Iron β-diketiminate complexes have great potential as catalysts. Previous work into the coordination chemistry of complexes bearing the β-diketiminate ancillary ligand (Chapter 1) attest to the useful properties of these complexes in catalysis. A handful of literature reports on catalytic systems hint that this could be further extended. Hydrophosphination is a growing field that continues to generate a lot of interest from industry and academia alike. The aims of this project are to investigate hydrophosphination reactions with iron β-diketiminate complexes, to achieve high degrees of regioselectivity from these sterically encumbered complexes and to investigate iron catalysed dehydrocoupling reactions. A combination of synthetic and mechanistic methodologies will be employed in order to achieve definitive insight via NMR spectroscopic analysis, kinetic studies and solid state crystallography. Initial work presented herein (Chapter 2) will focus on the synthesis of iron(II) β-diketiminate complexes. Previously reported literature methods will be explored in order to determine an optimum procedure to use these precatalyst complexes. Initial investigations into hydrophosphination activity of these iron species will then be explored with alkenes. Results of these studies led to serendipitous findings and unexpected results in phosphine dehydrocoupling. The scope of this reactivity was then probed and mechanistic considerations taken into account with findings detailed herein. Radical catalysed reactivity observed will be further discussed. Solvent selectivity will then be discussed with a simple yet highly effective solvent change yielding a complete shift in catalytic activity. Further studies (Chapter 3) highlight the orthogonal reactivity of iron(II) β-diketiminate complexes in hydrophosphination catalysis. Less electronically activated and more atypical substrates have been investigated to determine their activity in hydrophosphination reactions. The synthesis of phosphinoalkenes and phosphinoalkynes for cyclic intramolecular hydrophosphination reactions are detailed along with their catalytic activity. Preliminary mechanistic studies are discussed with radical species again proving crucial to catalytic activity. Selective intermolecular hydrophosphination reactions have been investigated with alkynes. A solvent based switch can be employed wherein the regioselectivity of the reaction is completely altered. Substrate scope, mechanistic considerations and potential future applications are examined in full detail. Dehydrocoupling catalysis can be extended in scope (Chapter 4) from iron catalysed phosphine homocoupling reactions to heterocoupling reactions. Phosphine-silane dehydrocoupling is found to be highly selective for the formation of silaphosphanes, preliminary mechanistic insight and reaction scope is discussed. Analogous amine-silane dehydrocoupling is explored in full. The substrate scope offers insight into reactivity and potential further applications in sequential and tandem catalysis. In depth mechanistic insight is discussed with kinetic analyses. Iron-amido complexes are observed to react in a metathesis mediated cycle via iron hydride species. Finally catalytic alcohol-silane dehydrocoupling is investigated as a synthetic route to protected natural products in organic synthesis. Unsaturated silazanes are potential targets for further dehydrocoupling reactions. Catalytic reactions with pinacolborane led to highly facile desilylation reactions (Chapter 5). Mechanistic considerations hint that the reactions occur via σ-bond metathesis could through iron hydride species. Desilylation activity is then extended to siloxanes and a model developed with potential applications in the depolymerisation of polysilazanes and polysiloxanes.

