Triimidosulfonates as Acute Bite‐Angle Chelates: Slow Relaxation of the Magnetization in Zero Field and Hysteresis Loop of a Co II Complex

Starting from a polyimido sulfonate the four‐coordinate, N , N′ ‐chelated Co II complex [Co{(N t Bu) 3 SMe} 2 ] ( 1 ) was synthesized, and its molecular structure was elucidated by single‐crystal X‐ray structural analysis. The acute N‐Co‐N bite angle imposed by the N , N′ ‐chelating ligand (N t Bu) 3 SMe − leads to pronounced C 2 v distortion of the tetrahedral coordination environment and thus to high anisotropy of the Co II ion ( D ≈−58 cm −1 ), favorable for single‐molecule‐magnet (SMM) properties. Magnetic measurements revealed a high barrier to spin reversal ( U eff =75 cm −1 ) that gives rise to the observation of slow relaxation of the magnetization in zero field and a hysteresis loop at 2 K for this unique complex.