0000000001301005
AUTHOR
Jan Klett
Die Reaktion von Neopentyllithium mit Kalium-tert -butoxid: Bildung einer alkanlöslichen Lochmann-Schlosser-Superbase
Gemische aus Alkyllithium und Alkoxiden der schweren Alkalimetalle eignen sich zur Herstellung der entsprechenden Alkylverbindungen. Sie zeichnen sich ebenfalls durch ihre Reaktivitat bei Metallierungsreaktionen aus. Diese metallorganischen Mischungen werden oft als LiC-KOR-Superbasen bezeichnet, doch trotz vieler Bemuhungen ist nur wenig uber ihren Aufbau bekannt. Hier werden dimetallische Alkalimetall-Alkyl/Alkoxy-Verbindungen vorgestellt, die durch die Reaktion von Neopentyllithium und Kalium-tert-butoxid gebildet werden. Dank guter Loslichkeit in Alkanen und Temperaturbestandigkeit der Neopentylverbindungen konnten die Losungen in n-Hexan bei Umgebungstemperatur gehandhabt werden und er…
Titelbild: Direct CH Metalation with Chromium(II) and Iron(II): Transition-Metal Host / Benzenediide Guest Magnetic Inverse-Crown Complexes (Angew. Chem. 18/2009)
Chrom und Eisen als die neuesten Erganzungen des Konzepts der alkalimetallvermittelten Metallierung stellen J. Klett, R. E. Mulvey et al. in ihrer Zuschrift auf S. 3367 ff. vor. Das elektropositivere Natrium ist wesentlich fur die Reaktion, doch das weniger elektropositive Chrom oder Eisen ist es, das Benzol tatsachlich deprotoniert. Diese neuartige Reaktivitat kann mit einem Schachspiel verglichen werden, bei dem die Konigin (Na) dem Konig Schach bietet und der Springer (Cr, Fe) Matt setzt.
Combining Neopentyllithium with Potassium tert-Butoxide: Formation of an Alkane-Soluble Lochmann-Schlosser Superbase.
Mixtures of alkyllithium and heavier alkali-metal alkoxides are often used to form alkyl compounds of heavier alkali metals, but these mixtures are also known for their high reactivity in deprotonative metalation reactions. These organometallic mixtures are often called LiC-KOR superbases, but despite many efforts their constitution remains unknown. Herein we present mixed alkali-metal alkyl/alkoxy compounds produced by reaction of neopentyllithium with potassium tert-butoxide. The key to success was the good solubility and temperature-stability of neopentyl alkali-metal compounds, leading to hexane-soluble mixtures, which allowed handling at ambient temperatures and isolation by crystalliz…
Towards the Next Generation of Lochmann-Schlosser Superbases: A Potassium Neopentyl/Alkoxy Aggregate used in the Tetra-Functionalization of Ferrocene
Lochmann-Schlosser superbases are formed by mixing alkyllithium with potassium alkoxides. These reagents could prove their synthetic usefulness and reliability in many reactions over five decades. However, despite many efforts, the real source of the exceptional reactivity remained a secret. The seemingly manageable system of four components (lithium, potassium atoms, alkyl groups, and alkoxy groups) and their interaction is obscured by poor solubility and fierce reactivity. Recent progress was achieved by using neopentyllithium, leading to alkane-soluble aggregates with varying lithium/potassium content and a flexible alkyl/alkoxy ratio. Herein, we isolated two new alkane-soluble alkyl/alk…
Structural Motifs of Alkali Metal Superbases in Non‐coordinating Solvents
Abstract Lochmann–Schlosser superbases (LSB) are a standard reagent in synthetic chemistry to achieve an exchange of a proton on an organic framework with an alkali metal cation, which in turn can be replaced by a wide range of electrophilic groups. In standard examples, the deprotonating reagent consists of an equimolar mixture of n‐butyllithium and potassium t‐butoxide. However, the nature of the reactive species could not be pinned down either for this composition or for similar mixtures with comparable high reactivity. Despite the poor solubility and the fierce reactivity, some insights into this mixture were achieved by some indirect results, comparison with chemically related systems,…
Bis[(trimethylsilyl)methyl]manganese: Structural Variations of Its Solvent-Free and TMEDA-, Pyridine-, and Dioxane-Complexed Forms
First synthesized in 1976 and recently taking on a new significance as a key precursor to heterobimetallic alkali-metal-manganese(II) complexes, bis[(trimethylsilyl)methyl] manganese has been structurally characterized by X-ray crystallography. It forms a polymeric chain structure of formula [{Mn(CH2SiMe3)(2)}(infinity)], 1, in which distorted tetrahedral, spiro Mn atoms are linked together via mu(2)-bonding alkyl ligands. The structure is notable for displaying two distinct categories of Mn-C bond lengths with a mean size differential of 0.225 angstrom and for being the first fully crystallographically characterized polymeric manganese(II) dialkyl compound. Magnetic measurements of 1 indic…
Sodium-mediated manganation: direct mono- and dimanganation of benzene and synthesis of a transition-metal inverse-crown complex.
