SPECTRA AND STRUCTURE OF SILICON-CONTAINING COMPOUNDS OF THE GENERAL FORMULA CH2CHSI(CH3)(N)CL3-N

Variable temperature ( - 60 to - 100 degrees C) studies of the infrare d spectra of dimethyl vinyl chlorosilane, CH2CHSi(CH3)(2)Cl, and methy l vinyl dichlorosilane, CH2CHSiCH3Cl2, dissolved in liquefied xenon ha ve been recorded. For both of these molecules the cis and gauche confo rmers have been identified in the fluid phases but only the conformer with the methyl group eclipsing the double bond remains in the solid. From these data, the enthalpy difference for dimethyl vinyl chlorosila ne has been determined to be 41 +/- 9 cm(-1) (117 +/- 26 cal mol(-1)) with the gauche conformer being the more stable rotamer and, for methy l vinyl silane, the enthalpy difference has been determined to be. 77 +/- 8 cm(-1) (220 +/- 23 cal mol(-1)) with the cis conformer being the more stable rotamer. Ab initio calculations have been performed using the MP2/6-31G basis set and a comparison between the calculated skel etal structural parameters for both molecules is made with those obtai ned for vinyl trichlorosilane as well as with some electron diffractio n data. (C) 1997 Elsevier Science B.V.