The intensity of GeH stretching modes and conjugation effects in organogermanium compounds

Abstract

It has been shown that the integrated intensity ( A) of GeH stretching modes in the IR spectra of triorganogermanes, R 3GeH, containing no d π p π bonds between the germanium atom and the substituents is related to the sum of the Taft constants σ* of the substituents R (Σσ*) by the equation A 1 2 = 1.32 − 0.12 Σσ*. If a molecule contains substituents X capable of forming D π p π bonds with teh germanium atom, A depends not only on the — I effect of the substituents X but also on the effect of the d π p π interaction in the GeX bonds. The d π p π interaction in the molecule increases with increasing positive effective charge on the germanium atom. The values of A in alkyl-substituted compounds are indicative of the σ,σ-conjugation effect.