Inside out approach: Twofold deprotonation of benzene by a sodium monoalkyl bisamido manganate(II) reagent derived from BuNa, 2,2,6,6-tetramethylpiperidine, and Mn(CH2SiMe3)2 has produced the first inverse-crown complex in which the transition-metal atoms are incorporated in the host (see X-ray structure, blue N, green Na, purple Mn). Variable-temperature magnetization measurements show that the complex is antiferromagnetic.
200 Years of Lithium and 100 Years of Organolithium Chemistry
The element lithium has been discovered 200 years ago. Due to its unique properties it has emerged to play a vital role in industry, esp. for energy storage, and lithium-based products and processes support sustainable technological developments. In addition to the many uses of lithium in its inorganic forms, lithium has a rich organometallic chemistry. The development of organometallic chemistry has been hindered by synthetic problems from the start. When Wilhelm Schlenk developed the basic principles to handle and synthesize air- and moisture-sensitive compounds, the road was open to further developments. After more information was available about the stability and solubility of such comp…
Tuning the Basicity of Synergic Bimetallic Reagents: Switching the Regioselectivity of the Direct Dimetalation of Toluene from 2,5‐ to 3,5‐Positions
Meta-meta metalation: Remarkably, toluene can be directly dimanganated or dimagnesiated at the 3,5-positions using bimetallic bases with active Me3SiCH2 ligands (see scheme, blue). In contrast, n-butyl ligands lead to 2,5-metalation (red). tmp=2,2,6,6-tetramethylpiperidide.
Polysubstituted ferrocenes as tunable redox mediators
A series of four ferrocenyl ester compounds, 1-methoxycarbonyl- (1), 1,1’-bis(methoxycarbonyl)- (2), 1,1’,3-tris(methoxycarbonyl)- (3) and 1,1’,3,3’-tetrakis(methoxycarbonyl)ferrocene (4), has been studied with respect to their potential use as redox mediators. The impact of the number and position of ester groups present in 1–4 on the electrochemical potential E1/2 is correlated with the sum of Hammett constants. The 1/1+–4/4+ redox couples are chemically stable under the conditions of electrolysis as demonstrated by IR and UV–vis spectroelectrochemical methods. The energies of the C=O stretching vibrations of the ester moieties and the energies of the UV–vis absorptions of 1–4 and 1+–4+ c…
Synthesis and Structure of a Potassium Potassiochromate: A Bis-Chromium(II) Molecule Held Together by Near-Square-Planar Potassium−Ligand Bridges
No Cr-Cr bonding is found in a new type of mixed-metal ate complex having two coordinatively unsaturated but sterically saturated bisamido-monoalkyl Cr(II) groups linked via an unusual near-square-planar-coordinated K atom in the moiety of the ate, while the cationic moiety is a separated iris-tmeda solvated second potassium atom.
The hetero-cubane structures of the heavy alkali metal tert-amyloxides [MOCMe2Et]4 (M = K, Rb, Cs)
A series of alkali metal (Li–Cs) alkoxides of tert-pentanol (1,1-dimethylpropan-1-ol) have been prepared by reaction of the corresponding metal with the alcohol in n-hexane or n-heptane. The compounds were purified by vacuum sublimation and crystallised in n-hexane to produce crystals suitable for single-crystal X-ray diffraction studies. The structures of the potassium, rubidium, and caesium compounds revealed tetrameric units with additional intra- and intermolecular interactions between the metal atom and alkoxide methyl groups, increasing with the size of the metal involved.
