Molybdän(VI)-hydroxylamin-komplexe II. Ternäre komplexe von molybdän(VI) mit hydroxylamin und chelonen sowie vergleich mit binären molybdän (V)-und molybdän(vi)-chelonaten

Abstract

It has been shown from u.v. absorption spectra that hexavalent molybdenum reacts with hydroxylamine with the formation of complexes. The chemical behaviour of these complexes and measurements of their i.r. spectra show that in them the hydroxylamine behaves as a bidentate ligand and is co-ordinated with the molybdenum both through the nitrogen and the oxygen. Spectral measurements in the u.v. and in the visible, i.r. spectra, sorption experiments with a chelate-forming exchange resin, and mass-analysis studies, show that the binary molybdenum(VI) hydroxylamine complex forms ternary complexes with ethylenediaminetetraacetic acid, diaminocyclohexanetetraacetic acid and nitrilotriaceticic acid. The ternary complex with EDTA contains molybdenum, hydroxylamine and EDTA in a molar ratio of 1:1:1. The infrared spectra show that all four carboxyl groups of the EDTA are bound in the same way to the molybdenum(VI), which indicates that six co-ordination sites of the central atom are occupied by the EDTA. The additional occupation of two co-ordination sites by the hydroxylamine provides evidence of an eight-fold co-ordination of hexavalent molybdenum in aqueous solution. Reference is made to the possibility of chelometric titration of hexavalent molybdenum with EDTA, DCTA or with NTA ∗ ∗ See list of abbreviations given on p. 163. . The advantages of this procedure are pointed out.