Half-Sandwich LaBn−/0 (n = 14–17): π Dually Aromatic Lanthanide Boride Complexes with Multicenter Fluxional Bonds

Novel lanthanide boride complexes with unique structural and bonding patterns have been observed in recent experiments. Based on extensive first-principles theory calculations, we predict herein the possible existence of half-sandwich C2v LaB14− (1), C1 LaB15 (2), C5v LaB16− (3), and Cs LaB17 (4) which all contain a La center coordinated by a bowl-like Bn ligand (n = 14–17). Detailed bonding analyses indicate that effective d-p coordination interactions exist between the La center and Bn ligand, making these half-sandwich complexes π dually aromatic in nature. Energy decomposition analyses reveal that electrostatic (50.2%) and covalent (49.8%) interactions contribute almost equally to the overall attraction in LaB14− (1), with the La centre serving as both electron donor and acceptor. Molecular dynamics simulations show that both LaB14− (1) (La[B4©B10]−) and LaB17 (4) (La[B©B5©B11]) with multicenter fluxional bonds behave like Wankel motors at finite temperatures.