Coinage-Metal Bond between [1.1.1]Propellane and M2/MCl/MCH3 (M = Cu, Ag, and Au): Cooperativity and Substituents

Can we quantitatively evaluate the mutual impacts of intramolecular metal-ligand bonds the same as intermolecular noncovalent bonds?

In this paper, we have reviewed several equations for calculating the cooperative energy of two chemical bonds between three fragments/species, regardless of whether they are atoms, ions or molecules, and whether the bonds between them are intra- or intermolecular. It is emphasized that two chemical bonds upon cooperation in a new compound change the bond dissociation energy of each other exactly by the same quantitative value, their cooperative energy, regardless of the nature of the bonds or whether one bond is very weak and another one is very strong. However, the final benefit/drawback of weak bonds from this cooperation can be considerably larger than that of strong bonds. The above statements are supported by a computational study on the various types of inter- and intramolecular chemical bonds.

Spodium bonding with noble gas atoms

The nature of the bonding between a neutral group 12 member (Zn3, Cd3 and Hg3) ring and a noble gas atom was explored using quantum chemical simulations. Natural bond orbital, quantum theory of atoms in molecules, symmetry-adapted perturbation theory, and molecular electrostatic potential surface analysis were also used to investigate the type of interaction between the noble gas atom and the metal rings (Zn3, Cd3 and Hg3). The Zn3, Cd3 and Hg3 rings are bonded to the noble gas through non-covalent interactions, which was revealed by the non-covalent interaction index. Additionally, energy decomposition analysis reveals that dispersion energy is the key factor in stabilizing these systems.

Beryllium bonding with noble gas atoms

Quantum chemical calculations were carried out to investigate the nature of the bonding between a neutral Be₃ ring and noble gas atom. Electronic structure calculation for these complexes was carried out at different computational levels in association with natural bond orbital, quantum theory of atoms in molecules, electron localization function, symmetry adapted perturbation theory, and molecular electrostatic potential surface analysis of Be₃ complexes. The Be atoms in the Be₃ moiety are chemically bonded to one another, with the BeBe bond dissociation energy being ~125 kJ mol^-1 . The Be₃ ring interacts with the noble gases through non-covalent interactions. The binding energies of the noble gas atoms with the Be₃ ring increases with increase in their atomic number. The non-covalent interaction index, density overlap region indicator and independent gradient model analyses reveal the presence of non-covalent inter-fragment interactions in the complexes. Energy decomposition analysis reveals that dispersion plays the major role towards stabilizing these systems.

Study of Beryllium, Magnesium, and Spodium Bonds to Carbenes and Carbodiphosphoranes

The aim of this article is to present results of theoretical study on the properties of C⋯M bonds, where C is either a carbene or carbodiphosphorane carbon atom and M is an acidic center of MX2 (M = Be, Mg, Zn). Due to the rarity of theoretical data regarding the C⋯Zn bond (i.e., the zinc bond), the main focus is placed on comparing the characteristics of this interaction with C⋯Be (beryllium bond) and C⋯Mg (magnesium bond). For this purpose, theoretical studies (ωB97X-D/6-311++G(2df,2p)) have been performed for a large group of dimers formed by MX2 (X = H, F, Cl, Br, Me) and either a carbene ((NH2)2C, imidazol-2-ylidene, imidazolidin-2-ylidene, tetrahydropyrymid-2-ylidene, cyclopropenylidene) or carbodiphosphorane ((PH3)2C, (NH3)2C) molecule. The investigated dimers are characterized by a very strong charge transfer effect from either the carbene or carbodiphosphorane molecule to the MX2 one. This may even be over six times as strong as in the water dimer. According to the QTAIM and NCI method, the zinc bond is not very different than the beryllium bond, with both featuring a significant covalent contribution. However, the zinc bond should be definitely stronger if delocalization index is considered.

Assessing the Orbital Contribution in the "Spodium Bond" by Natural Orbital for Chemical Valence-Charge Displacement Analysis

The term "spodium bond" (SpB) has been recently proposed to describe the noncoordinative interaction that can be established between a polarized group 12 metal and a mild Lewis base (LB). Most of the systems showing short metal-donor distances compatible with SpB are characterized by the coexistence of multiple weak interactions, including hydrogen and halogen bonding, making the assessment of real importance of SpB difficult. Here, we show that the relative importance of each contribution can be probed by dissecting the orbital component of the interaction through the extended transition state-natural orbital for chemical valence-charge displacement analysis (ETS-NOCV-CD). The latter gives useful information about relative energies and electrons involved, for model systems ([(thiourea)₂MX₂]···LB; M = Zn, Cd, and Hg; X = Cl and I; and LB = CH₂S, CH₂O, CH₃CN, and CO) and a variety of structures extracted from experimentally characterized adducts, allowing us to demonstrate the lack of a direct correlation between a favorable metal-base distance and the presence of an orbital contribution for the SpB.

Highly Regioselective Addition of Allylic Zinc Halides and Various Zinc Enolates to [1.1.1]Propellane

We report a range of highly regioselective openings of [1.1.1]propellane with various allylic zinc halides, as well as zinc enolates of ketones, esters and nitriles. The resulting zincated bicyclopentanes (BCPs) were trapped with a range of electrophiles including acyl chlorides, sulfonothioates, hydroxylamino benzoates, tosyl cyanide as well as aryl and allyl halides, generating highly functionalized BCP-derivatives. The unusually high regioselectivity of these reactions has been rationalized using DFT calculations. A bioisostere of the synthetic opioid pethidine was prepared in 95 % yield in one step using this method.

Tetrel Bonding Interactions Involving Carbon at Work: Recent Advances in Crystal Engineering and Catalysis

The σ- and π-hole interactions are used to define attractive forces involving elements of groups 12–18 of the periodic table acting as Lewis acids and any electron rich site (Lewis base, anion, and π-system). When the electrophilic atom belongs to group 14, the resulting interaction is termed a tetrel bond. In the first part of this feature paper, tetrel bonds formed in crystalline solids involving sp3-hybridized carbon atom are described and discussed by using selected structures retrieved from the Cambridge Structural Database. The interaction is characterized by a strong directionality (close to linearity) due to the small size of the σ-hole in the C-atom opposite the covalently bonded electron withdrawing group. The second part describes the utilization of two allotropic forms of carbon (C60 and carbon nanotubes) as supramolecular catalysts based on anion–π interactions (π-hole tetrel bonding). This part emphasizes that the π-hole, which is considerably more accessible by nucleophiles than the σ-hole, can be conveniently used in supramolecular catalysis.

Regium Bonds between Silver(I) Pyrazolates Dinuclear Complexes and Lewis Bases (N2, OH2, NCH, SH2, NH3, PH3, CO and CNH)

A theoretical study and Cambridge Structural Database (CSD) search of dinuclear Ag(I) pyrazolates interactions with Lewis bases were carried out and the effect of the substituents and ligands on the structure and on the aromaticity were analyzed. A relationship between the intramolecular Ag–Ag distance and stability was found in the unsubstituted system, which indicates a destabilization at longer distances compensated by ligands upon complexation. It was also observed that the asymmetrical interaction with phosphines as ligands increases the Ag–Ag distance. This increase is dramatically higher when two simultaneous PH3 ligands are taken into account. The calculated 109Ag chemical shielding shows variation up to 1200 ppm due to the complexation. Calculations showed that six-membered rings possessed non-aromatic character while pyrazole rings do not change their aromatic character significantly upon complexation.