Millimeter-Wave Spectroscopy Of Silene, Ch2sih2

Free CH2 = SiH2 (1) has been observed in the gas phase by millimeter wave spectroscopy. A total of 142 rotational lines of the Si-28 species were measured, the search being guided by recent ab initio calculations. The identification of the molecule has been confirmed by the observation of many isotopomers : H2CSiD2, H2CSiHD, (H2CSiD2)-Si-29 and D2CSiH2. The ab initio and experimental rotational constants of 1 with a planar C-2v structure agree within about 0.5 %. Silene was produced by vacuum pyrolysis of Ar-seeded 5,6-bis (trifluoromethyl)-2-silabicyclo [2.2.2] octa-5,7-diene; it decomposes with a 1/e lifetime of the exponential decay at ambient temperature of 30 +/- 2 ms.