Synthesis, Structure and Reactivity of Bismuth(III) and Aluminum(III) Complexes Supported by Nitrogen Donor Ligands

Das Hauptaugenmerk der vorliegenden Arbeit liegt auf der Synthese von Bismut und Aluminiumverbindungen in den Oxidationsstufen III welche durch sperrige Liganden stabilisiert werden. Die vorliegende Arbeit ist in vier Abschnitte aufgeteilt. Der erste Teil der Arbeit befasst sich mit der Synthese eines Bismutamid-Komplexes und seiner Reaktion mit Verbindungen aus ungesättigten C-O, C-C und C-N-Bindungen. Die Hauptmotivation für die Forschung im Bereich der Bismut-Chemie ist die Rolle der Bismut-Verbindungen in der Katalyse und der nicht toxischen Wirkung die für die Pharmakologie von Besonderem Interesse ist. L1BiNMe2 1 wurde durch die Reaktion von 1,8-Bis[(trimethylsilyl)amino]naphthalin mit Bi(NMe2)3 hergestellt. Zur Untersuchung der Reaktivität von Bismut-Stickstoff-Bindung im Vergleich zur Kohlenstoff-Sauerstoff-Bindung führten wir Reaktionen von 1 mit Aldehyden -und Ketonen durch. Um die Erkenntnisse auch auf Kohlenstoff-Kohlenstoff-Bindungen zu übertragen, ließen wir 1 mit Alkenen und Alkinen reagieren. Aufgrund des basischen Charakters der NMe2 Gruppe wurde Verbindung 1 dazu genutzt, um eine Reihe von heterobimetallischer Oxide herzustellen. Der zweite Teil der Arbeit beschreibt die Bemühungen Sauerstoff-verbrückten heterobimetallische Komplexe des Bismuts mit Hauptgruppenelementen und Übergangsmetallen herzustellen, die schwer durch andere Methoden synthetisiert werden können. Der letzte Teil beschäftigt sich mit der Herstellung und Charakterisierung von einer Vielzahl an viergliedrigen Ringen aus Aluminium die mit Halogen-, Methyl-und Hydrid-Substituenten versehen sind

1,8-Bis(silylamido)naphthalene complexes of magnesium and zinc synthesized through alkane elimination reactions

The reactions between magnesium or zinc alkyls and 1,8-bis(triorganosilyl)diaminonaphthalenes afford the 1,8-bis(triorganosilyl)diamidonaphthalene complexes with elimination of alkanes. The reaction between 1,8-C10H6(NSiMePh2H)2 and one or two equivalents of MgnBu2 affords two complexes with differing coordination environments for the magnesium; the reaction between 1,8-C10H6(NSiMePh2H)2 and MgnBu2 in a 1:1 ratio affords 1,8-C10H6(NSiMePh2)2{Mg(THF)2} (1), which features a single magnesium centre bridging both ligand nitrogen donors, whilst treatment of 1,8-C10H6(NSiR3H)2 (R3 = MePh2, iPr3) with two equivalents of MgnBu2 affords the bimetallic complexes 1,8-C10H6(NSiR3)2{nBuMg(THF)}2 (R3 = MePh2 2, R3 = iPr3 3), which feature four-membered Mg2N2 rings. Similarly, 1,8-C10H6(NSiiPr3)2{MeMg(THF)}2 (4) and 1,8-C10H6(NSiMePh2)2{ZnMe}2 (5) are formed through reactions with the proligands and two equivalents of MMe2 (M = Mg, Zn). The reaction between 1,8-C10H6(NSiMePh2H)2 and two equivalents of MeMgX affords the bimetallic complexes 1,8-C10H6(NSiMePh2)2(XMgOEt2)2 (X = Br 6; X = I 7). Very small amounts of [1,8-C10H6(NSiMePh2)2{IMg(OEt2)}]2 (8), formed through the coupling of two diamidonaphthalene ligands at the 4-position with concomitant dearomatisation of one of the naphthyl arene rings, were also isolated from a solution of 7

