Insights Into Metal−π Arene Interactions of the Highly Lewis Acidic Rh₂⁴⁺ Core with a Broad Set of π-Ligands: From Ethylene to Corannulene and C₆₀-Fullerene

The first systematic theoretical investigation of interactions of the Lewis acidic Rh(II) centers with a number of pi-ligands having isolated unsaturated carboncarbon bonds (acetylene and ethylene) or delocalized pi-systems with planar (benzene, naphthalene, acenaphthylene, and pyrene) or curved surfaces (corannulene and the C(3)-hemifullerene), including the C(60)-fullerene, has been undertaken. The effect of size, geometry, site specificity, and curvature of pi-ligands on their interaction energy with Rh(II) has been examined. The geometric and electronic structures of pi-adducts have been modeled at the DFT level of theory by using the hybrid Perdew-Burke-Ernzerhof parameter free exchange-correlation functional (PBE0). The nature of Rh(II)-pi interactions was found to be similar in all products with the bonding energy ranging from 14.59 kcal/mol in the benzene adduct to 50.13 kcal/mol in the fullerene complex. Importantly, the quantitative evaluation of two bonding components, namely, ligand-to-metal and metal-to-ligand contributions, allowed us to rationalize the observed trends in pi-binding affinity of the selected ligands as well as in stability of the resulting products. These trends deduced from DFT calculations are important for considering the synthetic feasibility of novel pi-complexes in these systems.