Benzvalene-like Carboranes: Genuine Rule Breakers and Good Kinetic Stability.

Substituents are widespread in chemistry, but it has remained quite difficult to reliably determine the thermodynamic and kinetic stabilities of substituted compounds, though they are key to helping establish a structural rule and synthetic viability, respectively. As an important class of valence isomers in the benzene family, benzvalene-like structures have been extensively studied in systems associated with electron-neutral (i.e.

Double Direct C-H Bond Arylation of Thiophenes with Aryl Chlorides Catalyzed by the -Heterocyclic Carbene-PdCl-1-methylimidazole Complex.

With the combination of the -heterocyclic carbene-PdCl-1-methylimidazole complex and CuO, we succeeded in the first example of double direct C-H bond arylation reactions between thiophenes and aryl chlorides, giving the desired 2,5-diarylated thiophenes in moderate to high yields under suitable conditions, consistent with the density functional theory calculations.

Building a New Platform for Significantly Improving Performance of Hartree-Fock and CCSD(T) Correlation Energy Based on Two-Point Complete Basis Set Extrapolation Schemes.

The leading cause of high expense in gold standard coupled cluster theory is that calculations of electronic energies converge exceedingly slowly with an increased basis set size. Extrapolation principally allows for achieving higher-quality outcomes at reduced costs. Numerous extrapolation formulas have been developed, with attempts to predict energies up to the complete basis set limit.

Achieving Accuracy and Economy for Calculating Vertical Detachment Energies of Molecular Anions: A Model Chemistry Composite Methods.

The vertical detachment energy (VDE) is a vital factor for predicting the stability of anions that have important applications in the atom, molecule and cluster science. Due to the synthetic or characterization difficulty of anions, accurate and efficient predictions of VDE independent of laboratory data have always been an appealing task to remedy the experimental deficiencies. Unfortunately, the generally adopted CCSD(T) and electron propagator theory (EPT) methods have respectively been proven to be reliable but very cost-expensive, and cost-effective but sometimes problematic when Koopman's theorem is invalid.

Free and Complexed Fluoropentazoles: Anomalous Ring Charge and Appreciable Kinetic Stability.

Fluoronitrogens are strongly related to high-energy density materials. Fluoropentazole (-FN) with hitherto the highest N/F ratio at ambient pressure belongs to the family of well-known and 119-year-old pentazoles. Due to the presence of the overwhelmingly electronegative F element, -FN is the only pentazole to date that contains a cationic N ring.

All-nitrogen spiropentadiene-N.

Of the pentanitrogen cation (N ) family, the only experimentally known isomer is the V-shaped structure 01. Here, we showed that a super-high-energy (∼100 kcal/mol above 01) all-nitrogen spiropentadiene 02 with considerable σ-delocalization deserves pursuit as the first spirocyclic all-nitrogen molecule, at least spectroscopical.

A more effective catalysis of the CO fixation with aziridines: computational screening of metal-substituted HKUST-1.

A vital issue for the fixation and conversion of CO into useful chemical products is to find effective catalysts. In this work, in order to develop more effective and diverse catalysts, we implemented the first computational screening study (at M06-2X//B3LYP level) on the cycloaddition of CO with aziridines under eighteen metal-substituted HKUST-1 MOFs and tetrabutylammonium bromide (TBAB) as a co-catalyst. For all considered catalytic systems, the ring-opening of aziridine is calculated to be the rate-determining step.

How stable can the pentanitrogen cation be in kinetics?

For the 22 year-old pentanitrogen cation N5+ (01), we surprisingly found that the previously reported transition states (TSs) do not correspond to N2-extrusion. We located the real N2-extrusion TS, which can well reconcile the hitherto remaining inconsistency between the gas-phase and salt-like forms of 01 both in structure and energetics.

Arylpentazoles with surprisingly high kinetic stability.

The more-than-one-century-old arylpentazoles can only be used in situ in generating the pentazole anion due to their unfavourable kinetic stability. We successfully increased the N2-leaving barrier to reach hitherto the highest value of 40.83 kcal mol-1 at the CBS-QB3 level via a newly proposed co-stabilization method, making the broader applications of arylpentazoles feasible.

