This work is mainly concentrated on the development of new versatile ligand based on N,N’-disubstituted-1,8-diaminonaphthalene (1,8-DAN) for main group chemistry. Therefore, our initial efforts were made on the design of new ligand scaffold by using 1,8-DAN. Following that, new ligand family supported by 1,8-DAN was applied as ligands to main group elements (B, Al, In, Ga, and C). Furthermore, six-membered ring carbenes which are derived from the reaction between N,N’-disubstituted-1,8-diaminonaphthalene and carbon are also investigated. In addition, the stable carbenes were implied as a new ligand system for palladium, leading to the formation of metal ligand complexes. Therefore, the synthesis and reactivity of these complexes are also reported. Chapter I gives an explanation on the basic concepts in terms of the ligand designs and reports the reasons why N,N’-disubstituted-1,8-diaminonaphthalene has been chosen as the framework of for these ligands. Chapter II presents the approach to synthesize ligands depending on the substitution. Regarding this, three methods were successfully used: reductive amination, application of acyl halide followed by reduction, and copper catalyzed C-N coupling reactions. Chapter III describes the reactions between the N,N’-disubstituted-1,8-diaminonaphthalene and main group elements B, Al, Ga, and In in 13 group. In this chapter, a variety of mononuclear and dinuclear complexes are investigated and fully characterized. Furthermore, some computational studies are also reported for the comparison with experimental results. Chapter IV deals with new ligand family, carbene, which is derived from N,N’-disubstituted-1,8-diaminonaphthalene. Therefore, not only fundamental concepts for the NHC (N-heterocyclic carbene) are discussed but also synthetic pathways are introduced. Moreover, interesting features of free carbene are presented as well. Chapter V reports the potential of this new carbene ligand family as ligands for transition metal compound, especially, Pd(II) compounds. Several different pathways for synthesizing the desired metal carbene complexes are presented.

<p dir="ltr">This work describes the electronic and geometric structure of molecular metal complexes involving different ligand environments. These include the Cu-redox active ligand reduction series, Tp*₂U imido and anilido transformations, Lewis base activation by Tp*₂U, silyluranium synthesis and reactivity, and electrochemistry of plutonyl.</p>

<p> The synthesis and X-ray crystallographic determination of solid derivatives of homo- and heteropolyatomic anions derived from Zintl phases has generally yielded the least soluble of the ions present in solution. Many other species present in these solutions have remained unidentified until recently when considerable effort directed towards the investigation of the solution chemistries of Zintl anions has been put forth.</p> <p> The present work is mainly concerned with the characterization of new Zintl anions in solution using multinuclear magnetic resonance spectroscopy as the primary investigative tool. These studies include (1) the tetrahedral SnCh4^4- (Ch = selenium and/or tellurium), (2) the dimer of SnSe3^2-, Sn2Se6^4-, (3) several interesting but, as-of-yet, unidentified species present in solutions derived from ternary Na/Sn/Te alloys and present in the reaction of Sn(II) Cl2 with Te2^2-, and (4) a set of possible multi-thallium-tellurium species. Relevant chemical shifts and nuclear spin-spin coupling constants are reported and trends discussed.</p> <p>119Sn Mössbauer investigations of all tin-containing species is also presented as is a brief discussion of the X-ray crystallographically determined polytelluride, Te4^2-.</p> / Thesis / Master of Science (MSc)

High-oxidation state main-group metal complexes are potential alternatives to transition metals for electrophilic C-H functionalization reactions. However, there is little known about how selection of the p-block, main-group metal and ligand impact C-H activation and functionalization thermodynamics and reactivity. Chapter 2 reports density functional theory (DFT) calculations used to determine qualitative and quantitative features of C-H activation and metal-methyl functionalization energy landscapes for reaction between high-oxidation state d10s0 InIII, TlIII, SnIV, and PbIV carboxylate complexes with methane. While the main-group metal influences the C-H activation barrier height in a periodic manner, the carboxylate ligand has a much larger quantitative impact on C-H activation with stabilized carboxylate anions inducing the lowest barriers. For metal-methyl reductive functionalization