This thesis describes the synthesis, characterisation and reactivity of diamide-amine and bis(cyclopentadienyl) supported Group 4 hydrazido(2-) compounds towards unsaturated molecules. The mechanisms of these transformations are probed using a range of structural, kinetic and computational methods.

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Dans un monde où la fin du pétrole est prévisible, l’utilisation de ressources renouvelables, issues de la biomasse, pour la production de bio-carburants et de matières premières pour l’industrie chimique est un domaine de recherche intense. La transformation de dérivés d’acides gras a pu être réalisée par des réactions de métathèse croisée, catalysées au ruthénium. La synthèse de nitriles dits «courts» comme additifs pour le kérosène ainsi que de monomères pour l’industrie des polymères a été développée. La purification des ressources renouvelables a été étudiée. Un traitement thermique, simple à mettre en œuvre, a montré son efficacité pour la réalisation de réactions de métathèse toujours plus efficientes. Enfin, pour des réactions de catalyse toujours plus efficaces, la synthèse de nouveaux complexes de ruthénium à ligand indénylidène chélatant de seconde génération a été entreprise. / In the context of depletion of crude oil, the production of bio-fuels and raw materials from renewable resources for the chemical industry is a topic of tremendous research. The transformation of fatty acid derivatives was developed by using olefin metathesis, using ruthenium catalysts. Short nitriles as kerosene additives and monomers for the polymer industry were synthesized. Purification of the renewable feedstock was studied. A simple thermal treatment was found to promote an increased efficiency for cross-metathesis reactions with fatty acid derivatives. Finally, the synthesis of new second generation ruthenium complexes with a chelating indenylidene ligand was investigated for the development of active and robust catalysts for olefin metathesis reactions.

A reação de Morita-Baylis-Hillman (MBH) consiste em uma poderosa transformação química, podendo levar à formação de importantes blocos de construção em síntese orgânica. No entanto, a reação de MBH apresenta sérias limitações, principalmente no que diz respeito ao tempo reacional, ao uso de aceptores de Michael β-substituídos e à necessidade de eletrófilos secundários extremamente elétron-deficientes. Dentro desta temática, o presente trabalho investiga uma metodologia tricomponente do tipo Michael-aldol mediada por organocalcogenolatos metálicos, dando origem a adutos de MBH β-organocalcogeno funcionalizados como produto. Nestes estudos foram avaliados diferentes organocalcogenolatos metálicos (S, Se e Te), bem como diferentes aceptores de Michael (eletrófilo primário) e aldeídos (eletrófilo secundário) frente à metodologia. Tal estudo tornou possível a obtenção da (±)-Acaterina, um produto natural biologicamente ativo, em uma única etapa reacional, sendo a síntese mais curta e de maior rendimento até então relatada. Além disso, a metodologia tricomponente foi adaptada à adição de um terceiro eletrófilo no meio reacional, tornando possível a obtenção de derivados de adutos de MBH (ésteres, éteres de silício e carbonatos) também de maneira one-pot (reação tetra-componente do tipo Michael-aldol-O-funcionalização/eliminação de selenóxido). Investigando possíveis novas aplicações dos derivados de MBH produzidos, foi estudada a enolização de ésteres derivados de adutos de MBH onde se observou comportamento nucleofílico do LDA bem como de outras bases fortes. Utilizando cálculos computacionais baseados em DFT, uma coordenada de reação foi calculada para um dos sistemas nos quais LDA foi empregado e, o resultado teórico obtido está de acordo com os resultados obtidos experimentalmente. / The Morita-Baylis-Hillman reaction consists on a powerfull chemical transformation, leading to important building blocks in organic synthesis. However, the MBH presents some serious drawbacks, specially in respect to reactional time, the use of β- substituted Michael acceptors and the need for highly electron-deficient secondary electrophiles. Within this issue, the present work aims the investigation of a tricomponent Michael-aldol reaction mediated by metallic organochalcogenolates, leading to β-organochalcogen functionalized MBH adducts as products. In these studies the behavior of different metallic organochalcogenolates as well as different Michael acceptors (primary electrophile) and aldehydes (secondary electrophiles) were evaluated towards the methodology. Within this study it was possible to synthesize (±)-Acaterin, a natural bioactive compound, in a single reactional step, consisting in the shortest and higher yielding protocol related so far. Moreover, the tricomponent methodology was adapted to the addition of a third electrophile into the reactional media, allowing the preparation of MBH derivatives (esters, silicon ethers and carbonates) also in an one-pot manner (Michael-aldol-O-functionalization/selenoxide elimination four-component reaction). Investigating possible new applications of the produced MBH derivatives, the enolization of MBH esters was studied and a nucleophilic behavior was observed for LDA and for other strong bases. By means of DFT-based computational calculations, a reaction coordinate was calculated for a LDA-based enolization system and the obtained theoretical results are in agreement with the experimentally obtained results.