Planar Tetracoordinate Carbons in Allene-Type Structures.

The exhaustive exploration of the potential energy surfaces of CEM (E = Si-Pb; M = Li and Na) revealed seven global minima containing a planar tetracoordinate carbon (ptC). The design, based on a π-localization strategy, resulted in a ptC with two double bonds forming a linear or a bent allene-type E═C═E motif. The magnetic response of the bent E═C═E fragments support a σ-aromaticity.

Planar pentacoordinate silicon and germanium atoms.

The global minimum of XMgY (X = Si, Ge; Y = In, Tl) and SiMgIn contains a planar pentacoordinate atom of group 14 other than carbon. Its design is based on the "localization" approach, replacing one or two peripheral atoms in XMg by more electronegative ones. This change diminishes the repulsion and leads to stronger covalent X-Y bonds, stabilizing the planar pentacoordinate atom species.

A motif for heteronuclear C[triple bond, length as m-dash]E (E = Si, Ge, Sn, Pb) bonding: Lewis acid-base pair strategy.

The design and characterization of the heteronuclear group 14 C[triple bond, length as m-dash]E (E = Si, Ge, Sn, Pb) triple bonds have attracted intensive interest in the past few decades. In the current work, utilizing the advantages of N-heterocyclic carbenes (NHCs) and Lewis acid-base pair strategy, we theoretically designed a new class of compounds III-1, i.e.

Globally stabilized bent carbon-carbon triple bond by hydrogen-free inorganic-metallic scaffolding AlF.

For over 100 years, known bent C[triple bond, length as m-dash]C compounds have been limited to those with organic (I) and all-carbon (II) scaffoldings. Here, we computationally report a novel type (III) of bent C[triple bond, length as m-dash]C compound, , CAlF-01, which is the energetically global minimum isomer and bears an inorganic-metallic scaffolding and unexpected click reactivity.

Avoided spin coupling: an unexpected σ-σ diradical in global planar pentacoordinate carbon.

We present a global planar pentacoordinate carbon (ppC) featuring a hitherto unreported σ-σ diradical characteristic. Using the multi-reference approach combined with the CCSD(T)/aug-cc-pVTZ method, the ppC CLi was found to be an intriguing triplet ground state, in which the unpaired density is mostly located at three Li ligands. Chemical bonding analysis reveals that the 2pπ electrons of CLi are fully located at the C ring formed by C-C multiple bonds, in contrast to the perfect 2pπ-delocalization found in the well-known ppCs.

A sixteen-valence-electron carbon-group 13 family with global penta-atomic planar tetracoordinate carbon: an ionic strategy.

The design of planar tetracoordinate carbon (ptC) has always been a challenge due to its unique bonding mode that necessitates the perfect balance between the carbon center and surrounding ligands both electronically and mechanically. A unique type of 18-valence-electron (18ve) template, i.e.

Predicting viable isomers of [X,C,N] and [H,X,C,N] (X = Sn, Pb).

Metal cyanide/isocyanide and hydrometal cyanide/isocyanide compounds are key metal-carriers in interstellar space. Lighter group 14 elements (X = C/Si/Ge) cyanides/isocyanides and hydrocyanides/hydroisocyanides have been studied theoretically and experimentally. However, no reports are available on the analogues of tin (Sn) and lead (Pb).

Mono-silicon isoelectronic replacement in CAl : van't hoff/le bel carbon or not?

In cluster studies, the isoelectronic replacement strategy has been successfully used to introduce new elements into a known structure while maintaining the desired topology. The well-known penta-atomic 18 valence electron (ve) species and its Al /Si or Al/Si isoelectronically replaced clusters CAl Si , CAl Si , , and , all possess the same anti-van't Hoff/Le Bel skeletons, that is, nontraditional planar tetracoordinate carbon (ptC) structure. In this article, however, we found that such isoelectronic replacement between Si and Al does not work for the 16ve-CAl with the traditional van't Hoff/Le Bel tetrahedral carbon (thC) and its isoelectronic derivatives CAl X (X = Ga/In/Tl).

