Research on the chemistry and structural aspects of ortho-substituted-arylcopper and -cuprate compounds in which the ortho-substituents either interfere sterically with the C(ipso)-to-copper bonding or have a potentially coordinating heteroatom, is described. Concluded is that the simple arylcopper and ortho-ligand substituted arylcopper compounds have many similar structural features. However, the self-complexed copper compounds have an essential extra feature; i.e. the number of possible aggregates is much more restricted since only in a few aggregate structures can all ortho-ligands equally partake in the bonding to copper. At present, new achievements have been made in the rational design and synthesis of organo(arylthiolate)copper derivatives that contain a Lewis-acidic copper centre. The successful application of these mixed organo(arylthiolate)copper compounds in 1,4-addition reactions with alpha,beta-unsaturated ketones is ascribed to prior coordination of the unsaturated substrate to the Lewis-acidic copper centre.