The Name of the Game: Utilizing Experiential Learning in the Classroom to Engage, Empower and Reflect on Student Learning and Assessment

In the modern post-secondary classroom, there is a push for more experiential and active learning activities for students. A variety of benefits such as engagement, improved learning and self regulated learning have ensued with these different types of learning. Studies regarding these benefits have mostly centered on experiences carefully orchestrated by instructors, rather than experiences that were created by students under the guidance of instructors. Herein is a study of the benefits and efficiency, of the latter type of activity, which requires students to generate chemical puzzles in a large post-secondary classroom. The authors determined that not only is a puzzle generation activity possible, but students’ reflections on instructor examples highlights the potential for learning and for a new form of assessment. Going forward, however, the study also shows more support and examples are required in future iterations of the puzzle framework, to help students create a meaningful experience

Nickel complexes of allyl and vinyldiphenylphosphine

Monodentate phosphine-ligated nickel compounds, e.g., [Ni(PPh3)4] are relevant as active catalysts across a broad range of reactions. This report expands upon the coordination chemistry of this family, offering the reactivity of allyl- and vinyl-substituted diphenylphosphine (PPh2R) with [Ni(COD)2] (COD = 1,5-cyclooctadiene). These reactions provide three-coordinate dinickelacycles that are intermolecularly tethered through adjacent {Ni}-olefin interactions. The ring conformation of such cycles has been studied in the solid-state and using theoretical calculations. Here, a difference in reaction outcome is linked to the presence of an allyl vs vinyl group, where the former is observed to undergo rearrangement, bringing about challenges in clean product isolation

Organocobalt PCcarbeneP Complexes for Small Molecule Activation & SoTL Explorations in the Gamification of Learning in General, Organic, and Polymer Chemistry

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

Nickel Complexes of Allyl and Vinyldiphenylphosphine

Monophosphine-ligated nickel compounds e.g., [Ni(PPh3)4] are relevant as active catalysts across a broad range of reactions. This report expands upon the coordi-nation chemistry of this family, offering the reactivity of allyl- and vinyl-substituted diphenylphosphine (PPh2R) with [Ni(COD)2] (COD = 1,5-cyclooctadiene). These reac-tions provide three-coordinate dinickelacycles that are intermolecularly tethered through adjacent {Ni}-olefin interactions. The ring confirmation of such cycles has been studied in the solid-state and using theoretical calcula-tions. Here, a difference in reaction outcome is linked to the presence of an allyl vs. vinyl group, where the former is observed to undergo rearrangement, bringing about challenges in clean product isolation

Facile Deoxygenative Reduction of a Bridging Carbonato Ligand with Silyl and Boryl 4,4’-Bipyridinylidene Reagents

The reactivity of CO2 with a previously described PCcarbeneP cobalt(I) hydroxide is reported. Insertion of CO2 into the Co-OH bond followed by a dehydration reaction releasing water results in a cobalt(I) bridging carbonate species featuring fluctional κ1: κ1 and κ1: κ2 coordination of the central carbonate moiety. The reduction chemistry of the resulting cobalt(I) bridging carbonate species is explored utilizing deoxygenative reducing agents N,N′-bis(trimethylsilyl)- and N,N′-bis(pinacolatoboryl)-4,4′-bipyridinylidene. The three-electron reduction produces the corresponding PCcarbeneP cobalt(I) siloxide or boroxide complex alongside a PCcarbeneP cobalt(0) monocarbonyl, silyl/boryl ether, and 4,4’-bipyridine

A Monoboranyl Analogue of 1,2-bis(di-tert-butylphosphino)ethane

Examples of unsymmetric diphosphines, especially those with customized secondary coordination spheres, are rare. Herein, we provide an approach towards a Lewis acid-containing analogue of the bulky diphosphine, 1,2-bis(di-tert-butylphosphino)ethane that contains a single boron moiety. The coordination chemistry of this ligand and its allyl precursor have been explored using nickel(0)

