The vibrational spectra of (CH3)3MCCCCM(CH3)3, with M = C, Si, Ge, or Sn☆

Abstract Infrared spectra from 200 to 4000 cm −1 and Raman spectra from 80 to 4000 cm −1 have been recorded for the molecules (CH 3 ) 3 MCCCCM(CH 3 ) 3 with M = C, Si, Ge, or Sn. Solid samples and solutions in several solvents have been used. Assignments of the fundamentals were made on the assumption of D 3 d symmetry, which proved quite satisfactory. In all, 140 of the 188 spectroscopically-active fundamentals for the four molecules have been assigned. The in-phase CC stretch is 115–135 cm −1 higher than the out-of-phase one. This is in sharp contrast to cumulated double bonds, where the in-phase stretch is roughly half the out-of-phase one. A rationalization of this is given.