Dative behavior of N-heterocyclic carbenes (NHCs) with selenium in Se-NHC compounds

N-heterocyclic carbenes (NHCs) are an eminent class of carbenes having a heterocyclic ring in which a divalent carbon atom is attached directly to a nitrogen atom. In the NHCs, the donation of lone pair is another important research in the dative bonding and not only in NHCs the dative bond plays a functionalized role in the other classes of complex formation like ylidones L → E ← L and carbones L → C ← L. M–NHC bond is L-M sigma-dative bond and NHCs are considered as strong sigma-donor ligands. The clear picture of the M–NHC bond can be better understood by M–NHC pi-interaction. M-L pi interaction is comprised of two steps. One is L → M sigma-donation and M → L π* back bonding. This dative donor nature of NHC and also its behavior in organoselenium is studied through DFT in which it’s optimized structure, bond lengths, molecular vibrations are calculated.

Synthesis of Ni/NiAlOx Catalysts for Hydrogenation Saturation of Phenanthrene

The saturation of octahydrophenanthrene was the rate-determining step in the hydrogenation process from phenanthrene to perhydrophenanthrene, which was due to the steric hindrance and competitive adsorption of octahydrophenanthrene. In this work, a series of Ni/NiAlOx catalysts with a uniform electron-deficient state of Ni derived from the nickel aluminate structure was synthesized to overcome the disadvantage of noble catalyst and the traditional sulfided catalysts in the saturation hydrogenation process of phenanthrene. Results showed that the catalyst calcinated at 650°C possessed more Ni2+ (∼98%) occupying octahedral sites and exhibited the highest robs (1.53 × 10−3 mol kg−1 s−1) and TOF (14.64 × 10−3 s−1) for phenanthrene hydrogenation. Furthermore, its ability to overcome steric hindrance and promote the rate-determining step was proven by octahydrophenanthrene hydrogenation. Comparing the evolution of hydrogenation activity with the change in the electronic structure of surface Ni sites, it was shown that the increase of metallic electron deficiency hindered the π-back bonding between surface Ni and aromatic rings, which was unfavorable for aromatic adsorption. As a result, the phenanthrene hydrogenation saturation performance can be enhanced by stabilizing the electron-deficient state of surface Ni on an optimal degree.

Relevant electronic interactions related to the coordination chemistry of tetracyanometallates. An XPS study

In the K2[M(CN)4]·xH2O (M = Ni, Pd, Pt) series, the CN ligand is found to donate electron density to the K ion, which is detected as a decrease in the K 2p BE. The charge donated is proportional to that removed from the inner metal (M) via π-back bonding.