The behaviour of trioxo(diethylenetriamine)molybdenum(VI) and trioxo(diethylenetriamine)tungsten(VI) in solution

Abstract

Kinetic and thermodynamic studies on the reaction of 8-hydroxyquinoline (oxine) with the octahedral complex trioxo(diethylenetriamine)molybdenum(VI), MoO₃(dien), in aqueous solution, give almost identical results to those reported previously for the reaction of oxine with molybdate, MoO₄^2–. Raman spectra and conductivity measurements confirm that the complex, MoO₃(dien), is unstable in aqueous solution, and that it is hydrolysed to give molybdate and free diethylenetriamine which is protonated. Although the complex can be precipitated from aqueous solution by the addition of ethanol, in the presence of sodium ions the product is sodium molybdate. The preparation of an analogous tungsten(VI) complex, WO₃(dien), is described, and its solution chemistry shown to be similar to that of MoO₃(dien). Attempts to prepare a chromium(VI) analogue in the solid state or in solution were unsuccessful.