Halogen bonds on demand: I...S contacts in cocrystals oftrans-bis(thiocyanato-κN)tetrakis(4-vinylpyridine-κN)nickel(II) and 2,3,5,6-tetrafluoro-1,4-diiodobenzene

Abstract

Hydrogen bonds are considered a powerful organizing force in designing supramolecular architectures because they are directional, selective and reversible at room temperature.trans-Dithiocyanatotetrakis(4-vinylpyridine)nickel(II) is a popular host for the inclusion of small molecules and 2,3,5,6-tetrafluoro-1,4-diiodobenzene (TFDIB) represents a strong halogen-bond donor. These constituents cocrystallize in a 1:1 stoichiometry, [Ni(NCS)2(C7H7N)4]·C6F4I2, in the tetragonal space groupI41/a. Both residues occupy special positions,i.e.the pseudo-octahedral NiIIcomplex is located on a twofold axis and the TFDIB molecule sits about a crystallographic centre of inversion. The components interactviaa short S...I contact of 3.2891 (12) Å between the thiocyanate S atom of the host and the iodine substituent at the perhalogenated aromatic ring of the smaller guest molecule. This interaction meets the commonly accepted criteria for a halogen bond. Such halogen bonds to sulfur are significantly less common than to smaller electronegative atoms.