Oxidative degradation of the pentadentate ligand is observed when rac‐1 is allowed to react with O2, in solution. The products are 2, formaldehyde, and diphenyl disulfide. The first step of the reaction is most likely an addition of O2, to the Ni center, since solid rac‐1, in which the sixth coordination site of the Ni atom is occupied by an O atom of a second molecule of 1, is inert towards O2. (Figure Presented.) Copyright © 1990 by VCH Verlagsgesellschaft mbH, Germany