Spectroscopic Evidence of Si−H End Groups in Dialkylpolysilanes Synthesized via Wurtz Coupling

Abstract

We demonstrate unambiguously the presence of Si−H end groups in σ-conjugated polysilanes 1−5, with alkyl groups as side chains synthesized via Wurtz coupling by means of IR, 1H, 29Si, and {1H−29Si} heteronuclear correlation NMR spectroscopy. However, there were no detectable Si−Cl, Si−OH, and Si−OR groups that would be associated with end groups of polysilanes. This implies that either such groups are not present or are too small to be detectable by IR and NMR spectra. The presence of Si−H end groups in low as well as high molecular weight polysilanes suggests the sequential existence of silyl radicals and anions in Wurtz coupling reactions and termination reaction involving a radical coupling in the solvent phase as previously described.