Semicoordination Bond Breaking and Halogen Bond Making Change the Supramolecular Architecture of Metal-Containing Aggregates

The complex [Ni(S2COEt)(2)] (1) and 1,4-diiodo-tertafluorobenzene (1,4- FIB) or 1,3,5-triiodotrifluorobenzene (1,3,5-FIB) were cocrystallized to form solid adducts 1.2(1,4-FIB) and 1.2(1,3,5-FIB), respectively; the structures of the adducts were studied by X-ray crystallography. The introduction of any one of the FIBs dramatically changed the supramolecular architecture of 1, and the structure-directing interactions changed from predominantly Ni center dot center dot center dot S semicoordination (in 1) to I center dot center dot center dot S halogen bonding between an FIB and the electron-donating S atoms of 1 (in the adducts). The semicoordination bond breaking and halogen bond making upon the interaction of 1 with the FIBs make the employed crystal engineering approach relevant (or even similar) to the molecular synthesis of metal species. The DFT study indicates that the strength of both types of interactions in the adducts are comparable (-3.0 to -4.9 kcal/mol and -4.3 to -4.9 kcal/mol) but very different in regard to their physical nature. If the electrostatics determine the I center dot center dot center dot S halogen bonds, the Ni center dot center dot center dot S semicoordination bonding is basically dominated by orbital effects.