Reactivity of (TMS)2N(η1-Cp*)Si═Si(η1-Cp*)N(TMS)2 toward the Halides of Groups 13–15

Static and Dynamical Quantum Studies of CX3-AlX2 and CSiX3-BX2 (X = F, Cl, Br) Complexes with Hydrocyanic Acid: Unusual Behavior of Strong π-Hole at Triel Center

The set of TX₃-TrX₂ (T = C, Si, Ge; Tr = B, Al, Ga; X = F, Cl, Br) molecules offers a rather unique opportunity to study both σ-hole and π-hole dimerization on the tetrel and triel ends, respectively. According to the molecular electrostatic potential (MEP) distribution, the π-hole extrema (acidic sites) were more intense than their σ-hole counterparts. The molecules owning the most (CX₃-AlX₂) and least (SiX₃-BX₂) intense π-holes were chosen to evaluate their capacities to attract one and two HCN molecules (Lewis bases). We discovered that the energetic characteristics of π-hole dimers severely conflict with the monomers MEP pattern since the weakest π-hole monomer forms a dimer characterized by interaction energy compared to those created by the monomers with noticeably greater power in the π-hole region. This outcome is due to the deformation of the weakest π-hole donor. Furthermore, the MEP analysis for monomers in the geometry of respective dimers revealed a "residual π-hole" site that was able to drive second ligand attachment, giving rise to the two "unusual trimers" examined further by the NCI and QTAIM analyses. Apart from them, the π-hole/π-hole and σ-hole/π-hole trimers have also been obtained throughout this study and described using energetic and geometric parameters. The SAPT approach revealed details of the bonding in one of the "unusual trimers". Finally, Born-Oppenheimer Molecular Dynamics (BOMD) simulations were carried out to investigate the time evolution of the interatomic distances of the studied complexes as well as their stability.

Gradual Donor Stabilization of a Transient Ferrocene Bridged Bisphosphanyl Phosphenium Cation

A transient phosphenium cation embedded into a [3]ferrocenophane scaffold was formed via chloride abstraction. The cation has been trapped with phosphane, carbene, and silylene donors resulting in stable adducts or bond activation of the ferrocenophane bridge. In the absence of donors, dimerization of the phosphenium cation to the corresponding dication is observed or P-C bond activation with migration of a substituent leading to a putative phosphoniodiphosphene. Using 1,3-di-tert-butylimidazol-2-silylene as the donor, further reaction of the initially formed chlorosilane leads to activation of a P-P bond of the ferrocenophane scaffold with ring expansion of the ansa-bridge. The donor formation and bonding situation are investigated by density functional theory calculations as well as experimental methods (e.g., NMR spectroscopy and X-ray crystallography).

Computational Exploration of Mechanistic Avenues in Metal-Free CO2 Reduction to CO by Disilyne Bisphosphine Adduct and Phosphonium Silaylide

Recent years have seen a growing interest in metal-free CO₂ activation by silylenes, silylones, and silanones. However, compared to mononuclear silicon species, CO₂ reduction mediated by dinuclear silicon compounds, especially disilynes, has been less explored. We have carried out extensive computational investigations to explore the mechanistic avenues in CO₂ reduction to CO by donor-stabilized disilyne bisphosphine adduct (R1^M ) and phosphonium silaylide (R2) using density functional theory calculations. Theoretical calculations suggest that R1^M exhibits donor-stabilized bis(silylene) bonding features with unusual Si-Si multiple bonding. Various modes of CO₂ coordination to R1^M have been investigated and the coordination of CO₂ by the carbon center to R1^M is found to be kinetically more facile than that by oxygen involving only one or both the silicon centers. Both the theoretically predicted reaction mechanisms of R1^M and R2-mediated CO₂ reduction reveal the crucial role of silicon-centered lone pairs in CO₂ activations and generation of key intermediates possessing enormous strain in the Si-C-O ring, which plays the pivotal role in CO extrusion.