Square-planar Co(<scp>iii</scp>) in {O4} coordination: large ZFS and reactivity with ROS

Oxidation of distorted square-planar perfluoropinacolate Co compound [CoII(pinF)2]2−, 1, to [CoIII(pinF)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 χTIP = 1950 &#215; 10−6 cm3 mol−1. This Co(III) species, 2, reacts with ROS to oxidise two (pinF)2− ligands to form tetrahedral [CoII(Hpfa)4]2−, 3.