This thesis presented the synthesis and reactivity of metal complexes for the hydrophosphination of alkenes and dehydrocoupling of phosphines. The mechanism of these metal-catalyzed P-H activation reactions was explored. Half-sandwich Cp*Ru complexes (Cp*= 1,2,3,4,5-pentamethylcyclopentadienyl) were developed as catalysts for hydrophosphination, based on the previous work in the Rosenberg group. Cp*Ru phosphido complexes, Ru(h 5 -Cp*)(PR2 )(PR2 H)2 (Ru-1) were found to be the vital intermediates for the hydrophosphination. Preliminary mechanistic studies also indicate that the catalyst resting state is Ru(h5 -Cp*)(PR2 )(PR2 H)(P) (P = hydrophosphination product) and intramolecular P-H bond cleavage is turnover-limiting. These investigations provide sufficient parallels to our established chemistry of the indenyl analogues to imply that conjugate addition of metal phosphido at alkene plays a significant role in these half-sandwich catalytic systems. The increased steric crowding at the Cp*Ru fragment and P-basicity/nucleophilicity of its phosphido complexes lead to a 30-fold increase in the hydrophosphination activity in the Cp* system compared to the indenyl catalysts. A half-sandwich Co catalyst, Co(h 5 -Cp*)I 2 (CO) (Co-1), was also developed for hydrophosphination along the lines of the conjugate addition mechanism. Similar to the Cp*Ru system, the substrate scope for alkene is limited to electron-deficient alkene. However, the Cp*Co catalyst significantly expands the substrate scope for phosphines (PR2 H and PRH 2 , R = alkyl and aryl). A detailed mechanistic study on the Cp*Co system was performed. The results show that the Co-catalyzed hydrophosphination occurs through iv an outer-sphere mechanism and the stoichiometric formation of diphosphine is a critical catalyst activation step. Since the side product diphosphine was formed during the Co-catalyzed hydrophosphination, using complex Co-1 as a catalyst for dehydrocoupling phosphines was investigated. The preliminary studies reveal the role of base and Cp* ligand in the catalysis. Additionally, the study highlights the importance of removing dihydrogen throughout the process. Thus, hydrogen acceptors (HA) were used to facilitate the dehydrocoupling reactions. Last, the novel P-H activation process between Cp*Co complexes [Co(h5 -Cp*)(NCCH 3 ) 3 ][SbF 6 ] 2 (Co-5) and excess PPh2 H was investigated through various analytical techniques. / Graduate / 2023-09-08

Catalytic hydrophosphination has enormous potential in the selective preparation of value-added organophosphines, despite the challenge of the reaction. This dissertation aims to address the hurdles in catalytic hydrophosphination with respect to substrate scope, selectivity, and reaction conditions using [қ5 –N,N,N,N,C– (Me3SiNCH2CH2)2NCH2CH2NSiMe2CH2]Zr (1). Compound 1 readily engages with a suite of primary phosphines. These are challenging substrates for this reaction, but 1 readily provides high conversions with these substrates. Increasingly large primary phosphines, including chiral phosphines, undergo catalysis with 1. Furthermore, a variety of underreported unsaturated substrates can be functionalized in catalytic hydrophosphination with 1. Alkynes are underreported substrates, but 1 showed not only catalytic reactivity with internal alkynes, but also the first example of a double hydrophosphination with these substrates. Almost entirely absent from catalytic hydrophosphination are unactivated alkenes, yet 1 catalyzes them with TON and TOF that now rival those of styrenes. Additionally, a new tandem inter- and intramolecular diene hydrophosphination was reported to give cyclic phosphine products. The selectivity in catalytic hydrophosphination 1 in all processes is novel in many regards. In alkyne hydrophosphination, vinyl phosphines or double hydrophosphination products could be isolated as secondary phosphines, depending on reaction conditions. For alkenes, secondary or tertiary phosphines can be formed by modification of the reaction stoichiometry. Isolated secondary phosphines were further elaborated into chiral tertiary phosphines. Catalytic hydrophosphination with a chiral, air-stable primary phosphine gave chiral secondary phosphine products. Efforts to synthesize a chiral ligand to close the gap on catalysts (and therefore substrates) for asymmetric hydrophosphination are discussed. Catalysis with 1 proceeds under photolysis. Direct irradiation of 1 by ultraviolet or visible light during alkene hydrophosphination substantially enhanced catalytic activity. For example, previous reports of styrene hydrophosphination with 1 showed TON = 18 and TOF = 1.5 h-1. Under irradiation, the process is substantially more efficient (TON = 20 and TOF = 60 h-1) and the substrate scope is expanded. Computational and spectroscopic data indicate that photoexcitation results in a charge transfer in the active catalyst, which appears to accelerate catalysis by promoting substrate insertion based on a linear freeenergy relationship. The impressive substrate scope, mild conditions, and increased catalytic activity from photoexcitation, rather than heat, are among the best reported for the reaction. Identification of a photoexcitation event that promotes substrate insertion may enable enhanced reactivity from other metal catalysts for this transformation.

