Ruthenophanes: Evaluating Cation−π Interactions in [Ru(η⁶‑C₁₆H₁₂R₄)(NH₃)₃]^2+/3+ Complexes. A Computational Insight

The nature of cation−π interactions in a set of [Ru­(η⁶-C₁₆H₁₂R₄)­(NH₃)₃]²⁺³⁺ (R = F, CN, CH₃, and others), complexes was investigated with Su–Li energy decomposition analysis and the natural orbitals for chemical valence and the extended transition state method EDA-NOCV. The long-distance effects of electron-donating and electron-withdrawing substituents as well as protonation of the <i>ipso</i> carbon on the nature of cation−π interactions were investigated. Both energy decomposition analyses, Su–Li EDA and EDA-NOCV, are in total agreement, showing that the presence of electron-donating substituents such as CH₃, NH₂, and H₃CO tends to stabilize the ruthenium–arene interaction while electron-withdrawing substituents such as F, CN, and NO₂ tend to weaken such interactions. The electrostatic component of the ruthenium–arene interaction is the most affected by the substitution, despite the fact that the covalent character is much more significant than the electrostatic character. EDA-NOCV reveals that the most important orbital stabilization comes from donation and back-donation between the interacting fragments, while the σ density deformations present a moderate contribution to total orbital stabilization energy in ruthenium–arene interactions of complexes <b>1</b>–<b>8</b>

Experimental and Theoretical Studies of the Infrared Spectra and Bonding Properties of NgBeCO₃ and a Comparison with NgBeO (Ng = He, Ne, Ar, Kr, Xe)

The novel neon complex NeBeCO₃ has been prepared in a low-temperature neon matrix via codeposition of laser-evaporated beryllium atoms with O₂ + CO/Ne. Doping by the heavier noble gas atoms argon, krypton and xenon yielded the associated adducts NgBeCO₃ (Ng = Ar, Kr, Xe). The noble gas complexes have been identified via infrared spectroscopy. Quantum chemical calculations of NgBeCO₃ and NgBeO (Ng = He, Ne, Ar, Kr, Xe) using <i>ab initio</i> methods and density functional theory show that the Ng–BeCO₃ bonds are slightly longer and weaker than the Ng–BeO bonds. The energy decomposition analysis of the Ng–Be bonds suggests that the attractive interactions come mainly from the Ng → BeCO₃ and Ng → BeO σ donation

Mechanistic Insight into the Cu-Catalyzed C<i>–</i>S Cross-Coupling of Thioacetate with Aryl Halides: A Joint Experimental–Computational Study

The mechanism of the Ullmann-type reaction between potassium thioacetate (KSAc) and iodobenzene (PhI) catalyzed by CuI associated with 1,10-phenanthroline (phen) as a ligand was explored experimentally and computationally. The study on C–S bond formation was investigated by UV–visible spectrophotometry, cyclic voltammetry, mass spectrometry, and products assessment from radical probes. The results indicate that under experimental conditions the catalytically active species is [Cu­(phen)­(SAc)] regardless of the copper source. An examination of the aryl halide activation mechanism using radical probes was undertaken. No evidence of the presence of radical species was found during the reaction process, which is consistent with an oxidative addition cross-coupling pathway. The different reaction pathways leading to the experimentally observed reaction products were studied by DFT calculation. The oxidative addition–reductive elimination mechanism via an unstable Cu^III intermediate is energetically more feasible than other possible mechanisms such as single electron transfer, halogen atom transfer, and σ-bond methatesis

Carbene-Dichlorosilylene Stabilized Phosphinidenes Exhibiting Strong Intramolecular Charge Transfer Transition

The unstable species dichlorosilylene was previously stabilized by carbene. The lone pair of electrons on the silicon atom of (carbene)­SiCl₂ can form a coordinate bond with metal–carbonyls. Herein we report that (carbene)­SiCl₂ can stabilize a phosphinidene (Ar–P, a carbone analogue) with the general formula carbene→SiCl₂→P–Ar (carbene = cyclic alkyl­(amino) carbene (cAAC; <b>2</b>) and N-heterocyclic carbene (NHC; <b>3</b>)). Compounds <b>2</b> and <b>3</b> are stable, isolable, and storable at 0 °C (<b>2</b>) to room temperature (<b>3</b>) under an inert atmosphere. The crystals of <b>2</b> and <b>3</b> are dark blue and red, respectively. The intense blue color of <b>2</b> arises due to the strong intramolecular charge transfer (ICT) transition from π_SiP→π*_cAAC. The electronic structure and bonding of <b>2</b>, <b>3</b> were studied by theoretical calculations. The HOMO of the molecule is located on the π_SiP bond, while the LUMO is located at the carbene moiety (cAAC or NHC). The dramatic change in color of these compounds from red (<b>3</b>, NHC) to blue (<b>2</b>, cAAC) is ascribed to the difference in energy of the LUMO within the carbenes (cAAC/NHC) due to a lower lying LUMO of cAAC

