Tris(trimethylsilyl)silyl versus tris(trimethylsilyl)germyl: Radical reactivity and oxidation ability

A comparison of the tris(trimethylsilyl)silyl I and tris(trimethylsilyl)germyl II radical reactivity is provided. Their formation as well as their reactivity encountered in a large variety of chemical processes (addition to double bond, halogen abstraction, peroxyl radical formation…) is examined by laser flash photolysis, quantum mechanical calculations and electron spin resonance (ESR) experiments. The starting compound (TMS)3GeH is more reactive than (TMS)3SiH toward the t -butoxyl, the t -butylperoxyl and the phosphinoyl radicals. A similar behavior is noted for an aromatic ketone triplet state. II exhibits a lower absolute electronegativity: accordingly, the addition to electron rich alkenes is less efficient than for I. Radical II is also found less reactive for both the peroxylation View the MathML source(II+O2→II-O2) and the halogen abstraction reactions. The rearrangement of View the MathML sourceII-O2 is slower than for View the MathML sourceI-O2; this is related to the respective exothermicity of the processes.