Electroreductive Synthesis of Silicon Containing Polymers.

Abstract

The electroreduction of organochlorosilanes was carried out by using magnesium cathode and anode in a single compartment cell affording oligosilanes, polysilanes, and polycarbosilanes. The electroreductive coupling of organochlorosilanes gave the corresponding disilanes in high yield.

General Concepts and Recent Advances in the Electrochemical Transformation of Chloro‐ and Hydrosilanes

“…[75] In this context, the concentration of the supporting electrolyte can also have an impact on product formation, e. g. increased chain length in reductive polysilane synthesis. [56]…”

“…[56,79,81,87,94,123] Accordingly, tetrasilanes are achieved via the dimerization of monochlorodisilanes, [94] or by end capping of dichlorodisilanes. [56,58] Pentasilanes are accessible via reductive conversion of dichloromonosilanes and monochlorodisilanes. [94] Using hydrochlorosilanes as end capping agents, the resulting H-terminated oligosilanes can be functionalized for further SiÀ Si elongation.…”

“…With dichlorodisilanes and -oligosilanes as starting material, "back-biting" reactions dominate the early stage of reaction and cooling of the reaction to 0 °C is needed to shift the kinetics towards chain elongation instead of ring closure. [56,126] Especially in the synthesis of polysilanes, stabilization of the anionic polysilane intermediate plays a crucial part of the desired reaction. Polarity of the solvent, [47,51,52,127] as well as cationic species help to generate long chain polysilanes.…”

“…Anhydrous features represent also a prerequisite, which otherwise results in the undesired formation of Si−O bonds, [45] potentially coating the electrode surface [39] . Furthermore, the conductivity, [47] as well as the electron transfer, depending on the ions selected, contributes significantly to the desired conversion [56] . However, increase of conductivity is possible by using mixed salts, for example, the combination of LiCl and MgCl 2 in a 2 : 1 ratio results in the increase of conductivity by a factor of 100 compared to the individual components [57] .…”

“…By selective mixing of di‐ and monochlorosilanes, with the monochlorosilanes present in significant excess as chain terminators, synthesis of oligosilanes in various chain lengths can be achieved. The first representatives to be obtained are the corresponding trisilanes via end capping of a dichlorosilane by monochlorosilanes [56,79,81,87,94,123] . Accordingly, tetrasilanes are achieved via the dimerization of monochlorodisilanes, [94] or by end capping of dichlorodisilanes [56,58] .…”