Isolation and Oxygen Activation of Electron-Rich Co$^{II}$$_4$O Metallic Clusters Having a 3-Fold Symmetry

Two novel atomically precise tetra-nuclear cobalt clusters (3a–3b) having a Co$^{II}$$_4$O core with 3-fold symmetry, and three short Co–Co distances of 2.7046(4) Å are isolated with three chelating NP-donor mono-anionic ligands. 3a–3b are shown to react with O$_2$, producing dinuclear cobalt complexes (4a–4b), where the P-centres of the ligands are oxygenated. All complexes are structurally characterized by single-crystal X-ray diffraction, and further studied by UV-vis, IR spectroscopy, CV, magnetic susceptibility measurements, and DFT calculations.