M.Sc. / This study comprised the synthesis and characterization of new carbonyl carbene complexes of chromium, molybdenum and tungsten, prepared from thiazole precursors. In addition, the preparation and characterization of coordination compounds of chromium, tungsten and iron with new thiazole dithiocarboxylester ligands are reported.

Athanasios Markos Abstract This Thesis deals with denitrogenative transformations of N-fluoroalkyl-1,2,3-triazoles, easily available heterocycles via copper(I)-catalyzed azide-alkyne cycloaddition (CuAAC) of safe and stable N-fluoroalkyl azides and alkynes. The introductory chapter describes general approaches towards N1-substituted 1,2,3- triazoles, methods of N1-,-difluoroalkyl-1,2,3-triazoles preparation and both, transition metal-catalyzed and transition metal-free transformations of N1-substituted 1,2,3- triazoles. In the first part of the Thesis, rhodium-catalyzed reactions of N-fluoroalkyl-1,2,3-triazoles are described. Rhodium-catalyzed reactions of N-fluoroalkyl-1,2,3-triazoles in presence of suitable reagents provide access to five-membered N-fluoroalkyl heterocycles, 2- fluoroalkyl oxazoles and ketamides. In the second part of the Thesis, both Brønsted and Lewis acid-mediated transformations of N-fluoroalkyl-1,2,3-triazoles leading to stereodefined N-alkenyl compounds, such as enamides, enimines, amidines and other are discussed. The robustness of the method is showcased on gram scale syntheses and preparation of a drug analogue. At last, thermally-induced rearrangement of N-fluoroalkyl-1,2,3-triazoles to 3-fluoroalkyl-2H- azirines and the proposed mechanism of the reaction are described.

This dissertation summarizes my research in the Roy group on the development, synthesis, and study of new N-heterocyclic carbene (NHC) based ligands and nickel phsophinidene core compositions of molecular clusters, also known as superatoms. Chapter 1 introduces superatoms as atomically precise and discreet building blocks for use in the design and synthesis of novel materials. A brief history as well as selected synthetic strategies of superatoms will be introduced. The relevant materials properties of superatoms as well as their dependence on core composition and ligand structure will be discussed. Next, the use of superatoms with specialized or functionalizable ligands to synthesize new materials will be demonstrated. This chapter details the importance of the superatom ligands and core composition is the foundation that the subsequent chapters builds upon in developing these two areas. Chapter 2 introduces a functionalized NHC as a potential superatom ligand. While not necessary for all superatom ligands, ligands that enable electronic access to the superatom core are attractive. In this chapter, the conductance of potential NHC based ligands are probed through the scanning tunneling microscope-based break-junction (STM-BJ) method. A novel method of forming single molecule junctions in situ was used and these ligands are found to display a length dependent conductance with strong coupling to the Au electrode, confirming their potential use as ligands for superatoms. Chapter 3 describes the nature of the NHC–M bond in self-assembled monolayers (SAMs) on a Au(111) surface using high-resolution spectroscopy and theoretical calculations. This study was performed as a result of challenges and questions encountered during the work of Chapter 2. The results obtained from this study explore an important structure-function relationship of NHC ligands and have broader impact in materials chemistry beyond superatoms. Chapter 4 explores the synthesis of superatoms with NHC ligands beyond simple imidazolium-based NHCs. This chapter describes the two primary synthetic techniques used and the synthesis of NHC-ligated superatoms. This work is also ongoing and characterization is limited to crude single crystal X-ray diffraction structures and select NMRs. Finally, Chapter 5 details the use of uncommon organocyclophosphine reagents to synthesis novel nickel-phosphinidene molecular clusters, a potential new superatom. In this chapter the synthesis of a family of nickel-phosphinidene molecular clusters is described and studied. A potential application of these molecular clusters is explored through the thermolytic conversion to the industrially relevant Ni2P.

This dissertation describes my efforts in the Nuckolls lab to expand synthetic methods of wet-chemistry superatom synthesis, superatom surface ligand and core modification, and assembly of superatoms into materials with useful, cumulative properties. This work builds off of previous work from the Nuckolls lab describing photolabile ligand substitution and use of this technique to covalently bind superatoms to form various materials such as polymers and weaved sheets. This work will focus on the Chevrel-type M₆E₈L₆ metal-chalcogenide cluster Co₆Se₈, modification of its outer stabilizing ligands, and fusion of its core with other Co₆Se₈ superatoms to form fused dimers. Chapter 1 consists of a review of background material that forms a foundational basis for this work. The field of superatoms and superatomic materials will first be covered to contextualize this work in the field at large. Then, the prior work on wet-chemistry synthesis of Co₆Se₈ superatoms with replaceable, photolabile carbonyl (CO) ligands will be discussed. Finally, previous dimensionally-controlled assembly of materials using these carbonylated superatoms will be covered. Chapter 2 consists of the discovery of a masking carbene ligand generated from trimethylsilyl diazomethane (TMSD) and its use to create a new, electronically-coupled superatom dimer species (Co₁₂Se1₆(PEt₃)₁₀) that shows evidence of quantum confinement akin to nanoparticles and nanoparticle assemblies. Chapter 3 consists of new ligand substitution and methods to synthetically functionalize the fused dimer introduced in Chapter 2. The reactive carbene-ligated cluster is used to add new functional groups that were previously inaccessible to these cobalt-selenide clusters. New multi-carbene clusters are demonstrated as well as the use of site-differentiated clusters to form functionalized fused dimers from bis-carbonyl clusters. Chapter 4 consists of an investigation of the carbene cluster and insights that may be used in the future to finally expand cluster fusion into a chain. A reversible bridging of the carbene ligand based on temperature and oxidation state is analyzed experimentally and computationally. This information is used to synthesize a series of new carbene clusters which are used to try and assemble electronically-coupled, fused Co₆Se₈ superatomic materials.

