Metal-Ligand Cooperation (MLC) has been under study over the past two decades as a powerful tool for small molecule activation and functionalization. However, more mechanistic details are needed in order to understand the detailed steps that are enabled by the bifunctional cooperation between ligand and metal. In this regard, the hydroboration reaction offers a useful platform through which to assess the details of bifunctional reaction pathways and catalyst speciation. This dissertation focuses on the synthesis, characterization, and catalytic activity of base-metal complexes with cooperative N-, S-, and O-donor ligands to explore reaction pathways that are a consequence of diverging from traditional phosphine-based ligands. In Chapter 1 concepts and examples of MLC, especially as applied to hydroboration catalysis, are presented. In Chapter 2, three new Zn(II)-(κ²-SNS)₂ complexes were synthesized to directly compare the bifunctional catalytic activity rendered by amido and thiolate SNS ligands. Although all three complexes catalyzed carbonyl hydroboration, a detailed catalyst speciation study showed that the Zn amido complex reacts with pinacolborane (HBpin) to generate Zn-H and an unbound borylamido ligand. Subsequent substrate-derived zinc alkoxide formation followed by a second equiv of HBpin generates the product, regenerating the Zn hydride catalyst. In contrast, the Zn thiolate complex adds HBpin to the ligand imine unit, followed by aldehyde deoxygenation to give a benzothiazoline heterocycle and [Zn](OBpin). Reaction of the latter with HBpin then gives pinBOBpin and Zn-H, leading to the same active catalyst as that derived from the Zn amido precatalyst! For these systems, then, the bifunctional N- and S-donors serve to activate the catalyst rather than participating in a bifunctional catalytic cycle. Dissociation of the borylamido SNS ligand in Chapter 2 led us to reinvestigate a previously reported Cu(I) amido complex Cu[(κ²-SNS)(IPr) that was proposed to hydroborate carbonyls via an outer sphere process [IPr = bis(2,6-diisopropylphenyl)imidazol-2-ylidene]. Indeed, we showed that this complex also undergoes ligand borylation-dissociation to form the active catalyst [CuH(IPr)]₂ which had been reported previously as a carbonyl hydrosilylation catalyst. To compare these complexes with their heavier Group 10 analogue, we prepared and structurally characterized the silver amido SNS complex. Interestingly, this complex was not able to serve as a carbonyl hydroboration catalyst. Then we sought to use the MLC catalyst activation strategy to prepare an especially active Zn hydride hydroboration catalyst. Using a bidentate amine-pyrollide ligand with an aryl ether side-group, the 5-coordinate Zn complex, Zn(κ²-ONN)₂(DDI) (2.11Zn) was prepared and structurally characterized (DDI = 4,5-dichloro-1,3-dimethylimidazol-2-ylidene). On treatment with excess HBpin, formation of ONN(Bpin)₂ [(Bpin)₂-L3] gave rise to the reactive NHC-stabilized ZnH₂ catalyst that effected the rapid hydroboration of nitriles and quinoline derivatives under ambient conditions with only 0.01 and 0.05 mol% catalyst loading, respectively. In Chapter 3, in an attempt to prepare a cobalt complex containing both amido and thiolate SNS ligands, we obtained instead the Co(II) dithiolate complex, Co(κ³-SNS)(DDI) (3.2Co). This complex showed a unique selectivity for aldehyde hydroboration, over other functional groups such as ketones, cyanides, nitriles and olefins. A DFT study, in collaboration with Prof. Erin Johnson from Dalhousie University, showed that 3.2Co bifunctionally assembles the HBpin and aldehyde substrates, with Co binding the aldehyde oxygen and sulfur binding the boron of HBpin. With aromatic aldehyde substrates, interesting aromatic-aromatic dispersion effects led to catalyst inhibition which could be reversed by simply rinsing off the product with hexane. These effects were not observed for catalytic hydroboration of aliphatic aldehydes. In Chapter 4 we focused on expanding our MLC investigation to include additional donors beyond N and S. First, a dimeric Zn(II)-(κ⁴-NSNO) complex (4.1Zn) was synthesized and evaluated as a catalyst for nitrile dihydroboration to compare aryloxide and amido donors for B-H bond activation. In fact, 4.1Zn successfully catalyzed dihydroboration of a range of different aromatic and aliphatic nitriles under neat condition. Mechanistic studies determined that the aryloxide donor activates the B-H bond in the first step and the mechanism then likely proceeds through an inner-sphere insertion. As detected by our kinetic study, at high turnovers the catalyst decomposes when Bpin also binds to the amido donor. To compare the potential of other donors for B-H bond activation, a series of divalent NiᴵᴵX(κ³-NNN) complexes were synthesized, with X = bromide (4.3Ni), phenoxide (4.4Ni), thiophenoxide (4.5Ni), 2,5-dimethylpyrrolide (4.6Ni), diphenylphosphide (4.7Ni), and phenyl (4.8Ni), and employed as precatalysts for nitrile dihydroboration. Superior activity of the phenoxy derivative (vs. thiophenoxy or phenyl) suggests that B-H bond activation occurs at the Ni-X (vs. ligand Ni-N_pyrrolide) bond. Furthermore, stoichiometric treatment of 4.3Ni-4.8Ni with a nitrile showed no reaction, whereas stoichiometric reactions of 4.3Ni-4.8Ni with pinacolborane (HBpin) afforded the same Ni-H complex for 4.3Ni, 4.4Ni and 4.6Ni. Considering that only 4.3Ni, 4.4Ni and 4.6Ni successfully catalyzed nitrile dihydroboration reaction, we suggest that the catalytic cycle involves a conventional inner sphere pathway initiated by substrate insertion into Ni-H. In summary, our investigations confirm the importance of mechanistic studies and catalyst speciation for studies involving potential bifunctional catalysis. In Chapter 5 we summarize the findings of this thesis, placing them in the context of the current state of the art and speculating on future investigations they may enable.

