The kinetics of the reactions of (ethoxycarbonyl)methylcobalt tetracarbonyl (1) with 13CO, Ph3P, HCo(CO)4, and H2are consistent with initial reversible dissociation of EtOOCCH2Co(CO)4(1) to EtOOCCH2Co(CO)3and 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 °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)4at-30 °C is 45 s, t1/2for EtOOCCH2Co(CO)4at 15 °C is 18.8 min, and t1/2for EtOOCCo(CO)4(2) at 15 °C is 24.2 min. The complex 2 shows a slow 13CO incorporation into the acyl carbonyl group, t1/2 ≈ 50 h at 28 °C, presumably through an ethoxycobalt tetracarbonyl intermediate. The rate of 13CO exchange with Co2(CO)8is not influenced by the presence of HCo(CO)4at 0 °C in n-octane, indicating that exchange of cobalt centers between HCo(CO)4and Co2(CO)8is slow compared to carbonyl exchange.
ASJC Scopus subject areas
- Colloid and Surface Chemistry