reactions, the barrier heights, are correlated to bond heterolysis energies as model two-electron reduction energies.In Chapter 3, DFT calculations reveal that arene C-H functionalization by the p-block main-group metal complex TlIII(TFA)3 (TFA = trifluoroacetate) occurs by a C-H activation mechanism akin to transition metal-mediated C-H activation. For benzene, toluene, and xylenes a one-step C-H activation is preferred over electron transfer or proton-coupled electron transfer. The proposed C-H activation mechanism is consistent with calculation and comparison to experiment, of arene thallation rates, regioselectivity, and H/D kinetic isotope effects. For trimethyl and tetramethyl substituted arenes, electron transfer becomes the preferred pathway and thermodynamic and kinetic calculations correctly predict the experimentally reported electron transfer crossover region.In Chapter 4, DFT calculations are used to understand the C-H oxidation reactions of methane and isobutane with SbVF5. SbVF5 is generally assumed to oxidize methane through a methanium-methyl cation mechanism. DFT calculations were used to examine methane oxidation by SbVF5 in the presence of CO leading to the acylium cation, [CH3CO]+. While there is a low barrier for methane protonation by [SbVF6]-[H]+ to give the [SbVF5]-[CH5]+ ion pair, H2 dissociation is a relatively higher energy process, even with CO assistance, and so this protonation pathway is reversible. The C-H activation/[]-bond metathesis mechanism with formation of an SbV-Me intermediate is the lowest energy pathway examined. This pathway leads to [CH3CO]+ by functionalization of the SbV-Me intermediate by CO, and is consistent with no observation of H2. In contrast to methane, due to the much lower carbocation hydride affinity, isobutane significantly favors hydride transfer to give tert-butyl carbocation with concomitant SbV to SbIII reduction. In this mechanism, the resulting highly acidic SbV-H intermediate provides a route to H2 through protonation of isobutane.

Previous studies of supramolecular association through chalcogen-centred secondary bonding interactions (SBIs) demonstrated the versatility of 1,2,5-telluradiazoles and their annulated congeners, the benzo-2,1,3-telluradiazoles, as supramolecular building blocks. Key to the properties of those compounds is their propensity to undergo auto-association through the [Te-N]2 supramolecular synthon leading to dimers or supramolecular ribbon polymers. Moderate steric repulsion induces structural distortions of [Te-N]2 without dissociation and, in doing so, enables properties of practical interest such as chromotropism and second-order non-linear optical responses. However, moisture sensitivity discourages wide-spread application of these compounds. While being more tolerant of the atmosphere, the analogous selenadiazoles form weaker intermolecular interactions. Using a combined experimental and computational approach, this thesis investigates methods by which the selenium-centred supramolecular interactions can be enhanced and applied in the construction of supramolecular architectures. The quantum mechanical description of the SBIs formed by 1,2,5-chalcogenadiazoles was updated with the application of modern dispersion corrections to relativistic density functional theory calculations (PBE-D3, ZORA). While in all cases the dispersion effect on optimized SBI distances is small (< 0.03 Å), the dispersion corrections to the calculated interaction energy range from 6 to 10 kJ mol-1 and increase with the weight of the chalcogen. The total interaction energy increases faster, however, therefore the relative weight of dispersion for the telluradiazole (10%) is significantly less than for the sulfur analogue (40%). The same dispersion-corrected functional was applied to the identification of the secondary ions observed in the Laser Desorption Ionization mass spectrum of benzotelluradiazoles. The most stable structure of the [2M+H]+ ion was shown to feature the [Te-N]2 supramolecular synthon and would be preferred over alternatives held by hydrogen bonding alone, one TeN SBI, a combination of the two or -stacking. The [2M]+ would also feature the [Te-N]2 supramolecular synthon. Shortening of the TeN distances in these ions implies that electron withdrawing groups strengthen the SBIs. The updated computational method was also applied to characterize the bonding in the adducts of a N-heterocyclic carbene with benzo-2,1,3-telluradiazole and 3,4-dicyano-2,1,5-telluradiazole recently prepared by the Zibarev group. The long TeC distances (2.53 and 2.34 Å) correspond to fractional bond orders (<0.6) but display a