A reação de Morita-Baylis-Hillman (MBH) consiste em uma poderosa transformação química, podendo levar à formação de importantes blocos de construção em síntese orgânica. No entanto, a reação de MBH apresenta sérias limitações, principalmente no que diz respeito ao tempo reacional, ao uso de aceptores de Michael β-substituídos e à necessidade de eletrófilos secundários extremamente elétron-deficientes. Dentro desta temática, o presente trabalho investiga uma metodologia tricomponente do tipo Michael-aldol mediada por organocalcogenolatos metálicos, dando origem a adutos de MBH β-organocalcogeno funcionalizados como produto. Nestes estudos foram avaliados diferentes organocalcogenolatos metálicos (S, Se e Te), bem como diferentes aceptores de Michael (eletrófilo primário) e aldeídos (eletrófilo secundário) frente à metodologia. Tal estudo tornou possível a obtenção da (±)-Acaterina, um produto natural biologicamente ativo, em uma única etapa reacional, sendo a síntese mais curta e de maior rendimento até então relatada. Além disso, a metodologia tricomponente foi adaptada à adição de um terceiro eletrófilo no meio reacional, tornando possível a obtenção de derivados de adutos de MBH (ésteres, éteres de silício e carbonatos) também de maneira one-pot (reação tetra-componente do tipo Michael-aldol-O-funcionalização/eliminação de selenóxido). Investigando possíveis novas aplicações dos derivados de MBH produzidos, foi estudada a enolização de ésteres derivados de adutos de MBH onde se observou comportamento nucleofílico do LDA bem como de outras bases fortes. Utilizando cálculos computacionais baseados em DFT, uma coordenada de reação foi calculada para um dos sistemas nos quais LDA foi empregado e, o resultado teórico obtido está de acordo com os resultados obtidos experimentalmente. / The Morita-Baylis-Hillman reaction consists on a powerfull chemical transformation, leading to important building blocks in organic synthesis. However, the MBH presents some serious drawbacks, specially in respect to reactional time, the use of β- substituted Michael acceptors and the need for highly electron-deficient secondary electrophiles. Within this issue, the present work aims the investigation of a tricomponent Michael-aldol reaction mediated by metallic organochalcogenolates, leading to β-organochalcogen functionalized MBH adducts as products. In these studies the behavior of different metallic organochalcogenolates as well as different Michael acceptors (primary electrophile) and aldehydes (secondary electrophiles) were evaluated towards the methodology. Within this study it was possible to synthesize (±)-Acaterin, a natural bioactive compound, in a single reactional step, consisting in the shortest and higher yielding protocol related so far. Moreover, the tricomponent methodology was adapted to the addition of a third electrophile into the reactional media, allowing the preparation of MBH derivatives (esters, silicon ethers and carbonates) also in an one-pot manner (Michael-aldol-O-functionalization/selenoxide elimination four-component reaction). Investigating possible new applications of the produced MBH derivatives, the enolization of MBH esters was studied and a nucleophilic behavior was observed for LDA and for other strong bases. By means of DFT-based computational calculations, a reaction coordinate was calculated for a LDA-based enolization system and the obtained theoretical results are in agreement with the experimentally obtained results.

Graphene is foreseen to be the basis of future electronics owing to its ultra thin structure, extremely high charge carrier mobility,  high thermal conductivity etc., which are expected to overcome the size limitation and heat dissipation problem in silicon based transistors. But these great prospects are hindered by the metallic nature of pristine graphene even at charge neutrality point, which allows to flow current even when a transistor is switched off. A part  of the thesis is dedicated to invoke electronic band gaps in graphene to overcome this problem. The concept of quantum confinement has been employed to tune the band gaps in graphene by  dimensional confinement along with the functionalization of the edges of these confined nanostructures. Thermodynamic stability of the functionalized zigzag edges with hydrogen, fluorine and reconstructed edges has been presented in the thesis. Keeping an eye towards the same goal of band gap opening,  a different route has been considered by admixing insulating hexagonal boron nitride (h-BN) with semimetal graphene. The idea has been implemented in two  dimensional h-BN-graphene composites and three dimensional stacked heterostructures. The study reveals the possibility of tuning band gaps by controlling the admixture. Occurrence of defects in graphene has significant effect on its electronic properties. By random insertion of defects, amorphous graphene is studied, revealing a semi-metal to a metal transition. The field of molecular electronics and spintronics aims towards device realization at the molecular scale. In this thesis, different aspects of magnetic bistability in organometallic molecules have been explored in order to design  practical spintronics devices. Manipulation of spin states in organometallic molecules, specifically metal porphyrin molecules, is achieved by controlling surface–molecule interaction. It has been shown that by strain engineering in defected graphene, the magnetic state of adsorbed molecules can be changed. The spin crossover between different spin states can also be achieved by chemisorption on magnetic surfaces. A significant part of the thesis demonstrates that the surface-molecule interaction not only changes the spin state of the molecule, but allows to manipulate magnetic anisotropies and spin dipole moments via modified ligand fields. Finally, in collaboration with experimentalists, a practical realization of switching surface–molecule magnetic interactions by external magnetic fields is demonstrated.

