Beyond Single-Ligand Superhalogen Coordination: Unveiling the d -Orbital Contribution as the Electronic Origin in Heteroleptic Silver-Based Hyperhalogens

Abstract Traditional hyperhalogen design relies heavily on homoleptic coordination between a metal center and superhalogen ligands, a constraint that fundamentally limits structural diversity in this field. Here, we report a new class of heteroleptic hyperhalogens, [Ag(BO2)(B2O4)]−, [Ag2(BO2)(B2O4)]−, and [Ag2(BO2)(B3O6)]−, which were synthesized in the gas phase and characterized by time-of-flight (TOF) mass spectrometry and quantum chemical calculations. Experimental results show that precise control over the spectral conditions enables the selective synthesis of these clusters. Theoretical calculations demonstrate that the heteroleptic design endows the clusters with exceptional hyperhalogen properties. Electronic structure analysis further reveals a positive correlation between hyperhalogen behavior and the d-orbital contribution from the Ag atoms to the highest occupied molecular orbital (HOMO). This discovery suggests that synergistic interactions between different superhalogen moieties could have broad applicability in synthetic design, offering new perspectives on the coordination chemistry of superatomic clusters and opening a transformative avenue for hyperhalogen research.