Halogen and Chalcogen Bonding Between the Triphenylphosphine Chalcogenides (Ph₃ P=E; E=O, S, Se) and...

A series of cocrystals of Ph₃ P=E (E=O, S, Se) with organoiodines were studied to understand the roles of noncovalent interactions including chalcogen (ChB) and halogen (XB) bonding in their formation. The structure of the cocrystal of Ph₃ P=S and 1,2-diiodotetrafluorobezene was determined, which demonstrates a similar chalcogen⋅⋅⋅iodine XB pattern to the previously reported isomorphic Ph₃ P=Se structure. The cocrystalline structures resulting from the combination of 1,3-diiodotetrafluorobenzene (1,3-F₄ DIB), as well as iodopentafluorobenzene, with all three triphenylphosphine chalcogenides, were also determined. The (Ph₃ P=Se) ⋅ (1,3-F₄ DIB) cocrystal presents a rare example of a selenium⋅⋅⋅organoiodine ChB. The observed ChB and XB interactions have normalized distance parameters (R_XB ) ranging from 0.80 to 0.98. The strength of the XB and ChB interactions were analyzed using natural bond orbital (NBO) theory, with calculated energies falling between 3.14 kcal/mol and 12.81 kcal/mol.