Nickel(ii) in chelate N2O2 environment. DFT approach and in-depth molecular orbital and configurational analysis

Abstract

The O-N-N-O-type tetradentate ligands H2S,S-eddp (H2S,S-eddp stands for S,S-ethylenediamine-N,N'-di-2-propionic acid) and H2edap (H2edap stands for ethylenediamine-N-acetic-N'-3-propionic acid) and the corresponding novel octahedral nickel(II) complexes have been prepared and characterized. N2O2 ligands coordinate to the nickel(II) ion via four donor atoms (two deprotonated carboxylate atoms and two amine nitrogens) affording octahedral geometry in the case of all investigated Ni(II) complexes. A six coordinate, octahedral geometry has been verified crystallographically for the s-cis-[Ni(S,S-eddp)(H2O)2] complex. Structural data correlating similarly chelated Ni(II) complexes have been used to carry out an extensive configuration analysis. Molecular mechanics and Density Functional Theory (DFT) have been used to model the most stable geometric isomer, yielding, at the same time, significant structural and spectroscopic (TDDFT) data. The results from density functional studies have been compared to X-ray data. Natural Bond Orbital (NBO) and Natural Energetic Decomposition Analysis (NEDA) have been done for the [Ni(edda-type)(H2O)(2-n)] and nH2O fragments. Molecular orbital analysis (MPA) is given as well. The infra-red and electronic absorption spectra of the complexes are discussed in comparison to the related complexes of known geometries.

Mechanistic Insights into the Nickel-Catalyzed Cross-Coupling Reaction of Benzaldehyde with Benzyl Alcohol via C–H Activation: A Theoretical Investigation

“…The active H a atom in TS4/5 does certainly not show strong interaction with the nickel d orbital, even though a very short distance Ni–H a (1.508 Å) is discovered. In addition, a fragment molecular orbital analysis was conducted to reveal a better comprehension of the electron reorganization in nickel reaction system. − This kind of analysis has been frequently used in diverse organometallic and metal catalytic reactions. − The whole molecule of TS4/5 is decomposed into Frag. A, Frag.…”