Cette thèse décrit l'étude réalisée sur des complexes portant le ligand pince indendiide, incluant leur synthèse et caractérisation ainsi que leur activité en catalyse coopérative métal/ligand de cycloisomérisation d'acide alcynoïques et N-tosyl alkynylamides. Le premier chapitre fait un point bibliographique non-exhaustif du domaine de la catalyse coopérative métal/ligand, des premiers travaux précurseurs de Noyori sur les processus d'hydrogénation avec des complexes amido de ruthénium aux récents travaux de Milstein avec des complexes pince à base de pyridine déaromatisée. Le deuxième chapitre porte sur le développement de nouveaux complexes pince indendiide du Pd et leur application en catalyse coopérative métal/ligand. La modification structurale réalisée, remplacement des substituants Ph sur l'atome de phosphore par des iPr, visait à augmenter la robustesse des complexes et améliorer ainsi leur performance en catalyse. Deux nouveaux complexes ont été préparés et entièrement caractérisés (RMN, IR, DRX). Les premières évaluations d'activité catalytique ont en effet révélé une meilleure activité de ces nouveaux complexes comparés à leurs prédécesseurs, puisqu'ils sont capables de cycloisomériser de manière efficace les N-tosyl alkynyl amides. Une large gamme de substrats a été étudiée, incluant N-tosyl alkynyl amides linéaires non-substituées et substituées, d'autres à base de squelette phénylène, et même celles à alcyne en position interne. De manière générale, une majorité d'exo-lactames est formée avec des très bons rendements (~90%) sauf lorsque l'alcyne est en position interne, cas dans lequel l'endo-lactame est formée préférentiellement. Il est important de souligner que le résultat phare de ce chapitre est la préparation pour la première fois de methylène lactames à 7-chainons par cycloisomérisation. Malgré les avancées notables atteintes dans ce chapitre, la grand modularité des complexes pince étudiés permet d'espérer des améliorations du système catalytique. Ces améliorations sont présentées lors du troisième chapitre. Il s'agit ici de remplacer l'atome de Pd par le Pt. Les nouveaux complexes préparés ont été évalués dans la cycloisomérisation de acides alcynoïques et N-tosyl alcynyl amides et le meilleur d'entre eux a été identifié (dimère à groupement iPr sur l'atome de P). A nouveau une large gamme de substrats, acides et amides, a été étudiée faisant varier la taille de cycle et la position de l'alcyne. La stratégie s'est avérée fructueuse puisque de manière générale ce complexe de Pt s'est montré plus actif que l'équivalent à base de Pd. En particulier, ce complexe présente une activité remarquable pour la transformation d'alcynes internes et la formation de cycles à 6 et 7-chaînons. La connaissance approfondie du mécanisme de la réaction a conduit aussi à l'utilisation d'additifs donneurs de liaison H afin de favoriser la réaction de cyclisation. Grâce à l'utilisation du pyrogallol, la vitesse de réaction et la sélectivité 6-endo (vs 5-exo) et 6-exo (vs 7-endo) ont été améliorées de manière significative. Pour la première fois, une grande variété de d et e-lactones et lactames ont pu être préparées avec des très bonnes sélectivités et rendements. L'ensemble de ces résultats souligne les propriétés uniques de ces complexes pince indendiide et étend leurs applications catalytiques. / This work contributes to the study of new indenediide pincer complexes, including their synthesis, characterization, and finally their activity in metal-ligand cooperative catalytic cycloisomerization of a range of alkynoic acids and N-tosyl alkynylamides. The 1st chapter compiled a non-exhaustive bibliographical survey of the field of metal-ligand cooperation in catalysis, from the pioneering work of Noyori using amido-Ruthenium complexes for hydrogenation, to the recent work of Milstein with pincer complexes based in dearomatized pyridine. The 2nd chapter of this thesis is dedicated to the development of the newly-tuned Pd indenediide pincer complexes and their application in metal-ligand cooperative catalysis. A structural modulation, by varying the R substituents Ph at phosphorus with iPr, was performed in attempt to increase the robustness of the Pd pincer complexes and enhance thereby their catalytic performance. Thus, two novel complexes were successfully synthesized and fully characterized (NMR, IR, XRD). Initial study demonstrated a better performance of the new complexes