On the Realties of Base Metal Catalysis: An Overview

This perspective invites conversation concerning base metal catalysis as a green and sustainable solution in industrial and academic contexts. We explore what it means to be ‘sustainable’ and provide information on current efforts in synthetic chemistry. We establish a definition of a base metal and reflect on what considerations might apply to that definition. Throughout, we offer recent case studies, highlighting topics relevant to ligand development, metal sourcing, recyclability, and comparative reactivity using precious metal relatives. We challenge non-specialist readers to consider how, where, and why base metal catalysts are utilized. Finally, we offer social context, asking broad questions relevant to social acceptability. For example, decisions related to catalyst development are often driven by factors including costliness, safety, social adoptability, and performance. How can we move base metal catalysis to the forefront? Does society really care if materials are fabricated from nickel instead of palladium or platinum? How can our community guide this knowledge translation? Is this a job for us alone

Carbene Character in a Series of Neutral PCcarbeneP Cobalt(I) Complexes – Radical Carbenes Versus Nucleophilic Carbenes

Cobalt(I) complexes supported by a series of PCcarbeneP pincer ligands of varying donicity, differing in the aryl group linking the phosphine arms with the anchoring carbon donor, are described. Addition of the proligands to cobalt bromide results in the formation of a series of cobalt(II) tetrahedral complexes, Ln-1, which serve as excellent precur-sors to the corresponding PCalkylP and PCcarbeneP complexes. Square planar cobalt PCcarbeneP complexes, L2R-3-X (X = Cl, Br), are readily synthesized by addition of a bulky aryloxide radical to the corresponding PCalkylP complex, L1-2-Br or via addition of L2R to ClCo(PPh3)3 in the presence of trityl radical or by addition of NaHBEt3 and trityl radical to iso-lated L2R-1. For the L2NMe2 PCcarbeneP complexes, salt metathesis reactions with either CsOH·H2O, LiCH2TMS, or LiNH2 result in the corresponding hydroxo, alkyl, and amine complexes, L2NMe2-3-R (R = OH, CH2TMS, NH2). Reaction of L2NMe2-3-OH with benzoic acid affords the 2-O2CPh derivative The nature of the carbene bond in either ligand plat-form as well as the effects of the X-type capping ligand on the Co=C bond are explored computationally and show that triplet structures are relatively more stable in for the less electron donating ligand L1 while singlet Co(I) carbenes dominate for the more electron rich L2 derivatives. For L2NMe2 complexes, the effect of the trans ligand X was also probed. Pi donors imbue the carbene with singlet character while the strongly donating alkyl derivative exhibits significant triplet character

Oxygen Atom Transfer to Cationic PCPNi(II) Complexes Using Amine-N-Oxides

International audienceThree PCsp3P pincer ligands differing in the aryl group linking the phosphine arms with the anchoring carbon donor were used to support square planar Ni(II) bromide complexes 1-3(Br) Exchange of the coordinating bromide anion for the more wealdy coordinating triflate (OTf) or hexafluoroantimonate (SbF6) anions was accomplished by treatment with AgX or TIX salts to give compounds 1-3(x); compounds 1(OTf) 1(sbF6), 2(Br), 2(OTf), 3(Br) and 3(sbF6) were all characterized by X-ray crystallography. The reactions of these Ni(II) compounds with the amine-N-oxide oxygen atom transfer agents ONMe3 and ONMePh2 were explored. For ONMe3, reactions with 2 equiv gave products in which one arm of the pincer ligand was oxidized to a P=0 unit, with the other amine-N-oxide ligated to the Ni(II) center, forming products 5-6(x); compounds 4(OTf), 5(OTf), and 6(sbF6) were characterized crystallographically. Transient amine-N-oxide adducts prior to ligand oxidation were observed in some reactions. For the more effective 0 atom donor ONMePh2, reactions were very rapid and a second oxidation of the remaining phosphine arm was observed, producing a Ni(II) species with an OCO pincer ligand (7(sbF6)). All compounds were fully characterized. Experiments aimed at trapping transient Ni(IV) oxo intermediates (with cyclohexadiene, KH, and various Lewis acids) indicated that such species were not involved in the reaction. This was supported by density functional theory (DFT) computations at the B3PW91 level, which indicated that direct 0 atom insertion into the Ni-P bonds without the intermediacy of a Ni oxo species was the low-energy pathway