No description available.

The syntheses of a new class of polycyclic TriAmino DiCarbenes (TADCs), based on 3,9-diazajulolidine, and their precursors and adducts are described. Starting with 2,6-dimethyl-nitrobenzene, 2,6-bis ((alkylamino)methyl)anilines (alkyl = isopropyl, mesityl, and tert-butyl) were synthesized in 40% yield over five steps. These triamines were then di-cyclized stepwise to diformamidinium dications or formamidinium/2-methoxyformaminals using oxonium salts and trialkyl orthoformates. A diformamidinium dication was characterized by single-crystal X-ray diffractometry. Treatment with various bases, particularly lithium hexamethyldisilylazide, led to the novel TADCs and monocarbenes, two of which were isolated and characterized by 1H and 13C NMR spectroscopies. In both cases, treatment with elemental sulfur trapped the TADCs as dithiobiurets. No TADC-transition metal complexes were successfully isolated from reactions of the diformamidinium dications or LiHMDS TADC complex with a number of transition metal complexes. With the exception of these two cases, all other TADCs were not isolated because they rapidly reacted to form dimers, trimers, and tetramers. One of these dimers was isolated and its structure determined using 1D and 2D NMR spectroscopies, along with high-resolution electrospray ionization mass spectrometry. This revealed that the TADC had dimerized to form an ene-triamine, likely via 1,3-shift of a benzylic proton. Novel N-heterocyclic Carbene (NHC) complexes of molybdenum were also synthesized and characterized. Reaction of Cp2Mo2(CO)4 (Cp = C5H5) with dimesityl-imidazol-2-ylidenes (IMes) or dimesityl-imidazolidin-2-ylidenes (SIMes) yielded the molybdoradicals CpMo(CO)2(NHC) (NHC = IMes or SIMes). The carbonyl infrared stretching frequencies and the relative metal-to-NHC π-backbonding for IMes and SIMes complexes are compared. Reaction of the less bulky dimethyl-imidazol-2-ylidene (IMe) with Cp2Mo2(CO)4 yielded the Mo-Mo triple bond complex Cp2Mo2(CO)3(IMe) by CO substitution. This is the first example of an NHC-ligated metal-metal multiply bonded complex. Single crystal X-ray diffractometry of these new organomolybdenum and organodimolybdenum complexes is discussed.

Owing to the favored Coulombic attraction between the ammonium group and anion which stabilizes the B-F/B-CN bond against heterolysis, cationic borane [25]+ has great affinity toward anions than its neutral analog, and is capable of capturing fluoride or cyanide from water under bi-phasic conditions. By placing the fluorophilic silyl group adjacent to an electrophilic carbocation, a novel fluoride sensor [45]+ was obtained. Sensing occurs via a fluoride induced methyl migration from the silicon to adjacent electrophilic methylium center which is unprecedented. As a result of its strong fluoride affinity, [45]+ is able to react with KF in aqueous media at pH 7.0. The electrochemistry study of these cationic Lewis boranes reveals that the cationic character of these boranes serves to decrease their reduction potential and increase the stability of the resulting radicals. In this part of the research, we have prepared a cationic borane [27]+, which features two reversible reduction waves at -0.86 and -1.56 (vs. Fc/Fc+) corresponding to the formation of stable neutral and anionic derivatives. The one-electron reduction of [27]+ leads to the formation of a boron containing neutral radical featuring an unusual boron-carbon one-electron π bond. Further reduction of 27• results in the formation of the borataalkene derivative [27]-, which features a formal B=C double bond. The structural changes accompanying the stepwise population of the B-C π-bond are also determined, and this sequential population of B-C π-bonding orbital is also supported by theoretical computations. In order to understand the impact of the cationic nature of these boranes on their oxidative power, three novel cationic boranes ([34]+, [35]2+, and [36]3+) have been synthesized and their oxidative power were examined via cyclic voltammetry. The CV data of these compounds shows that the reduction potential of these triarylboranes is linearly proportional to the number of the pendant cationic substituents. Substitution of a mesityl group by an ArN+ group leads to an increase of the reduction potential by 260 mV.

京都大学 / 新制・課程博士 / 博士(理学) / 甲第24179号 / 理博第4870号 / 新制||理||1697(附属図書館) / 京都大学大学院理学研究科化学専攻 / (主査)准教授 水畑 吉行, 教授 若宮 淳志, 教授 倉田 博基 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DGAM