significant covalent character. Attachment of the carbene nearly erases the remaining σ-hole on tellurium, raises the LUMO energy and consequently prevents the dimerization of these adducts, in contrast to what has been observed with the pyridine and DMSO adducts of other telluradiazoles. Benzo-2,1,3-selenenadiazole reacted with boranes (BR3, R = Ph, F, Cl, Br) yielding 1:1 (R = Ph, F, Cl, Br) and 1:2 (R = Cl) adducts. The crystal structure the BPh3 adduct features molecules organized in pairs connected by long SeC SBIs but no SeN SBIs. The BF3 and BCl3 1:1 adducts dimerize forming the [Se-N]2 supramolecular synthon. In contrast, the BBr3 adduct does not dimerize although SeBr, BrBr SBIs are formed through the lattice. The 1:2 adduct displays SeCl SBIs accompanied by distortion of the N-B-Cl bond angle due to the enhanced electrophilicity of the chalcogen. DFT calculations were performed to evaluate the energies of dimerization of the 1:1 adducts, the calculated SBI energies are greater than those for the dimer of the parent heterocycle (benzo-2,1,3-selenadiazole, 3b). The products of the combination of benzo-2,1,3-selenenadiazole with chloride salts of divalent Mn, Fe, Co, Ni, and Cd crystallized from DMSO in two distinct structural types. While the smaller ions (FeII, CoII and NiII) form infinite chains of metal atoms N,N’-bridged by the heterocycle΄ the larger ions (MnII and CdII) stabilize infinite chains of metal atoms bridged by 2 halide ions. In the latter case, two heterocycle molecules cap each metal ion and are able to establish a link to the next chain in the lattice through the [Se‑N]2 supramolecular synthon. Despite the large (>9.2 Å) distance between [M(-Cl)2]∞ chains, the manganese derivative is only paramagnetic, not ferromagnetic. Symmetry-broken DFT calculations for small models were unable to quantitatively reproduce the measured couplings (J) but do indicate that the heterocycle acquires significant spin density in the MnII compound enabling paramagnetic coupling through the [Se‑N]2 supramolecular synthon. General methods for the synthesis of N-alkylated selenadiazolium cations were investigated. Methyl, iso-propyl and tert-butyl benzo-2,1,3-selenadiazolium cations were prepared by direct alkylation or cyclo-condensation of the alkyl-phenylenediamine with selenous acid. While the former reaction only proceeds with the primary and tertiary alkyl iodides, the latter is very efficient. Difficulties reported in earlier literature are attributable to the formation of adducts of benzoselenadiazole with its alkylated cations and side reactions initiated by aerobic oxidation of iodide. However, the cations themselves are resilient to oxidation and stable in acidic to neutral aqueous media. X-ray crystallography was used in the identification and characterization of the following compounds: [C6H4N2(R)Se]+X-, (R = CH(CH3)2, C(CH3)3; X = I-, I3-), [C6H4N2(CH3)Se]+I-, and [C6H4N2Se][C6H4N2(CH3)Se]2I2. Formation of SeN SBIs was only observed in the last structure because anion binding to selenium is stronger. The relative strengths of those forces and the structural preferences they enforce were assessed with DFT-D3 calculations supplemented by AIM analyses of the electron density. The methods developed for the preparation of N-alkyl benzoselenadiazolium cations were extended to the syntheses of dications intended for use as building blocks of supramolecular polymers. The structure of several salts was established by single-crystal X-ray diffraction. [H4C6NSeN-CH2-CH2-NSeNC6H4]Cl2 crystallized forming a macrocyclic structure in which two dications are bridged by SeCl SBIs; a third halide anion sits at the centre of the macrocycle. [1,2-(H4C6NSeN)2-C6H10]Cl2 features two selenadiazolium cations bridged by a 1‑(R),2‑(R)‑substituted cyclohexane and short SeCl SBIs. [1,4-(H4C6NSeN-CH2)2-C6H4](BF4)2, featuring a p-xylene bridge, crystallizes in two pseudopolymorphs; with dications in anti or syn conformations making SeF contacts. [H4C6NSeN-CH2-CH2-NSeNC6H4](CF3SO3)2 does dimerize though the [Se-N]2 supramolecular synthon, although SeO interactions with the anions cap the second selenium atom. In contrast, [H4C6NSeN-CH2-CH2-CH2-NSeNC6H4](CF3SO3)2 only displays SeO contacts. An oligonucleotide analogue containing N-substituted selenadiazolium cations was designed to create foldamers with structures controlled by main-group secondary bonding. The target structures take advantage of the methods developed in this thesis for the functionalization of selenadiazoles and is meant to be compatible with automated methods for oligonucleotide synthesis. The proposed synthesis begins with the preparation of 