La catalyse constitue un élément clé en synthèse chimique et la recherche actuelle tend à rendre les procédés catalytiques plus propres dans le contexte de la chimie verte. Dans cet esprit, cette thèse a impliqué la recherche de catalyseurs nanoparticulaires utilisés en milieu aqueux, sans ligand toxique et en très faible quantité. La synthèse des nanoparticules (NPs) catalytiques a utilisé des ions des éléments de transition de la droite du tableau périodique et des réducteurs capables de réduire rapidement ces cations en atomes de degré d’oxydation nul s’agrégeant en petites NPs métalliques très actives en catalyse. Les réducteurs choisis ont été des composés réservoirs d’électron organique (naphthyl sodium) ou organométalliques (complexes sandwichs à 19 électrons de valence du fer tel que [Fe(I)Cp*(ŋ6-C6Me6)] ou du cobalt tel que [Co(II)Cp*2], (Cp* = ŋ5-C5Me5)). Les supports limitant l’agrégation des NPs métalliques ont été le solvant (polyéthylène glycol, 1ère partie de la thèse), les cations des réservoirs d’électron organométalliques (2ème partie de la thèse) ou un réseau zéolitique imidazolate (MOF de type ZIF-8, 3ème partie de la thèse). Au lieu d’un cation métallique, il a aussi été possible d’utiliser un cluster tel que [Au25(SR)18] (R = CH2CH2Ph) comme précurseur, auquel cas la réduction peut se limiter à un simple transfer d’électron produisant un cluster anionique stabilisé par le contre-cation sandwich encombré du réservoir d’électron. Les petites NPs ainsi stabilisées se sont avérées d’excellents catalyseurs “verts” de plusieurs réactions de couplage C-C ou C-N et de production d’hydrogène par hydrolyse d’hydrures métalliques en milieu aqueux dans des conditions très douces. Cette dernière réaction a été efficacement catalysée par des NPs bimétalliques Ni2Pt NP@ZIF-8 avec une synergie spectaculaire entre les deux métaux. / Catalysis is a key element in chemical synthesis, and current research is focusing on making catalytic processes cleaner in the context of green chemistry. In this spirit, this thesis involves the research of nanoparticle (NP) catalysts used in aqueous medium, without toxic ligand and in very small quantities toward a variety of useful processes. The synthesis of the catalytic NPs used cations of the transition elements of the right of the periodic table and of reducing agents capable of rapidly reducing these cations to atoms of zero oxidation state aggregating into small catalytically active metal NPs. The chosen reducing agents were organic (naphthyl sodium) or organometallic (19-electron) sandwich complexes of iron such as [Fe(I)Cp*(ŋ6-C6Me6)] or cobalt such as [Co(II)Cp*2], (Cp* = ŋ5-C5Me5)) used as electron reservoirs. The supports limiting the aggregation of the metal NPs were the solvent (polyethylene glycol, first part of the thesis), the cations of the organometallic electron reservoirs (2nd part of the thesis) or a zeolitic imidazolate framework (MOF of ZIF-8 type, 3rd part of the thesis). Instead of a metal cation, it has also been possible to use a cluster such as [Au25(SR) 18] (R = CH2CH2Ph) as a precursor, in which case the reduction was limited to a simple electron transfer producing an anionic cluster stabilized by the congested sandwich counter cation of the electron reservoir. The small NPs thus stabilized proved to be excellent "green" catalysts for several C-C or C-N reactions and hydrogen production by hydrolysis of metal hydrides in an aqueous medium under very mild conditions. This latter reaction was efficiently catalyzed by Ni2Pt@ZIF-8 bimetallic NPs with a spectacular synergy between the two metals.