This Thesis reports the synthesis and reactions of new hydrazide, alkoxyimide and benzimidamide complexes (L)Ti=NX (X = NAr2, NOtBu or C(Ar)NO^tBu; L = dianionic supporting ligand or ligand set). The work is supported by DFT calculations which are used to rationalise the reaction outcomes observed and, in one case, the bonding in alkoxyimide complexes. <b>Chapter One</b> provides a background to hydrazide complexes, starting with their relevance to nitrogen fixation. In addition, Group 4 imide, alkylidene hydrazide and alkoxyimide complexes are also reviewed. The Chapter focuses in particular on the synthesis, structure, and stoichiometric and catalytic reactions of these complexes with unsaturated substrates. <b>Chapter Two</b> describes the development of the virtually unexplored 1,2-diamination reaction. The substrate scope and isolation of the vinylamine products are discussed. The protonation of the vinylimide complex Ti(N2N^Me){NC(Ph)C(Me)NPh2}(py) and the overall diamination reaction itself is then explored through an in-depth experimental and computational study. <b>Chapter Three</b> details the synthesis of cyclopentadienyl-amidinate supported alkoxyimide complexes. The first detailed reactivity study, supported by structural and computational studies, of any alkoxyimide complex is reported. Novel reactivity at Ti=Nα and, in one instance, Nα–Oβ reductive bond cleavage is observed. <b>Chapter Four</b> describes the reactivity of the benzimidamide complex Cp*Ti{PhC(NⁱPr)2}{NC(Ar^F5)NO^tBu} with a range of substrates including heterocumulenes, aldehydes, isonitriles and B(Ar^F5)3. Novel reactivity at Ti=Nα, and 3-component coupling is presented, and the experimental results supported by structural and computational studies. <b>Chapter Five</b> presents full experimental procedures and characterising data for the new complexes reported.

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第18997号 / 工博第4039号 / 新制||工||1622(附属図書館) / 31948 / 京都大学大学院工学研究科物質エネルギー化学専攻 / (主査)教授 辻 康之, 教授 大江 浩一, 教授 杉野目 道紀 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

This Thesis reports the synthesis and reactivity of scandium and titanium borylimides. New, versatile synthetic routes to such complexes of these two metals were targeted, and their reactions with small, unsaturated compounds were explored, with a particular focus being the reactivity of alkynes with these systems. <b>Chapter One</b> provides a background on Group 4 imido and hydrazido complexes. Group 4 alkoxyimides are also reviewed, as well as the developing field of rare earth imides. The Chapter focuses on the synthesis, structure, and stoichiometric and catalytic reactions of these complexes with unsaturated substrates, and ends with a description of the handful of known transition metal borylimides. <b>Chapter Two</b> first describes the synthesis and structures of new titanium borylimido synthons prepared from Ti(NMe₂)₂Cl₂. From the borylimide Ti{NB(NAr'CH)₂}Cl₂(py)₃ are then formed five new compounds supported by a range of tridentate, nitrogen-based ligands. <b>Chapter Three</b> describes the synthesis of half-sandwich titanium borylimides through tertbutylimide/borylamine exchange. A sandwich compound is also described, and the electronic structures of these complexes are analysed by DFT, QTAIM and NBO studies. Reactivity with heteroallenes, and exchange reactions with amines are also explored. <b>Chapter Four</b> describes the reactivity of diamide-donor-supported titanium borylimides with terminal alkynes. The principal reaction outcomes are [2+2] cycloadditions and C–H bond activations, and an interesting C–F bond activation is also described. Kinetic studies of some reactions are presented, and will be supported by further DFT studies. <b>Chapter Five</b> explores attempts to prepare the first rare earth borylimide. Kinetic and computational evidence is presented for the existence of a transient scandium borylimide which rapidly undergoes interesting sp, sp² and sp³ C–H bond activations. <b>Chapter Six</b> presents full experimental procedures and characterising data for the new complexes reported.

No description available.

The utility of computational study lies not only in rationalizing a chemical phenomenon but also in its predictive value. Broadly, the scope of my research work includes understanding of the structure and bonding of molecules as well as reaction mechanisms using computational techniques. Here I will discuss three research problems where computational results successfully rationalize and predict the experimental outcome. Firstly, we will describe the electronic structure and bonding of all the possible cyclic isomers of B2AlHnm (where n =3D 3 =96 6 and m =3D -2 to 1) = which is isoelectronic to the cyclopropenyl cation.1 A comparative study among all the isomers of homocyclic and heterocyclic three- membered boron and aluminum hydrides has also been done to understand the factors that differentiate their hydride chemistry. We will also discuss about two different approaches to stabilize neutral planar B3R3 rings. In a mechanistic study, we have designed a a priori system which can undergo two competing biradical generating processes, namely the Myers-Saito (MS) and Garratt-Braverman (GB) Cyclizations.2,3 We will present a detailed mechanistic study of both the reactions, which indicates the preference of the GB cyclization over MS cyclization. The theoretical prediction is in agreement with the experimental findings. We will also describe a conformational constraint-based strategy to switch the selectivity from GB to MS/Schmittel pathway.4 In another study, we will talk about a DFT study to illustrate the effect of the a) solvent, b) ancillary ligand, (L) c) leaving group, (Hal) and d) metal (M) on the equilibrium between metal boryl (1) and borylene (2) complexes (Scheme 1).5,6