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Nb₂©Au₆: a molecular wheel with a short Nb[triple bond, length as m-dash]Nb triple bond coordinated by an Au₆ ring and reinforced by σ aromaticity.

ABSTRACT: We report a photoelectron spectroscopy and high-resolution photoelectron imaging study of a bimetallic Nb₂Au₆ ^- cluster. Theoretical calculations, in conjunction with the experimental data, reveal that Nb₂Au₆ ^-/0 possess high-symmetry D _6h structures featuring a Nb-Nb axis coordinated equatorially by an Au₆ ring. Chemical bonding analyses show that there are two π bonds and one σ bond in the Nb₂ moiety in Nb₂©Au₆, as well as five totally delocalized σ bonds. The Nb[triple bond, length as m-dash]Nb triple bond is strengthened significantly by the delocalized σ bonds, resulting in an extremely short Nb-Nb bond length comparable to the quintuple bond in gaseous Nb₂. The totally delocalized σ bonding in Nb₂©Au₆ is reminiscent of σ aromaticity, representing a new bonding mode in metal-ligand systems. The unusually short Nb-Nb bond length in Nb₂©Au₆ shows that the Au₆ ring can serve as a bridging ligand to facilitate multiple bonding in transition metal dimers via delocalized σ bonding.

SUBMITTER: Jian T

PROVIDER: S-EPMC5694916 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:In a natural environment, Fe(ii) adsorbed onto the surfaces of natural particles to form various surface complex species can influence the transformation of contaminants. The reductive reactivity of the [[triple bond, length as m-dash]Fe(iii)]/[[triple bond, length as m-dash]Fe(ii)] couples are close correlated with the surrounding conditions. In this study, we investigated the effects of Si(iv) on the reductive reactivity of [[triple bond, length as m-dash]Fe(iii)]/[[triple bond, length as m-dash]Fe(ii)] couples adsorbed onto γ-Al2O3. Experiments were conducted under different conditions to investigate the effects of Si(iv) on the reactivity of [[triple bond, length as m-dash]Fe(iii)]/[[triple bond, length as m-dash]Fe(ii)] couples for 2-nitrophenol (2-NP, selected as the model pollutant) reduction in γ-Al2O3 suspensions. Kinetics results revealed that chemical adsorption is the rate limiting step in Fe(ii) and Si(iv) adsorption processes and the reduction of 2-NP is an endothermic reaction. The linear correlations between the reduced peak oxidation potential (E p) (versus SCE) and 2-NP reduction rate (ln k), and between the adsorbed Fe(ii) density (ρ Fe(II)) and ln k, illustrated that E p and ρ Fe(II) are two key factors in the inhibiting effects of Si(iv) on the reductive reactivity of Fe(iii)/Fe(ii) couples on γ-Al2O3. The results of Fe K-edge X-ray absorption spectroscopy revealed that the increase of Si(iv) concentration resulted in the gradual change in the composition of the adsorbed Fe species from pure [triple bond, length as m-dash]AlOFe+ (γ-Al2O3 surface-bound Fe(ii) species with higher reductive reactivity) to a mixture of [triple bond, length as m-dash]AlOFe+ and [triple bond, length as m-dash]SiOFe+ (SiO2 surface-bound Fe(ii) species with lower reductive reactivity), leading to the decrease in ρ Fe(II), the positive shift in E p, the increase in activation energy (E a), and consequently the decrease in the reduction rate (ln k) of 2-NP.

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Nb₂©Au₆: a molecular wheel with a short Nb[triple bond, length as m-dash]Nb triple bond coordinated by an Au₆ ring and reinforced by σ aromaticity.

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Nb2©Au6: a molecular wheel with a short Nb[triple bond, length as m-dash]Nb triple bond coordinated by an Au6 ring and reinforced by σ aromaticity.

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OmicsDI is part of the ELIXIR infrastructure

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Nb₂©Au₆: a molecular wheel with a short Nb[triple bond, length as m-dash]Nb triple bond coordinated by an Au₆ ring and reinforced by σ aromaticity.