapter 5 through Chapter 10) reports adducts with bi-dentate bis(diphenylpnicogeno)alkane ligands, Ph2E(CH2)xEPh2 (whereE=P,AS,Sb and x=1-6). The structural types and copper(I) coordination environments are influenced by CuX (salt) : ligand stoichiometry, the stereochemistry and basicity of the ligand, the type and size of the counter-ion (where applicable) and crystallization solvent. The structural types found for copper(I) (pseudo-)halide and oxyanion species are similar to those found for their silver(I) analogues, although the transitions between structural types may occur with different pnicogen and halide atoms, consequent on the smaller size of the copper(I) ion and differences in stereochemical preferences.