29Si-NMR spectral assignments of polydisilahydrocarbons synthesised from diorganodichlorosilanes and styrene

In order to unambiguously assign the 29Si-NMR chemical shifts of polydisilahydrocarbons containing structural units –CH2Si1(R1R2)Si2(R1R2)CHPh–, where R1=R2=Me or Ph, a model polymer viz., poly(tetramethyldisilyleneethylene) was synthesised through the dechlorination of 1,2-bis(chlorodimethylsilyl)ethane using potassium in toluene. The 29Si-NMR spectrum of this polymer shows only one resonance peak at δ=−15.1 ppm due to Si atoms in the structural units, –CH2Si(Me)2Si(Me)2CH2– which unambiguously reveals that the chemical shift in the up field region of polydisilahydrocarbons containing structural units –CH2Si1(R1R2)Si2(R1R2)CH(Ph)– is due to Si1, i.e., silicon attached to –CH2– and accordingly, the chemical shift in the down field region is due to Si2, i.e., silicon attached to –CH(Ph)–.