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.