A redox-switchable ligand, N,N′-dimethyldiaminocarbene[3]ferrocenophane (5), was synthesized and incorporated into a series of Ir- and Ru-based complexes. Electrochemical and spectroscopic analyses of (5)Ir(CO)₂Cl (15) revealed that 5 displayed a Tolman electronic parameter value of 2050 cm⁻¹ in the neutral state and 2061 cm⁻¹ upon oxidation. Moreover, inspection of X-ray crystallography data recorded for (5)Ir(cis,cis-1,5-cyclooctadiene)Cl (13) revealed that 5 was sterically less bulky (%V_Bur = 28.4) than other known diaminocarbene[3]ferrocenophanes, which facilitated the synthesis of (5)(PPh₃)Cl₂Ru(3-phenylindenylid-1-ene) (18). Complex 18 exhibited quasi-reversible electrochemical processes at 0.79 and 0.98 V relative to SCE, which were assigned to the Fe and Ru centers in the complex, respectively, based on UV-vis and electron pair resonance spectroscopic measurements. Adding 2,3-dichloro-5,6-dicyanoquinone over the course of a ring-opening metathesis polymerization of cis,cis-1,5-cyclooctadiene catalyzed by 18 ([monomer]₀/[18]₀ = 2500) reduced the corresponding rate constant of the reaction by over an order of magnitude (pre-oxidation: k_obs = 0.045 s⁻¹; post-oxidation: k_obs = 0.0012 s⁻¹). Subsequent reduction of the oxidized species using decamethylferrocene restored catalytic activity (post-reduction: k_obs = up to 0.016 s⁻¹, depending on when the reductant was added). The difference in the polymerization rates was attributed to the relative donating ability of the redox-active ligand (i.e., strongly donating 5versus weakly donating 5⁺+++++) which ultimately governed the activity displayed by the corresponding catalyst.