MB₁₆ ^- (M=Sc, Y, La): Perfect Bowl-Like Boron Clusters

The introduction of transition-metal doping has engendered a remarkable array of unprecedented boron motifs characterized by distinctive geometries and bonding, particularly those heretofore unobserved in pure boron clusters. In this study, we present a perfect (no defects) boron framework manifesting an inherently high-symmetry, bowl-like architecture, denoted as MB₁₆ ^- (M=Sc, Y, La). In MB₁₆ ^-, the B₁₆ is coordinated to M atoms along the C_5v-symmetry axis. The bowl-shaped MB₁₆ ^- structure is predicted to be the lowest-energy structure with superior stability, owing to its concentric (2 π+10 π) dual π aromaticity. Notably, the C_5v-symmetry bowl-like B₁₆ ^- is profoundly stabilized through the doping of an M atom, facilitated by strong d-p_π interactions between M and boron motifs, in conjunction with additional electrostatic stabilization by an electron transfer from M to the boron motifs. This concerted interplay of covalent and electrostatic interactions between M and bowl-like B₁₆ renders MB₁₆ ^- a species of exceptional thermodynamic stability, thus making it a viable candidate for gas-phase experimental detection.