Electrochemistry and Computations of Stable Silylenes and Germylenes

Abstract

Stable silylenes, 1 and 2, and germylenes, 3 and 4, have been studied computationally and by cyclic voltammetry (CV). Electron affinities (EA) and ionization potentials (IP) were calculated; the latter agree well with available gas phase photoelectron spectroscopy data. All CV measurements in THF−Bu4NClO4 exhibit irreversible waves for all compounds, for both oxidation and reduction processes. However, in 1,2-dichlorobenzene−Bu4NClO4, 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 Bu4NBF4 or Bu4NHSO4, 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 IP's and EA's, probably due to kinetic and surface effects.