AbstractThe synthesis and properties of the molecular reduction device7b(CoII–V 5++) consisting of a reduction catalyst (a derivative of vitamin B12, CoII) and a covalently linked 10‐electron reservoir (five viologen units, V++) is described. The five viologen subunits were introduced at C(2) and C(3) of the side chainscand g and b,eandf, respectively, of an appropriate derivative of heptamethyl cob(III)yrinate byN‐alkylation of 1‐methyl‐4,4′‐bipyridinium iodide (seeScheme). The pentaviologen‐linked corrinatocobalt(II) complex7bbehaves as a molecular electron trap with respect to the CoIII/CoIIredox couple. The phenomenon is related to the structural and thermodynamic relation of the corrin and viologen subunits in7b, i.e. the relative redoc energies and the spherical inner‐outer arrangement of the types of redox systems. When completely reduced to CoI–V 50,7bexhibits multiple reductive elimination oftrans‐1,2‐dibromocyclohexane to cyclohexene under concomitant oxidation to CoII–V 5++. Rate measurements indicate that the reduction occursviaCoIwhich is regenerated by intramolecular electron transfer from the periphery of