1-(α,β)-O-methyl-2-deoxy-D-ribose, which was chlorinated and treated with phenylenediamine. High-resolution mass spectrometry confirmed the attachment of the diamine to the ribose, however, the yield was too low to continue this synthetic project. A ground-breaking development in the application of secondary bonding in supramolecular chemistry is the discovery of the reversible auto-association of iso-tellurazole N-oxides through TeO SBIs into annular structures. These rings are persistent in solution and behave as actual macrocycles able to complex transition metal ions, form adducts with fullerenes, and host small molecules. Single-crystal X-ray diffraction was critical to the characterization of these structures and required careful disorder modelling for tetrahydrofuran molecules included in a macrocyclic hexamer and the occupational disorder of CH2Cl2 and BF4- anions due to metal depletion in the crystal of a PdII complex. / Thesis / Doctor of Philosophy (PhD) / Supramolecular chemistry is a prominent area of research that pursues the construction of large structures by the spontaneous assembly and organization of molecular building blocks. Its fundamental premise is that the judicious use of intermolecular forces allows the design of a structure and control of its properties. Most of the work in supramolecular chemistry has relied on hydrogen atoms bridging molecules and the bonding of metal ions to atoms rich in electrons. This thesis pursued the use of a different type of intermolecular force, termed “secondary bonding”, which is characteristic of the heaviest elements at the right of the periodic table (the “main-group” of elements). Previous work at McMaster demonstrated that cyclic molecules containing carbon, nitrogen and tellurium were particularly efficient as supramolecular building blocks. However, they are easily degraded by atmospheric water, this fact severely limits practical applications of these compounds. In this thesis, the tellurium atoms are replaced by selenium, a lighter element in the same family. The resulting molecules are more tolerant of atmospheric conditions but form weaker intermolecular links. Through a combination of quantum mechanical, synthetic, spectroscopic and structural studies, it is shown that certain modifications to the molecular structure increase the affinity of the selenium atoms for electrons. In this way, it is possible to strengthen the intermolecular interactions and promote the spontaneous assembly of supramolecular structures. These investigations eminently fall in the category of fundamental research but have broad-reaching implications for practical applications in optical and electronic technologies.

This thesis describes selected reactivity studies of the N-heterocyclic carbene, IPr, towards a range of main group compounds. The synthesis and characterisation of sixty-three compounds, all of which incorporate IPr as a ligand in one of three coordination modes, are detailed herein. The deprotonation of IPr allowed for the isolation of an anionic source of the aIPr: ligand which was synthesised as a novel potassium salt and along with the previously reported lithium salt, was employed in reactions with group 12 and 14 bis(trimethylsilyl)amides and tetrahalides. The further chemistry of such novel products was investigated towards both electrophilic and nucleophilic reagents making use of both the pendant nucleophilic carbene functionality and the electrophilic main group centre. An alternative route to such species was investigated by the spontaneous isomerisation of IPr in the coordination sphere of group 14 tetrabromides and group 15 tribromides. The scope of this reactivity was subsequently investigated and was found to provide a simpler route to access the abnormal coordination mode of IPr. The aIPr ligand which is generated may be deprotonated by additional IPr thereby affording aIPr: ligands. The addition of halide abstracting agents allowed for the synthesis of cationic species stabilised by the coordination of either IPr or aIPr ligands. A unique, spontaneous reductive coupling of two phosphorus centres was discovered to take place upon heating a THF solution of (IPr)PBr₃. This allowed for the isolation of a bromide bridged P–P bond with reduced phosphorus centres. This facile reduction chemistry was further explored by reaction with mild reducing agents which provide access to low oxidation state phosphorus compounds in high yields. This chemistry was found to be possible (and more effective) due to the presence of the weaker phosphorus bond to bromine relative to the commonly employed chlorine ligands.

No description available.

