Stable silylenes, 1 and 2, and germylenes, 3 and 4, have been studied computationally and by cyclic voltammetry (CV). Electron affinities (E A ) and ionization potentials (I P ) were calculated; the latter agree well with available gas phase photoelectron spectroscopy data. All CV measurements in THF-Bu 4 NClO 4 exhibit irreversible waves for all compounds, for both oxidation and reduction processes. However, in 1,2-dichlorobenzene-Bu 4 NClO 4 , the germylene derivative 3 shows a single reversible oxidation couple, whereas 4 exhibits a reversible couple at its second oxidation step, the first one being irreversible. In both cases, the redox couples become irreversible by replacing the electrolyte with either Bu 4 NBF 4 or Bu 4 NHSO 4 , indicating the importance of the counteranion on the stability of the intermediates. The CV results also show that the unsaturated 1 and 3 are more easily oxidized than their saturated counterparts 2 and 4, and oxidation is easier for the silylenes 1 and 2 than for their germanium analogues. However the measured oxidation and reduction potentials do not correlate with the calculated I P 's and E A 's, probably due to kinetic and surface effects.

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The anodic oxidation potentials of a series of 16 silylarenes have been determined by cyclic voltammetry in acetonitrile. All oxidation steps have been found to be irreversible. The effect of substituents and substitution patterns on the oxidation potentials can be presented as a linear correlation between the experimental oxidation potentials and the calculated vertical ionization energies of the silylarenes, using correlated ab initio methods at the MP2 level of theory. This correlation is useful to predict oxidation and ionization potentials of other silylarenes.