The X-ray structure analysis based on high-quality single-crystal data obtained at room temperature and 100K using a high-intensity Cu Kα beam produces a molecular structure of the title compound that was in disagreement with IR, 1H and 13C NMR data. Vibrations of the double CC bond lack in IR spectrum whereas signals of two methylene groups are visible in the 1H NMR spectrum. 13C NMR shows a spectrum of a C2 or Cs-symmetric ...