Unexpected reduction pathway of a Co2+ salt to [HCo(CO)4] via [Co2(CO)8] in an ionic liquid

In the 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide ionic liquid ([BMI][NTf2]), [Co(NTf2)2] is reduced under 5.5 MPa of H2–CO to [Co2(CO)8] prior to [HCo(CO)4], provided a pyridine ligand is present in the medium.