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 X3 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 X3 (X = Br or I) interactions result in the formation of 2-dimensional sheetlike structures.