The isolation of two series of entirely new types of 4-co-ordinated copper complex, in the pare state, has been described. These are of the type [(X)2.Cu.(A.)] and [(B).Cu.(A)] where A and B repre­sent molecules of two different bifunctional ligands, and X is a neutral molecule like H2O a negatively charged ion like Cl’ or \({1 \over 2}SO_4\)''. The mono-biguanide and glycine-bignanide complexes of copper represent these two interesting types of font co-ordination compounds. The constitution of these compounds has been discussed in the light of their physical and chemical properties including a study of their magnetic susceptibilities and absorption spectra.