Abstract
Both D-glucose (D-Glc) and D-mannose (D-Man) reacted with nickel(II)-tmen complex, [Ni(H2O)2(tmen)2]Cl2 (tmen =1-dimethylamino-2-(methylamino)ethane) to give the identical green complex [3], containing only D-mannose as a sugar component. In order to elucidate the factor that caused the stereoselective uptake of one of the two C-2 epimeric aldoses by nickel(II) complexes, we have investigated the nickel(II) complexes containing N-glycosides by means of EXAFS (Extended X-ray Absorption Fine Structure) spectroscopy. X-Ray absorption measurements were carried out with a laboratory EXAFS system for the samples. (a) nickel foil, (b) [Ni(L-Rha-tn)2]2+ [I], (c) nickel binuclear complex [2], μ-Man-[Ni2(CH3OH)(N-(D-Man)-dmen) (N, N'-(D-Man)2-dmen)]2+ and (d) complex [3](unknown sample). The results of the present EXAFS study show that the complex [3]has a nickel polynuclear structure involving the N-mannofuranoside bridging. In addition, it is assumed that the coordination ability of the N-mannofuranoside bridging brings about the stereoselective complexation.
