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While main group elements have four valence orbitals accessible for bonding, quadruple bonding to main group elements is extremely rare. Here we report that main group element boron is able to form quadruple bonding interactions with iron in the BFe(CO)3- anion complex, which has been revealed by quantum chemical investigation and identified by mass-selected infrared photodissociation spectroscopy in the gas phase. The complex is characterized to have a B-Fe(CO)3- structure of C3v symmetry and features a B-Fe bond distance that is much shorter than that expected for a triple bond. Various chemical bonding analyses indicate that the complex involves unprecedented B≣Fe quadruple bonding interactions. Besides the common one electron-sharing σ bond and two Fe→B dative π bonds, there is an additional weak B→Fe dative σ bonding interaction. This finding of the new quadruple bonding indicates that there might exist a wide range of boron-metal complexes that contain such high multiplicity of chemical bonds.

The concept of oxidation state (OS) is based on the concept of Lewis electron pairs, in which the bonding electrons are assigned to the more electronegative element. This approach is useful for keeping track of the electrons, predicting chemical trends, and guiding syntheses. Experimental and quantum-chemical results reveal a limit near +8 for the highest OS in stable neutral chemical substances under ambient conditions. OS=+9 was observed for the isolated [IrO4 ]+ cation in vacuum. The prediction of OS=+10 for isolated [PtO4 ]2+ cations is confirmed computationally for low temperatures only, but hasn't yet been experimentally verified. For high OS species, oxidation of the ligands, for example, of O-2 with formation of . O-1 and O-O bonds, and partial reduction of the metal center may be favorable, possibly leading to non-Lewis type structures.

The concept of oxidation state (OS) is based on the concept of Lewis electron pairs, in which the bonding electrons are assigned to the more electronegative element. This approach is useful for keeping track of the electrons, predicting chemical trends, and guiding syntheses. Experimental and quantum-chemical results reveal a limit near +8 for the highest OS in stable neutral chemical substances under ambient conditions. OS=+9 was observed for the isolated [IrO4 ]+ cation in vacuum. The prediction of OS=+10 for isolated [PtO4 ]2+ cations is confirmed computationally for low temperatures only, but hasn't yet been experimentally verified. For high OS species, oxidation of the ligands, for example, of O-2 with formation of . O-1 and O-O bonds, and partial reduction of the metal center may be favorable, possibly leading to non-Lewis type structures.

The thermal and dynamic effects of the special topography of the Qinghai–Tibet Plateau have a significant impact on rainfall in China. Utilizing NCEP/NCAR monthly reanalysis data alongside precipitation observations from 1936 monitoring stations across China spanning from 1966 to 2022, this study establishes a location index for the thermal low-pressure center situated over the Qinghai–Tibet Plateau. Temporal variations in the location index and summer (July) precipitation patterns in China were studied. Over the past six decades, thermal low-pressure centers have been predominantly positioned near 90° E and 32.5° N within a geopotential height of 4360 gpm, with their distribution extending from east to west rather than from south to north. The longitudinal and latitudinal position indices showed the same linear trend, with a negative trend before the 21st century, and then began to turn positive. Mutation analysis highlights pronounced weakening mutations occurring in 1981 and 1973, with the longitudinal index transitioning from an interannual cycle of approximately 6–8 years, while the latitudinal index displays quasi-cyclic oscillations of 5 and 8 and 12–14 years. Strong negative correlations are evident between the location indices and precipitation along the southeastern edge of the Qinghai–Tibet Plateau and in southern China, contrasting with the positive correlations observed in the central-eastern plateau, northwest, north, and the Huang-Huai region of China. The center of the thermal low is located to the east and north, corresponding to the deeper surface thermal low in most areas east of China, and the stronger transport of warm and wet air from the southwest wind, leading to greater convergence of southwest wind and northwest wind in China's northern region. The south of the Yangtze River is controlled by the strengthening West Pacific subtropical high and South Asia high, resulting in a significant decrease in precipitation, and the warm and humid air from the southwest on the west side of the West Pacific subtropical high is also transported to the north, increasing the precipitation in most parts of the north. [ABSTRACT FROM AUTHOR]

Aluminium is one of the most abundant metals in the universe and impacts the evolution of various astrophysical environments. Currently detected Al‐bearing molecules represent only a small fraction of the aluminium budget, suggesting that aluminium may reside in other species. AlO and AlOH molecules are abundant in the oxygen‐rich supergiant stars such as VY Canis Majoris, a stellar molecular factory with 60+ molecules including the prebiotic NC‐bearing species. Additional Al‐bearing molecules with N, C, O, and H may form in O‐rich environments with radiation‐accelerated chemistry. Here, we present spectroscopic identification of novel aluminium‐bearing molecules composed of [Al, N, C, O, H] and [Al, N, C, O] from the reactions of Al atoms and HNCO in solid argon matrix, which are potential Al‐bearing molecules in space. Photoinduced transformations among six [Al, N, C, O, H] isomers and three [Al, N, C, O] isomers, along with their dissociation reactions forming the known interstellar species, have been disclosed. These results provide new insight into the chemical network of astronomically detected Al‐bearing species in space. [ABSTRACT FROM AUTHOR]

