Autoxidation of Poly(hydrosilane)s

Abstract

Poly(hydrosilane)s obtained by dehydrocoupling of the corresponding RSiH3 were found to be air sensitive. Analyses based on GPC, IR, and heterocorrelated 1H−29Si NMR indicate the formation of some siloxane-type structures on the polymer backbone. Kinetic studies carried out by EPR spectroscopy using fusinite as a paramagnetic probe of the oxygen concentration allowed the oxidizability of some polysilanes to be obtained. Oxidizability values of 1.2 × 10-2 and 1.8 × 10-2 M-1/2 s-1/2 were found for poly(n-hexylsilane) and poly(phenylsilane), respectively. Model studies on the oxidation of (Me3Si)2Si(H)Me with a mixture of 16O2 and 18O2 suggest that the main reaction path proceeds via a free-radical chain mechanism and involves either two or three consecutive, unimolecular steps. Poly(hydrosilane)s react with nitroxides (TEMPO) under free-radical conditions and in the absence of molecular oxygen to give the corresponding amine in good yields.

Generation and Coupling of [Mn(dmpe)2(CCR)(CC)]. Radicals Producing Redox‐Active C4‐Bridged Rigid‐Rod Complexes

“…Under the given conditions, TEMPO acts as an oxygen donor [65] The formation of the new species 14, and the lower yield of [11] + obtained when an excess of TEMPO is added, support the idea of the radical nature of 10 and 13. Despite the fact that the new complex 14 could not be isolated as a pure solid, its structure could be determined by an X-ray diffraction study since a few single crystals were separable from the impure material.…”

A Radical Approach to Hydroxylaminotrichlorosilanes: Synthesis, Reactivity, and Crystal Structure of TEMPO‐SiCl3 (TEMPO = 2,2,6,6‐Tetramethylpiperidine‐N‐oxyl)

“…[2][3][4][5][6][7][8] In recent years, the unpaired electron situated at the oxygen atom was used to perform spin labeling of biomolecules such as peptides or proteins to gain structural information of, for example, the surface topology of the protein, which can be obtained by the determination of pseudocontact shifts (PCS). [9] We became interested in the relaxation enhancement properties of TEMPO because of its high solubility in a wide variety of organic solvents as well as its volatility, which facilitates the separation of the enhancer and sample after the NMR spectroscopic measurement.…”

“…[10] Although we found that TEMPO is a good alternative to other known relaxation enhancers in 29 Si NMR spectroscopy, we also realized that very sensitive compounds may react with TEMPO. For organosilicon compounds, it is known from literature that silylenes [11][12][13][14] and H-silanes [2,3,5,6] are oxidized in the presence of TEMPO under certain conditions. It is also known that hypervalent silicon-porphyrin complexes can react with TEMPO upon irradiation with UV light.…”

Investigation into Effects of Instability and Reactivity of Hydride-Passivated Silicon Nanoparticles on Interband Photoluminescence

“…[137][138][139][140] With this in mind, we hypothesized that TEMPO should also be able to sequester Si radicals on the surfaces of H-Si NPs, which would be expected to both increase PL intensity and slow or prevent further reactivity and changes in PL energy.…”

“…TEMPO has previously been shown to effectively passivate Si-based radicals on planar Si and as well as within polysilanes. 129,131,[133][134][135][136][137][138][139]141 Therefore, we began this work with the proposal that TEMPO would also effectively passivate Si based radicals on the surfaces of Si NPs. However, homolytic cleavage of the relatively weak Si-H surface bond could produce more Si surface radicals over time.…”