Triangular Halogen−Halogen−Halogen Interactions as a Cohesive Force in the Structures of Trihalomesitylenes

The structures and molecular packing of tribromo- and triiodomesitylene are reported and compared to that of trichloromesitylene. Attractive triangular X 3 interactions dominate the molecular packing in all three structures. The nonspherical atomic charge distribution on the halogens results in the formation donor−acceptor interactions in which each halogen atom is simultaneously a donor and an acceptor. These triangular X 3 (X = Br or I) interactions result in the formation of 2-dimensional sheetlike structures.