This thesis describes the reactivity of Zintl ions of groups 14 [E₉]^4– (E = Ge and Sn)and 15 [E'₇]^3– (E' = P and As) towards a number or transition, post-transition and main group reagents. The synthesis and characterisation of the resulting novel cluster anions is described herein. Coordination compounds of group 14 Zintl ions were synthesised when K₄Ge₉ was reacted with Zn[N(SiMe₃)₂]₂ to give the simple coordination compound [Ge₉ZnN(SiMe₃)₂]^3–. The heavier analogue K₄Sn₉ reacts with the same metal precursor to give the paramagnetic species [Sn₉ZnNSiMe₃]^3– where a trimethylsilyl group has been lost. K₄Ge₉ reacts with [Ru(COD)(&eta;³-CH₂C(CH₃)CH₂)₂] to form the paramagnetic endohedral compound [Ru@Ge₁₂]^3– and with [Co(PEt₂Ph)₂(mes)₂] to form the prolate endohedral compound [Co₂@Ge₁₆]^4–, which has two metal centres encapsulated inside the sixteen atom germanium cage. Regarding group 15 Zintl ion reactivity, the reactions between pyridine solutions of [HP₇]^2– and E[N(SiMe₃)₂]₂ (E = Ge, Sn and Pb) have been found to yield coordination compounds of the type [P7E(N(SiMe3)2]2–. The germanium containing species [P₇GeN(SiMe₃)₂]^2– quickly decomposes at room temperature to give rise to the thermodynamic product [(P₇)₂Ge₂N(SiMe₃)₂]^3–, a process that involves the loss of an amide moiety. Activation products were also synthesised from the reaction of [E'₇]^3– with varying stoichiometries of VCp₂. The reaction with 0.7 equivalents of VCp₂ yields the sandwich complexes [CpV(&eta;⁵-E'₅)]^n– (E' = P: n = 1; E' = As, n = 1 and 2) whereas with 2.5 equivalents the products are the triple-decker sandwich complexes [(CpV)₂(&eta;^x-E'_x)]– (E' = P: x = 6; E' = As: x = 5).

Coordination chemistry usually applies to transition metals, but has recently been extended to the p-block elements. For the pnictogen atoms (group 15), this type of coordination chemistry has already been applied to antimony and bismuth, where they behave as Lewis acceptor centres. However, complexes with nitrogen and phosphorus as Lewis acidic centres are rare, due to their relatively small atomic radii and inherent basic nature. Instead, these elements (Pn(III)) are typically observed as donor centres because they are better at donating their electron pair, than they are at accepting them. To enhance the Lewis acidity at the phosphorus and nitrogen centres, a cationic charge can be introduced by heterolytically abstracting a halide and replacing it with a weakly coordinating anion, providing more opportunities for new reactivity. The presence of a stereochemically active lone pair at the acceptor site also introduces new reactivity patterns to be explored. The formation of these main group coordination complexes opens doors to potential applications in catalysis, small molecule activation, or as material precursors. 2,2’-bipyridine (bipy) has been a prototypical ligand used in transition metal coordination chemistry due to its high basicity and oxidative resistance. This property has been exploited to enable a comprehensive study of a series of Pn(III) tricationic and dicationic complexes using 2,2’-bipyridine (bipy); 4,4’-di-tert-butyl-2,2’-bipyridine (tBu2bipy); 4-dimethylaminopyridine (DMAP); and other main group containing ligands. / Graduate

Chemical synthesis of materials is facing enormous challenges at the present time. The necessary transition toward more sustainable economic processes requires new materials as well as optimized production of well-established materials. However, inorganic materials (e.g., ceramics or alloys) are typically produced industrially by high-temperature processes at up to 2000 °C. A relatively new approach for inorganic synthesis is based on so-called ionic liquids. Ionic liquids (ILs) — often defined as salts with melting points below 100 °C[1] — are usually composed of sterically demanding organic cations and (often) polyatomic anions, which can be selected in order to tune the properties of the IL. Owing to the distinctive physicochemical properties of ILs (e.g., wide liquidus range, high redox and thermal stability, (usually) negligible vapor pressure, tunable polarity), they have gained interest for a wide range of applications. Among the numerous inorganic materials accessible in ILs have been remarkable examples, especially in main-group element chemistry. For instance, a new metastable modification of germanium in the clathrate-II structure[2] or the largest known naked, main-group element cluster [Sn36Ge24Se132]24– (“Zeoball”).