Extended H$ddot{u}$ckel molecular calculations have been used to analyze how the magnitude of exchange coupling is influenced by the structural distortions in a series of dinuclear six-coordinate copper(II) complexes bridged by the planar bis-bidentate oxalate anion. Copper(II) ions have distorted octahedral surroundings, one being axially elongated and the other compressed. The magnetic interaction is strong in the former complexes and very weak in the latter. This is interpreted as resulting from a switching of magnetic spin orbitals due to the structural distortions (bond elongation or compression) of the copper sites.