A spin-crossover Co(II) complex catalyzes the activation of sp3 C–H bonds by two-electron oxidants.

Graphical abstract A spin-crossover cobalt(II) complex is found to be a catalyst for the oxidation of weak C–H bonds by the two-electron oxidants iodosobenzene and meta -chloroperbenzoic acid. The complex is incapable of being oxidized to a cobalt(III)-peroxo species and cannot participate in aldehyde deformylation reactions. Highlights • A non-organometallic cobalt(II) complex was found to catalyze the oxidation of weak C–H bonds by two two-electron oxidants. • The cobalt(II) complex differs from the other known non-organometallic catalyst in that it is not entirely high-spin. • The cobalt(II) complex cannot form a cobalt(III)-peroxo complex and cannot participate in aldehyde deformylation. Abstract We recently found that a high-spin Co(II) complex with N,N' -dibenzyl- N,N' -bis(2-pyridylmethyl)-1,2-cyclohexanediamine (bbpc) was capable of catalyzing the oxidation of weak sp3 C–H bonds by iodosobenzene (PhIO) and meta -chloroperbenzoic acid (MCPBA). The bbpc compound could also be oxidized to a Co(III)-peroxo species capable of reacting with aldehydes. The ligand N -benzenesulfonyl- N,N’ -bis(2-pyridylmethyl)-1,2-cyclohexanediamine (bsbpc) reacts with Co(ClO 4) 2 to yield a spin-crossover complex, [Co(bsbpc)(MeCN) 2 ](ClO 4) 2. The bsbpc complex catalyzes the oxidation of benzylic and allylic C–H bonds by PhIO and MCPBA to approximately the same extent as the high-spin bbpc compound. The bsbpc complex differs more substantially from the bbpc compound in that it cannot be oxidized to a stable Co(III)-peroxo complex and shows no reactivity with aldehydes. [ABSTRACT FROM AUTHOR]