Planar tetracoordinate beryllium in σ-aromatic Li4Be and Na4Be clusters: A missing member in first-octal row planar tetracoordinate family.

While planar tetracoordinate (pt) centers have been extensively explored from carbon to other octal-row elements or their heavier analogs, their counterparts involving alkali (A) and alkaline-earth metals (Ae) remain elusive due to the large atomic radius and absence of p orbitals. In this work, we found six hitherto unknown anionic ptA (A4A-) and neutral ptAe (A4Ae) centers through an extensive exploration of potential energy surfaces. The D4h-symmetry ptBe structures in Li4Be and Na4Be emerge as the lowest-energy configurations, and all the other ptA/ptAe structures are higher in energy or saddle points.

Planar Pentacoordinate Halogens.

Planar hypercoordinate motifs represent an intriguing frontier in chemistry, challenging traditional bonding norms. As electronegativity of the central atom increases, achieving planar hypercoordination becomes more difficult due to restricted delocalization, making the design of planar hypercoordinate halogens particularly puzzling. Here, we conduct an extensive computational survey of LiX (n=4, 5, 6; X=F, Cl, Br, I) clusters, revealing a starlike D-symmetry global minimum in LiX (X=F, Cl, Br) with a planar pentacoordinate halogen (ppX), where X is located at the center of LiX crown.

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).

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.

Exploring the Use of "Honorary Transition Metals" To Push the Boundaries of Planar Hypercoordinate Alkaline-Earth Metals.

The quest for planar hypercoordinate atoms (phA) beyond six has predominantly focused on transition metals, with dodecacoordination being the highest reported thus far. Extending this bonding scenario to main-group elements, which typically lack d orbitals despite their larger atomic radius, has posed significant challenges. Intrigued by the potentiality of covalent bonding formation using the d orbitals of the heavier alkaline-earth metals (Ae = Ca, Sr, Ba), the so-called "honorary transition metals", we aim to push the boundaries of planar hypercoordination.

In Silico Design and Characterization of a New Molecular Electride: Li@Calix[3]Pyrrole.

Electrides, in which anionic electrons are localized independently of the atoms in the compound, have shown promise, especially as catalysts and optoelectronic materials. Here, we present a new computationally designed molecular electride, Li@calix[3]pyrrole (Li@C3P). Electron density and electron localization function analyses unequivocally confirm the existence of localized electride electron density, outside the system, independent of any specific atoms.

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.

Stabilizing Monoatomic Two-Coordinate Bismuth(I) and Bismuth(II) Using a Redox Noninnocent Bis(germylene) Ligand.

The formation of isolable monatomic Bi complexes and Bi radical species is challenging due to the pronounced reducing nature of metallic bismuth. Here, we report a convenient strategy to tame Bi and Bi atoms by taking advantage of the redox noninnocent character of a new chelating bis(germylene) ligand. The remarkably stable novel Bi cation complex , supported by the new bis(iminophosphonamido-germylene)xanthene ligand [(P)Ge(Xant)Ge(P)] , [(P)Ge(Xant)Ge(P) = PhP(NBu)Ge(Xant)Ge(NBu)PPh, Xant = 9,9-dimethyl-xanthene-4,5-diyl], was synthesized by a two-electron reduction of the cationic BiI precursor complex with cobaltocene (CpCo) in a molar ratio of 1:2.

Analysis of the Unusual Chemical Bonds and Dipole Moments of AeF (Ae=Be-Ba): A Lesson in Covalent Bonding.

Quantum chemical calculations of the anions AeF (Ae=Be-Ba) have been carried out using ab initio methods at the CCSD(T)/def2-TZVPP level and density functional theory employing BP86 with various basis sets. The detailed bonding analyses using different charge- and energy partitioning methods show that the molecules possess three distinctively different dative bonds in the lighter species with Ae=Be, Mg and four dative bonds when Ae=Ca, Sr, Ba. The occupied 2p atomic orbitals (AOs) and to a lesser degree the occupied 2s AO of F donate electronic charge into the vacant sp(σ) and p(π) orbitals of Be and Mg which leads to a triple bond Ae F.

Transition Metal Behavior of Heavier Alkaline Earth Elements in Doped Monocyclic and Tubular Boron Clusters.

Quantum chemical calculations are carried out to design highly symmetric-doped boron clusters by employing the transition metal behavior of heavier alkaline earth (Ae = Ca, Sr, and Ba) metals. Following an electron counting rule, a set of monocyclic and tubular boron clusters capped by two heavier Ae metals were tested, which leads to the highly symmetric AeB, AeB, and AeB clusters as true minima on the potential energy surface having a monocyclic ring, two-ring tubular, and three-ring tubular boron motifs, respectively. Then, a thorough global minimum (GM) structural search reveals that a monocyclic B ring capped with two Ae atoms is indeed a GM for CaB and BaB, while for SrB it is a low-lying isomer.

Li E Li : Tetrel Sandwich Complexes with 10-Ï€-Electrons.

When (4n +2) π-electrons are located in single planar ring, it conventionally qualifies as aromatic. According Hückel's rule, systems possessing ten π-electrons should be aromatic. Herein we report a series of D  Li E Li sandwich structures, representing the first global minima featuring ten π-electrons E ring (E=Si-Pb).

