N‑Heterocyclic\nCarbene-Derived Carbon Disulfide\nRadical Ligands for Palladium Diradicals

N-heterocyclic\ncarbenes (NHCs) are recognized for their ability\nto stabilize various main group radicals; however, NHC-derived, sulfur-based\nradicals remain rare. In this study, we successfully synthesized and\ncharacterized a series of palladium diradical complexes that featured\nnew sulfur-based radical ligands from NHC–carbon disulfide\nadducts. Spectroscopic and computational characterizations of the\npalladium complexes confirmed the open-shell singlet ground state,\nwhich resulted from the antiferromagnetic coupling of two unpaired\nelectrons on each ligand. Proton nuclear magnetic resonance relaxometry\nwas used to experimentally confirm the presence of these unpaired\nelectrons. Moreover, the redox behavior of the complexes was localized\non the ligand center, confirming the redox activity of the ligands.\nThe discovery of this sulfur-based, redox-active radical ligand underscores\nthe versatility and significance of NHC-derived radicals, thereby\nexpanding the repertoire of radical ligands and opening new avenues\nfor advanced material and catalytic systems.