| Abstract: | A new orthorhombic polymorph of tri(p-tolyl)boroxine (Pmn21) with relatively short intermolecular B–O distances of 3.321 Å was crystallized from CDCl3 at ambient temperature. The crystal structure of the orthorhombic polymorph of tri(p-tolyl)boroxine shows the shortest intermolecular B–O contact yet found in boroxines. The cell dimensions of the orthorhombic polymorph of tri(p-tolyl)boroxine are a = 21.888(4) Å, b = 9.304(2) Å, and c = 4.7804(10) Å. The structural features of the orthorhombic polymorph of tri(p-tolyl)boroxine are quite different from a previously reported monoclinic (Beckett et al., J. Organomet. Chem. 1997, 535, 33–41) but similar to that of tri(p-bromophenyl)boroxine (Avent et al., Coll. Czech. Chem. Commun. 2002, 67, 1051–1060). Obviously, electronic effects of substituents on the boron centers influence the structural features of substituted boroxines less than discussed in earlier reports (Boese et al., Angew. Chem. 1987, 99, 239–241). |
