Surprising Homolytic Gas Phase Co−C Bond Dissociation Energies of Organometallic Aryl‐Cobinamides Reveal Notable Non‐Bonded Intramolecular Interactions

Aryl-cobalamins are a new class of organometallic structural mimics vitamin B12 designed as potential ‘antivitamins B12’. Here, the first cationic aryl-cobinamides described, which were synthesized using newly developed diaryl-iodonium method. The obtained pairs coordination isomers, stereo-structure was unambiguously assigned based on homo- and heteronuclear NMR spectra. availability isomers with axial attachment aryl group, either at ‘beta’ or ‘alpha’ face cobalt-center allowed for an unprecedented comparison reactivity such pairs. homolytic gas-phase bond dissociation energies (BDEs) coordination-isomeric phenyl- 4-ethylphenyl-cobinamides determined by ESI-MS threshold CID experiments, furnishing (Co−C )-BDEs 38.4 40.6 kcal mol−1, respectively, two β-isomers, larger BDEs 46.6 43.8 mol−1 corresponding α-isomers. Surprisingly, observed Coβ-aryl-cobinamides smaller than )-BDE Coβ-methyl-cobinamide. DFT studies magnitudes experimental revealed relevant contributions non-bonded interactions in aryl-cobinamides, notably steric strain between cobalt-corrin moieties among peripheral sidechains.