Cobalt(II)-promoted hydrolysis of cephalexin: Crystal structure of the cephalosporoate–cobalt(II) complex

The cobalt(II) ion-promoted hydrolysis of the widely used cephalosporin antibiotic cephalexin is confirmed by solid crystallographic characterization of the cephalosporoate–cobalt(II) complex [Co(cephalosporoate)2] · 6H2O (1), obtained from an aqueous solution containing Co(OAc)2 and cephalexin. The crystal structure analysis results prove that the double bond of dihydrothiazine ring in cephalosporoate undergoes a shift from position 3–4 to 4–5 in aqueous media at low pH, with the consequent uptake of a proton at C(3) by the α face.