Phosphorus-containing metallacycles formed from the [2+2] cycloaddition of unsaturated substrates at the Ru-P π-bond of [Ru(η5-indenyl)(PCy2)(PPh3)] (2) were examined as possible intermediates relevant to hydrophosphination. Reagents, intermediates, products, and by-products involved in the [2+2] cycloaddition were identified and analyzed for reactivity and stability. The products, metallacycles of the form [Ru(η5-indenyl)(κ2-RCHCH2PCy2)(PPh3)] (4), were found to undergo facile cycloreversion. An ethylene η2-coordination adduct was directly observed by low temperature 31P{1H} NMR as an intermediate in the [2+2] cycloaddition mechanism. Steric and electronic effects of alkene substituents on metallacycle formation and selectivity were investigated in detail through rate constant and activation parameter determination, as well as collaborative computational DFT analyses and the construction of a Hammett plot. Preliminary attempts at releasing phosphinated products from ruthenacycle complexes via protonolysis and phosphine substitution were conducted. An unexpected metallacyclic product of one of these attempts, [Ru(η5-indenyl)(κ2-CHCHPCy2)(PPh3)] (10), was identified and characterized. / Graduate

La chimie des métaux alcalino-terreux lourds (calcium, strontium et baryum) a longtemps été décrite comme difficile et imprévisible contrairement à la chimie du magnésium, leur plus léger congénère. Cependant, au cours des dernières décennies, de nombreux complexes basés sur ce type de métaux ont émergés en tant que précatalyseurs efficaces pour un grand nombre de transformations organiques (polymérisation, hydroélémentation, couplage déshydrogénants, etc..). Cette thèse décrit la synthèse et l’étude (expérimentale et théorique) de nouveaux complexes de baryum de basse coordinance basée sur l’utilisation de ligands alcoolates pauvres en électrons. L’étude de ces composés a permis d’améliorer notre compréhension des différents phénomènes nécessaires à la stabilisation de tels composés. Dans un second temps, deux nouveaux systèmes de couplages déshydrogénants BO‒H/H‒Si et SiO‒H/H‒Si ont été développés et étudiés. Ces systèmes ont permis la formation catalytique de borasiloxanes et de siloxanes dissymétriques de façon sélective. Enfin, ces travaux montrent la synthèse et l’utilisation de nouveaux ligands ancillaires pour la formation de complexes hétéroleptiques de baryum stables. Ces derniers ont démontré une forte activité catalytique en hydrophosphination intermoléculaire avec des TOF pouvant atteindre 200 h-1 pour l’hydrophosphination du styrène par la HPPh2. / Heavy alkaline earth metals chemistry (calcium, strontium and barium) has been described as difficult and unpredictable for a long time, unlike the chemistry of magnesium, their lightest congener. However, in the last decades, many complexes based heavy alkaline earth metals have emerged as effective precatalysts for many applications and organic transformations (polymerization, hydroelementation, dehydrogenating coupling, etc.). This thesis describes the synthesis and study (experimental and theoretical) of new low-coordinate barium complexes based on electron-poor alkoxide ligands. The study of these compounds has improved our understanding of the different phenomena required to stabilize such compounds. Then, two new dehydrocoupling systems BO-H/H-Si and SiO-H/H-Si were developed and studied. These systems have allowed the catalytic formation of borasiloxanes and asymmetric siloxanes in a selective manner. Finally, this work shows the synthesis and use of new ancillary ligands for the formation of stable heteroleptic barium complexes. The latter have demonstrated strong catalytic activity in hydrophosphination with TOFs up to 200 h-1 for the intermolecular hydrophosphination of styrene by HPPh2.

