A benzyl–carbon bond dissociation energy of one-third the normal value: a quantitative study of benzyl–carbon bond homolysis in [CoIII(L2–CH2Ph)I], a cobalt-to-carbon benzyl migration product derived from the coenzyme B12 model complex [CoIII(L1)(CH2Ph)I]

Abstract

Benzyl–carbon bond thermal homolysis studies using the TEMPO radical-trapping method reveals a low benzyl–carbon bond dissociation energy (BDE) in [Co^III(L₂–CH₂Ph)I] of 25 ± 3 kcal mol^–1, a value one-third the normal BDE of ca. 76 kcal mol^–1 and approximately equal to the cobalt–carbon homolytic BDE in the parent complex [Co^III(L¹)(CH₂Ph)I]; such little-documented low BDEs relate back to Gomberg's classic example of Ph₃C–C₆H₅CPh₂ and its ca. 11 kcal mol^–1 carbon–(p-phenyl)carbon BDE (1 cal = 4.184 J).