Rational Design of Antimony-Based Zintl Clusters: Unveiling Unconventional Bonding and Architectures.

ConspectusThe past decade has witnessed rapid growth in the synthesis of main-group element clusters, driven by advances in the design of Zintl phase precursors and their integration with organometallic reagents. These strategies have unlocked unprecedented structural motifs and bonding patterns, greatly enriching the landscape of main-group cluster chemistry. Among them, antimony-based clusters stand out for their diverse architectures and unique electronic properties, serving as ideal models to explore metalloid aromaticity, multicenter bonding, and unconventional Sb-Sb or Sb-metal interactions.

Aromaticity and antiaromaticity in the cyclic 6π and 4π molecules of carbon and silicon EH and EH (E = C, Si).

Quantum chemical calculations using density functional theory at the BP86/def2-TZVPP level are reported for the structures and aromaticities of the monocyclic molecules EH and EH (E = C, Si). The results reveal drastic differences between the carbon and silicon homologues. Benzene (1b) is the global energy minimum on the CH PES whereas planar SiH (2d) is not an energy minimum and the form 2c is higher in energy than the prismane isomer 2a.

Chemical Bonding of Low-Valent Radical Magnesium Species and Computational Design of Low-Valent Radical Calcium Complexes.

The synthesis of mononuclear low-valent calcium species remains a significant challenge. In this study, we initially investigated the electronic structure and bonding nature of experimentally synthesized mononuclear low-valent radical magnesium species . It reveals that the stability of this system arises from the CAAC ligand's strong π-electron-accepting and σ-electron-donating properties, combined with the inductive effect of the Am ligand, which enhances electron transfer to the CAAC ligand.

Mechanistic Insights into Copper-Catalyzed Alkene Aminofluorination and Rational Design of a Metal-Free Strategy.

The β-fluoroalkylamine motif holds great value in drug development due to the unique properties imparted by fluorine incorporation. Currently, the most promising way for accessing this motif involves alkene aminofluorination, which heavily relies on transition-metal (TM) catalysts. Inspired by a control experiment reported in a related previous study, we herein rationally design a novel metal-free strategy for alkene aminofluorinations.

Clarification of Some Bonding Concepts: Virial Theorem, Electron Pair Repulsion, and Rotational Barriers.

The molecular virial theorem relates kinetic and potential energies (T & V) to total energy and forces (E & R·∂E/∂R); it is a useful tool for analyzing the data, but does not provide clues on the origin of the stability of the "bonded" state. A strict conceptual distinction between cause and effect is recommended. Depending on the physical relationships, the induced change of one variable of the system leads to a resulting change of another variable; relaxation or response of the system can either moderate this change (in the sense of Le Chatelier's principle), enhance it, or even reverse it.

Synthesis of triple-decker sandwich compounds featuring a M-M bond through cyclo-Bi and cyclo-Sb rings.

The cyclopentadienyl anion is a π-aromatic five-membered ring ligand that is widely used in organometallic chemistry. By replacing the CH groups in cyclopentadiene with isoelectronic group-15 elements, an inorganic analogue can be obtained. In this line, Pn (Pn = P, Sb) rings have been stabilized in a triple-decker sandwich structure, prepared via high-temperature reactions, and an example of a Bi ring stabilized in a cobalt-based inverse-sandwich-type complex has been reported.

PPh/Isocyanide and N/Isocyanide Exchange: Pathways to Isolable Alkali Metal Keteniminyl Anions.

Keteniminyl anions hold significant promise for advancing ketenimine chemistry, yet their isolation has remained elusive until now. Drawing inspiration from recent advances in ligand exchange reactions at carbon, we report the successful synthesis of a series of isolable alkali metal keteniminyl anions through substitution of the phosphine ligand in metalated ylides or the N₂ ligand in diazomethanides with isocyanides. The exchange reactions were found to proceed more rapidly with aryl isocyanides than with the more electron-rich alkyl-substituted derivatives and were also more efficient when starting from the diazo compounds.

From Bis(borylene)-Substituted Xanthenes as Reactive Intermediates to Diboraoxirane Complexes.

The first -heterocyclic carbene (NHC)-stabilized diboraoxirane complex [NHC = IPr = C{N(iPr)CMe}] was synthesized through the reduction of the corresponding bis(dichloroboryl-IPr)xanthene with potassium graphite. Intriguingly, its formation stems from a diboron(I)-mediated C-O-C deoxygenation of the xanthene spacer via a bis(borylene)xanthene as a reactive intermediate. Consistent with the proposed pathway, bis(borylene)xanthene with three-coordinate B(I) atoms could be isolated when the sterically less demanding NHC ligand IMe [IMe = C{N(Me)CMe}] was employed.

Isolation and Structure Elucidation of the Heterocumulene Anions [NCC-L] (L=CO, CS, N).

Cumulenes are molecules characterized by a series of consecutive double bonds. They serve as important reagents and intermediates in the synthesis of polymers and a wide variety of functionalized compounds, including various heterocycles. Understanding the properties of cumulenes and developing synthetic routes to these often highly reactive species is essential for unlocking new applications.

Spectroscopy and Bonding Analysis of ArBO ( = 1-3) Cations That Possess Argon-Boron Multiple Bonds.

