Über die Chemie des [Me3Si]+ - Ions

Im Rahmen dieser Arbeit wurde eine Reihe von Trityl-Verbindungen als Präkursoren für die Darstellung entsprechender TMS-Salze untersucht. Die synthetisierten TMS-Präkursoren konnten erfolgreich für die Synthese von persilylierten Sulfat-, Phosphat- und Sulfid-Ionen genutzt werden. Ferner konnte das Verhalten der neutralen silylierten Spezies gegenüber Basen untersucht werden. Die Chemie entspricht somit weitestgehend der der protonierten Mineralsäuren. Bisher schwer zugängliche Wasserstoffsäuren wie HNSO & HPCO konnten auf eine neue und einfache Weise synthetisiert und charakterisiert werden.Within the scope of this work, a series of new trityl compounds was investigated as precursors for the synthesis of corresponding TMS salts. The synthesized TMS precursors were successfully used for the preparation of persilylated sulfate, phosphate and sulfide cations. It was possible to investigate the behavior against bases and therefore generate mono-/bissilylated anionic species. Thus, this chemistry largely corresponds to that of the protonated acids. Hydrogen acids hitherto difficult to access, such as HNSO & HPCO, could be synthesized and characterized with a new synthetic procedure

HPCO - A phosphorus-containing analogue of isocyanic acid

We describe the isolation and spectroscopic characterization of the heavier phosphorus‐containing analogue of isocyanic acid (HPCO), and its isotopologue (DPCO). This fundamental small molecule, which has been postulated to exist in interstellar space, has thus far only been observed at low gas phase concentrations or in inert gas matrices. In this report we describe its synthesis, spectroscopic properties, and reactivity in solution

Synthesis of the First Persilylated Ammonium Ion, [(Me₃Si)₃NSi(H)Me₂]⁺, by Silylium-Catalyzed Methyl/Hydrogen Exchange Reactions

This work describes the unexpected synthesis and characterization of the first persilylated ammonium ion, [(Me₃Si)₃NSi­(H)­Me₂]⁺, in the reaction of (Me₃Si)₃N with [Me₃Si–H–SiMe₃]­[B­(C₆F₅)₄]. NMR and Raman studies revealed a transition-metal-free silylium ion catalyzed substituent redistribution process when [Me₃Si–H–SiMe₃]⁺ was used as the silylating reagent. These observations were affirmed in the reaction with [Et₃Si–H–SiEt₃]­[B­(C₆F₅)₄]. A Lewis acid catalyzed scrambling process always occurs if an excess of silanes is present in the formation of silylium cations while employing the standard Bartlett–Schneider–Condon type reaction. Additionally, the thermodynamics of this process was accessed by DFT computations at the pbe1pbe/aug-cc-pVDZ level, indicating alkyl substituent exchange equilibria at the silane and preference of the formation of [(Me₃Si)₃NSi­(H)­Me₂]⁺ over [(Me₃Si)₄N]⁺

Synthesis of the First Persilylated Ammonium Ion, [(Me₃Si)₃NSi(H)Me₂]⁺, by Silylium-Catalyzed Methyl/Hydrogen Exchange Reactions

This work describes the unexpected synthesis and characterization of the first persilylated ammonium ion, [(Me₃Si)₃NSi­(H)­Me₂]⁺, in the reaction of (Me₃Si)₃N with [Me₃Si–H–SiMe₃]­[B­(C₆F₅)₄]. NMR and Raman studies revealed a transition-metal-free silylium ion catalyzed substituent redistribution process when [Me₃Si–H–SiMe₃]⁺ was used as the silylating reagent. These observations were affirmed in the reaction with [Et₃Si–H–SiEt₃]­[B­(C₆F₅)₄]. A Lewis acid catalyzed scrambling process always occurs if an excess of silanes is present in the formation of silylium cations while employing the standard Bartlett–Schneider–Condon type reaction. Additionally, the thermodynamics of this process was accessed by DFT computations at the pbe1pbe/aug-cc-pVDZ level, indicating alkyl substituent exchange equilibria at the silane and preference of the formation of [(Me₃Si)₃NSi­(H)­Me₂]⁺ over [(Me₃Si)₄N]⁺

