Structural study of compounds modelling elementary polymer units, 1. Molecular and crystal structures of 1,3,5‐tris(4‐biphenylyl)‐benzene and 1,3,5‐tris[4‐(C‐o‐carboranylmethyl)phenyl]benzene

Abstract

AbstractFor elucidating the structural features of elementary units of polyphenylene type polymers, prepared by polycondensation of di‐ and mono‐acetylaromatic compounds, and X‐ray study of two model compounds was performed, viz. 1,3,5‐tris(4‐biphenylyl)benzene (1) and 1,3,5‐tris[4‐(C‐o‐ carboranylmethyl)phenyl]benzene (2) (diffractometer: R = 0,063 (1) and 0,061 (2))· 1 0,5 C6H6 crystals were found to be rhombohedral, a = 20,168 (3), c = 13,678 (3) Ǎ, space group R3c, Z = 6;2· CHCl3 crystals are triclinic, a = 15,7528 (2), b = 12,7004 (6), c = 15,460 (2) Å, α = 109,97(1) β = 111,92(1) γ = 100,69 (2) °, space group P1, Z = 2. In the crystal the molecule 1 has a 32 symmetry with a propeller‐like orientation of the biphenyl fragments with respect to the central ring (the rotation of the disubstituted benzene rings relative to the central one is 47,2° and relative to the therminal ones, it is 35,9°). In2 the disubstituted benzene rings are rotated with respect to the central one by different values (dihedral angeles are 31,7 ‐ 30,7, and 52,5°). In all benzene rings of both molecules a decrease of the endocyclic bond angles at the ipso‐atoms is observed which in 2 depends on the dihedral angeles between the planes of bonded benzene rings. All there carboranylmethylphenyl fragements in 2 have the same conformation: the CH‐group of the carborane skeleton “hangs” over the benzene ring plane. The crystal packing of 1and 2 is characterized by sufficiently large cavities which are occupied by solvent molecules. In crystals of 2 the carborane parts of the molecules are associated into separate structural motives.