In this thesis, the synthesis and reactivity of metal complexes containing phosphido (PR2−) and phosphenium (PR2+) ligands for the hydrophosphination of alkenes were investigated. The mechanisms of hydrophosphination mediated by these M-PR2 fragments were explored. Based on previous work in the Rosenberg group, Ru(η5-indenyl) complexes were explored and developed as catalysts for hydrophosphination. It was determined that Ru-phosphido complexes are key intermediates in the hydrophosphination of electron-deficient alkenes. A detailed study on the mechanisms of hydrophosphination catalyzed by the phosphido complexes Ru(η5-indenyl)(PPh2)(L)(PPh3) (4a, L = NCPh; b, L = PPh2H; c, L = CO) was performed. Evidence for product inhibition was found for this catalyst system using Reaction Progress Kinetic Analysis. Product inhibition is consistent with the observed catalyst resting state of a complex containing product phosphines and the determination that substitution of the product phosphine from Ru is rate-limiting. The ancillary ligands (L) of 4 were found to influence catalytic activity by enabling catalyst deactivation (L = NCPh) or off-cycle processes including alkene telomerization (L = CO). Proposed mechanisms for catalysis were devised based on these findings. These results are important mechanistic insights that will be useful for designing new catalysts for hydrophosphination. The unprecedented viability of metal phosphenium complexes as intermediates in hydrophosphination was also explored. Three Mo phosphenium complexes were synthesized via P-H bond hydride abstraction from coordinated secondary phosphines, PR2H. These complexes were found to mediate the stoichiometric hydrophosphination of alkenes and ketones. In particular, trans-[Mo(CO)3(PPh2H)2(PPh2)]+ (13) mediates the hydrophosphination of a wide scope of alkenes that includes ethylene, propene and 1-hexene, which are challenging substrates for metal-catalyzed hydrophosphination. Preliminary attempts were conducted to render this synthetic phosphenium-mediated hydrophosphination catalytic. These results provide evidence for the putative steps of a hydrophosphination cycle utilizing metal phosphenium complexes as intermediates. The phosphenium complexes trans-[Mo(CO)4(PR2H)(PR2)] (12a R = Tolp2, b R = Ph) were also investigated as Lewis acid catalysts for hydrosilylation. A tentatively-assigned η1-HSiEt3 adduct of 12a, [Mo(CO)4(PTolp2H)(PTolp2{HSiEt3})] (20a), was observed by low temperature 31P{1H} NMR and was studied computationally. Complex 12b is proposed to behave as a Lewis acid catalyst for hydrosilylation. An off-cycle equilibrium is proposed that results in the formation of EtSi+. This work is a unique example of P(III) Lewis acid catalysis, of which there are few examples in the literature. / Graduate / 2020-07-29

Investigation of catalytic main-group bond forming reactions is the basis of this dissertation. Coupling of group 14 and 15 elements by several different methods has been achieved. The influence of Si–N heterodehydrocoupling on the promotion of α-silylene elimination was realized. Efficient Si–N heterodehydrocoupling by a simple, earth abundant lanthanide catalyst was demonstrated. Significant advances in hydrophosphination by commercially available catalysts was achieved by photo-activation of a precious metal catalyst. Exploration of (N3N)ZrNMe2 (N3N = N(CH2CH2NSiMe3)33–) as a catalyst for the cross-dehydrocoupling or heterodehydrocoupling of silanes and amines suggested silylene reactivity. Further studies of the catalysis and stoichiometric modeling reactions hint at α-silylene elimination as the pivotal mechanistic step, which expands the 3p elements known to engage in this catalysis and provides a new strategy for the catalytic generation of low-valent fragments. In addition, silane dehydrocoupling by group 1 and 2 metal bis(trimethylsilyl)amide complexes was investigated. Catalytic silane redistribution was observed, which was previously unknown for d0 metal catalysts. La[N(SiMe3)2]3THF2 is an effective pre-catalyst for the heterodehydrocoupling of silanes and amines. Coupling of primary and secondary amines with aryl silanes was achieved with a loading of 0.8 mol % of La[N(SiMe3)2]3THF2. With primary amines, generation of tertiary and sometimes quaternary silamines was facile, often requiring only a few hours to reach completion, including new silamines Ph3Si(nPrNH) and Ph3Si(iPrNH). Secondary amines were also available for heterodehydrocoupling, though they generally required longer reaction times and, in some instances, higher reaction temperatures. By utilizing a diamine, dehydropolymerization was achieved. The resulting polymer was studied by MS and TGA. This work expands upon the utility of f-block complexes in heterodehydrocoupling catalysis. Stoichiometric and catalytic P–E bond forming reactions were explored with ruthenium complexes. Hydrophosphination of primary phosphines and activated alkenes was achieved with 0.1 mol % bis(cyclopentadienylruthenium dicarbonyl) dimer, [CpRu(CO)2]2. Photo-activation of [CpRu(CO)2]2 was achieved with a commercially available UV-A 9W lamp. Preliminary results indicate that secondary phosphines as well as internal alkynes may be viable substrates with this catalyst. Attempts to synthesize ruthenium phosphinidene complexes for stoichiometric P–E formation have been met with synthetic challenges. Ongoing efforts to synthesize a ruthenium phosphinidene are discussed. The work in this dissertation has expanded the utility of metal-catalyzed main-group bond forming reactions. A potential avenue for catalytic generation low-valent silicon fragments has been discovered. Rapid Si–N heterodehydrocoupling by an easily obtained catalyst has been demonstrated. Hydrophosphination with primary phosphines has been achieved with a commercially available photocatalyst catalyst, requiring only low intensity UV light.

