One electron reduction transforms high-valent low-spin cobalt alkylidene into high-spin cobalt(ii) carbene radical.

One electron reduction of formally CoIV(OR)2(CPh2) forms the [CoII(OR)2(CPh2)]- anion. Whereas low-spin Co(OR)2([double bond, length as m-dash]CPh2) demonstrated significant alkylidene character, the high-spin [Co(OR)2(CPh2)]- anion features a rare Co(ii)-carbene radical. Treatment of [Co(OR)2(CPh2)][CoCp*2] with xylyl isocyanide triggers formation of two new C-C bonds, and is likely mediated by nucleophilic attack of deprotonated CoCp*2+ on a transient ketenimine.