Rapidly fatal leishmaniasis in resistant C57BL/6 mice lacking TNF

The resolution of infections with the protozoan parasite Leishmania major in mice requires a Th1 response that is closely associated with the expression of IL-12, IFN-{gamma}, and inducible NO synthase. Previous Ab neutralization studies or the use of mice deficient for both TNF receptors suggested that TNF plays only a limited role in the control of parasite replication in vivo. In this study we demonstrate that resistant C57BL/6 (B6.WT) mice locally infected with L. major rapidly succumb to progressive visceral leishmaniasis after deletion of the TNF gene by homologous recombination. A reduction of the parasite inoculum to 3000 promastigotes did not prevent the fatal outcome of the disease. An influence of the altered morphology of secondary lymphoid organs in C57BL/6-TNF-/- (B6.TNF-/-) mice on the course of disease could be excluded by the generation of reciprocal bone marrow chimeras. Although infected B6.TNF-/- mice mounted an L. major-specific IFN-{gamma} response and expressed IL-12, the onset of the immune reaction was delayed. After in vitro stimulation, B6.TNF-/- inflammatory macrophages released 10-fold less NO in response to IFN-{gamma} than B6.WT cells. However, in the presence of a costimulus, e.g., L. major infection or LPS, the production of NO by B6.WT and B6.TNF-/- macrophages was comparable. In vivo, inducible NO synthase protein was readily detectable in skin lesions and draining lymph nodes of B6.TNF-/- mice, but its expression was more disperse and less focal in the absence of TNF. These are the first data to demonstrate that TNF is essential for the in vivo control of L. major

Synthesis and Characterization of Silylated Phosphonium [P(OSiMe₃)₄]⁺ and Phosphate [O₂P(OSiMe₃)₂]⁻ Salts

Starting from an optimized synthesis of silylated phosphoric acid, OP­(OSiMe₃)₃, a borate salt bearing the [P­(OSiMe₃)₄]⁺ cation was generated in the reaction of OP­(OSiMe₃)₃ with [Me₃Si–H–SiMe₃]­[B­(C₆F₅)₄], isolated, and fully characterized. Analogously to the protonated species, phosphoric acid (H₃PO₄) reaction of OP­(OSiMe₃)₃ with a base led to the formation of the unknown [O₂P­(OSiMe₃)₂]⁻ anion, which could be crystallized as potassium salt and structurally characterized, too. Both [P­(OSiMe₃)₄]⁺ and [O₂P­(OSiMe₃)₂]⁻ can be regarded as the formal autoprotolysis products of OP­(OSiMe₃)₃

On Silylated Oxonium and Sulfonium Ions and Their Interaction with Weakly Coordinating Borate Anions

Attempts have been made to prepare salts with the labile tris(trimethylsilyl)chalconium ions, [(Me3Si)3E]+ (E=O, S), by reacting [Me3Si-H-SiMe3][B(C6F5)4] and Me3Si[CB] (CB−=carborate=[CHB11H5Cl6]−, [CHB11Cl11]−) with Me3Si-E-SiMe3. In the reaction of Me3Si-O-SiMe3 with [Me3Si-H-SiMe3][B(C6F5)4], a ligand exchange was observed in the [Me3Si-H-SiMe3]+ cation leading to the surprising formation of the persilylated [(Me3Si)2(Me2(H)Si)O]+ oxonium ion in a formal [Me2(H)Si]+ instead of the desired [Me3Si]+ transfer reaction. In contrast, the expected homoleptic persilylated [(Me3Si)3S]+ ion was formed and isolated as [B(C6F5)4]− and [CB]− salt, when Me3Si-S-SiMe3 was treated with either [Me3Si-H-SiMe3][B(C6F5)4] or Me3Si[CB]. However, the addition of Me3Si[CB] to Me3Si-O-SiMe3 unexpectedly led to the release of Me4Si with simultaneous formation of a cyclic dioxonium dication of the type [Me3Si-μO-SiMe2]2[CB]2 in an anion-mediated reaction. DFT studies on structure, bonding and thermodynamics of the [(Me3Si)3E]+ and [(Me3Si)2(Me2(H)Si)E]+ ion formation are presented as well as mechanistic investigations on the template-driven transformation of the [(Me3Si)3E]+ ion into a cyclic dichalconium dication [Me3Si-μE-SiMe2]22+. © 2019 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA