The nature and the variation of Ge–O bonding in germanates

Abstract

Abstract A survey of 42 germanates has revealed that the bond lengths of the GeO4 groups linearly decrease with increasing the Ge–O–Ge angles on account of the increase of π-bond character between Ge and O atoms. The amount of π-bond character which gives rise to the Ge–O bond shortening is influenced not only by the Ge–O–Ge angles but also the average electronegativity of all the cations contained. In a diagram showing the amount of π-bond character versus bond shortening, entries for the TO4 groups with T belonging to the third row of the periodic table (e.g. Al and Si etc.) closely lie in a line, while those with T belonging to the fourth row (e.g. Ga and Ge etc.) in another line. This situation suggests that the amount of π-bond character basically depends on the electron configuration of T atoms.