Basic principles governing redox activation of the 18-electron complexes of transition metals areconsidered. In essence, this process converts the above complexes to 17-electron or 19-electron radical-ions viathe abstraction or addition of an electron, respectively. The latter radical-ions exhibit significantly enhancedreactivity. The feasibility of the electrochemical initiation of the isomerization reactions for complexes withpolydentate ligands, which occur concomitant with a change in the metal coordination site, is shown usingsandwich and semisandwich -complexes of transition metals. Particular emphasis is placed on examiningreactions of inter-ring haptotropic isomerization for -complexes of metals with polycyclic aromatic ligandsthat are induced by electron transfer. The isomerization involves migration of the metal from one ring to anotheralong the plane of the -electron system of the ligand.