Kinetics of the Reactions of (Ethoxycarbonyl)methylcobalt Tetracarbonyl with 13CO, Ph3P, HCo(CO)4, and H2. A Comparison of the Reactivities of RCo(CO)4 (R=CH2COOEt, COOEt, and H) Complexes

Article abstract of DOI:10.1021/ja00289a019

The kinetics of the reactions of (ethoxycarbonyl)methylcobalt tetracarbonyl (1) with 13CO, Ph3P, HCo(CO)4, and H2 are consistent with initial reversible dissociation of EtOOCH2Co(CO)4 (1) to EtOOCCH2Co(CO)3 and CO.The alkylcobalt tricarbonyl then reacts competitively with the other reaction partner.The relative reactivities of 2 toward Ph3P, CO, HCo(CO)4, and H2 are 1.82, 1.0, 0.078, and 0.0006 at 25 deg C in n-heptane.The rate of 13CO substitution has also been measured for HCo(CO)4, Co2(CO)8, and (ethoxycarbonyl)cobalt tetracarbonyl (2).The half-life for HCo(CO)4 at -30 deg C is 45 s, t_1/2 for EtOOCCH2Co(CO)4 at 15 deg C is 18.8 min, and t_1/2 for EtOOCCo(CO)4 (2) at 15 deg C is 24.2 min.The complex 2 shows a slow 13CO incorporation into the acyl carbonyl group, t_1/2 ca. 50 h at 28 deg C, presumably through an ethoxycobalt tetracarbonyl intermediate.The rate of 13CO exchange with Co2(CO)8 is not influenced by the presence of HCo(CO)4 at 0 deg C in n-octane, indicating that exchange of cobalt centers between HCo(CO)4 and Co2(CO)8 is slow compared to carbonyl exchange.