The microwave spectrum of trimethyl silyl isocyanate (CH3)3SiNCO

The microwave spectrum of trimethyl silyl isocyanate has been investigated in the region 26.5–40 GHz. The spectrum belonging to the ground vibrational state is characteristic of a symmetric top indicating that the equilibrium configuration of the SiNCO chain is either linear or very nearly so. The ground state B₀ value is 1203.83 MHz which is consistent with the structure observed for SiH₃NCO. The ground state transitions are accompanied by many vibrational satellites belonging to the lowest bending mode whose frequency was estimated to be 64 ± 15 cm⁻¹. These results are consistent with electron diffraction results from which the SiNC angle is deduced to be ≈ 150°.