The formation of HCo(CO)4 from Co2(CO)8 or Co4(CO)12. A high pressure IR and UV spectroscopic study

Under high pressure tetracobalt dodecacarbonyl reacts first with CO to give dicobalt octacarbonyl. The latter reacts with H2 to HCo(CO)4 via an associative or a dissociative mechanism depending on the partial pressure of CO. Reversible kinetics of the type are applied for the equilibrium CO2(CO)8 + H2 ⇌ 2HCo(CO)4 at P(H2) = 45 bar and 80°C. For P(CO) < P(H2) the rate constant depend on the partial pressure of CO. For P(CO) ≥ P(H2) the rate constants are k1 = 0.0040 min−1 and k2 = 0.10 l⇌mol min, independent of CO pressure.