Abstract Magnetic, spectrophotometric and dielectric measurements have been made with a series of tetraco-ordinated complexes of copper(II) with N-alkylsalycylaldimines, in order to account for the orientation polarization shown by these chelates in benzene and dioxane solution. The magnetic moments of these compounds measured between 90 and 400°K lie between 1·83 and 1·90 B.M. and are essentially independent of temperature. They remain practically unchanged when the solids are dissolved in benzene. This is not to be expected if the compounds have a tetrahedral structure in solution. The high values of the difference P 2∞− P E found for these chelates even in “non-co-ordinating” solvents like cyclohexane and carbon tetrachloride do not support the assumption that asymmetrical pentaco-ordinated adducts with a mole of solvent are formed in solution. Such results are in accord with the hypothesis already put forward by us that in solution the above complexes have a flattened pyramidal structure.