Molecular-based quantum cellular automata (m-QCA), as an extension of quantum-dot QCAs, offer a novel alternative in which binary information can be encoded in the molecular charge configuration of a cell and propagated via nearest-neighbor Coulombic cell-cell interactions. Appropriate functionality of m-QCAs involves a complex relationship between quantum mechanical effects, such as electron transfer processes within the molecular building blocks, and electrostatic interactions between cells. In the first part of this document, the influence of structural distortions in single m-QCA is addressed within a minimal model using an diabatic-to-adiabatic transformation. Thus, it is shown that even small changes of the classical square geometry between driver and target cells, such as those induced by distance variations or shape distortions, can make cells respond to interactions in a far less symmetric fashion, modifying and potentially impairing the expected computational behavior of the m-QCA. The model has been further extended to consider time-dependent external electric fields in which a special emphasis is given to the profiles in which this external parameter can interact with the associated molecular complex. The results of the model have been validated by a direct comparison with first-principle calculations allowing to conclude the plausibility to induce the intra-molecular charge transfer process in a controllable manner via the interaction with the external electric field. The influence played by the electric field profile in the response of the molecular complex is also investigated. The results suggests a major role played by this variable in terms of the time length in which the intra-molecular charge transfer can be observed. In the second part, first-principle theoretical calculations of the self-assembly properties and electronic structure of Ferrocene-functionalized complexes have been carried out. Hence, five different molecular complexes which offer a potential playground to realistic implement the m-QCA paradigm have been investigated. The main emphasis is given to study the interaction between localized charge-carrier molecular states and the delocalized surface states. The results of these calculations demonstrate the possibility to obtain real systems in which intra-molecular charge localization can be combined with self-assembly scaffolding and absorbed on either Highly oriented pyrolytic graphite (HOPG) or metallic-surfaces. Finally, the validation of these findings is carried out via comparison with accesible experimental results and opening the gate to plausible strategies where the paradigm can be implemented.

Group 3 and 4 complexes bearing linked cyclopentadienyl amido ligands, often referred to as constrained geometry complexes (CGCs), have experienced considerable interest due to their superior ability to copolymerise ethylene and higher alpha-olefins when activated with suitable co-catalyst.The work presented in this thesis aimed to replace the most commonly applied bridge in CGCs, which is silicon based, by one containing boron. The potential of the bridging element to have Lewis acidic character was expected to positively alter the catalytic activity of the activated species and possibly allowing for self-activation.Synthetic approaches to ligand precursors based on aminoboranes, diaminodiboranes(4) and ferrocenylboranes are described. Starting from the dihalo derivatives of these boranes, sequential substitution of the halides by one equivalent each of a cyclopentadienide derivative and an amide allowed the synthesis and isolation of a broad range of new CGC ligand precursors.Complexation of these ligand precursors to Group 4 metals was studied by utilising various protocols. The reaction with Group 4 tetraamides via amine elimination was the most successful yielding numerous new boron-bridged CGCs and related complexes in which the boron-bridged ligand binds in a non-chelating fashion.The newly synthesised compounds were fully characterised by multinuclear NMR spectroscopy, supplemented by X-ray diffraction studies where applicable.Studies on the reactivity of boron-bridged CGCs in the presence of alkylating agents indicated susceptibility of the boron atom to nucleophilic attack resulting in a decomposition of the linking moiety between the cyclopentadienyl and amido fragments. This is as well reflected in the data gathered from polymerisation experiments, in which methylaluminoxane activated boron-bridged CGCs displayed a low activity towards ethylene polymerisation, but a high activity towards styrene polymerisation. Such characteristics are comparable to unbridged compounds, e.g. [(eta5-C5H5)TiCl3], rather than silicon-bridged CGCs, thus suggesting degradation of the boron-bridged CGCs to unbridged complexes under polymerisation conditions.

Nowadays, the requirement to design highly valuable compounds is undoubtedly one of the major challenges in the field of organic and organometallic chemistry. The use of the versatile and efficient N-heterocyclic carbenes (NHCs) combined with transition metals represents a key feature in modern organometallic chemistry and homogeneous catalysis. In the course of this thesis, the straightforward design and synthesis of a library of Pd(0) bearing NHC ligands was achieved. Their catalytic performances (Chapter 1) and their phosphorescence properties in solution (Chapter 2) were disclosed. Currently, cross-couplings are some of the most important types of reaction in palladium catalysis. The formation of highly hindered biaryls substrates is one of the main requirements in cross-coupling chemistry. The design and synthesis of a palladium dimer bearing a bulky NHC ligand can fulfil this proposal (Chapter 4). The development of new classes of ligands is a topic of interest. For this reason, normal, abnormal, remote and mesoionic N-heterocyclic carbenes copper complexes were investigated and their reactivity compared in the [3+2] cycloaddition of azides and alkynes (Chapter 7). Air and moisture stable Cu(I)-NHC species have also been compared to their silver analogues for the alkynylation of ketones (Chapter 9). The different reactivity of the two latter organometallic species (Cu and Ag) with ethyldiazoacetate reagent via the formation of carbenes or C-H activated product is presented in Chapter 8. Recently, the development of a bimetallic catalytic system is strongly considered and has high impact. For this reason, two dual catalytic transformations (Pd-NHC and Cu-NHC) were studied for the C-H arylation (Chapter 5) and the synthesis of substituted alkenes products via a relay or cooperative mechanisms (Chapter 6). The isolation of intermediates and mechanistic studies were examined in each of these studies.