Oxidations of a trigonal-bipyramidal, high-spin Ni(II) dithiolate complex of a pentadentate, N3S2-donor ligand, N1,N9-bis(imino-2-mercaptopropane)-1,5,9-triazanonane) nickel(II), and the structurally analogous Zn(II) complex, lead to oxidations of the ligand. Oxidation of the Ni(II) complex with 12 produces a novel Ni(II) macrocyclic cationic complex containing a monodentate disulfide ligand (2). Crystals of the 13 salt of the complex form in the triclinic space group P, with cell dimensions a = 8.508(3) Angstrom, b = 9.681(2) Angstrom, c = 14.066(4) Angstrom, angles alpha = 90.97(2)degrees, beta = 91.61(3)degrees, gamma = 90.83(2)degrees, and Z= 2. The structure was refined to R = 6.31% and R-w = 16.63% (l > 2sigma(l). Oxidation of the Ni(II) complex with O-2 leads to the formation of a novel pentaclentate bis-iminothiocarboxylate complex with trigonal-bipyramidal geometry (3). This neutral product crystallizes in the monoclinic space group P2(1)/c with cell dimensions a = 13.625(3) Angstrom, b = 7.605(5) Angstrom, c = 14.902(4) Angstrom, angles alpha = gamma = 90degrees, beta = 102.81(2)degrees, and Z = 4. The structure was refined to R = 7.18% and R-w = 17.86% (l > 2sigma(l)). Oxidation of the Zn(II) dithiolate analogue with 02 leads to the formation of the Zn(II) complex of the pentaclentate bis-iminothiocarboxylate ligand. The neutral complex is isomorphous with the Ni(II) complex and crystallizes in the monoclinic space group P2(1)/c with cell dimensions a = 13.8465(4) Angstrom, b = 7.6453(2) Angstrom, c = 15.0165(6) Angstrom, angles alpha = gamma = 90degrees, beta = 103.2140(11)degrees, and Z = 4. The structure was refined to R = 3.96% and R-w = 9.45% (l > 2sigma(l). Details of the crystal structures are reported. Kinetics of the O-2 reactions show that the reactions of the Ni(II) and Zn(II) dithiolates follow the rate law, Rate = k2[l][O-2], with k2 = 1.81 M-1 s(-1) for the Ni(II) complex and k(2) = 1.93 x 10(-2) M-1 s(-1) for the Zn(II) complex. The O-2 oxidation of the high-spin Ni(II) thiolate complex was found to follow a similar oxidation mechanism to those of low-spin Ni(II) complexes, which form transient persulfoxide intermediates that yield S-oxidation products, In the case of the high-spin system reported here, the transient persulfoxide intermediate gives rise to an alternative ligand oxidation product, a bis-iminothiocarboxylate complex, because of the reactivity of the ligand, which contains a methylene with acidic H atoms alpha to the thiolate sulfur, The proposed mechanism is supported by studies of the analogous Zn dithiolate complex, which gives rise to the analogous bis-iminothiocarboxylate product (5).