Donor–acceptor duality of the transition-metal-like B(2) core in core–shell-like metallo-borospherenes La(3)&[B(2)@B(17)](−) and La(3)&[B(2)@B(18)](−)

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 D(3h) La(3)&B(18)(−) (1) (Chen, et al., Nat. Commun., 2020, 11, 2766) and based on extensive first-principles theory calculations, we predict herein the first and smallest core–shell-like metallo-borospherenes C(2v) La(3)&[B(2)@B(17)](−) (2) and D(3h) La(3)&[B(2)@B(18)](−) (3) which contain a transition-metal-like B(2) core at the cage center with unique donor–acceptor duality in La(3)&B(n)(−) spherical trihedral shells (n = 17, 18). Detailed energy decomposition and bonding analyses indicate that the B(2) 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(6) 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.