Acyclic Germylones: Congeners of Allenes with a Central Germanium Atom

The cyclic alkyl­(amino) carbene (cAAC:)-stabilized acyclic germylones (Me₂-cAAC:)₂Ge (<b>1</b>) and (Cy₂-cAAC:)₂Ge (<b>2</b>) were prepared utilizing a one-pot synthesis of GeCl₂(dioxane), cAAC:, and KC₈ in a 1:2:2.1 molar ratio. Dark green crystals of compounds <b>1</b> and <b>2</b> were produced in 75 and 70% yields, respectively. The reported methods for the preparation of the corresponding silicon compounds turned out to be not applicable in the case of germanium. The single-crystal X-ray structures of <b>1</b> and <b>2</b> feature the C–Ge–C bent backbone, which possesses a three-center two-electron π-bond system. Compounds <b>1</b> and <b>2</b> are the first acyclic germylones containing each one germanium atom and two cAAC: molecules. EPR measurements on compounds <b>1</b> and <b>2</b> confirmed the singlet spin ground state. DFT calculations on <b>1</b>/<b>2</b> revealed that the singlet ground state is more stable by ∼16 to 18 kcal mol^–1 than that of the triplet state. First and second proton affinity values were theoretically calculated to be of 265.8 (<b>1</b>)/267.1 (<b>2</b>) and 180.4 (<b>1</b>)/183.8 (<b>2</b>) kcal mol^–1, respectively. Further calculations, which were performed at different levels suggest a singlet diradicaloid character of <b>1</b> and <b>2</b>. The TD-DFT calculations exhibit an absorption band at ∼655 nm in <i>n</i>-hexane solution that originates from the diradicaloid character of germylones <b>1</b> and <b>2</b>

Acyclic Germylones: Congeners of Allenes with a Central Germanium Atom

The cyclic alkyl­(amino) carbene (cAAC:)-stabilized acyclic germylones (Me₂-cAAC:)₂Ge (<b>1</b>) and (Cy₂-cAAC:)₂Ge (<b>2</b>) were prepared utilizing a one-pot synthesis of GeCl₂(dioxane), cAAC:, and KC₈ in a 1:2:2.1 molar ratio. Dark green crystals of compounds <b>1</b> and <b>2</b> were produced in 75 and 70% yields, respectively. The reported methods for the preparation of the corresponding silicon compounds turned out to be not applicable in the case of germanium. The single-crystal X-ray structures of <b>1</b> and <b>2</b> feature the C–Ge–C bent backbone, which possesses a three-center two-electron π-bond system. Compounds <b>1</b> and <b>2</b> are the first acyclic germylones containing each one germanium atom and two cAAC: molecules. EPR measurements on compounds <b>1</b> and <b>2</b> confirmed the singlet spin ground state. DFT calculations on <b>1</b>/<b>2</b> revealed that the singlet ground state is more stable by ∼16 to 18 kcal mol^–1 than that of the triplet state. First and second proton affinity values were theoretically calculated to be of 265.8 (<b>1</b>)/267.1 (<b>2</b>) and 180.4 (<b>1</b>)/183.8 (<b>2</b>) kcal mol^–1, respectively. Further calculations, which were performed at different levels suggest a singlet diradicaloid character of <b>1</b> and <b>2</b>. The TD-DFT calculations exhibit an absorption band at ∼655 nm in <i>n</i>-hexane solution that originates from the diradicaloid character of germylones <b>1</b> and <b>2</b>

The Structure of the Carbene Stabilized Si₂H₂ May Be Equally Well Described with Coordinate Bonds as with Classical Double Bonds

