SPECTROPHOTOMETRIC AND NUCLEAR-MAGNETIC-RESONANCE STUDY OF W(VI)-ADONITOL COMPLEXES

In excess of organic ligand, the spectrophotometric study of the system tungsten(VI)-adonitol demonstrates the formation of a stable complex with 2:1 (M:L) stoichiometry, in addition to other two unstable 1:2 and 2:2 complexes present in an alkaline and acid medium, respectively From the 1D- and 2D H-1 and C-13-n.m.r. spectra an unambigous assignment for all protons and carbon atoms of the coordinated adonitol molecule can be carried out. For the 2:1 complex, the results obtained indicate that coordination occurs through one prymary ant three secondary alcoholic groups in adjacent positions. A comparative study for W(VI) and Mo(VI) shows a similar behaviour for both metals except for acidic pH, where Mo(VI) forms a 2:1 complex species.