In silico capture of noble gas atoms with a light atom molecule

Noble gas atoms (Ng = He, Ne, Ar, and Kr) can be captured in silico with a light atom molecule containing only C, H, Si, O, and B atoms. Extensive density functional theory (DFT) calculations on series of peri-substituted scaffolds indicate that confined spaces (voids) capable to energy efficiently encapsulate and bind Ng atoms are accessible by design of a tripodal peri-substituted ligand, namely, [(5-Ph₂B-xan-4-)₃Si]H (xan = xanthene) comprising (after hydride abstraction) four Lewis acidic sites within the cationic structure [(5-Ph₂B-xan-4-)₃Si]⁺. The host (ligand system) thereby provides an adoptive environment for the guest (Ng atom) to accommodate for its particular size. Whereas considerable chemical interactions are detectable between the ligand system and the heavier Ng atoms Kr and Ar in the host guest complex [(5-Ph₂B-xan-4-)₃Si·Ng]⁺, the lighter Ng atoms Ne and He are rather tolerated by the ligand system instead of being chemically bound to it, nicely highlighting the gradual onset of (weak) chemical bonding along the series He to Kr. A variety of real-space bonding indicators (RSBIs) derived from the calculated electron and pair densities provides valuable insight to the situation of an "isolated atom in a molecule" in case of He, uncovering its size and shape, whereas minute charge rearrangements caused by polarization of the outer electron shell of the larger Ng atoms results in formation of polarized interactions for Ar and Kr with non-negligible covalent bond contributions for Kr. The present study shows that noble gas atoms can be trapped by small light-atom molecules without the forceful conditions necessary using cage structures such as fullerenes, boranes and related compounds or by using super-electrophilic sites like [B₁₂(CN)₁₁]^- if the chelating effect of several Lewis acidic sites within one molecule is employed.

In silico activation of dinitrogen with a light atom molecule

The NN triple bond can be cleaved in silico with a light atom molecule containing only the earth abundant elements C, H, Si, and P. Extensive density functional theory (DFT) computations on various classes of peri-substituted scaffolds containing Lewis acidic and basic sites in the framework of frustrated Lewis pairs (FLP) indicate that the presence of two silyl cations and two P atoms in a flexible but not too flexible arrangement is essential for energy efficient N₂-activation. The non-bonding lone-pair electrons of the P atoms thereby serve as donors towards N₂, whereas the lone-pairs of N₂ donate into the silyl cations. Newly formed lone-pair basins in the N₂-adducts balance surplus charge. Thereby, the N-N bond distance is increased by astonishing 0.3 Å, from 1.1 Å in N₂ gas to 1.4 Å in the adduct, which makes this bond prone to subsequent addition of hydride ions and protonation, forming two secondary amine sites in the process and eventually breaking the NN triple bond. Potential formation of dead-end states, in which the dications ("active states") aversively form a Lewis acid (LA)-Lewis base (LB) bond, or in which the LA and LB sites are too far away from each other to be able to capture N₂, are problematic but might be circumvented by proper choice of spacer molecules, such as acenaphthalene or biphenylene, and the ligands attached to the LA and LB atoms, such as phenyl or mesityl, and by purging the reaction solutions with gaseous N₂ in the initial reaction steps. Charge redistributions via N₂-activation and splitting were monitored by a variety of real-space bonding indicators (RSBIs) derived from the calculated electron and electron pair densities, which provided valuable insight into the bonding situation within the different reaction steps.

Transition metal complexes of antimony centered ligands based upon acenaphthyl scaffolds. Coordination non-innocent or not?

The synthesis and structures of the di- and triorgano antimony compounds (6-Ph2P-Ace-5-)2SbCl (1) and (6-Ph2P-Ace-5-)3Sb (2) are presented along with their use as coordination non-innocent ligands for transition metals, leading to the complexes Cl(6-Ph2P-Ace-5-)2SbCuCl (3), Cl2(6-Ph2P-Ace-5-)2SbPdCl (4), Cl2(6-Ph2P-Ace-5-)2SbPtCl (5) and Cl(6-Ph2P-Ace-5-)3SbRhCl (6). The electronic structures of 1-6 were investigated by DFT computations using a set of topological and surface-based real-space bonding indicators derived from the Atoms-In-Molecules (AIM), Non-Covalent interactions Index (NCI), and Electron Localizability Indicator (ELI-D) methods, unravelling a dative Sb-Cu bond character in 3 and polar-covalent Sb-Pd/Pt/Rh interactions in 4-6.

Coordination of a stibine oxide to a Lewis acidic stiborane at the upper rim of the biphenylene backbone

The biphenylene backbone is used to support a stibine oxide stabilized intramolecularly by a SbO → Sb(v) donor–acceptor interaction.