New global minima of 6-vertex dicarboranes: classical but unexpected.

Dicarboranes generally adopt global minimum predicted by the well-known Wade-Mingos rules, although one classical non-closo structure in the benzvalene form has long been pursued and later synthesized. Here we predicted two new non-closo global minima for 6-vertex dicarboranes (C2B4R6), i.e.

Global Isomeric Survey of Elusive Cyclopropanetrione: Unknown but Viable Isomers.

Despite the great interest in energy storage application, stable neutral CO ( > 1) structures either in thermodynamics or kinetics have yet been largely limited due to the rather high tendency to release the very stable CO molecule. The neutral cyclopropanetrione (CO) cluster has long remained elusive since no isomer with sufficient kinetic stability has been found either experimentally or theoretically. In this work, we constructed the first global potential energy surface of singlet CO at the CCSD(T)/aug-cc-pVTZ//B3LYP/aug-cc-pVTZ level, from which the kinetic stability of a wide range of CO isomers can be determined by investigating their isomerization and fragmentation pathways.

A kinetically persistent isomer found for pentazole: a global potential energy surface survey.

Among the N5R family, pentazoles (A1) with a 103-year-old research history remain the only class of kinetically persistent isomers. Aided by the first global isomeric survey and substitution study of N5H at the composite CBS-QB3 level, we predicted a new N5R isomer (C1) with kinetic stability close to pentazoles.

CAlX (X = B/Al/Ga/In/Tl) with 16 valence electrons: can planar tetracoordinate carbon be stable?

As a perpetual chemical curiosity, planar tetracoordinate carbon (ptC) that violates the traditional tetrahedral carbon (thC) has made enormous achievements. In particular, the 18-valence-electron (18ve) counting rule has been found to be very effective in predicting ptC structures, as in CX (X = Al/Ga/In/Tl). By contrast, the corresponding neutral CX with 16ve each takes the thC form like methane.

Theoretical Designs for Organoaluminum CAlR with Well-Separated Al(I) and Al(III).

It is well-known that the chemistry of aluminum is dominated by Al(III) in the +3 oxidation state. Only during the past 2 decades has the chemistry of Al(I) and Al(II) been rapidly developed. However, if Al(I) and Al(III) are combined, the inherently high reactivities of Al(I) and Al(III) mostly result in their coupling with each other or interacting with surrounding elements, which easily results in significant deactivation or quenching of the desired oxidation states, as in the case of reported mixed valent Al-compounds.

Identifying the Hydrogenated Planar Tetracoordinate Carbon: A Combined Experimental and Theoretical Study of CAlH and CAlH.

The chemical curiosity "planar tetracoordinate carbon" (ptC) has greatly broadened one's knowledge of molecular bonding motifs apart from the traditional, tetrahedral, van't Hoff and LeBel's concept. Synthesized ptC examples have been reported either in the solid state or in the gas phase, where the ptC core is usually metalized or organometallized. Surprisingly, there has been no experimental report on hydrogenated ptC to date.

Theoretical Prediction on [5]Radialene Sandwich Complexes (CpM)(CH) (Cp = η-CH; M = Fe, Co, Ni): Geometry, Spin States, and Bonding.

[5]Radialene, the missing link for synthesis of radialene family, has been finally obtained via the preparation and decomplexation of the [5]radialene-bis-Fe(CO) complex. The stability of [5]radialene complex benefits from the coordination with Fe(CO) by losing free 1,3-butadiene structures to avoid polymerization. In light of the similar coordination ability of half-sandwiches CpM(Cp = η-CH; M = Fe, Co, Ni), there is a great possibility that the sandwiched complexes of [5]radialene with CpM are available.

Planar pentacoordinate carbon atoms embedded in a metallocene framework.

Viable planar pentacoordinate carbon (ppC) systems with a ppC bonded to a transition metal and embedded in a metallocene framework are reported. Our detailed global minima search shows that CAlMX (M = Zr and Hf; X = F-I and CH) clusters with ppCs are appropriate candidates for experimental realization in the gas phase. The fulfillment of the 18 electron rule and electron delocalization is found to be crucial for the stabilization of these ppC arrangements.