LAUSR

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 A). 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 A). Remarkably, for the relatively short regime (<3 A) of anagostic distances,...