ArBO ( = 1-3) complexes have been prepared and subjected to spectroscopic characterization in the gas phase. Mass-selected infrared photodissociation spectroscopy, in combination with theoretical calculations, reveals the coexistence of two nearly isoenergetic structural isomers in ArBO. One isomer entails two equivalent Ar atoms chemically bound to BO, while the other features an ArBO core ion accompanied by a weakly tagging argon atom.

Neutral 4π-electron tetrasilacyclobutadiene contains unusual features of a Möbius-type aromatic ring.

The search for stable compounds containing an antiaromatic cyclic 4π system is a challenge for inventive chemists that can look back on a long history. Here we report the isolation and characterization of the novel 4π-electron tetrasilacyclobutadiene, an analogue of a 4π neutral cyclobutadiene that exhibits surprising features of a Möbius-type aromatic ring. Reduction of RSiCl (R = (Pr)PCH) with KC in the presence of cycloalkyl amino-carbene (cAAC) led to the formation of corresponding silylene 1.

Chemical Bonding in [Fe(η-P)] and Related Complexes.

Quantum chemical calculations of the six valence isoelectronic complexes [FeL], [CoL], and NiL with L = η-P, η-CH using density functional theory have been carried out. The molecular structures were investigated with a variety of methods. The analysis of the electronic structure in [Fe(η-P)] shows that the bonding situation is very similar to valence isoelectronic Ni(η-CH).

Breakdown of the Total Dipole Moments of Diatomic Molecules into Individual Orbital Contributions.

Quantum chemical results at the CCSD(T)/def2-QZVPP and BP86/def2-QZVPP levels are reported for the neutral and charged diatomic molecules EF, EO (E = B-Tl), EF, EO, EN (E = C-Pb), EO, and EN (E = N-Bi). The theoretically predicted bond lengths and dipole moments are in good agreement with each other and with the available experimental values. It is shown that the total dipole moment of the molecules can be nicely separated into the contributions of the individual occupied molecular orbitals.

Unusual quadruple bonds featuring collective interaction-type σ bonds between first octal-row atoms in the alkaline-earth compounds AeOLi (Ae = Be-Ba).

Quantum chemical calculations are reported for the complexes of alkaline earth metals AeOLi (Ae = Be-Ba) at the BP86-D3(BJ)/def2-QZVPP and CCSD(T)/def2-QZVPPQZVPP levels. The nature of the Ae-OLi bond has been analyzed with a variety of methods. The AeOLi molecules exhibit an unprecedented σ donor bond Ae→OLi where the ()s lone-pair electrons of the Ae atom are donated to vacant O-Li antibonding orbitals having the largest coefficient at lithium.

Silylene-Stabilized Neutral Dibora-Aromatics with a B═B Bond.

The unprecedented silylene-supported dibenzodiboraoxepin and 9,10-diboraphenanthrene complexes and were synthesized. The (NHSi)B(xanthene) [NHSi = PhC(NtBu)(MeN)Si:] results from debromination of the bis(NHSi)-stabilized bis(dibromoboryl)xanthene with potassium graphite (KC); is capable of activating white phosphorus and ammonia to form the BP cage compound and HN-B-B-H diborane species , respectively. The thermal rearrangement of affords the 9,10-dihydro-9,10-diboraphenanthrene through a bis(NHSi)-assisted intramolecular reductive C-O-C deoxygenation process.

Correction: Deciphering the chemical bonding of the trivalent oxygen atom in oxygen doped graphene.

[This corrects the article DOI: 10.1039/D4SC00142G.].

Deciphering the chemical bonding of the trivalent oxygen atom in oxygen doped graphene.

Recently, planar and neutral tricoordinated oxygen embedded in graphene has been imaged experimentally (, 2019, , 4570-4577). In this work, this unusual chemical species is studied utilizing a variety of state-of-the-art methods and combining periodic calculations with a fragmental approach. Several factors influencing the stability of trivalent oxygen are identified.

Multiple Bonding in AeN (Ae=Ca, Sr, Ba).

Quantum chemical calculations using ab initio methods at the MRCI+Q(8,9)/def2-QZVPPD and CCSD(T)/def2-QZVPPD levels as well as using density functional theory are reported for the diatomic molecules AeN (Ae=Ca, Sr, Ba). The anions CaN and SrN have electronic triplet (Π) ground states with nearly identical bond dissociation energies D ~57 kcal/mol calculated at the MRCI+Q(8,9)/def2-QZVPPD level. In contrast, the heavier homologue BaN has a singlet (Σ) ground state, which is only 1.

Mono-Ortho-Beryllated Carbodiphosphoranes: Synthesis, Structure, Bonding and Reactivity.

The reaction of organoberyllium compounds with hexaphenylcarbodiphosphorane yields mono-ortho-beryllated complexes, which feature a double dative Be=C bond. The bonding situation in these compounds together with a simple carbodiphosphorane and an N-heterocyclic carbene adduct was analysed with energy decomposition analysis in combination with natural orbital for chemical valence as well as with quantum theory of atoms-in-molecules. Furthermore, the driving forces accountable for mono-ortho-beryllation were elucidated along with the reactivity of the Be=C bond.