The effect of the coordination of o-phenanthroline to zinc diisobutylxanthate (Zn(xant)(2)) and zinc diisobutyldithiocarbamate (Zn(dtc)(2)) on their inhibiting activity in the initiated oxidation of squalane C30H62 (S-q) with oxygen in a chlorobenzene solution at 75 degreesC was studied. In the absence of o-phenanthroline, Zn(xant)(2) and Zn(dtc)(2) retard the initiated oxidation of squalane, the former complex being more active. Additional coordination of o-phenanthroline to Zn(xant)(2) leads to the loss of the inhibiting activity by this complex and decreases the efficiency of Zn(dtc)(2) in the squalane oxidation process. The mechanism of the deactivating action of o-phenanthroline was proposed. The voltammetric parameters on a rotating graphite electrode were determined for the initial chelates and their adducts with o-phenanthroline.