than their predecessor, as the cycloisomerization of N-tosyl alkynyl amides can be efficiently achieved. Moreover, the N-tosyl alkynyl amide scope was extensively studied, from linear non-substituted C5-C7, then substituted, benzo-fused, and finally to internal alkyne ones. Eventually, a majority of exo lactams products, together with the unusual internal endo lactam can be prepared in excellent yields (most often 90 %). Note that the obtaining for the first time of 7-member ring methylene caprolactam via a cycloisomerization was pretty inspiring. Nevertheless, improvements for the current catalytic system remain. The 3rd chapter of this thesis is devoted to further modulation of the pincer complexes, in particular the switching of metal center from Palladium to Platinum. The newly-synthesized Pt complexes were evaluated in the cycloisomerization of N-tosyl alkynylamides and alkynoic acids, and the dimeric complex with iPr groups at the P atoms exhibited the best performance. The substrate scope was further extended to more challenging ones. In most cases, reactions were remarkably accelerated. Direct comparisons upon amides and acids bearing internal alkyne further indicated that the Pt complex outperformed its Pd analogue. In particular, the Pt pincer complex is extremely efficient for the formation of 6 and 7-membered rings. In light of in-depth understanding of the mechanism, several selected additives were employed as H-bond donor, to reinforce the cyclization. The reaction rate and selectivity for 6-endo (vs 5-exo) as well as 6-exo (vs 7-endo) cyclizations was greatly improved by using pyrogallol. For the first time, a large variety of d and e-lactones/lactams could be prepared with high selectivities and in very good yields. These results emphasize the unique properties of SCS indenediide pincer complexes and extend further their catalytic applications.

The purpose of this doctoral thesis is to investigate and develop catalytic processes mediated by iridium(III) complexes. By understanding the mechanisms, the weaknesses of the designed catalysts can be identified and be overcome in the following generation. The thesis is composed of two general sections dedicated to the synthesis and applications of homogeneous catalysts and to the preparation of heterogeneous catalysts based on metal-organic frameworks (MOFs). After a general introduction (Chapter 1), the first part of the thesis (Chapters 2-4, and Appendix 1) covers the use of several homogeneous bifunctional [Cp*Ir(III)] catalysts in a variety of chemical transformations, as well as mechanistic studies. Chapter 2 summarizes the studies on the N-alkylation of anilines with benzyl alcohols catalyzed by bifunctional Ir(III) complexes. Mechanistic investigations when the reactions were catalyzed by Ir(III) complexes with a hydroxy-functionalized N-heterocyclic carbene (NHC) ligand are discussed, followed by the design of a new generation of catalysts. The chapter finishes presenting the improved catalytic performance of these new complexes.    A family of these NHC-iridium complexes was evaluated in the acceptorless dehydrogenation of alcohols, as shown in Chapter 3. The beneficial effect of a co-solvent was investigated too. Under these base-free conditions, a wide scope of alcohols was efficiently dehydrogenated in excellent yields. The unexpected higher activity of the hydroxy-containing bifunctional NHC-Ir(III) catalysts, in comparison to that of the amino-functionalized one, was investigated experimentally. In the fourth chapter, the catalytic process presented in Chapter 3 was further explored on 1,4- and 1,5-diols, which were transformed into their corresponding tetrahydrofurans and dihydropyrans, respectively. Mechanistic investigations are also discussed. In the second part of the thesis (Chapter 5), a Cp*Ir(III) complex was immobilized into a MOF. The heterogenization of the metal complex was achieved efficiently, reaching high ratios of functionalization. However, a change in the topology of the MOF was observed. In this chapter, the use of advanced characterization techniques such as X-ray absorption spectroscopy (XAS) and pair distribution function (PDF) analyses enabled to study a phase transformation in these materials. / <p>At the time of the doctoral defense, the following paper was unpublished and had a status as follows: Paper 3: Submitted.</p>

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