Square-planar Co(III) in {O₄} coordination: large ZFS and reactivity with ROS

Oxidation of distorted square-planar perfluoropinacolate Co compound [Co^II(pin^F)₂]²⁻, 1, to [Co^III(pin^F)₂]¹⁻, 2, is reported. Rigidly square-planar 2 has an intermediate-spin, S = 1, ground state and very large zero-field splitting (ZFS) with D = 67.2 cm⁻¹; |E| = 18.0 cm⁻¹, (E/D = 0.27), g_⊥ = 2.10, g_‖ = 2.25 and χ_TIP = 1950 × 10⁻⁶ cm³ mol⁻¹. This Co(III) species, 2, reacts with ROS to oxidise two (pin^F)²⁻ ligands to form tetrahedral [Co^II(Hpfa)₄]²⁻, 3.