Towards the Synthesis of Robust Polystannanes: Exploration of Coupling Catalysts and Different Building Blocks

Abstract

Polystannanes are organometallic polymers which compose of a linear backbone of covalently bonded metal atoms. Traditionally, dialkyl and diaryl homopolystannanes are synthesised by reductive coupling of tin dichlorides or tin dihydrides. These polymers possess a backbone of σ-σ delocalised organotins envisioned for use as processable intrinsic semiconductors or printable polymeric wires. However, polystannanes have a considerable drawback in that they are sensitive to light and moisture. They easily further break down or degrade to linear or cyclic oligomers. If we wish to explore the intriguing properties of polystannanes, then we need to develop air-stable and light-stable polystannanes. This project focus on exploring the general synthesise of polystannanes from basic organotin monomers. We also wish to explore the possibility of stabilising the Sn-Sn bond by installing a bridge across distannanes. Polystannanes with different side chains synthesised with different catalysts had been described. RhCl(PPh3)3 (Wilkinson’s catalyst) was found to be most suited for di(n-butyl)tin dihydride. Dehydrocoupling utilising tetramethylethylenediamine (TMEDA) was found to be most suited for diphenyltin dihydride. A useful distannane precursor, hexaphenyldistannane has been synthesised via a dehydrocoupling reaction from triphenyltin hydrideusing TMEDA and showing a high yield. Lastly, a series of attempts were made to install a catechol bridge onto distannanes. Only one approach, which was catalytic dehydrocoupling of tetraphenyldistannane by utilising B(C6F5)3 showed promising results in the ESI-MS spectra. This bridge installed distannane will be further explored and forming as the monomer for robust polystannanes.