New polymorphism and structural sensitivity in triphenylmethylphosphonium trihalide salts

Abstract

PPh3MeX3 (X = I, Br) is studied on the basis of temperature and halide composition revealing new polymorphism structure types.

Halogen Bonding of Organoiodines and Triiodide Anions in (NMe3Ph)+ Salts

“…While all the salt‐solvate cocrystals exhibited depressed melting points compared to the pure organoiodine compounds, the relative trend in cocrystal melting points followed that of the organoiodines (TIE>1,3,5‐F 3 I 3 B> p ‐F 4 DIB> o ‐F 4 DIB). These melting points are also lower than the corresponding triphenylmethylphosphonium triiodide salt‐solvate cocrystals with the same organoiodines [20] . Decomposition of the NMe 3 PhI 3 ⋅RI cocrystals occurs from the melt and occurs over a similar temperature range of around 130–230 °C for all samples.…”

“…These melting points are also lower than the corresponding triphenylmethylphosphonium triiodide salt-solvate cocrystals with the same organoiodines. [20] Decomposition of the NMe 3 PhI 3 •RI cocrystals occurs from the melt and occurs over a similar temperature range of around 130-230°C for all samples. Based on the mass loss in this range, we surmise the total loss of the organoiodine species as well as I 2 from the decomposition of the triiodide anion.…”

“…[17,18] We have recently been interested in the behavior of the trihalide anions and have observed great structural variety in the trihalide salts of triphenylmethylphosphonium (PPh 3 MeX 3 , X=I, Br) as well as in the long-range halogen bonding motifs in the cocrystals of PPh 3 MeI 3 with organoiodines (RI). [19,20] The interactions of the triiodide anion and organoiodine molecules in these salt•solvate cocrystals are interesting in the context of crystal engineering, since the triiodide anion creates a directional, linear arrangement of iodine atoms, while the organoiodine molecules can connect the anions into larger discrete units or continuous chains, sheets, or frameworks via I•••I halogen bonding. Organoiodines such as tetraiodoethylene (TIE), 1,4-diiodotetrafluorobenzene (p-F 4 DIB), 1,2-diiodotetrafluorobenzene (o-F 4 DIB), and 1,3,5-trifluoro-2,4,6-triiodobenzene (1,3,5-F 3 I 3 B) are useful linkers that differ in their number and spatial arrangement of iodine atoms, accounting for significant structural variety in the resulting cocrystals.…”

“…We have recently been interested in the behavior of the trihalide anions and have observed great structural variety in the trihalide salts of triphenylmethylphosphonium (PPh 3 MeX 3 , X=I, Br) as well as in the long‐range halogen bonding motifs in the cocrystals of PPh 3 MeI 3 with organoiodines (RI) [19,20] . The interactions of the triiodide anion and organoiodine molecules in these salt⋅solvate cocrystals are interesting in the context of crystal engineering, since the triiodide anion creates a directional, linear arrangement of iodine atoms, while the organoiodine molecules can connect the anions into larger discrete units or continuous chains, sheets, or frameworks via I⋅⋅⋅I halogen bonding.…”