Rare Spin Avoided σ-σ Diradical Planar Tetracoordinate Boron Cluster: A Proto-Star for Planar Pentacoordination

We report a global planar star-like cluster B₃ Li₃ featuring three planar tetracoordinate boron centres with a rare spin avoided σ-σ diradical character. The cluster was found to be stable towards dissociation into different fragments. The spin density was found to be localized solely on the three boron atoms in the molecular plane. This spin avoided σ-σ diradical character leads to the extension of the coordination number to yield a neutral B₃ Li₃ H₃ and a cationic B₃ Li₃ H₃ ⁺ cluster with three planar pentacoordinate boron centres in their global minimum structures. The planar geometry of the aninonic B₃ Li₃ H₃ ^- cluster is slightly higher in energy. The planar global clusters were found to maintain planarity in their ligand protected benzene bound complexes, B₃ Li₃ (Bz)₃ , B₃ Li₃ H₃ (Bz)₃ and B₃ Li₃ H₃ (Bz)₃ ⁺ with high ligand dissociation energies offering candidature for experimental detection.