Can an alkalide act as a perfect Lewis base?

Classical versus Collective Interactions in Asymmetric Trigonal Bipyramidal Alkaline Metal-Boron Halide Complexes

Collective interactions are a novel type of chemical bond formed between metals and electron-rich substituents around an electron-poor central atom. So far only a limited number of candidates for having collective interactions are reported. In this work, we extend the newly introduced concept of collective bonding to a series of neutral boron complexes with the general formula M2BX3 (M=Li, Na, and K; X=F, Cl, and Br). Our state-of-the-art ab initio computations suggest that these complexes form trigonal bipyramidal structures with a D3h to C3v distortion along the C3 axis of symmetry. The BX3 unit in the complexes distorts from planar to pyramidal akin to a sp3 hybridized atom. Interestingly, the interaction of the metals with the pyramidal side of BX3, where the lone pair in a hypothetical [BX3]2- should be located, is weaker than the interactions of metals with the inverted side, i. e., the middle of three halogen atoms. The origin of this stronger interaction can be explained by the formation of collective interactions between metals and halogen atoms as we explored via energy decomposition within the context of the theory of interacting quantum atoms, IQA.

Anti-electrostatic cation⋯π-hole and cation⋯lp-hole interactions are stabilized via collective interactions

Collective interactions are a novel type of bond between metals and AX3 fragments with an electropositive central atom, A, and electronegative X substituents. Here, using electrostatic potential maps and state-of-the-art bonding analysis tools we have shown that collective interactions are anti-electrostatic cation⋯π-Hole or cation⋯lp-Hole interactions.

Inter-Alkali-Metal Dative Bond in the MMN3 - (M=Alkali Metal) Cluster

Alkali metals are generally Lewis acids. On the contrary, Lewis basic character of alkali metals forming donor - acceptor complexes is a very rare phenomenon. In this contribution, I have theoretically designed an anionic cluster MMN₃ ^- (M=alkali metals) on the basis of experimentally known reagent, alkali salt of azide ion MN₃ , which shows unprecedented M:^- →M donor-acceptor interaction. To the best of author's knowledge, the characterization of such donor-acceptor interaction among alkali metals is unprecedented. Formation of the 2c-2e donor-acceptor bonds have been confirmed by quantum theory of atoms in molecules and electron localization function analyses. The calculated bond dissociation energies are significant suggesting their possible spectroscopic identification.