RESUMO
We have quantum chemically investigated the origin of the atypical blueshift of the H-C bond stretching frequency in the hydrogen-bonded complex X- â¢â¢â¢H3 C-Y (X, Y=F, Cl, Br, I), as compared to the corresponding redshift occurring in Cl- â¢â¢â¢H3 N and Cl- â¢â¢â¢H3 C-H, using relativistic density functional theory (DFT) at ZORA-BLYP-D3(BJ)/QZ4P. Previously, this blueshift was attributed, among others, to the contraction of the H-C bonds as the H3 C moiety becomes less pyramidal. Herein, we provide quantitative evidence that, instead, the blueshift arises from a direct and strong X- â¢â¢â¢C interaction of the HOMO of A- with the backside lobe on carbon of the low-lying C-Y antibonding σ* LUMO of the H3 C-Y fragment. This X- â¢â¢â¢C bond, in essence a tetrel bond, pushes the H atoms towards a shorter H-C distance and makes the H3 C moiety more planar. The blueshift may, therefore, serve as a diagnostic for tetrel bonding.
RESUMO
The front cover artwork is provided by the TheoCheM group at the Vrije Universiteit Amsterdam. The image shows how, in X- â¢â¢â¢H3 C-Y complexes, the Lewis base X- tetrel-binds to the central C while sterically pushing the H atoms towards C; hence, the compression and blueshift of the H-C bonds. Read the full text of the Research Article at 10.1002/cphc.202300480.
RESUMO
Nickelacyclobutanes are mostly invoked as reactive intermediates in the reaction of nickel carbenes and olefins to yield cyclopropanes. Nevertheless, early work suggested that other decomposition routes such as ß-hydride elimination and even metathesis could be accessible. Herein, we report the isolation and characterization of a stable pentacoordinated nickelacyclobutane incorporated in a pincer complex. The coordination of different coligands to the nickelacyclobutane determines its selective decomposition along cyclopropanation, metathesis or apparent ß-hydride elimination pathways. DFT calculations shed light on the mechanism of these different pathways.