Synthetic, structural, spectroscopic and calculational studies of a lithium β-diketinimate complex

Synthesis and properties of alkaline metal complexes with new overcrowded β-diketiminato ligands

“…In particular, crowded b-diketiminato ligands having bulky substituents at the nitrogen atoms, e.g., [{(Dip)NC(Me)} 2 CH] À (Dip = 2,6-diisopropylphenyl), have been applied to the synthesis of various complexes of main group elements and transition metals, such as low coordinate complexes, low oxidation state complexes, complexes having activities as catalysts, and model complexes for protein active sites. Most of these complexes were derived from the corresponding alkaline metal b-diketiminates, and their syntheses and properties have been studied extensively [3][4][5][6][7][8][9][10][11][12]. In general, the alkaline metals in these complexes are coordinated by bases, such as ethers, amines, or nitriles, due to their extremely high Lewis acidity.…”

Amidolithium-mediated enolization: does proton transfer occur via a dimer intermediate with bridging carbonyls?

“…Such amide substrates come in the form of the diazapentadienyl anion, in which the nitrogen-centred negative charge is delocalized over a 5 atom p-framework. 25 A compound in which the neutral ligand hexamethylphosphoric triamide is found in a bridging role, while the diazapentadienyl anion adopts a terminal position, has been prepared.25 Currently, only reduced ketones (e.g. benzophenone)26 or minor canonical contributions, such as the ketone-enamide form of a deprotonated enaminone,27 point to such a bridging capacity of carbonyls between two lithium atoms.…”

Reversible C–C bond formation: solid state structure of the aldol-like addition product of adamantanone to a 1,5-diazapentadienyllithium, and its solution state retro-aldol dissociationElectronic supplementary information (ESI) available: preparative and characterization details. See http://www.rsc.org/suppdata/cc/b2/b211745b/

“…A similar structure is known where hexamethylphosphoramide acts as the bridge. 6 Furthermore, a computational study confirmed the capacity of carbonyls to bridge in lithium dimers. 7 Consequently, the target was the isolation of a model for the precursor of ketone enolization by amidolithium bases, in support of the hypothesis that such reactions proceed via bridging ketones.…”