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

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 (RXB ) 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.