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High-level electronic structure calculations are carried out to obtain optimized geometries and excitation energies of neutral lithium, sodium, and potassium complexes with two ethylenediamine and one or two crown ether molecules. Three different sizes of crowns are employed (12-crown-4, 15-crown-5, 18-crown-6). The ground state of all complexes contains an electron in an s-type orbital. For the mono-crown ether complexes, this orbital is the polarized valence s-orbital of the metal, but for the other systems this orbital is a peripheral diffuse orbital. The nature of the low-lying electronic states is found to be different for each of these species. Specifically, the metal ethylenediamine complexes follow the previously discovered shell model of metal ammonia complexes (1s, 1p, 1d, 2s, 1f), but both mono- and sandwich di-crown ether complexes bear a different shell model partially due to their lower (cylindrical) symmetry and the stabilization of the 2s-type orbital. Li(15-crown-5) is the only complex with the metal in the middle of the crown ether and adopts closely the shell model of metal ammonia complexes. Our findings suggest that the electronic band structure of electrides (metal crown ether sandwich aggregates) and expanded metals (metal ammonia aggregates) should be different despite the similar nature of these systems (bearing diffuse electrons around a metal complex). 

Mass spectrometric analysis of the anionic products of interaction between platinum atomic anions, Pt⁻, and methane, CH₄and CD₄, in a collision cell shows the preferred generation of [PtCH₄]⁻and [PtCD₄]⁻complexes and a low tendency toward dehydrogenation. [PtCH₄]⁻is shown to be H−Pt−CH₃⁻by a synergy between anion photoelectron spectroscopy and quantum chemical calculations, implying the rupture of a single C−H bond. The calculated reaction pathway accounts for the observed selective activation of methane by Pt⁻. This study presents the first example of methane activation by a single atomic anion.

 

Mass spectrometric analysis of the anionic products of interaction between platinum atomic anions, Pt⁻, and methane, CH₄and CD₄, in a collision cell shows the preferred generation of [PtCH₄]⁻and [PtCD₄]⁻complexes and a low tendency toward dehydrogenation. [PtCH₄]⁻is shown to be H−Pt−CH₃⁻by a synergy between anion photoelectron spectroscopy and quantum chemical calculations, implying the rupture of a single C−H bond. The calculated reaction pathway accounts for the observed selective activation of methane by Pt⁻. This study presents the first example of methane activation by a single atomic anion.