Donor-acceptor duality of the transition-metal-like B core in core-shell-like metallo-borospherenes La&[B@B] and La&[B@B].

Transition-metal doping induces dramatic structural changes and leads to earlier planar → tubular → spherical → core-shell-like structural transitions in boron clusters. Inspired by the newly discovered spherical trihedral metallo-borospherene La&B (1) (Chen, , Nat. Commun., 2020, , 2766) and based on extensive first-principles theory calculations, we predict herein the first and smallest core-shell-like metallo-borospherenes La&[B@B] (2) and La&[B@B] (3) which contain a transition-metal-like B core at the cage center with unique donor-acceptor duality in La&B spherical trihedral shells ( = 17, 18). Detailed energy decomposition and bonding analyses indicate that the B core in these novel complexes serves as a π-donor in the equatorial direction mainly to coordinate three La atoms on the waist and a π/σ-acceptor in the axial direction mainly coordinated by two B triangles on the top and bottom. These highly stable core-shell complexes appear to be spherically aromatic in nature in bonding patterns. The IR, Raman, and photoelectron spectra of 2 and 3 are computationally simulated to facilitate their spectroscopic characterizations.