Stabilization of Cyclic C by Four Donor Ligands: A Theoretical Study of (L)C (L = Carbene).

Quantum chemical studies using density functional theory were carried out for the (L)C complexes with L = cAAC, DAC, NHC, SNHC, MIC1, and MIC2. The results show that the title complexes are highly stable with respect to dissociation, (L)C → C + 4L. However, their stability with respect to (L)C → 2(L)C is crucial for the assessment of their experimental viability.

Mimicking the C molecule: MB and MB clusters (M = Li, Na) and the reactivity of the N-heterocyclic carbene bound LiB complex.

C has attracted considerable attention from the scientific community for its debatable bonding situation. Herein, we show that the global minima of MB and MB (M = Li, Na) possess similar covalent bonding patterns to C. Because of strong charge transfer from M/M to B dimer, they can be better described as [M][B] and [M][B] salt complexes with the B core surrounded perpendicularly by two and three M atoms, respectively.

Planar pentacoordinate s-block metals.

The presence of a delocalized π-bond is often considered an essential criterion for achieving planar hypercoordination. Herein, we show that σ-delocalization could be sufficient to make the planar configuration the most stable isomer in a series of planar pentacoordinate s-block metals. High-level computations reveal that the global minimum of a series of interalkali and interalkali-alkaline earth clusters (LiNa, LiMg, NaMg, KCa, CaRb, RbSr, and SrCs) adopts a singlet structure with a planar pentacoordinate lithium or alkaline earth metal (AE = Mg, Ca, Sr).

Clusters and bulky Lewis acid protected complexes with planar hexacoordinate beryllium and magnesium.

Planar hexacoordination (ph) is only rarely reported in the literature. So far, only a few neutral and cationic molecules possessing phE (E = C, Si, B, Al, Ga) in the most stable isomer are predicted theoretically. Present electronic structure calculations report hitherto unknown anionic planar hexcoordinate beryllium and magnesium, phBe/Mg, as the most stable isomer.

Structural Characterization and Bonding Analysis of [Hg{Fe(CO)}] [SbF].

The non-classical carbonyl complex [Hg{Fe(CO)}] [SbF] is prepared by reaction of Hg(SbF) and excess Fe(CO) in anhydrous HF. The single-crystal X-ray structure reveals a linear Fe-Hg-Fe moiety as well as an eclipsed conformation of the eight basal CO ligands. Interestingly, the Hg-Fe bond length of 2.

Global Planar Tetra-, Penta- and Hexa-coordinate Silicon Clusters Constructed by Decorating SiO with Alkali Metals.

The achievement of the rule-breaking planar hypercoordinate motifs (carbon and other elements) is mainly attributed to a practical electronic stabilization mechanism, where the bonding of the central atom p π electrons is a crucial issue. We have demonstrated that strong multiple bonds between the central atom and partial ligands can be an effective approach to explore stable planar hypercoordinate species. A set of planar tetra-, penta- and hexa-coordinate silicon clusters were herein found to be the lowest-energy structure, which can be viewed as decorating SiO by alkali metals in the MSiO , M SiO and M SiO (M=Li, Na) clusters.

B Be B : A Boron-Beryllium Sandwich Complex.

Planar boron clusters have often been regarded as "π-analogous" to aromatic arenes because of their similar delocalized π-bonding. However, unlike arenes such as C H and C H , boron clusters have not previously shown the ability to form sandwich complexes. In this study, we present the first sandwich complex involving beryllium and boron, B Be B .

Quest of Quadruple Bonding Between Two Main-Group Atoms in AeB and AeC (Ae=Ca, Sr, Ba) and the Role of d Orbitals of Heavier Alkaline-Earth Atoms in Covalent Interactions.

Quantum chemical calculations using ab initio methods at the MRCI+Q(6,8)/def2-QZVPP and CCSD(T)/def2-QZVPP levels as well as density functional theory are reported for the diatomic molecules AeB and isoelectronic AeC (Ae=Ca, Sr, Ba). The boride anions AeB have an electronic triplet ( Σ ) ground state. The quintet ( Σ ) state is 5.

Synthesis of a rhodium(III) dinitrogen complex using a calix[4]arene-based diphosphine ligand.

The synthesis and characterisation of the rhodium(III) dinitrogen complex [Rh(2,2'-biphenyl)(CxP)(N)] are described, where CxP is a -spanning calix[4]arene-based diphosphine and the dinitrogen ligand is projected into the cavity of the macrocycle.

Comment on "The oxidation state in low-valent beryllium and magnesium compounds" by M. Gimferrer, S. Danés, E. Vos, C. B. Yildiz, I. Corral, A. Jana, P. Salvador and D. M. Andrada, 2022, , 6583.

We challenge the assignment of the oxidation state +2 for beryllium and magnesium in the complexes Be(cAAC) and Mg(cAAC) as suggested by Gimferrer , 2022, , 6583 in a recent study. A careful review of the data in the ESI contradicts their own statement and shows that the results support the earlier suggestion that the metals are in the zero oxidation state. The authors reported wrong data for the excitation energies of Be and Mg to the D (np) state.