Iron and Cobalt Base-Metal Asymmetric Catalysis: Sustainable Alternatives to Precious Metals

April 20, 2026 Metal Catalysis, Science iron, cobalt, base metal, sustainable, asymmetric hydrogenation, epoxidation, chiral

The drive to replace scarce, expensive precious metals (Ru, Rh, Ir, Pd) with earth-abundant base metals (Fe, Co, Mn, Ni, Cu) is reshaping asymmetric catalysis. Iron and cobalt, the lightest first-row transition metals, offer compelling combinations of low cost, low toxicity, and rich redox chemistry. Chiral Fe and Co complexes now catalyze asymmetric hydrogenation, epoxidation, and cyclopropanation reactions that were formerly the exclusive domain of Ru, Rh, and Mn.

Iron Asymmetric Catalysis

Fe-BINOLate and Fe-BISPIDINE Complexes

Chiral Fe(II)-BINOLate complexes catalyze asymmetric sulfide oxidation and epoxidation. Fe-BISPIDINE complexes catalyze asymmetric cis-dihydroxylation of olefins — a sustainable alternative to OsO₄.

Fe-Pincer Asymmetric Hydrogenation

Chiral Fe(II)-PNP pincer complexes, developed by Morris and others, catalyze asymmetric transfer hydrogenation of ketones and imines in isopropanol or formate/water. These catalysts achieve >90% ee on aryl ketones and represent the leading Fe-based alternative to Ru-TsDPEN in ATH.

Fe-BOX Lewis Acid Catalysis

Fe(II)-t-Bu-BOX complexes catalyze asymmetric Diels–Alder and Mukaiyama–Michael reactions, complementing the established Cu-BOX and Zn-BOX systems.

Cobalt Asymmetric Catalysis

Co-Salen Epoxidation (Hydrolytic Kinetic Resolution)

Co(III)-salen complexes, developed by Jacobsen, catalyze hydrolytic kinetic resolution (HKR) of terminal epoxides — a multi-ton industrial process for producing enantiopure epoxides. The Co-salen scaffold is closely related to the Mn-salen epoxidation catalyst but operates by a different mechanism (Co-bound hydroxide opens the epoxide).

Co-Pincer Asymmetric Hydrogenation

Chiral Co(II)-PNP pincer complexes, developed by Hanson and others, catalyze asymmetric hydrogenation of ketones, aldehydes, and imines under H₂. Cobalt is particularly effective for imine hydrogenation, where it rivals Ir catalysts.

Co-BOX and Co-PyOx Cross-Coupling

Cobalt with chiral bisoxazoline and pyridoxime ligands catalyzes enantioselective cross-coupling and cyclopropanation, complementing Cu and Ni systems.

Why Iron and Cobalt Matter

  • Cost: Fe and Co are ~10⁴–10⁵× cheaper than Rh and Ir.
  • Toxicity: Both are essential human nutrients at trace levels; ICH Q3D permits higher residual levels than Pd, Ru, Rh.
  • Sustainability: No geopolitical supply concentration; recyclable.
  • Redox flexibility: Fe(II)/Fe(III)/Fe(IV) and Co(II)/Co(III) cycles enable diverse transformations.

Frontier and Outlook

Fe and Co asymmetric catalysis is the fastest-growing segment of base-metal catalysis. Recent milestones include: (1) Fe-catalyzed asymmetric hydrogenation of unfunctionalized olefins (rivaling Ir), (2) Co-catalyzed enantioselective hydroboration, and (3) Fe/photoredox dual catalysis for radical asymmetric coupling. As ligand design catches up with the established Ru/Rh/Ir platforms, Fe and Co are positioned to capture significant share of industrial asymmetric catalysis over the next decade.

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