Coenzyme B12 model studies : synthesis and axial ligation of alkyl(aquo)cobaloximes with biologically important ligands

Department of Chemistry, Osmania University, Hyderabad-500 007, India

E-mail : ssnsirasani@yahoo.com

Manuscript received 12 February 2002. revised 19 July 2002, accepted 27 August 2002

Alkyl(aquo)cobaloximes, RCo(DH)₂OH₂ (R = BrCH₂, CH₃, C₂H₅) have been prepared. These aquo complexes upon reacting with imidazoles, substituted imidazoles, histamine and histidine give alkyl(ligand)complexes [RCo(DH)₂L]. All the ligands are coordinated through endocyclic nitrogen (N₃). The characteristic absorption hand of C=N of dimethylglyoximato ligand in the alkyl cohaloximes shifts tn lower wave numbers as the donating power of the base ligand increases, where C=N shifts to higher wave numbers when the withdrawing power of alkyl group increases. The formation of alkyl ligand cobaloximes is confirmed by the spectral data.