نبذة مختصرة : Two new polymorphs of the ion pair LiI(C4H8O)3 (trigonal, space group P ; tetragonal, space group I41 cd) show different three-dimensional arrangements in the crystal structure and co-exist at the same temperature.
Two new trigonal and tetragonal polymorphs of the title compound, iodidotris(tetrahydrofuran-κO)lithium, are presented, which both include the isolated ion pair Li(THF)3 +·I−. One Li—I ion contact and three tetrahydrofuran (THF) molecules complete the tetrahedral coordination of the lithium cation. The three-dimensional arrangement in the two polymorphs differs notably. In the trigonal structure, the ion pair is located on a threefold rotation axis of space group P-3 and only one THF molecule is present in the asymmetric unit. In the crystal, strands of ion pairs parallel to [001] are observed with an eclipsed conformation of the THF molecules relative to the Li⋯I axis of two adjacent ion pairs. In contrast, the tetragonal polymorph shows a much larger unit cell in which all atoms are located on general positions of the space group I41 cd. The resulting three-dimensional arrangement shows helical chains of ion pairs parallel to [001]. Apart from van der Waals contacts, no remarkable intermolecular forces are present between the isolated ion pairs in both structures.
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