The MCM reaction mechanism begins with homolytic cleavage of AdoB12's C-Co(III) bond, the C and Co atoms each acquire one of the electrons that formed the cleaved electron pair bond. The Co ion, therefore, fluctuates between its Co(III) and Co(II) oxidation states [the two states are spectroscopically distinguishable: Co(III) is red and diamagnetic (no unpaired electrons), whereas Co(II) is yellow and paramagnetic (unpaired electrons)].
The MCM reaction mechanism involves homolytic cleavage of AdoB12's C-Co(III) bond, leading to the cobalt ion fluctuating between its Co(III) and Co(II) oxidation states. These two states are spectroscopically distinct: Co(III) is red and diamagnetic (no unpaired electrons), while Co(II) is yellow and paramagnetic (unpaired electrons).