Investigations on the Interaction Between sp 2 -Sulfur Atoms and Iodine Molecules Using the Cambridge Structural Database

Abstract

The interaction between sp 2 -sulfur and iodine was investigated using the Cambridge structural database (CSD). A CSD search for fragments containing at least two iodine atoms bonded to each other and exhibiting an S·;·;·;I distance less than 5.0 Å to sp 2 -sulfur atoms yields 136 fragments. The distribution of the number of fragments over the S·;·;·;I distances shows that there are two different groups. The first group contains only fragments with S·;·;·;I distances between 2.4 and 3.1 Å and the second group between 3.5 and 5.0 Å. The analysis of the orientation of the iodine atoms and the sulfur atoms shows that in the structures of the first group the iodine atoms are oriented predominantly in the direction of the lone-pairs of the sulfur atoms, whereas for S·;·;·;I distances larger than 3.5 Å a random distribution is found. This preferred orientation can be regarded as a donor acceptor interaction which also is shown by the distribution of the S·;·;·;I-I angles. For the group with S·;·;·;I distances between 2.4 and 3.1 Å S·;·;·;I-I angles of about 180°; are found, whereas for S·;·;·;I distances larger than 3.5 Å a random distribution of these angles occurs. In agreement with these results a correlation between the intermolecular S·;·;·;I and the intramolecular I-I distances is found in the group of structures with shorter S·;·;·;I bond lengths. These results are discussed as a model for the hypothetical reaction between thioketones and iodine under formation of a cationic species.