Polymerization of silicon‐containing acetylenes. 5. Polymerization of 1‐silyl‐1‐propynes by TaCl5‐based catalysts

Abstract

AbstractPolymerization of homologues of 1‐(trimethylsilyl)‐1‐propyne [CH3CCSi(CH3)3] was studied. CH3CCSi(CH3)2(n‐C6H13) (I) polymerized with 1 : 1 mixtures of TaCl5 and organometallic cocatalysts (e.g., Ph4Sn and Ph3Bi) to produce in good yields a polymer having a weight‐average molecular weight (Mw) over 1 × 106. CH3CCSi(CH3)2 Ph (II) and CH3CCSi(C2H5)3 (III) formed polymers having Mw's of ∼ 5 × 105 in moderate yields in the presence of TaCl5‐based catalysts. In contrast, none of CH3CCSi(CH3)2(i‐C3H7), CH3CCSi(CH3)2(t,‐C4H9), C2H5CCSi(CH3)3, and n,‐C4H9CCSi(CH3)3 polymerized, which is attributed to the steric effect of the monomers. Some other 1‐silyl‐1‐propynes also failed to polymerize. The three new polymers formed from (I)–(III) had the structure \documentclass{article}\pagestyle{empty}\begin{document}$\rlap{--} [{\rm CCH}_{\rm 3} \hbox{=\hskip-2pt=} {\rm C(SiRR'R''}\rlap{--} ]_n$\end{document} according to IR and 13C‐NMR spectra. They were white solids, soluble in low‐polarity solvents (e.g., toluene and chloroform) and stable enough in air at room temperature.