Organocobalt PCcarbeneP Complexes for Small Molecule Activation & SoTL Explorations in the Gamification of Learning in General, Organic, and Polymer Chemistry
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2021-12
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Abstract
As global energy and environmental challenges increase, chemists have shifted their focus to the development of sustainable chemical systems for the conversion of small molecule chemical feedstocks (H2, H2O, NH3, CH4, etc.) to value-added products. For example, the capture and conversion of carbon dioxide has become a prominent feature in discussions surrounding the encroaching climate crisis and remains a global initiative for sustainability platforms moving forward. Electrochemistry and synthetic organometallic chemistry have made strides, converting CO2 to alternative C1 chemical feedstocks such as CO, CH4, and various carbonates. One method to evoke small molecule activation beyond classical oxidative addition or Werner’s coordination, is to introduce catalysts capable of metal ligand cooperation in which both the metal and the ligand participating in the bond activation. One such example is the use of metal carbene complexes which have been found to perform 1,2-addition chemistry across the metal-carbon bond. While many carbene complexes utilizing 2nd and 3rd row transition metals have been found effective at activating small molecules, chemists are focusing on the implementation of abundant, low cost first row transition metals (Fe, Co, Ni) into these frameworks for the development of sustainable catalytic systems. This thesis presents the synthesis and characterization of a variety of new PCcarbeneP cobalt complexes featuring the well established PCP ligands developed in the Piers group. The electronic state of the carbene bond was found to be highly dependant on the electron donicity of the ligand framework. More strongly donating pincer ligands were found to increase the energy gap between a singlet (S = 0) and triplet (S = 1) state carbene, resulting in electrophilic characteristics at the donor carbon. The effects of the X-type capping ligand on the singlet-triplet energy gap were also explored utilizing the promising dimethylamino-anthracene based ligand. Strong π-donors were found to increase the energy gap while σ-donors were found to stabilize the triplet state. With newly developed PCcarbeneP cobalt(I) complexes in hand, the activation and reduction of CO2 was explored. Addition of CO2 to PCcarbeneP cobalt(I) hydroxide results in the formation of a bridging carbonate species upon release of H2O. Stoichiometric reduction of the bridging carbonate species was accomplished through addition of 1.5 equivalents of N,N′-bis(trimethylsilyl)- or N,N′-bis(pinacolatoboryl)-4,4′-bipyridinylidene resulting in the two-electron reduction of CO2 to CO, and reduction of one cobalt center to Co(I) yielding a cobalt(0) monocarbonyl complex and cobalt(I) siloxide or boroxide species. Each of the new complexes was able to be separately synthesized. Future applications of a PCcarbeneP cobalt(I) chloride with N2O are discussed alongside additional reactivity of the bridging carbene complex. Finally, this thesis describes a series of chemistry learning activities focused on experiential and gamified learning for use in postsecondary classrooms. Activities such as ChemEscape, a hybrid escape room game, incorporating chemistry learning objectives were developed for a series of courses including general, organic, and materials chemistry. The activities were found to be highly engaging and motivating for students, providing a new avenue for skill application. Activity alterations to provide similar gamified learning in an online environment in response to the COVID-19 pandemic are discussed.
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Clapson, M. (2021). Organocobalt PCcarbeneP complexes for small molecule activation & SoTL explorations in the gamification of learning in general, organic, and polymer chemistry (Doctoral thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca.