A new model compound for vitamin B12 coenzyme: synthesis and crystal structure of a tetraazamacrocyclic alkylcobalt(III) compound with a pendant coordinating alkyl arm

Abstract

A novel reaction between norbornene and the cobalt(II) complex of the tetraazamacrocyclic ligand 5,14-dihydro-6,8,15,17-tetramethyldibenzo[b,i][1,4,8,11]tetraazacyclotetradecine(H2L), in the presence of oxygen, gives the 5,16-dihydro-16-(exo-norbornane-2,3-diyl-κC2)-6,8,15,17-tetramethyldibenzo[b,i][1,4,8,11]tetraazadecinato-κ4N5,9,14,18cobalt(III) cation (A); this was isolated as [mono(acetone)-{5,16-dihydro-16-(exo-norbornane-2,3-diyl-κC2)6,8,15,17-tetramethyldibenzo[b,i[1,4,8,11]tetraazadecinato-κ4N5,9,14,18}cobalt(III)] tetraphenylborate, and its X-ray crystal structure establishes the presence of a pendant alkyl–cobalt bond.