Comparative study of C(2) epimerization of D-glucose and D-mannose catalyzed by water soluble organometallic complexes with nitrogen ligands

Epimerization of D-glucose and D-mannose, catalyzed by the water soluble complexes of Cu(II), Ni(II), Co(II) and Cd(II) with bisnitrogen ligands 4-7, and by Mo(VI) complexes prepared in situ from ammonium heptamolybdate (AHM) with ligands 4-9 is compared. All examined complexes exhibit lower catalytic activity than AHM; strong coordination of the ligands by both (N,O) heteroatoms to metal ions, presumably affords catalytically less active species. Some free ligands and their metal (II) complexes catalyze both C(2) epimerization and isomerization of aldoses to D-fructose.