Nature of Cation-π Interaction in Mono- and Inverted Sandwich Ga(I) Complexes. Insights Into the Ga(I)-π Features and NMR Patterns from GaCp, GaCp*, [Ga2Cp]+, and [Ga2Cp*]+

Cation-π interactions involve different metallic cations, where the bonding characteristics depend on the involved species. Here, we unravel the interaction nature features for Ga(I)-π interactions, where different contributing terms ensure an efficient coordination of one and two Ga(I)-atoms towards a common aromatic ring. Our results show a more balanced contribution of about ~70 % from electrostatic character and of ~30 % from orbital interaction for the prototypical GaCp, GaCp*, [Ga₂Cp]⁺ and [Ga₂Cp*]⁺ species. Such description strongly contrasts with the highly electrostatic character in alkali and alkaline-earth metals counterparts. The variation from mono to inverted sandwich complexes leads to a decrease in the interaction energy from −180.9 to −148.1 kcal/mol for Cp based species, and from −184.4 to −155.5 kcal/mol in Cp* counterparts, owing to a decrease in both electrostatic and orbital stabilizing contributions. Thus, the aromatic rings exhibit coordination versatility towards one or two Ga(I) cations, retaining a sizable stabilization of the Ga(I)-π interaction. Thus, cation-π interactions are able to exhibit different types according to the involved metal cation, which relies on a more electrostatic/orbital balanced interaction, which serves to evaluate further mono and inverted sandwich complexes sharing a common aromatic ring.