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, or skillful deductions. Recent results, mainly based on new soluble compounds, delivered structural evidence. These new insights lead to advanced and more detailed conclusions about the interplay of the involved components.

Sodium and Potassium Complexes of Anionic N‐Heterocyclic Carbenes

“…For future applications of WCA‐NHC ligands, sodium and potassium complexes such as 1 and 6 can serve as convenient carbene transfer and transmetalation reagents, in addition to their widely employed lithium congeners. For a reliable metalation of the NHC ligands such as IDipp, however, the combination of n ‐BuLi with other bases such as alkoxides (Lochmann‐Schlosser superbases) [26] might lead to a more straightfoward formation of lithium‐free sodium and potassium complexes.…”

Mechanism of Potassiumtert-Butoxide-Catalyzed Ketones Hydrogenation in the Solution Phase

“…Here, the term "clusters" 68 implies aggregates of two or more metal atoms with bridging ligands or glued through noncovalent interactions, not necessarily implying that metal−metal bonds are present (which is a more strict definition of the term "cluster" in organometallic chemistry). Potassium tert-butoxide is known for the formation of aggregates in aprotic solvents, 69 the gas phase, 68 and the solid state. 70,71 Out of several possible clusters, the tetrameric cubane-type cluster shown in equilibrium 2 is often proposed as reactive species in several catalytic reactions.…”

Latest Advances in Protein-Recovery Technologies from Agricultural Waste

“…Other research was conducted using chromatography for the purification of lithium [59]. Lithium is an alkali metal that is highly reactive, contains highly soluble salts, and possesses a low ionic charge [60]. Chromatography recovered lithium at a higher efficiency than extraction using the conventional liquid-liquid extraction (LLE) method [59].…”