[3] The introduction of Lewis-acidic ILs has enhanced the convenience of polycation syntheses and enabled substitution of carcinogenic or toxic substances like benzene, SO2, or AsF5.[4] A considerable number of polycations of group 15 or 16 elements has been synthesized in ILs. The utilization of an IL as reaction medium can be decisive for the composition, structure, and physical properties of the (polycationic) reaction product.[5] In order to broaden the knowledge on synthesis techniques for inorganic materials near ambient temperature based on ILs, this thesis aimed at two goals: • Explorative synthesis of new inorganic compounds in ILs • Elucidating the influence of ILs on product formation For these two goals, metal-rich (polycationic) compounds of group 15 were chosen as promising chemical system, owing to the effectiveness of alkylimidazolium-based Lewis-acidic ILs for the synthesis of this class of compounds. A variety of new polycationic compounds has been successfully synthesized in Lewis-acidic ILs based on 1-n-butyl-3-methylimidazolium (or 1-ethy-3-methylimidazolium) halides and halogenido-aluminates. Determination of the crystal structures by single-crystal X-ray diffraction enabled analysis of their bonding situation supported by quantum-chemical calculations. In general, the employed ILs enabled syntheses with a high selectivity for the yielded polycation. Depending on the investigated chemical system, the following parameters were pinpointed to have significant influence: • Choice of starting materials • Choice of cation as well as anion of the IL • Reaction temperature • Concentration of starting materials in the IL The investigations were supported by NMR spectroscopy, which led to the discovery of nanoparticles of red phosphorus. This finding may stimulate the development of an easily accessible, reactive form of phosphorus without the hazardous drawbacks of the white allotrope. In addition, in situ NMR measurements in ILs were proven a viable option for mechanistic investigations. Conventional solid-state reaction as well as ionothermal syntheses yielded the new layered compounds M2Bi2S3(AlCl4)2 (M = Cu, Ag), which can be interpreted as Bi2S3 molecules embedded in MAlCl4 salts. The choice of starting materials was found to have a crucial influence on the crystallized polytype. Omitting the IL hindered the formation of crystals suitable for single-crystal structure determination. The three new main-group element heteropolycations [Bi6Te4Br2]4+, [Bi3S4AlCl]3+, and [Sb13Se16]7+ as well as known [Bi4Te4]4+ has been synthesized under ionothermal conditions. The Lewis-acidic ILs proved to be exceptional solvents for elements and their halides, and likewise for Bi2S3 and Bi2Te3. Hence, these solvents are not only advantageous reaction media for pnictogen and chalcogen chemistry but also potential (selective but expensive) ore-processing agents. These excellent solvent capabilities extend to complex ternary compounds including heavy transition metals such as Bi16PdCl22 and elemental platinum. This gave rise to the synthesis of metal-rich salts containing [Bi10]4+ antiprisms with an endohedral palladium or, for the first time, platinum atom. Furthermore, the filled bismuth polycation [Rh@Bi9]4+ or the complex cluster [Rh2Bi12]4+ could be obtained from dissolution and conversion of Bi12−xRhX13–x (X = Cl, Br) depending on the employed IL. Real-space bonding analysis revealed that [Rh2Bi12]4+ acquires a unique standing between dative bonding by bismuth polyions and mixed clusters following Wade-Mingos rules. References [1] J. S. Wilkes, P. Wasserscheid, T. Welton, in Ionic Liquids in Synthesis (Eds.: P. Wasserscheid, T. Welton), Wiley-VCH Verlag GmbH & Co. KGaA, 2007, pp. 1–6. [2] A. M. Guloy, R. Ramlau, Z. Tang, W. Schnelle, M. Baitinger, Y. Grin, Nature 2006, 443, 320–323. [3] Y. Lin, W. Massa, S. Dehnen, J. Am. Chem. Soc. 2012, 134, 4497–4500. [4] E. Ahmed, D. Köhler, M. Ruck, Z. Anorg. Allg. Chem. 2009, 635, 297–300. [5] E. Ahmed, J. Beck, J. Daniels, T. Doert, S. J. Eck, A. Heerwig, A. Isaeva, S. Lidin, M. Ruck, W. Schnelle, et al., Angew. Chem. 2012, 124, 8230–8233; Angew. Chem. Int. Ed. 2012, 51, 8106–8109.