Bonding and electronic structures in W@Au₁₂AE complexes (AE= NO⁺, CO, BF, CN⁻, or BO⁻): analogies among ligands isoelectronic to carbon monoxide.

A theoretical study on the geometries and electronic structures of W@Au(12)AE (AE=NO(+), BF, CN(-), or BO(-)) was carried out to gain insight into interactions between W@Au(12) and ligands isoelectronic with CO. The best configuration for the adsorption site is on-top type for all five complexes. After complexing with boron ligands (BF or BO(-)), the axial Au-W bond distance in W@Au(12) is lengthened notably, but NO(+) has the opposite effect on the axial Au-W bond. A charge transfer and energy decomposition analysis shows that the metal-ligand bonds have enhanced sigma-donation strength from NO(+) to BO(-). Furthermore, the A-E bond strength in the complexes becomes weaker with stronger pi-back-donation interactions. Finally, W@Au(12)CO has the largest HOMO-LUMO gap, making it the most stable in terms of kinetic stability.