Kinetics and mechanism of the reaction of octacarbonyl dicobalt with ethyl diazoacetate

Kinetics of the reaction of octacarbonyl dicobalt with ethyl diazoacetate leading to [μ2-{ethoxycarbonyl(methylene)}-μ2-(carbonyl)-bis(tricarbonyl-cobalt)] (Co-Co) (1), dinitrogen, and carbon monoxide were investigated at 10 °C in heptane solution. The initial rate of the reaction was measured by following both the gas evolution and the decrease of the octacarbonyl dicobalt concentration. The rate is first order with respect to octacarbonyl dicobalt and a complex order with respect to ethyl diazoacetate and carbon monoxide depending on the ratio of their concentrations. This is in accord with the formation of a heptacarbonyl dicobalt reactive intermediate (k1 (10 °C) = (1.22 ± 0.06) × 10−3 s−1) for which carbon monoxide and ethyl diazoacetate compete (k−1/k2 (10 °C) = 1.34 ± 0.07).

Based on the kinetics of the reaction: Co2(CO)8 + EtO2CCHN2 → Co2(CO)7(CHCO2Et) + CO + N2, a mechanism was suggested in which carbon monoxide and ethyl diazoacetate compete for the reactive intermediate Co2(CO)7: (k1 (10 °C) = (1.22 ± 0.06) × 10−3 s−1) and (k−1/k2 (10 °C) = 1.34 ± 0.07) in heptane solution.Figure optionsDownload as PowerPoint slide