Halogen Bond Asymmetry in Solution

Halogen bonding is the noncovalent interaction of halogen atoms in which they act as electron acceptors. Whereas three-center hydrogen bond complexes, [D center dot center dot center dot H center dot center dot center dot D](+) where D is an electron donor, exist in solution as rapidly equilibrating asymmetric species, the analogous halogen bonds, [D center dot center dot center dot X center dot center dot center dot D](+), have been observed so far only to adopt static and symmetric geometries. Herein, we investigate whether halogen bond asymmetry, i.e., a [D-X center dot center dot center dot D](+) bond geometry, in which one of the D-X bonds is shorter and stronger, could be induced by modulation of electronic or steric factors. We have also attempted to convert a static three-center halogen bond complex into a mixture of rapidly exchanging asymmetric isomers, [D center dot center dot center dot X-D](+) (sic) [D-X center dot center dot center dot D](+), corresponding to the preferred form of the analogous hydrogen bonded complexes. Using N-15 NMR, IPE NMR, and DFT, we prove that a static, asymmetric geometry, [D-X center dot center dot center dot D](+), is obtained upon desymmetrization of the electron density of a complex. We demonstrate computationally that conversion into a dynamic mixture of asymmetric geometries, [D center dot center dot center dot X-D](+) (sic) [D-X center dot center dot center dot D](+), is achievable upon increasing the donor-donor distance. However, due to the high energetic gain upon formation of the three-center-four electron halogen bond, the assessed complex strongly prefers to form a dimer with two static and symmetric three-center halogen bonds over a dynamic and asymmetric halogen bonded form. Our observations indicate a vastly different preference in the secondary bonding of H+ and X+. Understanding the consequences of electronic and steric influences on the strength and geometry of the three-center halogen bond provides useful knowledge on chemical bonding and for the development of improved halonium transfer agents

Organobismuth(III) and Dibismuthine Complexes Bearing N,N′-Disubstituted 1,8-Diaminonaphthalene Ligand: Synthesis, Structure, and Reactivity

The organobismuth­(III) and dibismuthine complexes bearing N,N′-disubstituted 1,8-diaminonaphthalene ligand were prepared. The reaction of LBiNMe₂ (<b>1</b>) [L = 1,8-(NSiMe₃)₂C₁₀H₆] with ClSiMe₃ results in the elimination of Me₃SiNMe₂, while PhCCH, Cp*H, and PhOH proceed via HNMe₂ elimination and provide the complexes of LBiCl (<b>2</b>), LBiCCPh (<b>3</b>), LBiCp*­(<b>4</b>), and LBiOPh (<b>5</b>), respectively. Reaction of <b>1</b> with AlMe₃ in <i>n</i>-hexane yields LBiMe (<b>6</b>). Compound <b>1</b> reacts with diisopropylcarbodiimide and phenyl isocyanate under insertion at the Bi–NMe₂ bond to give the addition products LBi­(N-<i>i</i>Pr)₂CNMe₂ (<b>7</b>) and LBiN­(Ph)­C­(O)­NMe₂ (<b>8</b>). The reactions of <b>1</b> with sulfur and PhSiH₃ result in the formation of LBi–S–BiL (<b>9</b>) and LBi–BiL (<b>10</b>), respectively. Compounds <b>2</b>–<b>10</b> were characterized by elemental analysis, ¹H, ¹³C, and ²⁹Si NMR spectroscopy, and X-ray crystallographic studies

Carbon's Three-Center, Four-Electron Tetrel Bond, Treated Experimentally

Tetrel bonding is the noncovalent interaction of group IV elements with electron donors. It is a weak, directional interaction that resembles hydrogen and halogen bonding yet remains barely explored. Herein, we present an experimental investigation of the carbon-centered, three-center, four-electron tetrel bond, [N-C-N](+), formed by capturing a carbenium ion with a bidentate Lewis base. NMR-spectroscopic, titration-calorimetric, and reaction-kinetic evidence for the existence and structure of this species is reported. The studied interaction is by far the strongest tetrel bond reported so far and is discussed in comparison with the analogous halogen bond. The necessity of the involvement of a bidentate Lewis base in its formation is demonstrated by providing spectroscopic and crystallographic evidence that a monodentate Lewis base induces a reaction rather than stabilizing the tetrel bond complex. A vastly decreased Lewis basicity of the bidentate ligand or reduced Lewis acidity of the carbenium ion weakens or even prohibits the formation of the tetrel bond complex, whereas synthetic modifications facilitating attractive orbital overlaps promote it. As the geometry of the complex resembles the S(N)2 transition state, it provides a model system for the investigation of fundamental reaction mechanisms and chemical bonding theories