<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)Cl<sub>2</sub>]<sup>+</sup> and terminal alkynes (HC<sub>2</sub>Ar), in the presence of triethylamine, yielded a series of mono- and bis-alkynyl Co<sup>III</sup>(TIM) complexes, as discussed in Chapters 1 and 2. Interestingly, the use of electron-rich terminal alkynes (HC<sub>2</sub>Y) 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]<sup>+</sup>-type complexes (TIM' = the resulting derivative of TIM) were prepared through the addition of HC<sub>2</sub>Y to <i>trans</i>-[Co(TIM)Cl<sub>2</sub>]<sup>+</sup> in the presence of KOH. The unprecedented involvement of the TIM ligand was verified crystallographically and through <sup>1</sup>H 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)(C<sub>2</sub>Fc)Cl]<sup>+</sup> and <i>trans</i>-[Co(TIM')((HC=C)Fc)Cl]<sup>+</sup> (Fc = ferrocene). Moreover, the reactivity of the Co<sup>III</sup> center in the latter complexes is investigated via the reaction with KCN and AgOTf in CH<sub>3</sub>CN.</p><p dir="ltr">In Chapter 5, a new facet of Co<sup>III</sup>(TIM) reactivity is revealed through the reaction between <i>trans</i>-[Co(TIM)Cl<sub>2</sub>]<sup>+</sup> and HC<sub>2</sub>Ar, in the presence of NaBH<sub>4</sub>. 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<sup>III</sup>(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>
| Identifer | oai:union.ndltd.org:purdue.edu/oai:figshare.com:article/25590492 |
| Date | 12 April 2024 |
| Creators | Leobardo Rodriguez Segura (18349830) |
| Source Sets | Purdue University |
| Detected Language | English |
| Type | Text, Thesis |
| Rights | CC BY 4.0 |
| Relation | https://figshare.com/articles/thesis/_b_Put_A_Ring_On_It_The_Discovery_And_Investigation_Of_The_Non-Innocence_Of_TIM_In_CO_b_sup_strong_III_strong_sup_b_TIM_Complexes_b_/25590492 |
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