Microwave, infrared, and Raman spectra, structural parameters, vibrational assignments and theoretical calculations of 1,3-disilacyclopentane

The FT-microwave spectrum of 1,3-disilacyclopentane (c-C3H6Si2H4) has been recorded and 99 transitions for five isotopologues have been assigned for the twist form. The ground state rotational constants were determined from these assignments with following values for A = 4417.6710(7), B = 2887.0548(6), C = 1938.2171(6). From the experimentally reported microwave rotational constants and ab initio MP2(full)/6-311+G(d,p) predicted structural values, adjusted r0 parameters are reported for the most stable twist form distances (Å) rCαSi = 1.886(2), rSiCβ,Cβ′ = 1.888(2), rCβCβ′ = 1.552(2), and angles (°) ∠ SiCαSi = 103.9(3), ∠ CαSiCβ = 102.2(3), ∠ SiCβCβ′ = 106.4(3), and τCβSiCαSi = 11.5(3), τSiCβCβ′Si = 45.6(3). The conformational stabilities have been predicted from theoretical calculations with basis sets up to aug-cc-pVTZ from both MP2(full) and density functional theory calculations by the B3LYP method. Vibrational assignments have been made for the observed bands for the twist conformer and the interpretation is utilized by ab initio calculations to predict harmonic force constants, vibrational wavenumbers, infrared intensities, Raman activities and depolarization ratios. The results are discussed and compared to the corresponding properties of some related molecules.