First, two molecules of cobalt(II) complex A react with one molecule of the oxidant to form two molecules of cationic cobalt(III) complex and a fluorine ion, which are present as dinuclear cobalt fluoride  complex B (Figure ). Silylhydride then reacts to form the active species cobalt hydride C (this process has been accelerated by adding water, and the involvement of a cobalt aqua complex has also been reported). The hydrogen atom of the cobalt hydride is transferred to the alkene (MHAT mechanism) to form a radical pair D comprising a cobalt(II) complex and carbon radical; the regioselectivity of the MHAT system reaction may be attributed to the stability of this carbon radical. The radical pair comprising A and carbon radicals quickly collapses to generate the alkylcobalt(III) complex E, followed by a single-electron transfer from E to the residual cationic cobalt(III) complex to form a cationic alkyl cobalt(IV) complex F; A is regenerated. F is strongly electrophilic and can react with relatively weak nucleophiles. Cobalt(IV) complexes are particularly rare compared with cobalt(II) or cobalt(III) complexes. The displacement reactions of alkylcobalt(IV), which exhibit characteristic stereoinversion, have been discussed previously. In addition, studies on cobalt(IV) complexes using electron nuclear double resonance (ENDOR) spectroscopy and computational chemistry have been reported. As described above, we succeeded in bridging the reaction system that was treated as a radical mechanism to an ionic reaction system by adding an oxidant to the MHAT reaction system. Next, examples of reactions in the MHAT/RPC system discovered since 2016 are introduced.