The Crystal and Molecular Structures of Paracyclophadiynes

Abstract

Abstract The molecular structures of tetramethyl[3.3]paracyclophadine(I) and [3.4]paracyclophadiyne(II) have been determined by X-ray analysis. Both crystals are monoclinic, with the space group of P21/c. The crystal data are: a=9.170(4), b=9.208(3), c=18.232(7) Å, β=94.0(1)°, Z=4 for (I) and a=10.938(3), b=9.173(2), c=14.988(4) Å, β=116.1(1)°, Z=4 for (II). In both molecules, consisting of benzene and diacetylene groups linked by two methylene-bridges, the diacetylene chain is bent into a bow shape. The (I) molecule has Cs symmetry, and the distances (3.019–3.256 Å) between the atoms of the diacetylene group and the benzene plane are smaller than those of [3.3]paracyclophadiyne(Aono, Sakabe, Sakabe, Katayama, and Tanaka, 1975). The methylene-bridge of [3.4]paracyclophadiyne has a disordered structure.