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