Intramolecularly alkylated Costa complexes: New models for coenzyme B 12 with a cobalt-to-ligand carbon bridge

Abstract

The synthesis of Costa-type B 12 models 1 with a carbon bridge between the equatorial ligand and cobalt has been accomplished by condensation of butanedione monoxime and 2-(ω-functionalized)alkyl-1,3-diaminopropanes 8 followed by complexation with Co(II), introduction of a leaving group and intramolecular alkylation via Co(I) intermediates. The solution structure of intramolecularly alkylated Costa complexes with a bridge of two ( 1a) or of three ( 1b) methylene groups was investigated by NMR spectroscopy and compared with that of propyl(iodo) Costa complex 13.