<p dir="ltr">The use of redox non-innocent ligands to imbue third-row transition metal complexes with properties emulating those of their fourth- and fifth-row congeners has become an attractive strategy to overcome the limited resources and environmental implications associated with the latter class of metals. The tetra-imine macrocycle, TIM (2,3,9,10-tetramethyl-1,4,8,11-tetraza-cyclotetradeca-1,3,8,10-tetraene), which bears two sets of potentially redox-active α-diimine units, therefore, has been targeted as the ligand scaffold to investigate the structural and electronic properties of various organocobalt(III) complexes within this work.</p><p dir="ltr">First, the reaction between <i>trans</i>-[Co(TIM)Cl₂]⁺ and terminal alkynes (HC₂Ar), in the presence of triethylamine, yielded a series of mono- and bis-alkynyl Co^III(TIM) complexes, as discussed in Chapters 1 and 2. Interestingly, the use of electron-rich terminal alkynes (HC₂Y) favors the formation of products featuring a 1-aza-2-cobalt-cyclobutene unit. As detailed in Chapter 3, the <i>trans</i>-[Co(TIM')(HC=C)Y)Cl]⁺-type complexes (TIM' = the resulting derivative of TIM) were prepared through the addition of HC₂Y to <i>trans</i>-[Co(TIM)Cl₂]⁺ in the presence of KOH. The unprecedented involvement of the TIM ligand was verified crystallographically and through ¹H NMR and FT-IR spectroscopies. In Chapter 4, the properties and influences of the aza-cobalt-cyclobutene are further explored through UV-vis spectroelectrochemical studies on the constitutional isomers, <i>trans</i>-[Co(TIM)(C₂Fc)Cl]⁺ and <i>trans</i>-[Co(TIM')((HC=C)Fc)Cl]⁺ (Fc = ferrocene). Moreover, the reactivity of the Co^III center in the latter complexes is investigated via the reaction with KCN and AgOTf in CH₃CN.</p><p dir="ltr">In Chapter 5, a new facet of Co^III(TIM) reactivity is revealed through the reaction between <i>trans</i>-[Co(TIM)Cl₂]⁺ and HC₂Ar, in the presence of NaBH₄. The reaction generates both mono- and bis-alkenyl complexes along with products containing a 1-aza-2-cobalt-cyclopropane unit. The formation of the former class of products is postulated to proceed through a transient H-Co^III(TIM) intermediate, while the latter is believed to be accessed upon the reduction of an imine moiety within the TIM ligand. Moreover, the generation of the three-membered ring showcases another example of the non-innocent nature of the TIM ligand.</p>