posted on 2024-01-23, 18:41authored byMarc Biver, Montserrat Filella
The
formation constants of about 100 different complexes
of Ge(IV)
with some 50 organic, low-molecular-weight ligands, principally bidentate
oxygen and/or nitrogen donors, are determined by potentiometric titrations
at 25 °C and an ionic strength of 0.1 mol L–1 (KNO3). In the few cases for which literature data are
available, these older data are critically discussed and completed
in light of our new experimental data. The overall picture emerging
from our work is that such complexes are comparatively weak, except
when a chelate effect comes into play, as is observed with aminopolyols,
α-hydroxocarboxylic acids, and carbohydrate derivatives, where
even quantitative chelation of Ge is possible. No binding to amino
acids or peptides is detected. An important finding is our evidence
for the existence of a bridged dinuclear germanium(IV) tartrate complex
in the aqueous phase, whose occurrence in solids was confirmed by
X-ray diffraction beforehand. Our work has implications for the general
understanding of the aqueous coordination chemistry of Ge, its geochemical
cycling, and its behavior in environmental and biological systems.
Potentiometric raw data for use by other researchers are publicly
accessible in the repository Zenodo at CERN.