Planar hexacoordinate gallium†
We report the first planar hexacoordinate gallium (phGa) center in the global minimum of the GaBe6Au6+ cluster which has a star-like D6h geometry with 1A1g electronic state, possessing a central gallium atom encompassed by a Be6 hexagon and each Be–Be edge is further capped by an Au atom. The electronic delocalization resulting in double aromaticity (both σ and π) provides electronic stability in the planar form of the GaBe6Au6+ cluster. The high kinetic stability of the title cluster is also understood by Born–Oppenheimer molecular dynamics simulations. The energy decomposition analysis in combination with the ‘natural orbitals for chemical valence’ theory reveals that the bonding in the GaBe6Au6+ cluster is best expressed as the doublet Ga atom with 4s24p⊥1 electronic configuration forming an electron-sharing π bond with the doublet Be6Au6+ moiety followed by Ga(s)→[Be6Au6+] σ-backdonation and two sets of Ga(p‖)←[Be6Au6+] σ-donations.