Metal (iso)cyanides dominate the molecular inventory of metal-bearing species in the interstellar medium. Their oxide counterparts, metal (iso)cyanates, have potential as interstellar molecules and have received significant attention. However, cationic complexes HNCOM+ as precursors to metal (iso)cyanates are rarely studied. Herein, we investigated HNCOCa+ by exploiting infrared spectrometry with isotopic substitutions and quantum chemical calculations. For comparison, the light and heavy alkaline earth metal cationic complexes HNCOBe+ and HNCOBa+ were also explored. HNCOCa+ and HNCOBe+ rather than HNCOBa+ can be experimentally generated by the reactions of metal cations with HNCO. The observed antisymmetric and symmetric NCO stretching vibrations in HNCOCa+ (2362.6 and 1330.4 cm−1) are higher than those in free HNCO (2268.5 and 1320.3 cm−1) but lower than those in HNCOBe+ (2426.4 and 1355.2 cm−1). These shifts can be explained by the charge polarization within the NCO fragment in HNCOBe+ and HN-COCa+. Bonding analysis suggests that HNCO–Be+ bond favors covalent character (54%) while HNCO–Ca+ bond has higher electrostatic character (57%). The dominant electrostatic interaction (64%) in HNCO–Ba+ bond results in the low bond energy, which might account for its absence in experiments. [ABSTRACT FROM AUTHOR]

Trifluoroacetylacetone (TFAA) has two enol forms, which can switch to each other via proton transfer. While much attention has been paid to their conformational preferences, the influence of microsolvation on regulating the proton position remains unexplored. Herein, we report the rotational spectra of trifluoroacetylacetone–(water)n (n = 1–3) investigated by chirped pulse Fourier transform microwave spectroscopy in the 2–8 GHz frequency range. Two conformers were identified for both TFAA–H2O and TFAA–(H2O)2, while only one conformer was characterized for TFAA–(H2O)3. The results indicate that water binding on the CH3 side stabilizes the enolF form, whereas water binding on the CF3 side stabilizes the enolH form. The enolF form predominates over the enolH form in these hydrated complexes, which contrasts with the fact that only enolH exists in isolated TFAA. EnolH becomes preferred only when water inserts itself into the intramolecular hydrogen bond. Instanton theory calculations reveal that the proton transfer reaction is dominated by quantum tunneling at low temperatures, leading to the stable existence of only one enol form in each configuration of the hydrated clusters. [ABSTRACT FROM AUTHOR]

A series of coinage metal complexes in the form of TMC(CO)n− (TM = Cu, Ag, Au; n = 0–3) were generated using a laser-ablation supersonic expansion ion source in the gas phase. Mass-selected infrared photodissociation spectroscopy in conjunction with quantum chemical calculations indicated that the TMC(CO)3− complexes contain a linear OCTMCCO− core anion. Bonding analyses suggest that the linear OCTMCCO− anions are better described as the bonding interactions between a singlet ground state TM+ metal cation and the OC/CCO2− ligands in the singlet ground state. In addition to the strong ligands to metal σ donation bonding components, the π-bonding components also contribute significantly to the metal–ligand bonds due to the synergetic effects of the CO and CCO2− ligands. The strengths of the bonding of the three metals show a V-shaped trend in which the second-row transition metal Ag exhibits the weakest interactions whereas the third–row transition metal Au shows the strongest interactions due to relativistic effects. [ABSTRACT FROM AUTHOR]

The HBP radical was generated via the reaction of laser ablated boron atom with PH3 in a solid neon matrix, which is identified via IR spectroscopy with isotopic substitutions and quantum chemical calculations. The results show that HBP has a 2Π electronic ground state with a short B−P bond. Bonding analysis indicates that besides an electron‐sharing σ bond, there are two degenerate π bonding orbitals that are occupied by three electrons, resulting in a bond order of two and half between P and B. This is in sharp contrast to the bonding properties of the isovalent HNB, which was characterized to be a N≡B triply bonded σ radical with the unpaired electron locating on the B atom. [ABSTRACT FROM AUTHOR]

Heteronuclear magnesium–iron carbonyl anion complexes MgFe(CO)4− and Mg2Fe(CO)4− are produced in the gas phase and are detected by mass-selected infrared photodissociation spectroscopy in the carbonyl stretching frequency region. The geometric structures and the metal–metal bonding are discussed with the aid of quantum chemical calculations. Both complexes are characterized to have a doublet electronic ground state with C3v symmetry containing a Mg–Fe bond or a Mg–Mg–Fe bonding unit. Bonding analyses indicate that each complex involves an electron-sharing Mg(I)–Fe(– II) σ bond. The Mg2Fe(CO)4− complex involves a relatively weak covalent Mg(0)–Mg(I) σ bond. [ABSTRACT FROM AUTHOR]