Bonding in alkali and alkaline earth acetylacetonates

Boschmann, Erwin; Keller, R. N.

doi:10.1016/j.molstruc.2019.05.131

Cited by 4 publications

(1 citation statement)

References 21 publications

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“…[4] Depending on the concentration, the polarity of the solvent, and the temperature, the interactions between the enolates and their counterions are also retained in solution. Apart from so-called contact-ion pairs AM, [5] these two components can form other types of associates, such as solvent-separated ion pairs and socalled triple ions (Scheme 1). [6] These species all are connected via equilibria with each other as well as with the free ions A À and M + .…”

Section: Introductionmentioning

confidence: 99%

Gas‐Phase Alkali‐Metal Cation Affinities of Stabilized Enolates

Eisele,

Rahrt,

Giachanou

et al. 2023

Chemistry A European J

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The chemistry of alkali‐metal enolates is dominated by ion pairing. To improve our understanding of the intrinsic interactions between the alkali‐metal cations and the enolate anions, we have applied Cooks’ kinetic method to determine relative M+ (M = Li, Na, K) affinities of the stabilized enolates derived from acetylacetone, ethyl acetoacetate, diethyl malonate, ethyl cyanoacetate, 2‑cyanoacetamide, and methyl malonate monoamide in the gas phase. Quantum chemical calculations support the experimental results and moreover afford insight into the structures of the alkali‐metal enolate complexes. The affinities decrease with increasing size of the alkali‐metal cations, reflecting weaker electrostatic interactions and lower charge densities of the free M+ ions. For the different enolates, a comparison of their coordinating abilities is complicated by the fact that some of the free anions undergo conformational changes resulting in stabilizing intramolecular interactions. If these complicating effects are disregarded, the M+ affinities correlate with the electron density of the chelating functionalities, i.e., the carbonyl and/or the nitrile groups of the enolates. A comparison with the known association constants of the corresponding alkali‐metal enolates in solution points to the importance of solvation effects for these systems.

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Section: Introductionmentioning

confidence: 99%