Microwave spectra of trimethylsilylethyne, Me3SiC CH, 1-cyano-2-trimethylsilylethyne, Me3SiC CC N, and 1-cyano-4-trimethylsilylbutadiyne, Me3Si(C C)2C N

Abstract

The microwave spectra of the title compounds, recorded in the 26.5–40.0 GHz region, are characteristic of symmetric top molecules, complicated by internal rotation and accompanied by vibrational satellites attributed to low-frequency skeletal bending modes. For Me₃SiC CH, B₀= 1962.163 MHz and relative intensity measurements on the vibrational satellites give a value of 110 ± 15 cm^–1 for the degenerate Si—CC bending mode. Measurements on Me₃SiC CD have been made, and the Si—C bond length has been determined as 1.83 ± 0.01 Å. For Me₃SiC CC N, B₀= 711.8646 MHz, whilst for Me₃Si(CC)₂CN, twenty broad-band symmetric-top transitions, from J= 41 to 60, have been observed and a B value of 331 ± 2 MHz has been estimated.