MeSe and MeTe: Their Structures and Synergistic Effects of Halogen/Chalcogen Bonding with CFBr and CFI.

This work combines halogen and chalcogen bonding. Short, polarity directed C-X⋅⋅⋅Ch (X=Br or I, Ch=Se or Te) contacts were prepared by in situ low-temperature cocrystallization of liquid mixtures of neutral pentafluorohalogenobenzenes CFX and dimethyl chalcogenides MeCh. Solid-state structures of MeSe and MeTe were determined 150 and 125 years after their first description. Significant C-Ch⋅⋅⋅Ch contacts make MeSe dimeric and MeTe polymeric. The cocrystals comprise CFX⋅⋅⋅MeCh⋅⋅⋅XCF aggregates, except the combination X/Ch=I/Te which shows polymeric CFI⋅⋅⋅MeTe⋅⋅⋅TeMe⋅⋅⋅ICF aggregation. The observed C-X⋅⋅⋅Te interactions are the shortest of this type, and the C-I⋅⋅⋅Ch contacts are shorter than the corresponding C-Br⋅⋅⋅Ch interactions. Heteromolecular C-X⋅⋅⋅Ch contacts are accompanied by F⋅⋅⋅H/F and X⋅⋅⋅H contacts in the cocrystals. The analysis of packing and contacts in all (co)crystals was complemented by computational studies. They both show that short interactions can be designed and engineered with reasonable predictability.