Cobalt(II) Bis(1, 4, 7-trithiacyclononane): A Low-Spin Octahedral Complex

Cobalt(II) forms a bis complex with 1, 4, 7-trithiacyclononane (1, 4, 7-TTCN) with an unprecedentedly large overall formation constant of 8 X 10¹³. This complex has an effective magnetic susceptibility of 1.71 μB. Thus, this is a low-spin octahedral Co(II) complex, and such complexes are exceedingly rare. Cyclic voltammetry of Co(1, 4, 7-TTCN)₂²⁺shows three diffusion-controlled one-electron steps at 0.573,-0.292, and-0.998 V vs, SHE corresponding to Co(III)/Co(II), Co(II)/Co(I), and Co(I)/Co(0) reductions, respectively. The unique properties of this complex are suggested to be due to ligand conformational control.