Strengths of different Lewis bases in stabilizing titanium fluorides: A theoretical insight

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.

Isomerization of Functionalized Olefins Using the Dinuclear Catalyst [PdI(μ-Br)(PtBu3)]2: A Mechanistic Study

In a combined experimental and computational study, the isomerization activity of the dinuclear palladium(I) complex [Pd^I(μ‐Br)(P^tBu₃)]₂ towards allyl arenes, esters, amides, ethers, and alcohols has been investigated. The calculated energy profiles for catalyst activation for two alternative dinuclear and mononuclear catalytic cycles, and for catalyst deactivation are in good agreement with the experimental results. Comparison of experimentally observed E/Z ratios at incomplete conversion with calculated kinetic selectivities revealed that a substantial amount of product must form via the dinuclear pathway, in which the isomerization is promoted cooperatively by two palladium centers. The dissociation barrier towards mononuclear Pd species is relatively high, and once the catalyst enters the energetically more favorable mononuclear pathway, only a low barrier has to be overcome towards irreversible deactivation.

Yttrium germole dianion complexes with Y-Ge bonds

The reactions of dipotassium 3,4-dimethyl-2,5-bis(trimethylsilyl)-germole dianion K2[1] with YCl3 and Cp*YCl2 (Cp* = cyclopentadienyl) in THF at room temperature afforded the dianion salt [(K-cryptand-222)2][1-YCl3] (K2[2]) and the dimeric complex [1-Y-Cp*]2 (3), respectively. While the polymeric complex {[(1)2-Y-K(toluene)]2}n (4) was obtained from the reaction of K2[1] and half molar equivalent of YCl3(THF)3.5 in toluene at 80 °C. The germole dianions in complexes 3 and 4 feature η5/η1 coordination interactions with the yttrium atoms. They represent the first examples of rare earth (RE) complexes containing RE-Ge bonds other than the RE-GeR3 structural type.

B(C6F5)3-catalyzed dehydrogenative cyclization of N-tosylhydrazones and anilines via a Lewis adduct: a combined experimental and computational investigation

Tris(pentafluorophenyl)borane-catalyzed dehydrogenative-cyclization of N-tosylhydrazones with aromatic amines has been disclosed. This metal-free catalytic protocol is compatible with a range of functional groups to provide both symmetrical and unsymmetrical 3,4,5-triaryl-1,2,4-triazoles. Mechanistic experiments and density functional theory (DFT) studies suggest an initial Lewis adduct formation of N-tosylhydrazone with B(C6F5)3 followed by sequential intermolecular amination of the borane adduct with aniline, intramolecular cyclization and frustrated Lewis pair (FLP)-catalyzed dehydrogenation for the generation of substituted 1,2,4-triazoles.

Donor Stabilized Diatomic Gr.14 E2 (E = C-Pb) Molecule D-E2-D (D = NHC, aNHC, NNHC, NHSi, NHGe, cAAC, cAASi, cAAGe): A Theoretical Insight

Quantum chemical calculations have been carried out to explore the detailed electronic structure and bonding scenario in various bis-donor stabilized E₂ compounds (E = C-Pb). Our computational findings reveal that the thermodynamic stabilities of the E₂ core gradually decrease as we move down the group. A linear D-E-E'-D framework is observed for C₂ systems, while the heavier group 14 analogues possess trans-bent geometries. Consideration of few compounds as viable targets for synthesis is suggested by their corresponding calculated formation energies. In addition, the thermodynamic stabilities of C₂ systems notably increase with the saturation of the donor ring framework and are even more pronounced for boron-substituted saturated NHD ligand. QTAIM calculations affirmed that the covalent nature of E-E' bonds shifts toward the donor-acceptor region as one traverses from top to bottom along group 14. The E-D and E'-D bonds in the C₂ systems have covalent nature, whereas those in Si₂-Pb₂ systems are characterized by donor-acceptor bonds. In addition, we have computed proton affinities and vertical ionization potentials (VIPs) of these compounds. An excellent correlation was obtained between calculated VIPs and orbital energies of HOMOs. Furthermore, in the present study, we also explored the effect of bis-donors in the stabilization of heterodiatomic SiC compounds. Our calculations indicate that a typical bonding description of the SiC(D)₂ compounds should be represented by a combination of a classical double bond between C-D with significant donor-acceptor interaction in Si-D, i.e., D → Si═C═D. The SiC(D)₂ systems are found to be less stable than the corresponding dicarbon compounds C₂(D)₂, but they show significant stabilization compared to the corresponding disilicon systems Si₂(D)₂.