Spectra and structures of small ring compounds. LXIV. Raman and infrared spectra, vibrational assignment, and ab initio calculations of 1,1-diethynylsilacyclobutane☆

Abstract The Raman (3500−20 cm −1 ) and infrared (3500−50 cm −1 ) spectra of gaseous and solid 1,1-diethynylsilacyclobutane, c -C 3 H 6 Si(CCH) 2 , have been recorded. Additionally, the Raman spectrum of the liquid has been recorded and qualitative depolarization values have been obtained. These spectra have been interpreted on the basis of C s molecular symmetry where the ring is puckered and the two ethynyl groups are essentially linear. The assignments of the fundamental vibrational frequencies are compared with those obtained from a force field obtained by ab initio calculations employing the RHF/6-31G** basis set. Similar calculations have been carried out for silacyclobutane- d 0 and the Si- d 2 isotopomer. These results are discussed and compared with those obtained for some related molecules.