Crystal structures of two bis(iodomethyl)benzene derivatives: similarities and differences in the crystal packing

The isomeric derivatives 1,2-bis(iodomethyl)benzene, (I), and 1,3-bis(iodomethyl)benzene (II), both C8H8I2, were prepared by metathesis from their dibromo analogues. The ortho-derivative, (I), lies about a crystallographic twofold axis that bisects the C—C bond between the two iodomethyl substituents. The packing in (I) relies solely on C—H...I hydrogen bonds supported by weak parallel slipped π–π stacking interactions [inter-centroid distance = 4.0569 (11) Å, inter-planar distance = 3.3789 (8) Å and slippage = 2.245 Å]. While C—H...I hydrogen bonds are also found in the packing of (II), type II, I...I halogen bonds [I...I = 3.8662 (2) Å] and C—H...π contacts feature prominently in stabilizing the three-dimensional structure.