La synthèse de phosphines secondaires borane dérivées d’aminoacides ou de dipeptides, et leur application pour la préparation de ligands ou le greffage du fullerène, est décrite. Elle se fait sans racémisation avec des rendements atteignant 98%, par alkylation de phosphines borane primaires avec un dérivé γ-iodo aminoacide, dans les conditions de transfert de phase. Les diphosphines tertiaires dérivées d’aminoacides, obtenues après une seconde alkylation avec des rendements atteignant 70%, sont parmi les premiers exemples de diphosphines greffées par une liaison P-C sur la chaine latérale d’un aminoacide. Les mono et diphosphines dérivées d’aminoacides ont été testées en catalyse d’allylation ou d’hydrogénation asymétriques catalysées par des complexes de palladium ou de rhodium. D’un autre côté, un complexe de cis platine a été préparé à partir d'une diphosphine dérivée d'un aminoester. Ses propriétés cytotoxiques ont été testées sur des lignées cellulaires ovariennes cancéreuses A2780. Dans une seconde partie les phosphines secondaires borane d’aminoacides et de peptides ont été utilisées pour le greffage du fullerène, par hydrophosphination en transfert de phase. L’étude électrochimique du dérivé fullerène d’aminoester de benzyle, a permis d’établir que ce composé se décomposait par électrolyse, avec coupure de la liaison P-C, pour libérer le fullerène et la phosphine secondaire borane aminoester. Ces travaux ouvrent de nouvelles perspectives pour la chimie des dérivés phosphines ou fullerène d'aminoacides et de peptides. / The synthesis of secondary phosphine borane amino acids or dipeptides and their applications for the preparation of chiral ligands or for the grafting of fullerene, is described. These compounds were synthesized in good yield (up to 98%) without racemization. The principle of the synthesis is based on the alkylation of primary phosphine borane with a γ-iodo amino acid using phase transfer conditions. Tertiary diphosphine amino acids are obtained with 70% yield after a second alkylation. These compounds are one of the first examples of diphosphine grafted with a P-C bond on the side chain of amino acid. First of all, mono and diphosphine amino acid derivatives were used in asymmetric allylic substitution with palladium precursor or in asymmetric hydrogenation with rhodium precursor. In another hand, a cis platinum complex was synthesized with 60% yield from the diphosphine amino acid derivative. The cytotoxic properties of this complex were tested against human ovarian carcinogenic cell lines A2780. In the second part, the secondary phosphine borane amino acids and peptides have been used for grafting fullerene C60 by hydrophosphination using phase transfer conditions. The electrochemical study of the fullerene amino benzyl ester derivative has shown the cleavage of the P-C60 bond by electrolysis, affording the free fullerene and the secondary phosphine borane amino ester moiety. This work opens new perspectives for the chemistry of fullerene and phosphine derivatives of amino acids and peptides.