The Preparation of Tetramethyl 1,1′,3,3′-Ruthenocenetetracarboxylate and Tetramethyl 1,1′,3,3′-Osmocenetetracarboxylate, and a Simplified Synthesis for Tetramethyl 1,1′,3,3′-Ferrocenetetracarboxylate
Substituted metallocenes with more than two substituents have to be synthesized using doubly substituted cyclopentadiene rings in a reaction with a metal compound or by the introduction of additional functional groups to an already di-substituted metallocene. The direct formation of tetra-substituted metallocenes often suffers due to insufficient reactivity of the reagents or the resulting product mixtures, which are hard to separate. In this work, a protocol, which was successful in a tetra-substitution of ferrocene by a tetra-metalation followed by a reaction with carbon dioxide, is used to perform the tetra-substitution of ruthenocene and osmocene. In addition, a simplified protocol for …
Homo‐ and Heteroleptic Hypersilylcuprates — Valuable Reagents for the Synthesis of Molecular Compounds with a Cu−Si Bond
Unsolvated hypersilanides MHyp [Hyp = Si(SiMe3)(3)] of the heavier alkali metals (M-I = Na, K, Cs) react with copper tert-butoxide in toluene to yield crystalline heteroleptic cuprates [M-I(toluene)][tBuOCuHyp]. These cuprates proved to be valuable sources for pure hypersilylcopper and other cuprates bearing hypersilyl ligands such as the di(hypersilyl)cuprates M-I[CuHyp(2)]((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003).
Cover Picture: Direct CH Metalation with Chromium(II) and Iron(II): Transition-Metal Host / Benzenediide Guest Magnetic Inverse-Crown Complexes (Angew. Chem. Int. Ed. 18/2009)
Chromation and ferration are the latest additions to the concept of alkali-metal-mediated metalation, as described by J. Klett, R. E. Mulvey, and co-workers in their Communication on page 3317 ff. While the more electropositive sodium is essential for the reaction, it is the less electropositive chromium or iron that actually performs deprotonation of benzene. This novel reactivity can be likened to a game of chess in which the queen (Na) holds the king in check, while the knight (Cr, Fe) scores checkm(etal)ate.
Direct C-H metalation with chromium(ii) and iron(ii): transition- metal host/benzenediide guest magnetic inverse-crown complexes
Check M(etal)ate: The chessboard and the figures represent a special reaction in which different low-polarity metals can metalate arenes directly when they are brought into the right position. In a combination of queen (sodium) and knight (chromium or iron), it is possible for the knight (usually the weaker piece) to make a direct deadly hit on the king (benzene) in this game of elemental chess. Fil: Alborés, Pablo. Johannes Gutenberg Universitat Mainz; Alemania. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Carrella, Luca M.. Johannes Gutenberg Universitat Mainz; Alemania Fil: Clegg, William. University of Newcastle; Reino Unido Fil: García Álvarez, Pablo. Univ…
Endohedral Mixed Aggregates: Sodium Alkoxide Cages with Organic or Inorganic Central Anions and Variable Hull.