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第21126号 / 工博第4490号 / 新制||工||1698(附属図書館) / 京都大学大学院工学研究科合成・生物化学専攻 / (主査)教授 村上 正浩, 教授 杉野目 道紀, 教授 松田 建児 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DGAM

No description available.

<p> A series of 2-substituted Δ^3-1,3,4-oxadiazolines (i) were synthesized by oxidation of the corresponding hydrazones with lead-tetraacetate in alcohol, eq A. (See Diagram A in Thesis)</p> <p> These oxadiazolines, upon thermolysis, generated carbonyl ylide intermediates (ii). These ylides are known to undergo fragmentation into carbenes and carbonyl compounds, eq B. (See Diagram B in Thesis)</p> <p> A new series of products were found from the thermolysis of these types of oxadiazolines, ester azines iv and v. A possible mechanism for the formation of these ester azines involves carbene attack on the oxadiazoline to give an azomethine imine intermediate (iii) which can subsequently rearrange to give the azines and carbonyl compounds, eq C. (See Diagram C in Thesis)</p> <p> This mechanism is supported by the observation that the overall yields of ester azines rise with increasing initial concentration of oxadiazoline whereas the yield of propene, a rearrangement product of dimethyl carbene, falls with increasing initial concentration of oxadiazoline.</p> <p> The ester azines (R=CH3, CH2CH3 and CH(CH3)2) were found to be uniconfigurational and the E-configuration was assigned to ester azine iv and the E,E-configuration was assigned to ester azine v. Ester azines (R=C(CH3)3) were found to exist as configurational isomers. Equilibration studies were carried out on these ester azines and the thermodynamic parameters ΔG°, ΔH° and ΔS° were found for equilibration shown in eq D. (See Diagram D in Thesis)</p> <p> Changing the R' substituent of i to OCH2CCl3 or OCH2CF3 did not stop fragmentation of the derived ylide. Ester azines were found from the thermolysis of these oxadiazolines also. They were found to be uniconfigurational and were assigned the E-configuration.</p> / Thesis / Master of Science (MSc)

No description available.

This thesis describes the synthesis and isolation of silver, mercury, ruthenium and palladium complexes of bidentate N-heterocyclic carbenes (NHCs), derived from imidazolium-linked cyclophanes and related bis-imidazolium salts. The cyclophane structures contain two imidazolyl links between ortho- and meta- substituted aromatic rings and the related structures are ortho-, meta- and para-xylyl linked bis-imidazolium salts. The complexes have been characterised by NMR spectroscopy and X-ray crystallography. The synthesis of five new silver complexes has been achieved via a simple complexation reaction of the cyclophane and bis-imidazolium salts with the basic metal source Ag2O. The new silver carbene systems are thermally stable. Three of the complexes are dinuclear, cationic complexes, while two are mononuclear complexes, one cationic and one neutral. A number of mono- and di-nuclear mercury(II)-NHC complexes have been synthesised from the ortho- and meta-linked cyclophanes and the related meta-linked bis-imidazolium salts. The mercury complexes were prepared by direct mercuration method using mercury(II) acetate. The syntheses were perfomed in air and the complexes are stable to air and moisture. Mercury complexes I and II represent the first example of mononuclear metal complexes derived from meta-substituted imidazolium-linked cyclophanes. NHC-ligand transfer reactions from NHC-silver complexes and NHC-mercury complexes are described. An ortho-cyclophane ligand was successfully transfered from a silver complex to its palladium counterpart. Furthermore, palladium complex III, bearing a para-xylyl linked bis-NHC ligand, was made by transmetallation from both a silver and mercury complex. This is the first reported NHC-palladium complex of a para-xylyl linked bis-NHC ligand. A new redox transmetallation method for NHC ligand transfer, using a mercury complex, is presented. A palladium complex was made via redox transmetallation using a mercury complex of an ortho-NHC-cyclophane. A ruthenium(II)-NHC complex, IV containing an ortho-cyclophane ligand has been prepared via silver transmetallation and in situ complexation methods. In the transmetallation route, a silver complex of an ortho-cyclophane was treated with RuCl2(PPh3)3 to form IV. This complex represents the first example of a ruthenium complex bearing an NHC-cyclophane ligand, v and is also the first example of a metal complex derived from an imidazolium-linked cyclophane where the arene unit of the cyclophane is also involved in bonding to the metal centre.

The work described herein focuses on the synthesis and characterisation of copper(I) complexes bearing N-heterocyclic carbene (NHC) ligands, their use in catalysis as well as organometallic synthesis and related reaction mechanisms. Two classes of complexes were considered: neutral NHC-Cu(I) species and their cationic analogues. Concerning the former, initial efforts were focused on the development of a general and straightforward synthetic methodology towards complexes of the type [Cu(X)(NHC)] (X = Cl, Br, I). More than 10 NHC-Cu(I) species were synthesised in high yields under mild conditions, in air and using technical grade solvents. These complexes exhibited interesting activity in the catalytic dehydrogenation of formic acid/amine adducts proving in three times more efficiency than the copper salts previously employed in such a reaction. Hydroxide- and tert-butoxide analogues showed to be efficient catalysts in the N-methylation of amines with CO₂ as carbon source, and in the dehydrogenative coupling of silanes and carboxylic acids. Experimental and computational work were carried out in order to elucidate the mechanism of these transformations. Regarding the use of these species in organometallic synthesis, homo- and heteroleptic bis-NHC-Cu(I) complexes were employed as carbene transfer reagents to other transition metals. Aside from well-known cationic gold(I) species, two novel palladium(II) analogues were isolated and fully characterised.