Chameleon-like Nature of Anagostic Interactions and Its Impact on Metalloaromaticity in Square-Planar Nickel Complexes
(2019) Organometallics — Vol. 38, n° 9, p. 1973-1981 (2019)
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- Authors
Mitoraj, Mariusz P. 
Sagan, Filip Safin, Damir A
- Abstract
- Anagostic C–H···M (M = a metal center) intramolecular interactions, one of the most fundamental and elusive forces in organometallic chemistry, are intuitively considered as repulsive and purely electrostatic in nature because of significant metal–hydrogen distances (∼2.3–3.0 Å). Contrary to the current state of knowledge, it is shown herein by quantum chemical computations based on the case study of new square-planar NiII isomers based on N-thiophosphorylated thiourea that despite significant metal–hydrogen anagostic distances, the covalent-type charge delocalization contribution [Ni(dz2) → σ*(C–H) and σ(C–H) → Ni(dz2)] exists and it covers, together with the London dispersion energy, up to ∼40% of the overall anagostic stabilization. This charge delocalization component is found to amplify the metalloaromaticity phenomenon although a lack of any stabilizing charge transfer is expected at such long metal-hydrogen distances (>3 Å). Remarkably, for the relatively short regime (<3 Å) of anagostic distances, the electrostatic Coulomb forces are destabilizing, which leads to the repulsive anagostic interactions, whereas, surprisingly, an increase of anagostic distance above 3 Å makes anagostic interactions stabilizing mostly because of attractive Coulomb forces. It shows unprecedented agostic (attractive) ↔ anagostic (repulsive) transitions in ubiquitous d8 square-planar NiII complexes containing elongated metal–hydrogen distances
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Citations
Mitoraj, M. P., Babashkina, M., Robeyns, K., Sagan, F., Szczepanik, D. W., Seredina, Y. V., Garcia, Y., & Safin, D. A. (2019). Chameleon-like Nature of Anagostic Interactions and Its Impact on Metalloaromaticity in Square-Planar Nickel Complexes. Organometallics, 38(9), 1973-1981. https://doi.org/10.1021/acs.organomet.9b00062 (Original work published 2019)