Me₂Se and Me₂Te: Their Structures and Synergistic Effects of Halogen/Chalcogen Bonding with C₆F₅Br and C₆F₅I

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 C₆F₅X and dimethyl chalcogenides Me₂Ch. Solid-state structures of Me₂Se and Me₂Te were determined 150 and 125 years after their first description. Significant C-Ch⋅⋅⋅Ch contacts make Me₂Se dimeric and Me₂Te polymeric. The cocrystals comprise C₆F₅X⋅⋅⋅Me₂Ch⋅⋅⋅XC₆F₅ aggregates, except the combination X/Ch=I/Te which shows polymeric C₆F₅I⋅⋅⋅Me₂Te⋅⋅⋅TeMe₂⋅⋅⋅IC₆F₅ 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.