The cyclic alkyl­(amino) carbene stabilized Si₂H₂ has been isolated in the molecular form of composition (Me-cAAC:)₂Si₂H₂ (<b>1</b>) and (Cy-cAAC:)₂Si₂H₂ (<b>2</b>) at room temperature. Compounds <b>1</b> and <b>2</b> were synthesized from the reduction of HSiCl₃ using 3 equiv of KC₈ in the presence of 1 equiv of Me-cAAC: and Cy-cAAC:, respectively. These are the first molecular examples of Si₂H₂ characterized by single crystal X-ray structural analysis. Moreover, electrospray ionization mass spectrometry and ¹H as well as ²⁹Si NMR data are reported. Furthermore, the structure of compound <b>1</b> has been investigated by theoretical methods. The theoretical analysis of <b>1</b> explains equally well its structure with coordinate bonds as with classical double bonds of a 2,3-disila-1,3-butadiene

Acyclic Germylones: Congeners of Allenes with a Central Germanium Atom

The cyclic alkyl­(amino) carbene (cAAC:)-stabilized acyclic germylones (Me₂-cAAC:)₂Ge (<b>1</b>) and (Cy₂-cAAC:)₂Ge (<b>2</b>) were prepared utilizing a one-pot synthesis of GeCl₂(dioxane), cAAC:, and KC₈ in a 1:2:2.1 molar ratio. Dark green crystals of compounds <b>1</b> and <b>2</b> were produced in 75 and 70% yields, respectively. The reported methods for the preparation of the corresponding silicon compounds turned out to be not applicable in the case of germanium. The single-crystal X-ray structures of <b>1</b> and <b>2</b> feature the C–Ge–C bent backbone, which possesses a three-center two-electron π-bond system. Compounds <b>1</b> and <b>2</b> are the first acyclic germylones containing each one germanium atom and two cAAC: molecules. EPR measurements on compounds <b>1</b> and <b>2</b> confirmed the singlet spin ground state. DFT calculations on <b>1</b>/<b>2</b> revealed that the singlet ground state is more stable by ∼16 to 18 kcal mol^–1 than that of the triplet state. First and second proton affinity values were theoretically calculated to be of 265.8 (<b>1</b>)/267.1 (<b>2</b>) and 180.4 (<b>1</b>)/183.8 (<b>2</b>) kcal mol^–1, respectively. Further calculations, which were performed at different levels suggest a singlet diradicaloid character of <b>1</b> and <b>2</b>. The TD-DFT calculations exhibit an absorption band at ∼655 nm in <i>n</i>-hexane solution that originates from the diradicaloid character of germylones <b>1</b> and <b>2</b>

Acyclic Germylones: Congeners of Allenes with a Central Germanium Atom

The cyclic alkyl­(amino) carbene (cAAC:)-stabilized acyclic germylones (Me₂-cAAC:)₂Ge (<b>1</b>) and (Cy₂-cAAC:)₂Ge (<b>2</b>) were prepared utilizing a one-pot synthesis of GeCl₂(dioxane), cAAC:, and KC₈ in a 1:2:2.1 molar ratio. Dark green crystals of compounds <b>1</b> and <b>2</b> were produced in 75 and 70% yields, respectively. The reported methods for the preparation of the corresponding silicon compounds turned out to be not applicable in the case of germanium. The single-crystal X-ray structures of <b>1</b> and <b>2</b> feature the C–Ge–C bent backbone, which possesses a three-center two-electron π-bond system. Compounds <b>1</b> and <b>2</b> are the first acyclic germylones containing each one germanium atom and two cAAC: molecules. EPR measurements on compounds <b>1</b> and <b>2</b> confirmed the singlet spin ground state. DFT calculations on <b>1</b>/<b>2</b> revealed that the singlet ground state is more stable by ∼16 to 18 kcal mol^–1 than that of the triplet state. First and second proton affinity values were theoretically calculated to be of 265.8 (<b>1</b>)/267.1 (<b>2</b>) and 180.4 (<b>1</b>)/183.8 (<b>2</b>) kcal mol^–1, respectively. Further calculations, which were performed at different levels suggest a singlet diradicaloid character of <b>1</b> and <b>2</b>. The TD-DFT calculations exhibit an absorption band at ∼655 nm in <i>n</i>-hexane solution that originates from the diradicaloid character of germylones <b>1</b> and <b>2</b>