Abstract Alkali metal alkoxides are widely used in chemistry due to their Brønsted basic and nucleophilic properties. Potassium alkoxides assist alkyllithium in the metalation of hydrocarbons in Lochmann‐Schlosser‐bases. Both compounds form mixed aggregates, which enhance the thermal stability, solubility, and the basic reactivity of these mixtures. A very unusual spherical mixed alkoxy aggregate was discovered by Grützmacher et al., where a central dihydrogen phosphide anion is surrounded by a highly dynamic shell of thirteen sodium atoms and a hull of twelve tert‐butoxide groups. This structural motif can be reproduced by a reaction of trimethylsilyl compounds of methane, halogens, or pse…
Structural and Magnetic Insights into the Trinuclear Ferrocenophane and Unexpected Hydrido Inverse Crown Products of Alkali‐Metal‐Mediated Manganation(II) of Ferrocene
With the aim of introducing the diisopropylamide [NiPr(2)](-) ligand to alkali-metal-mediated manganation (AMMMn) chemistry, the temperature-dependent reactions of a 1:1:3 mixture of butylsodium, bis(trimethylsilylmethyl)manganese(II), and diisopropylamine with ferrocene in hexane/toluene have been investigated. Performed at reflux temperature, the reaction affords the surprising, ferrocene-free, hydrido product [Na(2)Mn(2) (mu-H)(2){N(iPr)(2)}(4)]2 toluene (1), the first Mn hydrido inverse crown complex. Repeating the reaction rationally, excluding ferrocene, produces 1 in an isolated crystalline yield of 62 %. At lower temperatures, the same bimetallic amide mixture leads to the manganati…
CCDC 2061409: Experimental Crystal Structure Determination
Related Article: Erkam Cebi, Jan Klett|2021|Chem.-Eur.J.|27|12693|doi:10.1002/chem.202100912
CCDC 2061412: Experimental Crystal Structure Determination
Related Article: Erkam Cebi, Jan Klett|2021|Chem.-Eur.J.|27|12693|doi:10.1002/chem.202100912
CCDC 1579177: Experimental Crystal Structure Determination
Related Article: Bianca Jennewein, Sascha Kimpel, Daniel Thalheim, Jan Klett|2018|Chem.-Eur.J.|24|7605|doi:10.1002/chem.201800608
CCDC 2061408: Experimental Crystal Structure Determination
Related Article: Erkam Cebi, Jan Klett|2021|Chem.-Eur.J.|27|12693|doi:10.1002/chem.202100912
CCDC 2061410: Experimental Crystal Structure Determination
Related Article: Erkam Cebi, Jan Klett|2021|Chem.-Eur.J.|27|12693|doi:10.1002/chem.202100912
CCDC 1837111: Experimental Crystal Structure Determination
Related Article: Maximillian Kaiser, Jan Klett|2018|Dalton Trans.|47|12582|doi:10.1039/C8DT01545G
CCDC 1837113: Experimental Crystal Structure Determination
Related Article: Maximillian Kaiser, Jan Klett|2018|Dalton Trans.|47|12582|doi:10.1039/C8DT01545G
CCDC 1837112: Experimental Crystal Structure Determination
Related Article: Maximillian Kaiser, Jan Klett|2018|Dalton Trans.|47|12582|doi:10.1039/C8DT01545G
CCDC 1579178: Experimental Crystal Structure Determination
Related Article: Bianca Jennewein, Sascha Kimpel, Daniel Thalheim, Jan Klett|2018|Chem.-Eur.J.|24|7605|doi:10.1002/chem.201800608
CCDC 2061407: Experimental Crystal Structure Determination
Related Article: Erkam Cebi, Jan Klett|2021|Chem.-Eur.J.|27|12693|doi:10.1002/chem.202100912
CCDC 2061411: Experimental Crystal Structure Determination
Related Article: Erkam Cebi, Jan Klett|2021|Chem.-Eur.J.|27|12693|doi:10.1002/chem.202100912
CCDC 1579179: Experimental Crystal Structure Determination
Related Article: Bianca Jennewein, Sascha Kimpel, Daniel Thalheim, Jan Klett|2018|Chem.-Eur.J.|24|7605|doi:10.1002/chem.201800608
CCDC 1455868: Experimental Crystal Structure Determination
Related Article: Philipp Benrath, Maximilian Kaiser, Thomas Limbach, Mihail Mondeshki and Jan Klett|2016|Angew.Chem.,Int.Ed.|55|10886|doi:10.1002/anie.201602792
CCDC 1455867: Experimental Crystal Structure Determination
Related Article: Philipp Benrath, Maximilian Kaiser, Thomas Limbach, Mihail Mondeshki and Jan Klett|2016|Angew.Chem.,Int.Ed.|55|10886|doi:10.1002/anie.201602792
CCDC 1837114: Experimental Crystal Structure Determination
Related Article: Maximillian Kaiser, Jan Klett|2018|Dalton Trans.|47|12582|doi:10.1039/C8DT01545G
CCDC 1579180: Experimental Crystal Structure Determination
Related Article: Bianca Jennewein, Sascha Kimpel, Daniel Thalheim, Jan Klett|2018|Chem.-Eur.J.|24|7605|doi:10.1002/chem.201800608