Determination of Co–C bond dissociation energies for organocobalt complexes related to coenzyme B12 using photoacoustic calorimetry

Abstract

Photolysis of organocobalt complexes with Schiff base equatorial ligand, bis(salicylidene)ethylenediamine (salen), has been investigated by pulsed, time-resolved photoacoustic calorimetry in methanol at ambient temperature. The observed enthalpy changes and measured cobalt–carbon bond dissociation energies for the above compounds lie within the range 80–170 kJ mol−1. The influence of the steric and electronic factors of both the alkyl group and trans base ligand on Co–C bond strength is discussed. It is interesting to note that we obtain the highest Co–CH3 bond dissociation energy (BDE) value of 168 kJ mol−1 for CH3Co(salen)H2O compared with those for coenzyme B12 and its model compounds.