New synthetic routes to nitrogen- and phosphorus-containing polymers have been investigated. These routes rely on amine- and phosphine-containing monomers bearing pendant alkyne substituents, and subsequent hydroamination, oxidation, or hydrophosphination polymerization. A series of primary amines of the form H2NC6H2R2C≡CR’ (R = H or iPr; R’ = Ph, SiMe3, nBu, or p-C6H4Me) is reported. These amines are deprotonated with nBuLi to give lithium amides, which react with zirconocene compounds to provide amidozirconium complexes. Characterization is achieved by multinuclear NMR spectroscopy, IR spectroscopy, high-resolution mass spectrometry, elemental analysis, X ray crystallography, and DFT calculations. Three routes were attempted towards nitrogen-containing oligomers: (1) thermolysis of amidozirconium complexes to afford [2+2] cycloaddition polymers; (2) Ti(IV)-catalyzed hydroamination of H2NC6H4C≡CPh; (3) chemical oxidation of H2NC6H4C≡CPh. The latter two strategies resulted in distinct nitrogen-containing oligomers. The oligomer formed by Ti(NR2)4-catalyzed hydroamination (R = Me, Et) contains up to 15 repeat units in the chain, with both imine and enamine moieties, and is capped by a molecule of HNR2 (R = Me or Et) originating from the catalyst. The oligomer formed by chemical oxidation contains up to 9 repeat units in the chain. A series of phosphines of the form X2PC6H2R2C≡CR’ is reported (X = NEt2, Cl, H; R = Me, iPr; R’ = Ph, SiMe3). Characterization is achieved by multinuclear NMR spectroscopy, IR spectroscopy, high-resolution mass spectrometry, elemental analysis, and X-ray crystallography. The primary phosphines, H2PC6H2R2C≡CR’, are relatively “user-friendly” in that they are not particularly malodorous, they are isolated as solids or highly viscous liquids, and they are stable when stored under N2 in the solid state and in solution. The primary phosphine H2PC6H2iPr2C≡CPh serves as a precursor for a zirconium phosphinidene and for the secondary phosphines RP(H)C6H2iPr2C≡CPh (R = CH2iPr, CH2Ph). Hydrophosphination polymerization gives cyclic P(III)-containing oligomers, which are converted to P(V)-based macromolecules by treatment with sulfur. The oligomers contain ca. 5 to 10 repeat units, and heating to 800 °C gives rise to phosphorus-containing ceramics. The mechanism of hydrophosphination is discussed with the use of DFT calculations.

New synthetic routes to nitrogen- and phosphorus-containing polymers have been investigated. These routes rely on amine- and phosphine-containing monomers bearing pendant alkyne substituents, and subsequent hydroamination, oxidation, or hydrophosphination polymerization. A series of primary amines of the form H2NC6H2R2C≡CR’ (R = H or iPr; R’ = Ph, SiMe3, nBu, or p-C6H4Me) is reported. These amines are deprotonated with nBuLi to give lithium amides, which react with zirconocene compounds to provide amidozirconium complexes. Characterization is achieved by multinuclear NMR spectroscopy, IR spectroscopy, high-resolution mass spectrometry, elemental analysis, X ray crystallography, and DFT calculations. Three routes were attempted towards nitrogen-containing oligomers: (1) thermolysis of amidozirconium complexes to afford [2+2] cycloaddition polymers; (2) Ti(IV)-catalyzed hydroamination of H2NC6H4C≡CPh; (3) chemical oxidation of H2NC6H4C≡CPh. The latter two strategies resulted in distinct nitrogen-containing oligomers. The oligomer formed by Ti(NR2)4-catalyzed hydroamination (R = Me, Et) contains up to 15 repeat units in the chain, with both imine and enamine moieties, and is capped by a molecule of HNR2 (R = Me or Et) originating from the catalyst. The oligomer formed by chemical oxidation contains up to 9 repeat units in the chain. A series of phosphines of the form X2PC6H2R2C≡CR’ is reported (X = NEt2, Cl, H; R = Me, iPr; R’ = Ph, SiMe3). Characterization is achieved by multinuclear NMR spectroscopy, IR spectroscopy, high-resolution mass spectrometry, elemental analysis, and X-ray crystallography. The primary phosphines, H2PC6H2R2C≡CR’, are relatively “user-friendly” in that they are not particularly malodorous, they are isolated as solids or highly viscous liquids, and they are stable when stored under N2 in the solid state and in solution. The primary phosphine H2PC6H2iPr2C≡CPh serves as a precursor for a zirconium phosphinidene and for the secondary phosphines RP(H)C6H2iPr2C≡CPh (R = CH2iPr, CH2Ph). Hydrophosphination polymerization gives cyclic P(III)-containing oligomers, which are converted to P(V)-based macromolecules by treatment with sulfur. The oligomers contain ca. 5 to 10 repeat units, and heating to 800 °C gives rise to phosphorus-containing ceramics. The mechanism of hydrophosphination is discussed with the use of DFT calculations.