Complementary Selenium•••Iodine Halogen Bonding and Phenyl Embraces: Cocrystals of Triphenylphosphine Selenide with Organoiodides

Se center dot center dot center dot I Halogen bonding (XB) between triphenylphosphine selenide and organoiodides: 1,2-diiodotetrafluorobenzene (1,2-F4DIB), 1,4-diiodotetrafluorobenzene (1,4-F4DIB), and tetraiodoethylene (TIE) has been used to assemble molecules into finite adducts, chains, and two-dimensional layers. Phenyl embraces involving the triphenylphosphine groups extend these moieties into additional dimensions, leading in two cases (1,4-F4DIB and TIE) to open structures, with filled or partially filled cavities. Comparison of structural parameters for 26 reported zigzag chains of embracing Ph3XY reveals that this synthon can adapt its registry to accommodate widely diverse structures. The strengths of the XB interactions were analyzed using natural bond orbital (NBO) theory, which provides an estimate of the energy of a donor-acceptor interaction (Delta E-d -> a) through localization of the molecular orbitals. Structures of 1:1 and 1:2 XB complexes of Ph3P=Se with 1,2-F4DIB and 1,4-F-4 were optimized at the DFT(B97-1)/BSI level. The bond distance and angles obtained are in reasonably good agreement with the experimentally observed structures.